Integrated Agriculture andAquaculture Systems (IAA) forEnhanced Food Production andIncome Diversification in Tanzania Deogratias Mulokozi
Deogratias M
ulokozi Integrated A
gricultu
re and A
quacu
lture System
s (IAA
) for Enh
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ction an
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in Tan
zania
Dissertations in Physical Geography No. 11
Doctoral Thesis in Physical Geography at Stockholm University, Sweden 2021
Department of Physical Geography
ISBN 978-91-7911-390-2ISSN 2003-2358
Deogratias MulokoziDeogratias has a background in fisheries,aquaculture and aquatic sciences. He holds aMSc. in Marine Sciences from University of Dares Salaam. His research relates to fisheriesscience and aquaculture with a focus onintegrated agriculture-aquaculture systems(IAA) for sustainable food production.
The aim of this thesis was to assess the status of fish pond farming witha focus on integrated agriculture and aquaculture (IAA) systems inTanzania, and to provide guidance on how these systems could befurther developed to help local farmers to diversify their foodproduction and income generation. The results showed that small scalefish farming contributed with 13% of the farmers’ income. About 38%of the fish was used for consumption and the remaining part was sold,contributing to both food security and livelihood diversification.Integration of tilapia and vegetables was the most common type of IAAsystem applied. The fish yield and net income from the IAA ponds were60% and 175% higher compared to non-IAA ponds respectively,because of a more frequent use of on-farm resources and bettermanagement, which resulted into higher yield and reduced cost. Majorconstraints included water problems, lack of technical skills and goodquality fish seeds and feeds. Overall, fish farmers had a positiveattitude towards fish farming and the majority were willing to continuewith fish farming, with IAA farmers being more positive than non-IAAfarmers. The multiple use of water in integrated tilapia-vegetablesystems increased the water use efficiency and reduced the need forsynthetic fertilizers. Considering that agriculture is already popular andthat fish farming is expanding, promotion of IAA systems couldprovide an entry point for an increased adoption of aquaculture amongrural farmers in Tanzania.
Integrated Agriculture and Aquaculture Systems(IAA) for Enhanced Food Production and IncomeDiversification in TanzaniaDeogratias Mulokozi
Academic dissertation for the Degree of Doctor of Philosophy in Physical Geography atStockholm University to be publicly defended on Thursday 11 February 2021 at 13.00 in DeGeersalen, Geovetenskapens hus, Svante Arrhenius väg 14 and digitally via conference (Zoom),public link https://stockholmuniversity.zoom.us/j/68951088257
AbstractAquaculture production in Tanzania has increased in recent years, responding to an increased demand for fish, partly because of an increasing population and declining catches of wild fish. However, the current aquaculture production is still low, dominated by small scale farming systems, that are struggling with a number of challenges such as lack of improved fish breeds, feeds, technical skills and low adoption rates.
This thesis aims to assess the status of fish pond farming with a focus on integrated agriculture and aquaculture (IAA) systems in Tanzania, and to provide guidance on how these systems could be further developed to help local farmers to diversify their food production and income generation.
Methodologies included field observations, interviews, structured questionnaires, field experiments and laboratory analyses. Two field surveys in six districts and seven regions of Tanzania provided insights on the current status and the contribution of small-scale pond farming and IAA to household income and food production. Differences between IAA and non-IAA fish farming practices, and their influence on farm productivity and profitability were assessed. Also, opportunities, constraints and farmers’ future plans for fish farming were explored. Two field experiments were conducted on selected IAA systems identified during the surveys. One assessed the effect of including amaranth (Amaranthus hybridus) waste in locally produced fish feed on the yield of Nile tilapia (Oreochromis niloticus). Another investigated how the combination of different vegetables (A. hybridus and Brassica rapa pekinensis) and stocking densities of O. niloticus affected the water use efficiency, need for synthetic fertilizers and overall farm productivity and profitability.
The results show that small scale fish farming contributed with 13% of the farmers’ income. 38% of the fish was used for consumption and the remaining part was sold, contributing to both food security and livelihood diversification. Integration of tilapia and vegetables was the most common type of IAA system applied. Local feed ingredients contained medium to high content of crude protein, with high fat content in some animal by-products. The fish yield from the IAA ponds was 60% higher compared to non-IAA ponds because of a more frequent use of on-farm resources and better management. The net income from IAA ponds was 175% higher compared to non-IAA ponds, due to reduced costs and higher yields. Major constraints included water problems, lack of technical skills and good quality fish seeds and feeds. Overall, fish farmers had a positive attitude towards fish farming and the majority were willing to continue with fish farming, with IAA farmers being more positive than non-IAA farmers. The use of amaranth wastes as a fish feed ingredient in a tilapia-amaranth integrated system did not affect the fish growth and yield, but rather improved the feed conversion ratio. The multiple use of water in integrated tilapia-vegetable systems increased the water use efficiency and reduced the need for synthetic fertilizers. Although water from high fish stocking densities increased the vegetable yield, the overall farm productivity in the IAA system was negatively affected because of low fish growth and survival rates. Since agriculture is already popular and fish farming is expanding, promotion of IAA systems could provide an entry point for an increased adoption of aquaculture among rural farmers.
Keywords: Smallholder farmers, Oreochromis niloticus, Amaranthus hybridus, food production, household income diversification, water use efficiency, farm net income.
Stockholm 2021http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-187543
ISBN 978-91-7911-390-2ISBN 978-91-7911-391-9ISSN 2003-2358
Department of Physical Geography
Stockholm University, 106 91 Stockholm
INTEGRATED AGRICULTURE AND AQUACULTURE SYSTEMS (IAA) FORENHANCED FOOD PRODUCTION AND INCOME DIVERSIFICATION IN TANZANIA
Deogratias Mulokozi
Integrated Agriculture and AquacultureSystems (IAA) for Enhanced FoodProduction and Income Diversification inTanzania
Deogratias Mulokozi
©Deogratias Mulokozi, Stockholm University 2021 ISBN print 978-91-7911-390-2ISBN PDF 978-91-7911-391-9ISSN 2003-2358 Cover illustration: Example of an integrated agriculture and aquaculture system (IAA) in Tanzania, by Deogratias Mulokozi Printed in Sweden by Universitetsservice US-AB, Stockholm 2021
To my parents PiusLyangombe andMariageorgina Muyaga
Abstract
Aquaculture production in Tanzania has increased in recent years, responding to an increased demand for
fish, partly because of an increasing population and declining catches of wild fish. However, the current
aquaculture production is still low, dominated by small scale farming systems, that are struggling with a
number of challenges such as lack of improved fish breeds, feeds, technical skills and low adoption rates.
This thesis aims to assess the status of fish pond farming with a focus on integrated agriculture and
aquaculture (IAA) systems in Tanzania, and to provide guidance on how these systems could be further
developed to help local farmers to diversify their food production and income generation.
Methodologies included field observations, interviews, structured questionnaires, field experiments and
laboratory analyses. Two field surveys in six districts and seven regions of Tanzania provided insights on
the current status and the contribution of small-scale pond farming and IAA to household income and food
production. Differences between IAA and non-IAA fish farming practices, and their influence on farm
productivity and profitability were assessed. Also, opportunities, constraints and farmers’ future plans for
fish farming were explored. Two field experiments were conducted on selected IAA systems identified
during the surveys. One assessed the effect of including amaranth (Amaranthus hybridus) waste in locally
produced fish feed on the yield of Nile tilapia (Oreochromis niloticus). Another investigated how the
combination of different vegetables (A. hybridus and Brassica rapa pekinensis) and stocking densities of
O. niloticus affected the water use efficiency, need for synthetic fertilizers and overall farm productivity
and profitability.
The results show that small scale fish farming contributed with 13% of the farmers’ income. 38% of the
fish was used for consumption and the remaining part was sold, contributing to both food security and
livelihood diversification. Integration of tilapia and vegetables was the most common type of IAA system
applied. Local feed ingredients contained medium to high content of crude protein, with high fat content in
some animal by-products. The fish yield from the IAA ponds was 60% higher compared to non-IAA ponds
because of a more frequent use of on-farm resources and better management. The net income from IAA
ponds was 175% higher compared to non-IAA ponds, due to reduced costs and higher yields. Major
constraints included water problems, lack of technical skills and good quality fish seeds and feeds. Overall,
fish farmers had a positive attitude towards fish farming and the majority were willing to continue with fish
farming, with IAA farmers being more positive than non-IAA farmers. The use of amaranth wastes as a
fish feed ingredient in a tilapia-amaranth integrated system did not affect the fish growth and yield, but
rather improved the feed conversion ratio. The multiple use of water in integrated tilapia-vegetable systems
increased the water use efficiency and reduced the need for synthetic fertilizers. Although water from high
fish stocking densities increased the vegetable yield, the overall farm productivity in the IAA system was
negatively affected because of low fish growth and survival rates. Since agriculture is already popular and
fish farming is expanding, promotion of IAA systems could provide an entry point for an increased adoption
of aquaculture among rural farmers.
Sammanfattning
Omgärdad av stora sjöar som Victoriasjön, Tanganyikasjön, Malawisjön samt Indiska Oceanen, så är det
inte konstigt att fisk utgör en viktig matvara i Tanzania. Ungefär 30% av det animaliska protein-intaget hos
befolkningen kommer från fisk. Under de senaste åren har dock fiskfångsterna stagnerat, vilket har lett till
en ökad efterfrågan av fisk. En ökad produktion av fisk från vattenbruk har lyfts fram som en möjlighet att
möta den ökande efterfrågan. Den nuvarande produktionen av fisk via vattenbruk är dock fortfarande låg,
och domineras av småskaliga odlingar, som kämpar med ett antal utmaningar, som brist på fisk-yngel och
foder av god kvalitet, samt tekniska färdigheter hos både befolkningen och myndigheter.
Med avseende på dessa utmaningar, föreslås det i denna avhandling att främjandet av Integrerade
jordbruks-vattenbruks-system (IAA) kan utgöra ett viktigt sätt att öka antalet fiskodlingar bland småskaliga
jordbrukare, genom att bygga på deras erfarenhet av att sköta småskaliga jordbruk. Baserat på synergier
och resursåtervinning mellan de delsystem som ingår i integrerade odlingssystem (IAA,) så finns det en
stor potential att öka jordbrukets produktivitet och lönsamhet samtidigt som de negativa effekterna på
miljön minimeras. Ett viktigt syfte med denna avhandling var således att bedöma statusen för fiskodling i
dammar och IAA-system i Tanzania, och att ge en vägledning om hur dessa system kan utvecklas vidare
för att hjälpa lokala jordbrukare att diversifiera sin livsmedelsproduktion och inkomst i Tanzania.
Avhandlingens empiriska studier är baseras på fältobservationer, intervjuer, strukturerade frågeformulär,
fältförsök och laboratorieanalyser. Först genomfördes en fältundersökning i sex distrikt och sex regioner i
Tanzania för att få en bättre överblick av hur småskalig fiskodling samt IAA fungerar i Tanzania och i
vilken utsträckning dessa bidrar till hushållens inkomst och livsmedelsproduktion. Studien undersökte
också hur metoder för att odla fisk skilde sig mellan bönder som bara odlade fisk och de som integrerade
fisk med olika grödor, och i vilken utsträckning eventuella skillnader påverkade produktiviteten och
lönsamheten. Slutligen analyserades böndernas syn på möjligheter, begränsningar och framtida planer för
att odla fisk. Fältundersökningen skapade en viktig bakgrund för utformningen av de efterföljande
fältförsöken. Två fältförsök genomfördes för att få en djupare förståelse av hur några utvalda IAA-system
fungerade. Det första experimentet undersökte effekten av att använda avfall från växten amarant
(Amaranthus hybridus) som en tillsats i lokalt producerat fiskfoder, som används i ett tilapia (Oreochromis
niloticus) amaranth-integrerat system. Det andra försöket undersökte hur olika grönsaker kunde kombineras
med olika mängder fiskyngel för en optimerad vattenanvändningseffektivitet, minskad tillförseln av
kemiska gödningsmedel samt totalt ökad produktion och lönsamhet.
Resultaten visade att småskalig fiskodling är den vanligaste typen av vattenbruk i Tanzania, och bidrar
med cirka 13% av jordbrukarnas inkomst. Cirka 38% av den producerade fisken konsumerades inom
hushållet och den återstående delen såldes för att betala för andra hushållskostnader. Fiskodling bidrog till
diversifierade försörjningsmöjligheter och förbättrad tillgång till näringsrika livsmedel. Integrering av
tilapia med grönsaker var den vanligaste typen av IAA system. Grönsaker, jämfört med andra grödor,
krävde mindre mängd arbetskraft och utrymme, kortare odlingsperiod samt mindre mängd vatten för
bevattning. Grönsaksavfallet kunde användas som mat till den odlade fisken. De flesta av de lokala
ingredienserna som användes som fisk-foder innehöll en medelhög mängd protein med relativt högt
fettinnehåll i vissa animaliska ingredienser. Fiskproduktionen i de integrerade systemen (IAA) var 60%
högre jämfört med produktionen i de system som inte var integrerade med olika grödor, ofta på grund av
att fisken matades mer frekvent med avfall från gården och en bättre skötsel av fisken eftersom jordbrukare
som bedrev integrerade system ofta hade en längre erfarenhet och bättre utbildning. Nettoinkomsten från
integrerad fiskodling var 175% högre jämfört med fiskodling som inte var integrerad, på grund av lägre
kostnader och högre avkastning och intäkter från de integrerade fiskodlingarna. De största utmaningarna
för fiskodling inkluderade vattenproblem, brist på teknisk kompetens och fisk-yngel och foder av låg
kvalitet. Överlag hade fiskodlarna en positiv inställning till fiskodling och majoriteten var villiga att
fortsätta med fiskodling.
Användningen av amarantavfall (AW) som en tillsatts i fiskfoder i ett tilapia-amaranth-integrerat system
påverkade inte fiskens tillväxt negativt utan förbättrade snarare foderomvandlingsförhållandet (FCR).
Återanvändningen av vatten för att odla både fisk och grönsaker i det integrerade systemet ökade
vattenanvändningens-effektiviteten och minskade behovet av kemiska gödningsmedel. Även om vattnet
från dammar med en hög mängd fiskyngel ökade grönsaksproduktionen väsentligt, påverkades
fisktillväxten och den totala produktiviteten i det integrerade systemet negativt, på grund av en minskad
överlevnad hos fiskynglen. Då många bönder i Tanzania är vana att bedriva småskaligt jordbruk, så skulle
fiskodling integrerat med olika grödor kunna utgöra ett realistiskt sätt att öka produktionen av odlad fisk i
Tanzania, som skulle kunna bidra till ekonomisk tillväxt, social rättvisa och förbättrad miljö.
Included list of papers
Paper I. Mulokozi, D. P., Mmanda, F. P., Onyango, P., Lundh, T., Tamatamah, R. and Berg, H. (2020).
Rural aquaculture: Assessment of its contribution to household income and farmers’ perception in selected
districts, Tanzania. Aquaculture Economics and Management.
https://doi.org/10.1080/13657305.2020.1725687
Paper II. Mmanda, F. P., Mulokozi, D. P., Lindberg, J. E., Haldén, A. N., Mtolera, M., Kitula, R. and Lundh
T. (2020). Fish farming in Tanzania: the availability and nutritive value of local feed ingredients. Journal
of applied aquaculture. https://doi.org/10.1080/10454438.2019.1708836
Paper III. Mulokozi, D. P., Berg, H., Onyango, P., Lundh, T. and Tamatamah, R. Assessment of pond and
integrated aquaculture (IAA) systems in selected districts, Tanzania-Submitted to Journal of Agriculture
and Rural Development in the Tropics and Subtropics.
Paper IV. Mulokozi, D. P., Berg, H. and Lundh, T. (2020). An ecological and economical assessment of
integrated Amaranth (Amaranthus hybridus) and Tilapia (Oreochromis niloticus) farming in Dar es Salaam,
Tanzania. Fishes, 5(3), 30. https://doi.org/10.3390/fishes5030030
Paper V. Mulokozi, D. P, Berg, H., Tamatamah, R., Lundh, T. and Onyango, P. Integration of tilapia
(Oreochromis niloticus) and vegetables (Amaranthus hybridus and Brassica rapa pekinensis) for improved
water use efficiency and nutrient recycling–Manuscript.
Author contributions
The contributions from listed authors are divided as follows for each article.
Paper I. My contribution: I designed and conceived the study, led the fieldwork, and wrote the earlier
versions of the paper. I did all data analyses.
Others’ contributions: FPM assisted in the field work and manuscript writing. HB, PO, TL and RT
participated in the inception of the study, supervised the methodology, discussed results and conclusions,
and co-edited the paper.
Paper II. My contribution: I was the second author in the paper, involved in designing and conception of
the study. I assisted in the fieldwork, and editing the earlier versions of the paper.
Others’ contributions: FPM was the main author, conceived the study, did the field survey and laboratory
analysis, processed the data, wrote the earlier versions of the paper. JEL, ANH, MM, RK and TL involved
in study designing, supervised the methodology, contributed to the discussion section and co-edited the
manuscript.
Paper III. My contribution: I designed and conceived the study, led the fieldwork and data analysis, and
wrote the earlier versions of the paper.
Others’ contributions: HB, PO, TL and RT Involved in Conceptualization, supervised the methodology,
discussed results and conclusions, and co-edited the paper.
Paper IV. My contribution: I designed the study, led the field experiment and data analysis, wrote the
earlier versions of the manuscript.
Others’ contributions: HB was involved in conceptualization, reviewed and edited the manuscript. TL
investigated, reviewed and edited the manuscript.
Paper V. My contribution: I designed and conceived the study, led the field experiment and data analysis.
I wrote the earlier versions of the paper.
Others’ contributions: HB involved in designing of the study, discussed results and conclusions, and edited
the manuscript. PO, TL and RT discussed results and conclusions, and co-edited the manuscript.
Abbreviation used: FPM - Francis Pius Mmanda, HB - Håkan Berg, PO - Paul Onyango, RT - Rashid
Tamatamah, TL - Torbjörn Lundh, JEL - Jan Erik Lindberg, ANH - Anna Norman Haldén, MM - Matern
Mtolera and RK - Rukia Kitula.
TABLE OF CONTENT
1. INTRODUCTION ...................................................................................................................... 1
2. BACKGROUND ........................................................................................................................ 2
2.1 Fish as food and livelihood ................................................................................................... 2
2.2 Aquaculture and its potential to meet the demands for fish.................................................. 3
2.3 Status of aquaculture in Tanzania ......................................................................................... 4
2.4 Integrated agriculture and aquaculture (IAA) ....................................................................... 6
3. THESIS RATIONALE AND AIM ............................................................................................. 9
4. METHODS ............................................................................................................................... 10
4.1 Study area............................................................................................................................ 10
4.2 Overview of the studies performed ..................................................................................... 12
4.3 Stakeholders consultations, interviews and field observations (Papers I, II and III). ......... 12
4.4 Field experiments (Paper IV and V) ................................................................................... 14
4.5 Assessment of fish and vegetable growth performance, economic returns and water use
efficiency................................................................................................................................... 17
4.6 Data analysis ....................................................................................................................... 19
5. RESULTS ................................................................................................................................. 20
5.1 Key findings ........................................................................................................................ 20
5.2 Socioeconomic profile of fish farmers (Paper I, II and III) ................................................ 21
5.3 Impact of fish farming on household income and fish consumption (Paper I) ................... 22
5.4 Fish pond characteristics and water sources (Paper III) ..................................................... 23
5.5 Fish pond management and performance of IAA and non-IAA systems (Paper III) ......... 24
5.6 Crops integrated with fish pond farming (Paper III, IV and V).......................................... 26
5.7 Financial performance of IAA and non-IAA systems (Paper III, IV and V) ..................... 28
5.8 Tilapia stocking densities and its effect on water use efficiency, water quality, fish growth
and yield in IAA farming (Paper V) ......................................................................................... 30
5.9 Famer’s perception on opportunities, constraints and future plans towards aquaculture
(Paper I and III) ......................................................................................................................... 31
6. DISCUSSION ........................................................................................................................... 33
6.1 Characteristics of fish farmers ............................................................................................ 33
6.2 Impact of fish farming on household income and fish consumption .................................. 34
6.3 Fish pond management and performance of IAA and non-IAA systems ........................... 35
6.4 The effect of integrating vegetable farming with fish farming ........................................... 37
6.5 Financial performance of IAA and non-IAA systems ........................................................ 38
6.6 Tilapia stocking densities and its effect on water use efficiency, water quality and fish
yield in IAA farming ................................................................................................................. 39
6.7 Famer’s perception of opportunities and constraints for fish pond farming and IAA ........ 39
7. CONCLUSION ......................................................................................................................... 41
8. FUTURE RESEARCH ............................................................................................................. 43
9. ACKNOWLEDGEMENTS ...................................................................................................... 44
9.1 Financial support ................................................................................................................. 45
10. REFERENCES ....................................................................................................................... 46
1
1. INTRODUCTION
Global fish demand is projected to keep growing due to population growth, increased urbanization and
rising incomes (FAO, 2020). Fisheries and aquaculture are a vital for food security and income, especially
for small-scale farmers and fishing communities (OECD/FAO, 2019). In 2017, fish accounted for about
17% and 7% of the global share of the animal and protein consumption respectively (FAO, 2020). The
contribution of fish to animal protein is even more apparent in Sub-Saharan Africa (SSA), where it
contributes to over 19% of the per capital protein intake (Chan et al., 2019). However, the per capita fish
consumption in SSA remain to be low compared to other regions of the world, and it is the only region
where it is decreasing and predicted to keep decreasing due to declining wild capture fisheries (OECD/FAO,
2019).
Worldwide, aquaculture is the fastest growing food production sector, with an annual growth rate of 5.3 %
per year in the period 2001–2018, contributing to 46 % of the global fish production, rising up from 25.7%
in 2000, thus expected to fill the gap of fish demands (FAO, 2020). In Africa, aquaculture production is
still low, contributing about 2.7% of the global aquaculture production (Halwart, 2020). However, there is
a great potential to increase aquaculture production due to the favorable climate conditions of large part of
the continent (Brummett et al., 2008). Based on a multi-factorial evaluation considering inputs such as
water availability, soil characteristics, farm-gate sales, infrastructures and other resources using a GIS
approach, it is estimated that 43% African continent is suitable for aquaculture with the potential of having
2 and 1.7 harvests per year for tilapia and catfish respectively (Ridler and Hishamunda, 2001; Aguilar-
Manjarrez and Nath, 1998). Moreover, it is reported that despite that 23% of SSA being suitable for
commercial aquaculture, only 5% has been utilized (Kapetsky, 1994; Aguilar-Manjarrez and Nath, 1998).
Wild caught fish has for many years been a major source of protein and income for a majority of the people
in Tanzania, accounting for 30% of animal consumption (URT, 2020a). This is because the country is
encompassed with a number of water bodies including Lake Victoria, Tanganyika, Nyasa and the Indian
Ocean. According to the Ministry of Agriculture, Livestock and Fisheries Development report (2020), fish
per capita consumption is at 8.6 kilograms, which is only about one third of the global per capita
consumption of 20 kilograms per year (URT, 2020a; FAO, 2020). As the gap between wild fish catch
supplies and a growing demand from a growing population keep widening, a decrease in fish supply is
experienced, particularly by rural households, suggesting a need for increased production from aquaculture
as an alternative fish source (Rothuis et al., 2014).
However, aquaculture production in Tanzania is still low, and reasons for this have been reported to be due
to lack extension services, low quality fingerlings and lack of good quality fish feeds (URT, 2016a; Rothuis
et al., 2014). By 2005, Tanzania was estimated to have a total of 13,011 fish ponds (Rukanda 2016). Recent
data from the Department of Aquaculture Development (URT, 2020b) indicates that there were 27,979 fish
ponds and 28,009 fish farmers in 2019/2020, with a total production of 17233 tons per year. Despite these
achievements, the contribution of aquaculture to fish production in Tanzania remains low, contributing only
5% of the share in the national fish production (URT, 2020a).
2
Considering the low number of people doing aquaculture and the fact that small scale agriculture is the
major livelihood in Tanzania, accounting for about 29% of the GDP, and employing more than 77% of the
workforce (URT, 2017), integrated agriculture-aquaculture (IAA) could provide a valuable entry point for
increasing the aquaculture adoption rate, and thus the fish production in rural Tanzania (Brummett and
Wiliams, 2000; Dey et al., 2010). Increased adoption of IAA farming would not only increase the fish
production but also increase the overall farm and food production through synergies among involved
subsystems. Examples from Malawi indicate that, adoptiom of IAA system led to 11% increase in farm
productivity and 134% higher income per hectare than non-IAA farming (Dey et al., 2010). Similar results
were reported in Tanzania in Tarime by Shoko et al. (2011a) and in Kilombero by Limbu et al. (2017).
Thus, small scale integrated fish farming, could be an important way to increase fish production and the
diversity of local farming activities in Tanzania (cf. Shoko et al., 2019; Kaleem and Sabi, 2020).
Diversification of crops and secured water, would help small scale farmers to become more resilient to
climate change by for example balancing economic losses on seasonal cropland (Dey et al., 2010). They
provide a design that can operate in more remote areas, and have been shown to enhance poor farmers`
livelihoods for decades (Karim et al., 2011). They have low or even positive environmental impact and
have often a positive social impact, through enhanced food security, water availability and income source
diversification. It is therefore proposed in this thesis that IAA systems should be part of Tanzania´s future
aquaculture portfolio, to assure an aquaculture development that contributes to both economic growth,
social justices and environmental qualities.
2. BACKGROUND
2.1 Fish as food and livelihood
In 2015, the United Nation’s 2030 development agenda outlined 17 Sustainable Development Goals
(SDGs) in line with 169 targets that will guide national, regional, and international agencies’ actions to
achieve sustainable development over the next decade [UNDP]. In particular, SDG2 is committed to ending
all forms of hunger including food and nutrition insecurity. Fish is an important source of food for people,
contributing about 17% of animal protein intake and 7% of all protein consumed by the world’s population
(FAO, 2020). More than 10% of the global population depend on fisheries and aquaculture for their
livelihoods (WorldFish, 2020; FAO, 2020). Fish consumption is increasing rapidly, having risen from 86
million tonnes in 1998 to 152.9 million tonnes in 2018 (FAO, 2000; FAO, 2020). The increased fish
consumption is related to the growing human population in many countries in Africa, Asia and Latin
America, which indicates the importance of a consistent supply to meet nutritional and financial demands
of a large portion of the worlds’ population (Chan et al., 2017; Chan et al., 2019). Currently, fish is one of
the few food sources that is still obtained from the wild, with capture fisheries accounting for about 54% of
the world’s fish supply (FAO, 2020). More recently however, wild fishery has not been able to meet the
growing fish demands and many fisheries are now in a stagnant or even decline stage (Zeller and Pauly,
2005; Costello et al., 2016). In the period 1961–2017, fish consumption has increased by 3.1% while the
supply from capture fisheries has almost remained stable (FAO, 2020). This has increased pressure on
capture fisheries, which has led to overfishing of some commercial fisheries.
3
2.2 Aquaculture and its potential to meet the demands for fish
The share of aquaculture to global fish production reached 46% in 2018 (Figure 1), rising from 26% in
2000. Regionally, the contribution of aquaculture to total fish production was about 17.9% in Africa, 17.0%
in Europe, 15.7% in the Americas and 12.7% in Oceania (FAO, 2020). The highest aquaculture contribution
to fish production in 2018 was reported from Asia (Excluding China), reaching 42%, rising from 19% in
2000 (OECD/FAO, 2019; FAO 2020). The expansion of the sector is due to increasing local demands from
growing human population, urbanization, growing incomes as well as investment in advanced farming
technologies, such as genetically improved fingerlings, intensive systems and high-quality feeds (Chan et
al., 2017; Tran et al., 2019; OECD/FAO, 2019). Aquaculture has therefore been, and expected to be a key
fish producer to meet the ever-increasing fish demands. However, global aquaculture production is not
evenly distributed. Asia account for 89% of the total global aquaculture share with China contributing to
about 58% of the total share in aquaculture production in 2018, falling from 59.9% in 1995 (FAO, 2018;
FAO, 2020). Africa contribute with about 2.7% of the world aquaculture production with Egypt, Nigeria
and Uganda being the first, second and third major producers, respectively (Halwart, 2020). Sub Saharan
Africa (excluding Nigeria) contributed with only 0.37% of the total global aquaculture production in 2018
(FAO, 2020). The reasons behind the low aquaculture production in SSA are related to lack of inputs,
markets and extension services (Kaminski et al., 2018; Adeleke et al., 2020). Despite its current low
production, Africa’s aquaculture sector recorded a twenty-fold increase in production, rising from 110,200
tons in 1995 to 2,196,000 tons in 2018 (Halwart, 2020). As human population in Africa is expected to
double in 2050 (UN-DESA, 2017), aquaculture has a significant role to play as a source of animal protein
to food and nutrition security in the continent (Chan et al., 2019).
Figure 1. World capture fisheries and aquaculture production, 1950-2018. (Source: FAO, 2020).
4
2.3 Status of aquaculture in Tanzania
Aquaculture in Tanzania started with the introduction of trout from Scotland, released into streams around
Kilimanjaro and Mbeya regions, for the purpose of sport fishing, which eventually marked the beginning
of aquaculture in the country (Balarin, 1985). This was followed by the introduction of experimental ponds
in 1950s in Korogwe and Malya areas, Tanga and Mwanza regions respectively, which were stocked with
tilapia fingerlings form Lake Victoria, Pangani and Congo rivers (Nilsson and Wetengere, 1993; FAO,
2012). It is estimated that the country had about 10,000 fish ponds with a surface area of 1,000 ha by 1960
(Rice et al., 2006). A remarkable development of aquaculture occurred between the years of 1970s and
1980s, which was due to a number of interventions assisted by various donors. By 1990, many projects
failed to meet the expected outcomes which led donors to withdraw from supporting aquaculture projects.
Since then, aquaculture production in Tanzania has remained low, dominated by freshwater fish farming
with Nile tilapia (Oreochromis niloticus) and African sharp tooth catfish (Clarias gariepinus) being the
most common cultured fish species (Kaliba et al., 2006). Other cultured fish species include Mozambique
tilapia (Oreochromis mossambicus Peters 1852) and Zanzibar tilapia (Tilapia hornorum Trewavas 1966)
(Shoko et al., 2011b). However, recent data show considerable development of aquaculture as reflected in
the increased number of ponds from 13,011 in 2005 to 29,979 fishponds in 2019/2020 (Figure 2). The
majority of the fish ponds (Figure 3) are found in Ruvuma, Iringa, and Mbeya located in the southern
highlands of Tanzania, and Kilimanjaro in the northern part of Tanzania (Rukanda, 2016; URT, 2016b).
Currently aquaculture contributes with about 5% (Figure 4) of the total fish production in Tanzania (URT,
2020a). The reported improvement in aquaculture could be related to the growing interests on fish farming
and increased emphasis put on aquaculture by the government through the Directorate of Aquaculture
Development (DAD) under the Ministry of Livestock and Fisheries Development (MLFD). Following its
establishment in 2008, DAD has put in place a National Aquaculture Development Strategy (NADS), which
is currently being implemented. Through DAD, four aquaculture service centers; Kingolwira in Morogoro,
Mwamapuli in Tabora, Ruhila in Ruvuma and Nyengedi in Lindi were renovated to bring aquaculture
services closer to the farmers. The role of these centers includes production of quality fingerlings and feeds
of affordable price and provision of extension services to farmers (URT, 2020a).
Cage fish farming in Lake Victoria, Lake Tanganyika and the Indian Ocean is currently drawing attention
of both the government and private sectors. Cage installments increased from 408 in 2018 to 431 in 2019
with 370 cages being installed in Lake Victoria, 9 cages in Lake Tanganyika, and 52 cages in other water
bodies (URT, 2020a). Other reported aquaculture practices include crab fattening, milkfish farming and
shrimp culture in the coastal areas (Shoko et al., 2011b). Tanzania is also among the top global seaweed
producers in the world and the production increased from 49.9 thousand tonnes, fresh weight in 2000 to
103.2 thousand tonnes, fresh weight in 2018 (FAO, 2020).
5
Figure 2. The trend in number of fish ponds in Tanzania 2005-2019 (Source: Rukanda, 2016; URT, 2020b).
Figure 3. Map of Tanzania showing the distribution of fish ponds at a district level (Source: URT, 2016a).
13,000
15,000
17,000
19,000
21,000
23,000
25,000
27,000
29,000
2005 2007 2009 2011 2013 2015 2017 2019 2021
Nu
mb
er o
f fi
sh p
on
ds
Years
6
Figure 4. Fish production in Tanzania in 2019/ 2020 (Source: URT, 2020a).
2.4 Integrated agriculture and aquaculture (IAA)
Integration of crops and animals is considered important for a sustainable development of agriculture
(Devendra and Thomas, 2002). Barghouti et al. (2004) and Erenstein (2006) distinguished three pathways
through which agriculture development can be achieved. These include: (i) extensification, increasing the
cultivated area while maintaining or decreasing farm inputs per hectare; (ii) intensification, increase farm
production per hectare through increased inputs and mechanisation (iii) diversification, integration of farm
subsystems and product for improved social, environmental and economic sustainability. One form of
diversification is the integration of agriculture and aquaculture systems (IAA). Prein (2002) defines IAA as
“concurrent or sequential linkages between two or more agricultural activities (one or more of which is
aquaculture), directly on-site, or indirectly through off-site needs and opportunities, or both”. Generally,
IAA systems are composed of three components which include agriculture, aquaculture and the household
as described below.
2.4.1. The agriculture component
IAA farming is generally the introduction of aquaculture component into already existing agriculture
system, though it could be the other way around (Zajdband, 2011). The way in which aquaculture is
incorporated in agriculture will depend on biophysical, social and climate factors, which determine the type
of IAA systems to be developed at each location in time. These systems are usually dominated by crop
cultivation, but widely also include livestock keeping. A typical example of IAA is the combination of rice
and fish farming in South East Asia, which also include annual and perennial cropping, such as mixed
gardens of vegetable and fruits on adjacent pond dykes and sometimes livestock husbandry, especially
poultry and pigs (Edwards et al. 1988; Huong et al., 2018). Few notable examples of IAA systems in Africa,
involving integration of fish (especially tilapia and catfish), livestock and vegetable have been reported in
81.8%
13.7%
4.5%
Inland fisheries: 336,661
tonnes
Marine fisheries: 56,272
tonnes
Aquaculture (marine and
freshwster production):
18,717 tonnes
7
Malawi, South Africa, Ethiopia and Kenya (Melaku and Natarajan, 2019). The introduction of aquaculture
in IAA systems may alter some management practice of the agriculture sub-component. For example,
introduction of fish in rice fields may reduce the use of agrochemicals to accommodate both fish and rice
(Berg, 2002; Berg et al., 2017). Additionally, introduction of aquaculture may result in establishment of
vegetable and fruits or ducks on the pond dike or adjacent fish pond, which benefit from pond water for
irrigation and swimming (Edwards, 2008).
2.4.2. The aquaculture components
The diversity in aquaculture systems is generally categorized based on their intensity and resource use. The
level of intensification is subject to a wide range of factors such as fish stocking density, feeding practices,
labor, capital, energy and technology (Lazard et al., 2010). IAA systems are often somewhere between
extensive to intensive type of aquaculture, and it often depends on some kind of fertilization for production
of phytoplankton and zooplankton as natural feed for the fish (Edwards et al., 2000). Aquaculture can be
further defined based on the structure used in the operation, including cage, pond and tank farming systems.
Most of the semi intensive aquaculture systems are practiced in ponds (FAO, 2020).
Aquaculture in IAA systems generally involve culture of fish species feeding at lower trophic levels i.e.
herbivores or omnivorous species such as tilapia, carp and catfish. The choice of cultured species often
depends on the local context and prevailing factors such as availability of fish feeds and seeds, facilities
and management practices (Edwards, 1998). Tilapia in particular is one of the suitable candidates in IAA
systems as they can be produced even in rural areas without the need for use of advanced technologies. As
opposed to carnivorous species, tilapia is also known to grow well feeding on natural food from pond
fertilization and supplementation of on farm wastes, such as vegetable wastes, rice and maize bran (Poot-
López et al., 2009; Limbu, 2019). Different species can be raised together in a poly-culture system to allow
efficient use of pond resources. In Tanzania catfish is sometimes combined with tilapia in IAA systems.
This helps to control pond overcrowding by catfish preying on O. niloticus fingerlings from prolific
breeding of tilapia, thus improving fish growth rate and yield (Shoko et al., 2015; Limbu et al., 2017).
However, proper stocking density and species ratio should be taken into consideration when combining
different species as it may result into negative impacts because some species can shift their feeding habits
and consume others (Rahman et al., 2008).
2.4.3. The household component
Understanding of the socio-cultural dynamics of the household is very important for introduction of
aquaculture (Wetengere, 2011). This is because characteristics of the household have great influence on
whether they do or do not adopt IAA farming. A study by Bosma (2007) indicated that IAA adoption is
mainly determined by family labor, area of homestead and farmer’s relative income. Farmers’ income
increases the ability to construct a fish pond which normally involve high initial capital, which is often not
affordable to the poorest farmers (Nhan et al., 2007). IAA farming is generally a family farming system,
in a sense that household members are the ones managing the farm and contribute with most of the labor,
although occasionally hired labor can be used (Wetengere, 2011). In addition to providing farm labor,
household members are the consumers and sometimes venders of different farm products. Nevertheless,
household size and structure can have great influence on available labor as well as consumers of the produce
8
i.e. the workers-consumers ratio of family members (Bosma et al., 2007). Farmers who adopted IAA
farming were reported to have a more positive attitude towards aquaculture due to the increased income
provided by fish farming (Duc et al., 2008). The potential of IAA system to increase food and nutritional
security of the household comes from its ability to increase fish and crop production, and income generation
for buying extra food (Ahmed and Lorica, 2002). As the household is the major source of labor, the impact
of IAA on creating job opportunities is less important, unless practiced in intensified manner (Murshed-e-
Jahan et al., 2010).
2.4.4. Component interactions and benefits in IAA system
The purpose of integrating aquaculture with agriculture is to optimize the positive interactions or synergies
between the components (Figure 5). These synergies, according to Edwards (1998), occur when “an output
from one sub-system in an integrated farming system, which may otherwise have been wasted becomes an
input to another sub-system, resulting in a greater efficiency of output of desired products from the
land/water area under the farmer’s control”. Thus, the fish in this case benefits from available on-farm
remains which comes as wastes from crops and livestock but can be used as fish feeds, and thus help to
minimize the fish feed costs. Being part of the system, the fish pond provides inputs, such as nutrient rich
waste water and sediments, that can be used for other agricultural activities, and thus help to reduce inputs
of synthetic fertilizers (Da et al., 2015). Fish stocked in rice fields can also serve as a biological control by
preying on pests as insects, snails and weeds, thus cut or reduce input of pesticides in the environment and
also the amount of water related diseases (Xie et al., 2013).
The diversity of activities in IAA can be useful in terms of spreading the risk of potential disasters, thus
increasing the farm and household resilience. For example, when a diseases or drought reduce the yield of
one of farm activity, the yield from another component may serve as a backup. Water from the pond can be
used for irrigation during periods of dry weather. Nutritionally, fish is widely recognized to be rich in high
quality metabolites such as amino acids, omega-3 fatty acids, minerals, especially iron, zinc, and vitamins
(Kawarazuka and Béné, 2011). Therefore, integration of fish with crops such as vegetable, which contain
high amount of vitamin and minerals (Odhav et al., 2007), can have great impact on household food security
and nutrition.
9
Figure 5. Possible on-farm interactions between IAA components (modified from Edwards et al., 1988).
3. THESIS RATIONALE AND AIM
The current drive in Africa, including Tanzania, is to promote commercial intensive systems as the way to
increase fish production, income generation and provide employment opportunities (Hishamunda and
Ridler, 2006; Kaminski et al., 2018). However, these systems often come with social and environment
implications (Naylor and Burke, 2005; Irz et al., 2007; Naylor et al., 2009; Tacon et al., 2010). While some
studies (Chopin et al. 2010; Nobre et al. 2010) describe the possibility of intensive commercial systems to
produce fish while minimizing negative impacts to the environment, fish produced in these systems are too
expensive for the poorest (Rivera-Ferr´e 2009; Genschick et al., 2018). Production of fish through semi
intensive system such as IAA may provide a more realistic way to increase the availability of fish in rural
and peri-urban areas in Tanzania (Brummett and Williams, 2000; Genschick et al., 2018; Kinkela et al.,
2019). This thesis argues that small scale aquaculture through integrated agriculture system, if given enough
consideration, can help to increase aquaculture adoption rates and fish production, by building on the
farmers experience on managing small scale agriculture systems. The reason behind promoting IAA
systems is not only to increase the adoption rates of aquaculture, considering that 75% of Tanzania are
small scale farmers, but also to take advantages of the positive synergies between agriculture and
aquaculture as shown in figure 5 above.
The overall objective of the thesis is to present an updated information on the status of integrated
aquaculture-agriculture systems (IAA) in Tanzania, and to provide guidance on how these systems could
be further developed to help local farmers to diversify their food production and income sources. The
hypothesis is that IAA farming practices provide a competitive alternative to fish and crops standalone
productions if the farmer takes full advantages of inputs and outputs of the integrated systems.
10
Specifically, the thesis had the following objectives:
1. To assess the contribution of rural fish farming to the household income and food production in some
selected districts of Tanzania and, identify major constraints and opportunities for fish pond farming in
Tanzania (Paper I and II).
2. To Identify the characteristics of existing pond and IAA systems in selected districts of Tanzania and
how they differed compared to non-IAA farming, as a basis to understand farmers’ reasons for practising
IAA or not (Paper II and III).
3. To assess management practices and their influence on fish pond productivity and profitability in IAA
and non-IAA systems (Paper III, IV and V).
4. To assess the feasibility of using local agriculture waste as a complementary fish feeds in IAA systems
(Paper II and IV).
5. To assess the effect of recycling fish pond water on the IAA systems’ production, economic profitability
and water use efficiency (paper III, IV, V).
4. METHODS
4.1 Study area
This work was conducted in Tanzania, a country located just below the equator in East Africa, having a
total land area of 947,303 km2 and a 1,424 km long coastline (URT, 2012). Inland lakes have a total
coverage of 59,000 km2 (URT, 2012). Tanzania’s total population was about 58 million people in 2019,
with 65.5% people living in rural areas and where small-scale agriculture is the major livelihood activity
(Worldbank, 2020). In 2019, the country average annual temperature varied between 19.2 °C and 29.3 °C
with an annual average total rainfall of 1283.5 mm (TMA, 2019). About 10% of the country’s surface area
is covered by wetlands (Wilson et al., 2017). This indicates the availability of labour, warm temperatures
and water, factors that are important for aquaculture development.
One fieldwork (paper I and III) was conducted in six districts of Tanzania including Kilombero, Mvomero,
Igunga, Songea Uraban, Songea Rural and Mbarali. The districts are characterized by unimodal rainfall
pattern except Mvomero which experiences bimodal rainfall. The overall rainfall ranges from 450 mm in
Igunga to 1,800 mm in Songea (NBS, 2018). The population mainly depends on agriculture. Irrigated rice
farming is commonly practiced in Kilombero, Mbarali, and Igunga, while maize production is more
common in urban and rural Songea. A mixture of maize, rice, and sorghum production is commonly found
in Mvomero (NBS, 2018). Pond fish farming is a more common practice in Songea Rural, Songea Urban,
Mbarali, and Mvomero as it was introduced some time ago compared to Kilombero and Igunga where it
was introduced recently (Nilson and Wetengere, 1994; Chenyambuga et al., 2014; Limbu et al., 2017). A
parallel field survey (paper II) was conducted in seven regions including Arusha, Dar es Salaam,
11
Kilimanjaro, Mbeya, Mwanza, Ruvuma and Zanzibar. The location of the study sites is presented in figure
6 below.
Figure 6. A map Tanzania indicating the location of the sites for the two field surveys and also where the
experiments were conducted.
12
4.2 Overview of the studies performed
The empirical work of this thesis was conducted in two phases. The first stage involved two parallel baseline
surveys in six districts (paper I and III) and seven regions (paper II) of Tanzania. The survey was conducted
through household and key informant interviews based on structured questionnaires. The survey in paper I
and III aimed at getting an updated status of pond and IAA systems, assess the contribution of fish farming
to the household income, examine management practices and their influence on pond and IAA productivity
and profitability, understand constraints to IAA and fish farming in general, and to assess farmers’
perceptions in regard to future plans on fish farming in Tanzania. The other survey in paper II focused on
the availability and nutritive value of local fish feeds in Tanzania.
In the second stage, field experiments were conducted to get a deeper understating on the performance of
some integrated systems identified during the baseline survey (paper IV and V). The first experiment was
conducted at the Tanzania Fisheries Research Institute in Dar es Salaam, with the aim to assess the potential
application of vegetable wastes as an ingredient in fish feeds, and the use of pond water for vegetable
farming in a tilapia-amaranth integrated system. The second field experiment was conducted in the Tanga
region at the Institute of Marine science, Mariculture centre, UDSM, with the aim to assess the impact of
IAA farming on the water use efficiency, and the effect of fish stocking densities on pond water quality and
its impacts in promoting vegetable growth and yield in an integrated tilapia- amaranth-spinach system. A
summary of methodologies applied in this thesis is provided in table 1 below.
Table 1. Overview of methods and analyses applied in this thesis’ research papers.
Methodologies and analyses Paper I Paper II Paper III Paper IV Paper V
Household interviews, key informant interviews and field
observations
✓ ✓ ✓
Interview with local fish feed producers and hatchery
owners.
✓
Field experiments ✓ ✓
Laboratory analysis ✓ ✓ ✓
4.3 Stakeholders consultations, interviews and field observations (Papers I, II and III).
4.3.1. Study design and data collection
For paper I, II, and III, interviews were conducted using semi-structured questionnaires with households
actively involved in fish pond and IAA farming. The surveyed districts were selected based on: (i) the
relative high number of fish farmers recorded in these districts by the Ministry of Livestock and Fisheries,
and (ii) previous reports on aquaculture technology transfer efforts such as IAA trainings, fish seeds and
feeds dissemination. Fish ponds were categorized into two groups; (i) ponds having a direct link with
adjacent cropping activities, frequently supplemented with agricultural remains and pond water used for
irrigating crops on pond dike or adjacent to the pond, herein after referred to as IAA ponds and; (ii) ponds
without adjacent cropping activities, without or rarely supplemented with agricultural byproducts, herein
after referred to as non-IAA ponds. Examples of IAA ponds are shown in figure 7.
13
Figure 7. Examples of IAA ponds with adjacent cropping activities during the field work. Left (a) vegetables
irrigated with fish pond water, right (b) Chinese cabbage farming integrated with a fish pond (Photos taken
by Deogratias Mulokozi in Songea district).
Some farmers reported to have farmlands away from fish ponds where they cultivate cereals crops like
maize and cassava. These farms were not considered as part of integrated farming as they had no direct link
with the fish ponds. Few farmers integrated fish with poultry farming. Due to difficulties of getting detailed
information about animals as they were kept in a free ranging mode, integrated fish-husbandry systems
were not included in the data analysis. In total, a sample of 65 IAA ponds and 64 non-IAA ponds from 89
fish farmers were surveyed in the first survey (Paper I and III). In the second survey (paper II), a sample of
202 tilapia farmers, local fish feed producers and hatchery owners in mainland Tanzania and in Zanzibar
Island were interviewed. Additionally, a sample of 60 different local feed ingredients were collected for the
analysis of their nutritive value in the laboratory.
The questionnaire in the first survey was composed of five sections: (i) fish farmer’s demographic and
social economic characteristics (age, gender, education level, family size and household income); (ii) fish
pond characteristics (pond size, pond depth, pond ownership, year of construction and water sources); (iii)
fish pond management practices and production (pond fertilization, species farmed, stocking density, feed
and feeding regimes, and yield); (iv) fish and integrated crop production costs and returns (pond
construction, labor, fingerling, water, transport, feeds, seed, fertilizers and net income); and (v)
opportunities and constraints to pond and IAA farming, and farmers’ future plans regarding fish farming.
4.3.2. Household survey and income assessment
Household annual income was estimated as sum of both on-farm and other income sources through in-
depth discussion with the household heads. As far as farming products were concerned, both value of cash
incomes obtained from marketed crops and those consumed by households were estimated and summed to
obtain the total annual household income (Duc, 2009; Karim et al., 2011). This method was applied due to
the lack of public data and written records on fish pond economic performance in Tanzania. This
information was used to assess the contribution of fish farming to household income generation.
14
Additionally, farmers were asked to estimate the share of farmed fish that was used for household
consumption relative to the portion sold for cash. This was done to get insights on the contribution of fish
to household food security. Supplementary information was collected through key informant interviews
and field observation for the purposes of cross checking some of the information obtained through
questionnaire, especially on fish pond characteristics and management. This helped to discover
discrepancies between reality and what participant said. Proximate chemical analysis and amino acid
composition of local fish feeds and ingredients in paper II, IV and V was carried out according to standard
methods (AOAC 1990,1999).
4.4 Field experiments (Paper IV and V)
The field experiments were conducted as a complement to the field surveys, with the aim to provide local
grounded examples on how agriculture and aquaculture could be combined, and to what extent the
integration of agriculture and aquaculture would affect the production efficiency of the systems (paper IV
and V). Although field experiments together with farmers could have provided an alternative approach, it
was felt that field station experiments provided a more controlled environment. Still the experiments were
designed to provide as realistic conditions as possible so they also would provide guidance on how future
IAA systems could be designed, and indicate their feasibility in terms of yields and economic profitability
and water utilization efficiency.
The first field experiments described in paper IV were conducted using 7m3 ponds located at TAFIRI in
Dar es Salaam (6o39051.57" S and 39o12045.32" E). The second field experiments, described in paper V,
used 1m3 tanks at the Institute of Marine Sciences, Mariculture Center (05o25´54.80"S; 38o57´28.87"E) in
Pangani, Tanga region. The first experiment (Paper IV) assessed the potential application of amaranth
(Amaranthus hybridus) wastes (AW) as a dietary ingredient for Nile tilapia (Oreochromis niloticus) in a
tilapia-amaranths integrated system. Amaranth was chosen because there is huge production of amaranth
waste in Dar es Salaam every year, and it was proposed that this could be used to replace some of the
ingredients in the fish feeds, because of its nutritional content. This could help to reduce the costs for fish
feeds for the farmer and at the same time decrease the amount of amaranth waste in the environment. The
experiment involved three stages (Figure 8): (i) A feeding experiment, where the fish were fed either the
control diet (CD) through-out the experiment (183 days) or the amaranth diet (AD) for the first 100 days
and then the control diet (CD) for the remaining 83 days; (ii) An amaranth fertilization experiment (90 days
after fish stocking), where amaranth plots were irrigated with either tap water or pond water from fish fed
the amaranth diet, and treated with or without fertilizers; (iii) Analysis of growth performance, yield and
economic benefits of pond and amaranth farming when practiced as an integrated system or as separate
activities. The experiment was purposely designed to replicate small scale fish famers in Dar es Salaam,
who traditionally combine two or more ingredients as feed for the fish.
The second experiment (paper V) was conducted to examine the effect of Nile tilapia stocking densities on
water use efficiency, water quality and its influence on fish and vegetable growth performance, yield and
financial profitability. Thus, this experiment also aimed to show the benefits of recycling fish-pond water
for enhanced crop production and decreased use of synthetic fertilizer, but also emphasized further the
advantages of an IAA system in terms of increased water use efficiency for food production, when using
the same amount of water for a combination of food products. Oreochromis niloticus were stocked at
15
different levels i.e. low, medium and high densities (table 2). The linked vegetable experiment involved
cultivation of Brassica pekinensis, and Amaranthus hybridus in different fertilization regimes including
irrigation with tap water and pond water from various fish stockings. The water and soil nutrients were
analysed according to standard methods (Morris and Riley, 1963; Koroleff, 1970a; Koroleff, 1970b;
Koroleff, 1976; Boyd and Tucker 1998; APHA, 2005;). Water pH was measured using a pH meter (model
Combo H198129), dissolved oxygen (DO) and temperature measurements were taken using a multiprobe
kit (model Ecosense DO 200A).
Figure 8. Schematic representation of the study design in paper IV. (Adopted from paper IV: Mulokozi et
al., 2020b). CD = control diet, AD = amaranth diet.
4.4.1. Fish experiments
In paper IV, fish were stocked at a rate of 8 fish m-3. Amaranth wastes (AW) i.e. both unsold and unused
amaranth leaves, were obtained from a nearby vegetable market. It was cleaned with tap water to remove
sediments and then soaked in boiling water for about 10 min to reduce potential antinutritional factors
(Mosha et al., 1995). It was then solar dried under shade to a constant weight, powdered and then stored in
refrigerator until use. The AW powder was then used as an ingredient in the tilapia diet at 10% inclusion
for the experiment diet (Molina-Poveda et al., 2017). Other ingredients included shrimp meal, soybean, and
rice bran, which were ground separately using hammer a meal. The resulting mash was mixed accordingly
and then blended using water to form a dough. The dough was then made into pellets. The produced pellets
were solar dried under shade until complete dryness.
16
The pellets were hand-fed to the fish by dispensing it at the surface of each pond. Two treatments in
triplicate involved; (i) fish fed control feed (CD) without inclusion of the AW, hereafter referred to as non-
integrated fish ponds (non-IAA fish) and (ii) fish fed amaranth diet (AD), hereafter referred to as integrated
fish ponds (IAA fish), as the pond water was also used to irrigate the amaranth plots. Fish in the IAA ponds
were fed with experimental diet for the first 100 days and then shifted to the control diet (CD) for the
remaining 83 days until the end of the experiment. This is because AW is only readily available during the
dry season (July–October), which is the peak for amaranth production in Dar es Salaam (Putter et al., 2007).
In paper V, mono-sex O. niloticus fingerlings were obtained from a commercial hatchery and stocked at
different rates i.e. low (5 fish m-3, T5), medium (8 fish m-3, T8) and high (12 fish m-3, T12). Fish were fed
with a prepared feed containing a 35% protein dietary inclusion served at 5% body weight split into two-
portion, one given in the morning (around 9.00 am) and another in the afternoon (around 3.30 pm).
4.4.2. Vegetable irrigation and fertilization experiments
In both paper IV and V vegetable cultivation were done the during dry season, three months after fish
stocking to avoid the influence of rain, and also to allow nutrients to accumulate in the pond water for
vegetable growth. During this period, no water was exchanged in the fishponds, and water was only added
to compensate for the loss of water through evaporation. Vegetable plots were prepared adjacent to fish
ponds. After the vegetable cultivation had finished, one-third and full of pond water replacement was done
once a month in paper IV and V respectively. Irrigation (5 liters 1 m-2) was done once a day during the
evening. Water from the fish ponds with the same fish stocking density was blended and irrigated to the
vegetable plots (paper IV and V). Pond water for irrigation was compensated by adding tap water to
maintain the pond water level. The first experiment in paper IV had three treatments with six replicates and
the second experiment in paper V involved eight treatments with three replicates (Table 2).
The treatments (Figure 8) applied in paper IV were as follows: (i) amaranth plots irrigated with tap water
without fertilization, hereafter referred to as control amaranths, (ii) amaranth plots irrigated with water from
the IAA fish ponds above (section 4.4.1), and with only organic fertilizer applied, hereafter referred to as
integrated amaranth (IAA amaranth) and (iii) amaranth plots irrigated with tap water, and fertilized with a
combination of organic and synthetic fertilizers (a practice commonly used by farmers in Tanzania),
hereafter referred to as non-integrated amaranth (non-IAA amaranth).
In paper V, Chinese cabbage (B. pekinensis) and amaranth (A. hybridus) were cultivated in a plot size of
2m x 1m. Three seeds of Chinese cabbage were sown per point which were then thinned to one plant per
point. In both paper IV and V, amaranth sowing was done by mixing 10 g of amaranth seeds with 1 kg of
sand to obtain uniform stands, and then broadcasted at a rate of 1 g of seeds per m2 (Baitilwake et al., 2012).
The experimental vegetable plots (Figure 9) were prepared adjacent to the fish tanks and treatments in
triplicates were applied as outlined in table 2.
17
Table 2. Irrigation and fertilization treatments for vegetables applied in the experiment in paper V.
Vegetables irrigated with water from: No fertilizer applied Partially fertilized
Low fish stocking (T5) Lo L1
Medium fish stocking (T8) Mo M1
High fish stocking (T12) Ho H1
Tap water CTR (Control) NO (Normal)*
* Farmers usually start by applying manure as a planting fertilizer and then after two to three weeks they
apply a synthetic fertilizer as a booster fertilizer.
Figure 9. Experimental vegetables (Chinese cabbage and amaranth) under different irrigation and
fertilization regimes in paper V.
4.5 Assessment of fish and vegetable growth performance, economic returns and water use
efficiency
As the crop yield, economic return and water use is critical factor for the farmers, these were some of the
factors that was used to evaluate the technical and financial performance of the investigated IAA systems.
However, as outlined in figure 5, IAA systems also have several other synergistic effects, such as reduction
of nutrients in the fishpond water through the uptake by different crops and increased food security through
a diversification of crops, and although these were not quantitatively assessed, they still make up important
factors to be considered.
18
4.5.1. Fish and vegetable growth performance and yields
For the fish, data was collected at a monthly interval until the end of experiments when the ponds were
drained completely to assess the fish growth performance, yield and economic returns. Fish growth
performance was calculated using the Specific growth rate (SGR).
Where:
100)T
Ln W1-Ln W2 ( SGR =
Where: Ln = Natural Logarithm, W1 = Mean initial weight (g), W2 = Mean final weight (g).
Also, the feed conversion ratio (FCR) was used as a measurement on how efficient the added feed was
taken up by the fish for biomass production and calculated as following:
(g)gain weight Live
(g) intake feedDry FCR =
In experiment IV, also the Protein efficiency ratio (PER) was measured as it is a widely used method for
evaluating the quality of protein in food. It is based on the weight gain of the fish divided by its intake of
food protein during the test period and calculated as follows:
(g) intakeProtein
(g)gain weight Live PER =
The survival rate (SR) of fish was seen as a general indication of how suitable the system was for fish
production, where an optimal production of course should aim for 100% survival:
SR = NH
NS𝑋100
Where: NH = Number of fish harvested, NS = Number of fish stocked.
Yield was used as an overall indication of the systems productivity and in most cases, it was translated to a
production in tons per hectare.
)(A
TW(Kg) Yield
ha=
Where: TW= total fresh weight of the fish or vegetable harvested, A= pond or plot area.
Yield was also the main method used to assess the productivity of amaranths and Chinese cabbage (paper
IV and V). The above ground biomass of each sample was cleaned using a wet towel before weighing to
obtain the yield in fresh weight which in most cases was translated to tons per hectare to be able to calculate
the overall profitability by all crops (including fish) in an integrated system.
19
4.5.2. Economic return
The enterprises budget was used to assess the financial performance of the different farming systems when
farmed as standalone activities and when farmed in integration. The input costs included often pond
construction, fish fingerlings, fish feeds, vegetable seeds, manure, equipment, labour, transport and water.
For fixed costs (pond, tanks and equipment) an appropriate depreciation time of years was used. The value
of the fish and vegetable harvests were estimated from the prevailing market prices.
The Net Income (NI), Total Revenue (TR) and Benefit-Cost Ratio (BCR) were calculated as follows:
NI = TR - TC
TR = PQ
BCR = TR/TC
Where TC = Total cost, P = Unit price of output, Q = Total quantity of output.
4.5.3. Water use efficiency
The consumptive water use (CWU) of both fish and vegetables in paper V, was estimated by measuring the
amount of water supplied to the fish tanks, and the amount used for irrigating the vegetables (Boyd, 2005;
Abdul-Rahman et al., 2011). The water inputs included regular water addition and precipitation. The main
outflow included only the water drawn for vegetable irrigation and intentional discharges. A rain gauge was
installed near the fish ponds to measure the amount rain that went into fish tanks (Yoo and Boyd, 1992).
From the CWU, the water use efficiency and water productivity was calculated as follows based on the
method by Abdul-Rahman et al. (2011):
WUE (Kg m-3) = total yield/CWU, for both tilapia and vegetables as wet weight.
WP (USD m-3) = WUE X market price (USD/Kg) for both tilapia and vegetables.
Where: WUE = water use efficiency, CWU = consumptive water use, WP = water productivity.
4.6 Data analysis
In paper I and III, analysis of variance (ANOVA) was used to analyse the impact of livelihood
diversification on fish and household income. Multiple regression was conducted to assess how fish and
non-fish income explain household income. Correlation analysis was done to assess the influence of
farmer’s socio-economic characteristics on fish income and also the relationship between household income
and farmed fish utilization pattern. Correlation analysis was also performed in paper III to assess the
influence of pond size, cultivation cycle, manure and feed quantity and stocking density on fish pond
productivity. ANOVA was used in paper III, IV and V to compare the productivity and profitability between
IAA, non-IAA and overall fish farming. Chi-square was used in paper II to analyse the differences in
socioeconomic profile and farming characteristics between regions. Data were transformed to log base ten
in case of violation of the assumptions of normal distribution of data, and in case of non-conformity to
parametric assumption even after the transformation, alternative non-parametric tests were used. When
significant differences were detected, the Tukey post-hoc test was used to determine specific significant
differences among variables. All statistical analyses were performed using Microsoft Excel and SPSS
statistical software (Version 20) except in paper II in which data were analysed using SAS statistics program
20
(SAS (r) Proprietary Software 9.4). Results are presented as mean ± standard error (SE). All statistical
results were considered significant at p-values ≤ 0.05.
5. RESULTS
5.1 Key findings
Paper I: Rural aquaculture: Assessment of its contribution to household income and farmers’
perception in selected districts, Tanzania
(i) Rural fish farming is an important source of income, contributing with about 13% of the
household income of small-scale fish farmers in Tanzania.
(ii) Fish farming experience, technical skills and household income per person had large
influence on the income from fish farming.
(iii) Despite that 93% of the interviewed farmers were male, women played a significant
contribution in all aspects and stages of household pond fish farming.
(iv) Overall, fish farmers had a positive attitude towards fish farming and the majority were
willing to continue with fish farming at least at the current scale and were even willing to
expand their fish farming operations.
(v) Lack of technical skills and water related problems were the major perceived reasons by
farmers for low fish farming adoption rate.
(vi) Improved extension services, technical skills and good quality fish seeds and feed were
among the proposed solution towards increased fish farming adoption in Tanzania.
Paper II: Fish farming in Tanzania: the availability and nutritive value of local feed ingredients
(i) Earthen pond was the most common fish farming system in many regions except Dar es
Salaam.
(ii) Semi-intensively mixed-sex tilapia monoculture was the dominating fish farming practice
(iii) More than 80% of respondents relied on locally available feed ingredients as a major feed
supplement for their cultured fish, with maize bran being the most commonly used feed
ingredient.
(iv) Crude protein content in most local feed ingredients were medium to high, while crude fat
content was high in some animal and agricultural by-products, and medium to low in other
ingredients.
Paper III: Assessment of pond and integrated aquaculture (IAA) systems in selected districts,
Tanzania
(i) Tilapia-vegetables (Chinese cabbage) was the most common type of IAA practiced in
Tanzania.
(ii) IAA fish pond farming resulted in high farm productivity and profitability, due to reuse of on
farm resources and better management practices.
21
(iii) IAA farmers were more positive towards fish farming compared to non-IAA farmers.
(iv) Lack of IAA technical skills, physical factors (lack of space, unsuitable soils and weak pond
dykes) and lack of time were the major reason for not adopting IAA farming.
Paper IV: An ecological and economical assessment of integrated amaranth (Amaranthus hybridus)
and Nile tilapia (Oreochromis niloticus) farming in Dar es Salaam, Tanzania
(i) The use of amaranth wastes (AW) as a fish feed ingredient in a tilapia-amaranth integrated
system did not affect fish growth and yield but rather improved feed conversion ratio (FCR).
(ii) The use of pond water for irrigating amaranths in tilapia-amaranth system greatly increased
amaranth growth and production.
(iii) The overall farm profitability was improved when tilapia and amaranth were farmed in an
integrated system than when farmed separately.
Paper V: Integration of tilapia (Oreochromis niloticus) and vegetables (Amaranthus hybridus and
Brassica rapa pekinensis) for improved water use efficiency and nutrient recycling
(i) IAA increased water use efficiency and reduced synthetic fertilizer inputs, while increasing
farm income through increased productivity.
(ii) Irrigating vegetables with nutrient rich water from high fish stocking densities resulted in a
significant increase in farm productivity.
(iii) However, high fish stocking (12 mono-sex tilapia m-3) led to decreased survival rates due to
overstocking and bad pond water quality, which consequently affected fish yield and
profitability
(iv) A reduced medium fish stocking (8 mono-sex tilapia m-3) resulted in high fish production, and
the use of fish tank water for vegetable irrigation in a tilapia-vegetable integration benefited
the production of vegetables.
5.2 Socioeconomic profile of fish farmers (Paper I, II and III)
The results of this thesis show that small scale pond farming is the dominant aquaculture practice in
Tanzania, which is mainly operated at a subsistence level by male farmers (80-90%) (paper I, II and III).
Most farmers had a low educational level and over 57% of the farmers had only attended primary school
(paper I). The average time spent in school by all farmers was about nine years (Table 3). Most farmers
lack formal training in aquaculture and 45% of the farmers had less than 5 years of experience in fish
farming (Paper I). On average, IAA farmers had an experience of 16 years in fish farming compared to that
of 7 years among non-IAA farmers. (Table 3). IAA farmers were in minority but had more commonly
received some aquaculture training (65%) as compared to non-IAA fish farmers (38%), and lack of know
how was one reason for the current low adoption rate of IAA practices (paper III). The majority of the
farmers (55%) were in the age group of 40–60 years followed by the age group of 20–40 years (30%).
Despite the dominance of men as aquaculture owners, women made a significant contribution in all aspects
and stages of household pond fish farming. Most of the farmers (66%) had a household size of six or less
members, and the farms were often operated only with family labor (Paper III).
22
Table 3. Gender, household size, education level and experience among interviewed fish farmers in the
surveyed districts. “IAA” stands for farmers with IAA pond farming, “Non-IAA” for farmers with non-IAA
pond farming, and “IAA + non-IAA” for farmers with both IAA and non-IAA systems (means ± SE).
(Modified from paper III).
Farming type IAA (N=43) Non-IAA (N=37) IAA + non-IAA (N=9)
Gender (%): Male
Female
95
5
97
3
100
0
House hold size (number of individuals) 5.0 ± 0.3 6.0 ± 0.4 7.9 ± 1.1
Education (number of years spent in school) 10 ± 0.6 9.2 ± 0.7 8.2 ± 1.2
Experience in fish farming (years) 16.4 ± 1.9 7.1 ± 1.5 7.4 ± 1.5
5.3 Impact of fish farming on household income and fish consumption (Paper I)
All fish farmers had multiple sources of income with the majority (96 %) being involved in crop cultivation.
About 35% of farmers were involved in animal husbandry, 42% in small trade, 7% in public services, and
12% had other income-generating activities. About 50% of farmers had at least two more sources of income
in additional to fish farming, with a combination of crop farming, small business, and husbandry being the
most common. The average annual household income of the fish farmer was 1,681 US$ with crop farming
being the major income source. About 31% of the farmers had an average annual income below 694 US$
indicating that many farmers are poor. The average annual income from fish was 222 US$ which
corresponded to the contribution of about 13% of the average annual household income. There was a
significant negative correlation (r = - 0.43, p < 0.01) between the contribution of fish income to household
income and total household income. Multiple regression analysis results indicated that both fish and non-
fish income can jointly explain 96.4% variation on annual household income of the respondent fish farmers
(R = 0.982, F (2, 69) = 943.9, p < 0.01). About 36 % of the farmed fish was used for household consumption,
62% was sold and 2% was given away (Figure 10). There was a significant negative correlation between
total household income and the proportion consumed (rho = - 0.581, p < 0.01) and the proportion given
away (rho = - 0.272, p = 0.021). On the other hand, household income correlated positively with the portion
sold (rho = 0.595, p < 0.01).
Figure 10. Farmer’s estimates on how much of the farmed fish that was sold, consumed or given away
(modified from paper I: Mulokozi et al., 2020a).
0
10
20
30
40
50
60
70
Sold Consumed Given away
Res
po
nse
(%
)
23
5.4 Fish pond characteristics and water sources (Paper III)
Almost all of the surveyed fish ponds (93%) were under single ownership with the number of fish ponds
per farmer being 1.5 ponds. The majority of fish ponds were constructed after 2010 and the non-IAA ponds
were constructed more recently compared to IAA ponds (Table 4). The average pond size and depth were
388 m2 and 1.76 m respectively with no statistical difference (p < 0.05) between farming systems. Almost
all (95%) ponds were earthen. There was no reported use of chemicals such as antibiotics, synthetic fertilizer
and hormones in the fish ponds. The main water sources for fish farming included river streams (42%),
spring (34%) and irrigation canals (16%) (Figure 11).
Table 4. Characteristics (size, depth, ownership, age and water seepage) of IAA and non-IAA fish ponds in
the surveyed districts (adopted from paper III).
Characteristic Description IAA
(N=65)
Non-IAA
(N=64)
Overall
(N=129)
Pond size (means ± SE, m2)
398.5 ± 51.6 377.4 ± 73.4 388.0 ± 44.6
Pond depth (means ± SE, m)
1.74 ± 0.13 1.78 ± 0.11 1.76 ± 0.14
Ownership (%) Individual 91 94 93
Multiple 9 5 7
Leased 0 1 0
Pond type (%) Earthen 97 94 95
Concrete 3 6 5
Year of fish pond construction (%) <1985 6 3 4
1985-1995 20 11 16
1996-2005 40 10 25
2006-2010 9 20 15
>2010 25 56 40
Pond water seepage (%) Yes 54 65 60
No 46 35 40
24
Figure 11. Sources of water for pond fish farming in the surveyed districts (adopted from paper III).
5.5 Fish pond management and performance of IAA and non-IAA systems (Paper III)
5.5.1. Pond management practices
The majority of ponds (96%) were fertilized once or several times per fish growth cycle with cow-dung
being the most common type of manure used (Table 5). Fish ponds were mainly stocked with tilapia (78%),
catfish (16%) and a polyculture of tilapia and catfish (6%). The stocked fish were sourced from local
hatcheries (42%), neighbors (31%) and restarting (17%). In restarting, the fish farming cycle started by
removing all big fish from previous cycle and leave the small ones to grow to maturity. The overall average
fish stocking density was about 4.3 fish m-2 with a stocking of 3.9 fish m-2 in the IAA ponds, which were
lower than that of 4.7 fish m-2 in the non-IAA ponds. Fish feeding frequency ranged from once per day to
once per week with fish in IAA ponds being fed more frequently as compared to those in the non-IAA
ponds. Fish were mainly fed with a combination of bran (maize and rice bran) and vegetable remains
followed by bran alone (Table 5). On average, the total amount of feed (only bran and homemade diets,
excluding vegetable wastes and household leftovers) provided to the ponds was about 8.3 tons ha-1 yr-1. The
amount of feed applied on non-IAA ponds (9.0 tons ha-1 yr-1) was about 20% higher (p > 0.05) than that
provided to IAA ponds (7.6 tons ha-1 yr-1). No farmer reported to use commercial feeds.
0
5
10
15
20
25
30
35
40
45
River Spring Irrigation canal Multiple sources Water well
Res
po
nse
(%
)
Water sources for fish farming
25
Table 5. Species farmed, pond fertilization and feeding strategies in IAA and non-IAA pond farming in the
surveyed districts (adopted from paper III).
IAA ponds Non-IAA ponds Overall
Characteristic Description (%) (%) (%)
Species farmed Tilapia 72 83 78
Catfish 19 14 16
Tilapia-catfish polyculture 9 3 6
Fish seed sources Hatchery 43 40 42
Wild 8 13 10
Neighbours 32 30 31
Restarting/ Regeneration* 17 17 17
Common manure type Goat manure 5 0 3
Cow dung manure 71 80 76
Pig manure 2 0 0
Chicken manure 11 3 7
Duck manure 5 3 4
Combination of manure 6 8 7
No fertilization 2 6 3
Common fish feed types Bran only 17 27 22
Bran+vegetables 45 25 35
Bran+kitchen leftovers 2 16 9
Vegetable+kitchen leftovers 9 0 5
Bran+animal skin 2 6 4
Bran+kitchen leftovers+vegetable 17 2 9
Homemade formulated diet 9 25 17
Feeding frequency Once a day 25 9 17
3 to 4 times per week 37 14 26
Once a week 15 31 23
Biweekly 12 13 12
Once per month 8 10 9
Occasionally 3 23 13 *Cultivation cycle starts by harvesting the big fish and allow small fish to grow to maturity and reproduce.
5.5.2. Fish yield and growth performance (Paper III, IV and V)
The fish yield from the IAA ponds was 2.46 tons ha-1, which was significantly (p = 0.02) higher than the
yield of 1.54 tons ha-1 from the non-IAA ponds (Paper III). Similarly, results from field experiment (paper
26
IV) showed that, despite the use of less expensive amaranth diet (AD) which incorporated amaranth waste
(AW), a yield of 16.9 tons ha-1 from IAA ponds was statistically comparable (P > 0.05) to 17.7 tons ha-1
from non-IAA ponds. Additionally, the use of AW in IAA pond did not affect fish growth, but rather
improved the feed convention ratio and protein efficiency ratio. In the experiment in paper V, the yield
from medium fish stocking (T8) was 1.3 higher than that from low fish stocking, T5 (p > 0.05) and 2.8 times
higher than that from high fish stocking, T12 (p < 0.05). Additionally, stocking of fish at higher densities
and the use of better prepared diets in field experiments in paper IV and V, resulted in a yield that was about
seven times higher than that found in the field survey in paper III.
Table 6. Management practices and fish yield in IAA, non-IAA and overall fish farming in the surveyed
districts (means ± SE). (adopted from paper III).
Description IAA Non-IAA Overall
Cultivation cycle (months) 9.12 ± 0.43 8.76 ± 0.30 8.88 ± 0.27
Stocking density (fish m-2) 3.9 ± 2.4 4.7 ± 1.4 4.3± 2.2
Farmers who could estimate (%) 74 78 76
Farmers who could not estimate (%) 26 22 24
Average feed (tons ha-1 yr-1) 7.6 ± 1.1 9.0 ± 1.5 8.3 ± 0.9
Manure (tons ha-1 yr-1) 2.1 ± 0.2 2.2 ± 0.3 2.2 ± 0.2
Farmers who could estimate (%) 86 94 90
Farmers who could not estimate (%) 24 6 10
Fish weight at harvest (g) 158.6 ± 3.6a 112.1 ± 2.2b 135.1 ± 3.0a
Yield
tons pond-1 0.098 ± 0.02a 0.058 ± 0.01b 0.078 ± 0.01ab
tons ha-1 2.46 ± 0.29a 1.54 ± 0.19b 2.01 ± 0.18ab
tons ha-1 yr-1 3.24 ± 0.34a 2.11 ± 0.32b 2.72 ± 0.24ab
Numbers in the same rows with different superscript letters are significantly different (p < 0.05).
5.6 Crops integrated with fish pond farming (Paper III, IV and V)
The most common type of integrated systems identified during the field survey (paper III) was fish and
vegetables, especially tilapia (O. niloticus)-Chinese cabbage (Brassica spp) integration. Second to tilapia-
Chinese cabbage integration was tilapia with a combination of different vegetables. Example of IAA
systems identified in paper III are presented in figure 12. Results from the field experiment in paper IV
showed that, amaranths grown under an IAA system had about 46% higher yield than those grown under a
non-IAA system during the first harvest (p < 0.05), and comparable (p > 0.05) yields for the second harvest
and for the overall farming cycle (Figure 13). Similarly, for the field experiment in paper V, vegetable plots
(M1 and Ho) which were partially fertilized and irrigated with fish tank water from medium and high fish
stockings, without supplement of synthetic fertilizers, had similar yield (p > 0.05) as vegetables that were
irrigated with tap water and fertilized at higher rates (Figure 14). Additionally, vegetable that were irrigated
with fish tank water and without inputs of fertilizers, had significantly higher yield than the control
vegetables.
27
Figure 12. Common types of IAA systems in the surveyed districts (adopted from paper III).
Figure 13. Amaranth yield (wet-weight, tons ha-1) under different farming systems and harvesting periods
(modified from paper IV: Mulokozi et al., 2020b). Within each group (time period), bars with different
letters are significantly different, P < 0.05 (bars represent means ± SE).
aa
a
b
a
a
cb
b
0
5
10
15
20
25
30
First harvest (after 21 days) Second harvest (after 33 days) Overall
Yie
ld (
wet
-wei
gh
t, t
ons
ha-1
)
IAA
amaranths
Non-IAA
amaranths
Control
amaranths
0
5
10
15
20
25
30
35
Res
po
nse
(%
)
Types of integrated systems
28
Figure 14. Vegetable yield (wet-weight, tons ha-1) under different irrigation and fertilization regimes
(adopted from paper V). Within each vegetable group (Chinese cabbage or amaranth), bars with different
letters are significantly different, P < 0.05 (bars represent means ± SE). Lo: Vegetables irrigated with water from low fish stocking, no fertilizer applied.
L1: Vegetables irrigated with water from low fish stocking, partially fertilized.
Mo: Vegetables irrigated with water from medium fish stocking, no fertilizer applied.
M1: Vegetables irrigated with water from medium fish stocking, partially fertilized.
Ho: Vegetables irrigated with water from high fish stocking, no fertilizer applied.
H1: Vegetables irrigated with water from fish high stocking, partially fertilized.
NO: Vegetables irrigated with tap water with full fertilization, i.e. as usually done by farmers.
CTR (control): Vegetables irrigated with tap water, no fertilization at all.
5.7 Financial performance of IAA and non-IAA systems (Paper III, IV and V)
The field survey in paper III showed that the integrated systems had higher overall farm profitability than
non-integrated systems (Table 7). The total revenue from integrated fish and crops was 196% and 50%
higher than that from fish and crops when cultivated separately, respectively. Likewise, the net income
from integrated fish and crops was 180% and 60% higher than the net income from fish and crops when
grown separately. These results were similar to those found in the field experiment in paper IV, where IAA
amaranth farming had 12% and 34% higher revenue and net profit, respectively, than the non-IAA amaranth
farms. Tilapia-amaranth integration resulted in significantly higher (p < 0.05) net income than tilapia and
amaranth when grown in a standalone production. Likewise, (Figure 15), the net income from integrated
vegetables and fish stocked at medium densities (Mo + T8) was 160% and 60% higher than Mo and T8
when separated. Additionally, the net income from this integration was 270% higher than non-IAA (NO)
vegetables that were fertilized with synthetic fertilizers. A similar trend was also observed in the integration
a
b
bc
cc
d
c
e
a
b
cd
d
e
f
e
g
0
10
20
30
40
50
60
Lo L1 Mo M1 Ho H1 NO CTR
Veg
etab
le y
ield
(w
et-w
eig
ht,
to
ns
ha-1
)
Chinese cabbage
Amaranth
29
of tilapia-amaranth integration in paper V. High fish stocking densities (T12) resulted in high fish mortality,
and consequently led to a negative net income of the overall tilapia-vegetable integrated systems (Ho + T12
and H1 +T12).
Table 7. Costs, total revenues and net returns (USD/ha) of fish and crops when grown in combination and
separately (means ± SE). (Adopted from paper III).
Numbers in the same rows with different superscript letters are significantly different (p < 0 .05).
Figure 15. Net income (USD ha-1) for fish and Chinese cabbage grown as separate systems or as an integrated system
(adopted from paper V). Within each farming system, bars with different letters are significantly different (p < 0 .05).
Bars represent means ± SE. Lo: Vegetables irrigated with water from low fish stocking, no fertilizer applied.
L1: Vegetables irrigated with water from low fish stocking, partially fertilized.
Mo: Vegetables irrigated with water from medium fish stocking, no fertilizer applied.
M1: Vegetables irrigated with water from medium fish stocking, partially fertilized.
Ho: Vegetables irrigated with water from high fish stocking, no fertilizer applied.
H1: Vegetables irrigated with water from fish high stocking, partially fertilized.
NO: Vegetables irrigated with tap water with full fertilization, i.e. as usually done by farmers.
CTR (control): Vegetables irrigated with tap water, no fertilization at all
ab
c cd d
e
f
a a
b b
c c
a
a
b b
c c
-30000
-20000
-10000
0
10000
20000
30000
40000
Lo T₅ Lo+T₅ L1 T₅ L1+T₅ Mo T₈ Mo+T₈ M1 T₈ M1+T₈ Ho T₁₂ Ho+T₁₂ H1 T₁₂ H1+T₁₂ NO CTR
Net
inco
me
(US
D h
a⁻¹)
Chinese cabbage
Fish
Fish+Chinese cabbage
Parameters (USD/ha) IAA ponds Non-IAA ponds Crops Integrated fish and crops
Fixed cost 428.9 ± 67.0a 373.2 ± 80.5 a 51.0 ± 9.0 b 479.8 ± 97.6a
Variable costs 2801.3 ± 297.3 a 2864.5 ± 602.5 a 1442.1 ± 402.3b 4243.4 ± 712.0a
Total cost 3229.1 ± 330.0 a 3237.7 ± 663.2 a 1493.1 ± 399.1b 4722.2 ± 759.4a
Total revenue 6498.5 ± 626.5 a 4426.8 ± 425.9 b 3302.6 ± 1029.8b 9801.1 ± 1674.5c
Net income 3269.3 ± 1319.6 b 1189.1 ± 662.0 a 1809.5 ± 603.2ab 5078.9 ± 1494.8c
30
5.8 Tilapia stocking densities and its effect on water use efficiency, water quality, fish growth and
yield in IAA farming (Paper V)
Water productivity in vegetables irrigated with pond water from high fish stocking density was significantly
higher than in the other vegetable treatments (Table 8). In the Chinese cabbage plots, there were no
significant differences in WUE (Kg m-3) between L1 (4.36) and Mo (5.07), and neither between M1 (5.69),
Ho (5.56) and NO (5.21). The lowest WUE was exhibited by Chinese cabbage from CTR (1.92) followed
by the Lo treatment (3.33). The result for the water productivity (USD m-3) followed a similar pattern as
that of the water use efficiency (Kg m-3). For the fish (Figure 16), the WUE from T8 was 27% (p > 0.05)
and 186% (p < 0.05) higher than that from T5 and T12 respectively. The result for water productivity (USD
m-3) followed a similar trend as that of the water use efficiency (Kg m-3).
There was a significant (p < 0.05) difference in the water dissolved oxygen (mg l-1); 6.7, 4.9 and 3.8 for
low, medium and high fish stocking densities, respectively. There concentrations of NO3, NH4, and PO4 in
tanks stocked with fish at high stocking densities was significantly higher (p < 0.05) than those in tanks
with medium and low fish densities.
Table 8. Water use efficiency (WUE) and water productivity (WP) for vegetables under various irrigation
regimes (means ± SE). (Adopted from paper V).
Chinese cabbage Amaranth
Treatment WUE (Kg m-3) WP (USD m-3) WUE (Kg m-3) WP (USD m-3)
Lo 3.33 ± 0.09a 1.3 ± 0.04a 1.55 ± 0.14a 0.61 ± 0.05a
L1 4.36 ± 0.29b 1.71 ± 0.11b 2.33 ± 0.08b 0.91 ± 0.03b
Mo 5.07 ± 0.11bc 1.99 ± 0.04bc 3.23 ± 0.1cd 1.27 ± 0.04cd
M1 5.69 ± 0.15c 2.23 ±0.06c 3.59 ± 0.1d 1.41 ± 0.04d
Ho 5.56 ± 0.08c 2.18 ± 0.03c 4.14 ± 0.17e 1.62 ± 0.07e
H1 6.44 ± 0.11d 2.53 ± 0.04d 4.76 ± 0.1f 1.87 ± 0.04f
NO 5.21 ± 0.15c 2.04 ± 0.06c 2.91 ± 0.09c 1.14 ± 0.03c
CTR 1.92 ± 0.1e 0.75 ± 0.04e 0.56 ± 0.04g 0.22 ± 0.01g
Numbers in the same columns with different superscript letters are significantly different (p < 0.05).
Where;
Lo: Vegetables irrigated with water from low fish stocking, no fertilizer applied.
L1: Vegetables irrigated with water from low fish stocking, partially fertilized.
Mo: Vegetables irrigated with water from medium fish stocking, no fertilizer applied.
M1: Vegetables irrigated with water from medium fish stocking, partially fertilized.
Ho: Vegetables irrigated with water from high fish stocking, no fertilizer applied.
H1: Vegetables irrigated with water from fish high stocking, partially fertilized.
NO: Vegetables irrigated with tap water with full fertilization, i.e. as usually done by farmers.
CTR (control): Vegetables irrigated with tap water, no fertilization at all.
31
Figure 16. Water use efficiency (WUE) and water productivity (WP) for tilapia under three different
stocking densities of five (T5), eight (T8) and twelve (T12) fish m-3 (modified from paper V). Bars with
different letters for the same water use index are significantly different, P < 0.05 (bars represent means ±
SE).
5.9 Famer’s perception on opportunities, constraints and future plans towards aquaculture (Paper
I and III)
In general (paper I), fish farmers had a positive attitude towards fish farming with majority of them (64%)
expressing a willingness to continue with fish farming at least at the current scale, 15% wanted to expand
their activities, 9% wanted to quit while 12% had not decided whether to continue or not. The attitude
towards fish farming differed among farmers (Paper III), with 21% of IAA farmers expressing their
intention to expand their fish farming activities compared to only 8% of non-IAA farmers (Figure 17).
About 19% of the non-IAA farmers, but only 4% of the IAA farmers, had not yet decided whether to
continue with fish farming or not. About 2% of the farmers were specifically trained in fish pond
construction and played an important role for constructing fish ponds in the society. About 64% of the
respondents considered that the community fish farming uptake was poor, 18% very poor, 10% normal,
and 4% that it was in an emerging stage (Figure 18). Water related problems (e.g. water scarcity and water
use conflicts) were perceived to be the biggest challenges by a majority of both IAA and non-IAA farmers
(Table 9). Other fish farming challenges were perceived differently by the two types of farmers. For
example, lack of capital and good quality fish seeds were the second and third most common challenges
among IAA farmers as opposed to poaching and lack of good quality feeds among non- IAA farmers.
a
a
b
aa
b
0
0.5
1
1.5
2
2.5
T₅ T₈ T₁₂
Wat
er u
se i
nd
ex (
Kg/m
3o
r U
SD
/m3)
Tilapia stocking densities
WP (USD/mᶟ)
WUE (kg/mᶟ)
32
Figure 17. Farmer’s future plan regarding fish farming (adopted from paper III).
Figure 18. Farmer’s perception on the adoption rate of fish farming in the community (modified from paper
I: Mulokozi et al., 2020a).
0
10
20
30
40
50
60
70
80
Continue Expand Quit Undecided
Res
po
nse
(%
)
Farmer`s future plans for fish farming
IAA farmers
Non-IAA farmers
Farmers with both
IAA and non-IAA
systems
0
10
20
30
40
50
60
70
Very poor Poor Normal Good Emerging Don’t know
Res
ponse
(%
)
33
Table 9. The biggest problem in fish farming as perceived by IAA and non-IAA farmers (adopted from paper
III). Figures in the column are expressed in percentage (%).
Biggest problem IAA farmers,
N=43
Non-IAA
farmers, N=37
Farmers with both
IAA and Non- IAA
systems, N=9 Water related problems 23 35 22
Lack of capital 16 3 22
Lack of quality fish seeds 14 3 11
Stunted growth of fish 9 5 0
Weak pond wall and water seepage 9 8 0
Poaching 9 18 44
Lack of good quality fish feeds 5 14 0
Pests (monitor lizards and otter) 5 14 0
Lack of labour 5 0 0
Lack of space to add more ponds 5 0 0
6. DISCUSSION
This thesis shows that aquaculture in Tanzania is currently mostly a small-scale activity and usually not
practiced as a stand-alone economic activity, but rather as subsistence farming integrated with agricultural
activities and rearing of livestock (Mwaijande and Lugendo, 2015; van der Heijden and Shoko, 2018). Thus,
there are already strong links between agriculture and aquaculture and it is therefore argued in this thesis
that IAA could provide an important entry points for many farmers to adopt aquaculture practices, that
could contribute to improved income, environmental qualities and social benefits. Aquaculture production
in Tanzania has increased in recent years, responding to an increased demand for fish, but the scale and
productivity of smallholder aquaculture, which still dominate the sector (paper I, II and III), remains below
the level needed to support significant sector growth in Tanzania. Local governments efforts to develop and
implement aquaculture that is both sustainable and profitable is constrained by large challenges such as
inadequate human and financial resources; limited research; poor market infrastructure and access; a lack
of improved fish breeds, feeds and technical training (paper I and III; Rothuis et al., 2014; van der Heijden
and Shoko, 2018).
6.1 Characteristics of fish farmers
The majority of fish farmers in Paper I and II were between 26 and 55 years old, with majority (57%) of
them having a primary school level of education, which agrees with the findings by Mwaijanande and
Lugendo (2015). This suggests the presence of enough manpower but with less formal education.
Additionally, less than 52% of the farmers had received any training in aquaculture, and a large number of
the farmers had less than five years of experience in aquaculture. Thus, the lack of know-how could be one
reason for the fairly low fish yields and indicates a major constrain for aquaculture development in
Tanzania, which was confirmed by many of the interviewed farmers and also regional fisheries officers
(Berg et al., submitted). On the other hand, this may also indicate an opportunity to improve aquaculture
production as experience increases with time, since the majority of famers were within the working age
34
group and also motivated to continue with fish farming (paper I and II). In a questionnaire sent out to
regional fisheries officers in Tanzania, improved support by extension officers was seen as one of the most
import factors for expanding aquaculture in Tanzania (Berg et al., submitted).
When farmers were divided into farming systems (paper III), IAA farmers were more experienced in fish
farming compared to non-IAA farmers and the majority of them had received some sort of fish farming
training. This could be an important reason for the relatively low adoption rate of IAA technology, which
requires a relatively high knowledge to managed both fish and crops, reflecting reasons for not practicing
IAA farming among non-IAA farmers.
There is also a gender dimension in relation to capacity building for aquaculture development in Tanzania.
In paper I and II, almost all (over 90%) of the respondent fish farmers were males. This is in accordance
with cultural settings that household assets are under men ownership. The few women owning fish ponds
were mainly widows, divorced and unmarried. Similar findings were reported by Mwaijande and Lugendo
(2015), in a study which assessed fish farming value chain in six regions in Tanzania. However, this does
not mean that women do not contribute to fish farming in Tanzania. From findings in paper I, women played
an important role in fish farming by involving themselves in practices, such as fish feed preparation and
feeding, harvesting and selling to neighbors and local markets.
6.2 Impact of fish farming on household income and fish consumption
The results from this thesis shows that aquaculture, can make an important contribution to people’s income,
and especially to poor farmers (paper I). About 31% of the farmers had an average annual income below
694 US$, which according to the World bank indicate that these farmers are living in extreme poverty with
an income below the international poverty line of 1.90 US$ per day (Word Bank, 2019). The 13%
contribution of fish farming to the household income was in range with findings reported in other parts of
Africa. Kassam and Dorward (2017) compared the poverty impact of fish farming in Ghana, and indicated
a share of 8% from fish farming to the household income. Similarly, Dey et al. (2006), assessing the impact
of integrated fish farming in Malawi, reported a 12% contribution of fish farming to household income.
However, this contribution is still low compared to many countries in southeast Asia. Rahman et al. (2011),
for example, reported that up to 86% of some Bangladesh household incomes came from small scale fish
farming. A negative correlation between contribution of fish income and total household income suggests
that fish farming has a more significant contribution to poor household income when compared with the
well-off farmers. Similar results were reported by Brummett (1999) and Dey et al. (2010) in Malawi. Thus,
although the contribution for aquaculture may be small, it helps to generate an important amount of cash
for emergencies, school fees, etc. (Paper I; Brummett et al., 2008). In addition to direct income contribution,
fish farming had a potential impact on household food and nutrition security. This is because fish are rich
in protein and essential nutrients including vitamin A, calcium, iron and zinc, and in theory, fish farmers
are able to increase the intake of these nutrients directly from their farmed fish compared to non-fish farmers
(Kawarazuka and Béné, 2010).
The results from the regression analysis in paper I indicated that a percentage increase in fish income and
non-fish income lead to an increased household income by 0.18 and 0.79%, respectively. Despite relatively
low influence of fish farming on the household income, when compared with other sources, the contribution
35
was still statistically significant, suggesting that there is a potential for households to get more income from
fish, if enough emphasis is put on this sector. Lower production from fish farming compared to that from
agriculture and other activities could thus be related to lower input, poor management practices and the fact
that it is not usually a first priority income source (Brummett, 2000; Kassam and Dorward, 2017).
Fish farmers sold about 62% of their total harvested fish, and 36% was used for household consumption,
while 2% was given away as gifts to neighbors and relatives, which was an important way to strengthen
social relations. A negative correlation between total household income and the portion consumed indicates
that fish farming contributes more to food security among low income households as compared to high
income households. The reasons why farmers sold a larger portion of their harvested fish could be
associated partly with the need for cash for other costs or lack of cold storage facilities, especially in rural
areas. Similarly, Nzevu et al. (2018), assessing the contribution of fish farming to households in Kenya,
reported a relatively large portion of farmed fish being sold compared to that consumed. Furthermore,
Kassam and Dorward (2017) found that more than 60% of the fish harvested from aquaculture by both poor
and well-off farmers in Ghana were sold in the local market. The relatively high proportion of fish sold
could also indicate an increased demand for fish and availability of markets, which in turn indicates an
ongoing expansion of aquaculture in these countries, including Tanzania.
6.3 Fish pond management and performance of IAA and non-IAA systems
The overall average pond size of 388 m2 in paper III and 690 m2 in paper II were within ranges reported by
Kaliba et al. (2006) who reported a range of 150-300m2, Mwaijande and Luegndo (2015) reporting a pond
size of 200-400m2 and Chenyambuga et al. (2014) reporting a range of 345 -631 m2. A majority of the fish
ponds were earthen and under single ownership, a mode which is recommended over that of multiple
ownership. Wetengere and Kihongo (2011) reported that multiple ownership could easily lead to a passive
kind of management, misunderstandings between group members and consecutive abandonments of the
ponds.
Fish pond fertilization using manure is recommend in subsistence and semi intensive fish farming to support
growth of natural fish food due to lack of sufficient feeds (Green et al., 2002). In paper III, almost all of the
surveyed fish ponds were once or several times fertilized especially using cow dung manure. This confirms
the results by Chenyambuga et al. (2014) who reported that 89% of fish ponds in Mbarali district were
fertilized with cow dung manure. The predominance uses of cow dung manure was due to a high availability
compared to other types of manure.
The fish yield from the IAA ponds were 60% higher than that from the non-IAA ponds despite the fact that
fish in the non-IAA pond received 18% more feed and were stocked at higher densities than the fish in IAA
ponds. This imply that the difference in yield would have been even higher if the two farming systems
would have been stocked with the same number of fish, unless the stocking rate itself had a negative effect
on the yield, which was indicated by the negative correlation between fish yield and stocking density in
paper III, and also by the decreased survival rate among fish stocked at high densities in paper V.
The higher fish yield from the IAA pond is likely to be due to the supplemental effect of feeding the fish
with vegetable remains. This is because fish in the IAA ponds were mostly fed with a combination of bran
36
and farm vegetable wastes in contrary to the dominance of only maize bran in the non-IAA ponds. Tilapia,
which were the dominant cultured species, are known to be highly efficient in converting organic matter to
protein (Hall, 2011). Again, vegetables are recognized to be rich in protein, vitamin and minerals (Butnariu
and Butu, 2014). A combination of these factors could improve the fish growth and thus result in a higher
fish yield in the IAA ponds than in the non-IAA ponds. These results are corroborated with those by Dey
et al. (2010) in Malawi, who reported a 11% higher fish yield from IAA farms than non-IAA farms. These
results strengthen the arguments to further support the development of IAA systems among small scale
farmers as a way to increase aquaculture production in Tanzania. Despite lower yield compared to more
intensified commercial aquaculture systems, IAA can provide very important nutritional input to rural
farmers and if a portion of the harvested fish are sold for cash, either due to lack of access to wealthier
markets or out of a need to meet more local food security priorities, it generates a small, but important
amount of cash for other expenses. (Brummett et al., 2008; Paper I).
The reported higher fish yield from the IAA ponds could also be associated with the feeding regimes. The
fish in the IAA ponds were fed with smaller portions but more frequently as opposed to non-IAA fish,
which was given higher feed quantities but less frequently. This could be due to the fact that IAA farmers
had more time to attend their fish compared to non-IAA farmers. The higher fish yield in the IAA ponds
corresponds with the results by Wu et al. (2015), who reported improved juvenile golden pompano growth
and feed utilization as feeding frequency increased.
The IAA ponds were observed to be managed more actively as opposed to a more passive management of
the non-IAA ponds, a factor that also could be connected to the higher fish yield from the IAA ponds. For
instance, it was noted during the field work in paper III that the IAA ponds were visited more frequently
than the non-IAA ponds because when farmers attended the vegetables close to the ponds, they also
attended the ponds (feeding, cleaning and security aspects). Consequently, the IAA ponds were generally
in good shape, with less weed infestation than the non-IAA ponds. Additionally, fish losses from poaching
by humans and pests such as monitor lizards and otters, which were seen as one the critical challenges for
fish pond farming, were more predominant in the non-IAA ponds than in the IAA ponds, likely because
they were attended less frequently. This suggest that both an improved efficiency in recycling of organic
matters and nutrients, in combination with more efficient IAA management practices jointly contributed to
an increased fish yield and improved income for the IAA farmers. This improved management and
motivation by the farmers can be seen as an important benefit with IAA farming, and it is quite clear that
the longer experience and more frequent training in fish farming among IAA farmers had a positive
influence on the fish yield. Although the IAA ponds had higher fish yield than the non-IAA ponds, the
overall yield of 2.0 tons per ha was lower than 4.2 tons per ha reported in semi intensive IAA system by
Limbu et al. (2017) in Tanzania. The difference could be due to the fact that the majority of the fish ponds
were stocked with mixed sex tilapia as opposed to the tilapia-catfish poly culture used in the former study.
The catfish in a tilapia-catfish polyculture system prey on newborn tilapia, which control pond
overcrowding from tilapia prolific breeding and thus improve the fish growth and yield. Furthermore, the
lower fish yield in paper III could also be related to insufficient management practices like improper feeds,
feeding, and stocking densities, while the farms studied by Limbu et al. (2017) was managed under more
controlled conditions. The fish yield of about 17 tons per ha in paper IV were similar to that reported by
Toma et al. (2015) in Bangladesh, but were about three times higher than the yield reported by
Chenyambuga et al. (2014) in Mbarali and Mvomero in Tanzania. The differences could be due to the fact
37
that the former study (paper IV) involved the use of improved male tilapia fingerlings stocked at relatively
higher density (8 fish m-2) as opposed to the use of mixed sex tilapia stocked at less than 4 fish m-2 in the
previous studies in Tanzania (Chenyambuga et al., 2014).
In the experiment in paper V the yield from fish stocked at medium densities (8 fish m-2) resulted in a yield
of 15 tons per hectare which confirms that the yield from experiment IV is possible to achieve under well
managed conditions. This yield was 1.3 higher than that from the low stocking densities (p > 0.05),
indicating that farmers could probably increase their stocking densities somewhat. However, the yield was
also 2.8 times higher than that from high stocking density (12 fish m-2) (p < 0.05), because this stocking
densities resulted in substantive reduction in the survival rate among the fish, which provides a strong
argument for farmers to use moderate stocking densities as it reduces their risks for production losses.
The fish yield from the tanks with a stocking rate of 8 fish m-2 in paper IV and V was much higher compared
to the yield found in the ponds studied in the field survey (2.0 tons ha-1) in paper III. The reason for the
higher yield in the experiments was partly due to the higher stocking density (8 fish m-2) and a more
balanced diet applied in the experiments. Thus, although the experiments were designed to provide
examples of relevant IAA systems for rural Tanzania, it is clear that improved management skills are
necessary to increase the aquaculture production among small scale farmers. However, this also shows the
potential for an increased production among these farmers.
6.4 The effect of integrating vegetable farming with fish farming
The main type of IAA system identified in paper III, was fish-vegetable integration and especially tilapia-
Chinese cabbage, tilapia-amaranth and tilapia with a combination of various vegetables. This suggests that,
vegetables have many advantages for integrating with fish as compared to other crops, which was also
evidenced by the famers who were for example using vegetable remains as fish feeds and nutrient rich pond
water to irrigate vegetable grown close to their farm during dry periods. These findings are in line with
those by Chanyambuga et al. (2014), when evaluating the management and value chain of tilapia pond
farming in Morogoro, Tanzania. Tilapia are herbivorous species capable of feeding on plant material. On
the other hand, compared to other types of crops, vegetable require relatively short cultivation cycles and
have high marketability (Schreinemachers et al., 2018). Combination of these factors provides a good link
between tilapia and vegetable, which could be a reason for the practice of this type of IAA system. The fish
pond water also secure nutrient rich water for crops over the year, and reduce the need for synthetic
fertilizers. The diversification of livelihoods is another important argument for IAA farming, where either
crops or fish could provide food and cash even if one would fail. Thus, the overall combination of fish and
crops in IAA can help the farmers to spread their risks and to become more resilient to future environmental
changes. For example, in Paper IV, the integration of tilapia and amaranth resulted in 1.4 and 5.5 times
higher yields than non-IAA and control plots respectively, in the first harvest. The increased yield for the
non-IAA amaranths plots in the second harvest was likely due to the increase in the nitrogen supply from
urea, which was provided as a booster fertilizer only in this treatment. Furthermore, the overall amaranth
yield in paper IV was comparable with those by Baitilwake et al. (2012) but two times higher than the yield
reported by Mulandana et al. (2009) in South Africa. The differences in amaranth yields between these
studies could be related to the differences in amaranth species used and also farming approaches between
these studies. For example, in paper IV and V, sowing was done by broadcasting, long cultivation cycle,
38
and use of fishpond water for irrigation as opposed to transplant planting and non-integrated farming
systems in previous studies.
While it is recognized that the use of synthetic fertilizers can significantly increase crop yield, these
fertilizers can be harmful to the environment and lead to problems such as changing the soil pH and nutrient
enrichment. In this regard, vegetable farming based on organic manure and nutrients from fishponds is more
sustainable, from an environmental point of view, as compared to farming systems which rely solely on
synthetic fertilizers (Savci, 2012). The plots irrigated with fish pond water without synthetic fertilizers had
higher vegetable yield than those irrigated with tap water and with synthetic fertilizer in paper IV and V.
This result indicates that the nutrients in fishpond water sufficiently replaced the input of synthetic
fertilizers in vegetable cultivation, which was also reflected by higher nutrient accumulation in the soil from
the IAA vegetables than in the soils in non-IAA vegetables.
6.5 Financial performance of IAA and non-IAA systems
The results from paper III indicated that IAA ponds had 1.5 and 3 times higher revenue and net income,
respectively, than non-IAA ponds. The higher returns from the IAA ponds compared to the non- IAA ponds
was mainly due to the higher revenue as a result of higher yield, but also because of the reduced cost for
feed, which was made possible through an increased recycling of vegetable and other on farm byproducts.
Fish feed accounted for 58% of the production costs. The high feed costs could be associated with high
competition of bran (a main feed ingredient identified in paper II and III) from other sectors including pig
and poultry husbandry (Mbwambo et al., 2016). Considering the risks for future competition for fish feeds,
IAA compared non-IAA practices provide the opportunity to not only reduce the costs for fish feeds, but
also reduces the dependence on off-farm fish feeds and thus the reliance on external inputs. For example,
Limbu et al. (2019) investigated the effect of on-farm produced feeds on growth, survival, yield and feed
cost of juvenile African sharptooth catfish (Clarias gariepinus) and reported a 36% reduction in feed costs
compared to when commercial feeds were used. The integration of fish and crops resulted in a significantly
higher total revenue and net return than when these subsystems were analysed separately. As mentioned
before, the yield is further increased by an improved management of the fish pond and vegetable plots.
Similar results were found in paper IV in which the integration of fish and vegetables resulted to higher net
return than IAA vegetable, non-IAA vegetables, IAA fish and non-IAA fish. These findings agree with
those by other researchers in Tanzania and Africa. Limbu et al. (2017) in Kilombero, reported a higher
annual net cash flow from integrated tilapia-catfish-spinach farming, than when fish and vegetables were
farmed separately. This is because the IAA system builds on a more efficient production through an
increased recycling of nutrients and organic matter between fish and crops (irrigation of nutrient rich water
from the fish pond to the vegetables and the use of vegetable waste to feed the fish), which provides room
for diversification of the outputs from existing sub-systems, and thus increased overall farm yield and
income (Prein, 2002; Tipraqsa et al., 2007).
39
6.6 Tilapia stocking densities and its effect on water use efficiency, water quality and fish yield in
IAA farming
Aquaculture can be regarded as a water efficient food production system, if the water in the pond is not
depleted but remains available, and can thus still be used for other purposes (Ahmed et al., 2014). One way
to utilize the fish pond water is through crop irrigation in an IAA system, which can lead to increased water
use efficiency (WUE, Kg m-3) and water productivity (WP, USD m-3) because aquaculture becomes a non-
consumptive water component in an IAA system, which does not compete with crop irrigation (Abdul-
Rahman et al., 2011). Results from paper V indicated that vegetable irrigated with fish tank water had both
significantly higher WUE and WP than the control vegetables that was irrigated with tap water. Similarly,
van der Heijden, (2012) in Egypt reported an improved water use efficiency when fish ponds were
integrated with fruits (mango, banana and orange trees), vegetables, flowers and alfalfa. Additionally, in an
experiment involving fish and vegetables, Abdul-Rahman et al. (2011) found a 20% increase in WUE and
WP from radish irrigated with effluent from tilapia tanks than when irrigated with well water.
In paper V, the use of tank water from the high fish stocking density (T12) led to significantly higher
vegetable WUE due to high nutrient concentrations. However, high stocking densities resulted in bad water
quality and consequently decreased survival rates of only 28% for the fish, which consequently affected the
overall yield and economic returns in this IAA system. This indicate the need to optimize fish stocking
densities and other management practices such as feeding and water exchange, in order to balance the
tradeoffs for both fish and crops in an IAA system. In this study, a medium stocking density of 8 fish m-3
had better WUE and WP for both fish and vegetables.
6.7 Famer’s perception of opportunities and constraints for fish pond farming and IAA
Farmers experience of opportunities and constraints for adoption of food production technologies, and
understanding their perception is crucial for developing better food production strategies and policy
interventions (Jha et al., 2020). This is because farmers are the primary actors and grassroot beneficiaries
of the food production systems (in this case aquaculture) and their grounded knowledge and experience
provide valuable input for the development of the aquaculture sector in Tanzania. For example, Wossink
and Boonsaeng (2003) reported that many promising agriculture policies failed because they were
inappropriate to farmer’s needs and perceptions.
In paper I, farmers felt that the adoption rates of fish farming were poor, which was mainly due to lack of
appropriate technical skills. The lack of technical skills was also reflected by the fact that only half of the
farmers had attended fish farming trainings. For example, during the field survey in paper I and III, a large
number of farmers did not know exactly the size of their fish ponds. Knowing the size of the pond is
important in fish farming as many of the pond inputs such as number of fish to be stocked, fertilization
regimes, and feed quantity are determined by the pond size. Failure to know the pond size may lead to
negative implications on the resource use efficiency and pond productivity in general, thus leading to
suboptimal yields, where farmers may become discouraged to continue with fish farming.
A number of underlying factors were mentioned by farmers that support or hinder the adoption of IAA. The
results showed that lack of technical skills to handle both fish and crops currently was the most critical
40
factor for IAA adoption, which was also reflected by the fact that most of the IAA farmers had received
some training and also had higher experience in fish farming than non-IAA farmer. This was probably a
key asset for these farmers to be able to adopt IAA, and thereby improving their farm productivity and
economic returns. Similar findings were found by Sheheli et al. (2014), who reported lack of knowledge
being a major factor hindering fish pond productivity in Bangladesh. The 2% of the farmers that were
trained in fish pond construction played a significant role in disseminating fish farming technology to other
farmers, as they acted as local engineers in pond construction in the community, again indicating the
demand for practical support and know-how in the field.
In additional to lack of proper technical skills, farmers also saw water related problems including recently
water use regulations, and water competition with other sectors to be a constraint for aquaculture, and a
reason for poor adoption rate of aquaculture in the community. In responses to water problems, a number
of suggestion were put forward to improve the situation: (i) there should be a strategy to protect water
catchment areas through planting of trees and environmental conservation; (ii) there is a need for a closer
relationship between farmers and water management authorities in order to reduce misunderstandings and
have a common understanding of existing water regulations; (iii) there is also a need to identify alternative
water sources for fish farming, such as well drilling with the support from both the government and no-
government institutions as this would be too expensive for individual famers to explore.
Farmers also felt that the government had not provided enough support to fish farming and that it was
considered as a less priority compared to agriculture. Since small scale agriculture is well established in
Tanzania, a promotion of IAA could be a strategic way to diversify livelihoods and expand aquaculture,
which could help to improve the productivity of both crops and fish (paper III and IV), as well as the use
of water (paper V), a resource that is increasingly becoming scarce. These benefits from IAA farming
practices were also reported by Limbu et al. (2017) in Tanzania, Dey at al. (2010) in Malawi and Kinkela
et al. (2017) in DR Congo.
Apart from water availability and management practices (e.g. feeding and water quality), availability of
quality fish seeds is one of the critical factors for the sustainable development of aquaculture sector (Mohan,
2007). In paper III, famers ranked lack of a good quality fish fingerlings as the third biggest problem in fish
farming, which is also reflected to the fact that majority of ponds were stocked with fish obtained from
neighbor fish ponds or from the wild. This confirms the findings by Rukanda (2016) in Tanzania, who
reported that in some areas farmers had to travel up to 650 km to buy fish fingerlings. Since tilapia (O.
niloticus) is the most cultured species (Paper III), a fish species known for its prolific reproduction
(Duponchellé et al., 2000; Shoko et al., 2015), there is a risk for pond overcrowding, causing competition
in feeding and space, which could be connected to a reported fish stunted growth (Paper III).
Development of high-quality feeds for semi intensive fish farming is critical for development of the
aquaculture sector in Tanzania (Rothuis et al., 2014). A majority of the farmers in paper II and III relied on
the use of single ingredients, such as maize and rice bran, as the main supplementary feed for the fish, and
they saw the lack of good quality feeds as one of the major challenges in fish farming operations. The use
of commercial industrially produced feed, however, is often not affordable for rural farmers, who are
fighting against poverty, with incomes that are often very low (Paper I). Considering the importance of
quality feeds in fish farming, and the fact that feed account for over 50% of the operating cost (Vassiliou et
41
al., 2015), the use of formulated diets made of locally available or unconventional ingredients could be a
way to increase the fish pond productivity among local farmers. The use of vegetable wastes as a fish feed
ingredient in a locally made diet in paper IV increased the feed conversion ratio, and led to a 12% decrease
in feed costs. In similar study, Mmanda et al. (2020) reported a 34% reduction in feed costs per kg feed,
and 27% weight gain in the fish, when spent yeast from breweries was used as a feed ingredient in tilapia
diets. Other studies in Tanzania evaluated cassava leaves (Madalla et al., 2016), fly maggots (Hezron et al.,
2019) and spirulina (Mulokozi et al., 2019) as feed ingredients for tilapia, and reported improved fish
growth. Thus, it is possible that the use of locally available and non-conventional feed ingredients in fish
diets formulated at farm levels, would reduce feed cost and improve the long-term sustainability of
aquaculture production in Tanzania.
7. CONCLUSION
Aquaculture production in Tanzania has increased in recent years, responding to an increased demand for
fish, partly because of declining catches of wild fish. With an increasing human population, the demand for
fish is expected to increase in the future, and aquaculture could help to meet this demand if further
developed. As indicated in this thesis there is a good potential for aquaculture in Tanzania, but the sector is
still in its infancy, and it is constrained by many factors including a lack of improved fish breeds, feeds and
technical training; weak research capacity; inadequate human and financial resources; poor market
infrastructure and access; and weak governance and regulations (Brummett et al., 2008; Rothuis et al., 2014;
van der Heijden and Shoko, 2018; Chan et al., 2019)
Still similar to many other countries in Sub Saharan Africa, aquaculture is in an emerging stage, and it is
increasingly contributing to peoples’ income and livelihoods. This study showed that 13% of the fish famers
household income comes from fish farming. In absolute terms, fish income increased with increase in
household income, while its relative contribution to household income increased with decreased household
income. Also, the proportion of fish consumed tended to increase with a decrease in household income as
oppose to the proportion sold, suggesting that fish farming provide important contributions to both the
household economy and food security, especially among low income families.
In addition to contributing to the household income generation and food production, fish farming helped in
strengthening the social capital through in-kind giving of the produce, though the amount given was only
2% of the harvest. Fish ponds were also used as water reservoirs for other domestic uses. This also provided
a potential to strengthen social relations if the pond water could be shared with non-pond owning neighbors.
In rural Tanzania agriculture is still the main economic activity and will probably be so in the foreseeable
future, why this thesis suggest that aquaculture integrated with agriculture (IAA) could be an important
entry point for an increased adoption rate of aquaculture, building on the farmers’ experiences. About 31%
of the farmers surveyed in paper I were living in extreme poverty, with an income below the international
poverty line of 1.90 US$ per day, and aquaculture could be an important way to provide complementary
income and nutritional food for farmers and thus help in reaching SDG goals, such as no poverty, no hunger
and good health and wellbeing.
42
As shown in both the field survey and the experiments, IAA could help to further improve the farmers’
income through decreased production costs and increased yields. Fish-feed constitute the major production
cost in fish-farming, which can be reduced by recycling of locally available resources. As shown in paper
II already today more than 80% of the respondents relied on locally available feed ingredients as a major
feed supplement for their cultured fish. As in the case of Amaranth waste, this could provide inputs of high
nutritional value without any extra cost, and a balanced fish feed could be obtained by mixing different
local feed ingredients (Paper II, IV).
Rivers and streams were the most common source of water used by the majority of respondents for pond
farming (Paper III). Utilizing water from streams comes with the advantage that, if the terrain is good,
pumping into ponds may be unnecessary. Additionally, water from streams usually has high concentration
of oxygen, which is good for the fish. On the other hand, stream water for fish farming is prone to
environmental degradation, climate change and pollution. This suggest the need for strong initiative to
protect water catchment areas for the future development of aquaculture in Tanzania.
As shown in paper III, IV and V the nutrient rich water from the fishponds provide valuable input to the
crops and helps to ensure a stable availability of water over the year, and could help to decreased the input
and costs for fertilizers. The recycling of water between fish and crops also improves the water use and
production efficiency, which decreases the cost for water and make the system less vulnerable to droughts.
It also seems that IAA farmers are more skilled in operating their farms than non-IAA farmers, partly
because of longer experience and more training, but also because of a higher motivation and closeness to
their farms. Altogether this has a positive impact on the fish yield. Despite higher fish feed quantity and
stocking density in non-IAA ponds, IAA ponds had an average fish yield of 2.5 tons ha-1, which was
significantly higher than the fish yield of 1.5 tons ha-1 found for non-IAA ponds (paper III).
In an addition to a more efficient production of fish, the combination of crops leads to an overall higher,
and often more efficient production of food, through the recycling of nutrient, water and organic matter.
This was seen in both the field experiments and field surveys where the IAA ponds had 2.8 times higher
net profit than the non-IAA ponds.
Thus, the majority of the farmers (79%), had a positive attitude towards aquaculture and wanted to continue
with fish farming, and IAA famers were even more positive towards fish farming compared to non-IAA
farmers, with 20% of the IAA farmers wanting to expand their activities.
However, an expansion of aquaculture in Tanzania would require more technical support and training as
emphasised both by farmers and fisheries officers. Major constraints include not only technical issues like
stunted growth and limited access to water but also lack of extension services and commitment from the
government.
The majority of the studied pond farms were at a low, often subsistence level, run by farmers with limited
experience in fish farming. Although the IAA farmers had higher fish yields than the non- IAA farmers,
the yield found in the field survey were still quite low compared to the yields from ponds with fish farmed
43
under more controlled conditions (paper IV, V), and there is thus considerable potential for increased yields
with improved management strategies.
In conclusion, Tanzania has good environmental conditions, including climate, soil and terrain, for pond
farming of warm water species such as Nile Tilapia and catfish (Berg et al., submitted). The demand for
fish is increasing and fish farmers seems to have an overall positive experience from small scale
aquaculture. An increased adoption of IAA farming could help to increase food production with positive
environmental impact as indicated in this thesis. The results further show that these systems can have a
positive social impact through enhanced income, food security, water availability and poverty alleviation.
If integrated with others crops in IAA, fish farming provides means for livelihood diversification and water
security and can help farmers to become more resilient to environmental change. The low scale of
production and comparatively low production costs makes these systems less dependent on well-established
fish markets and infrastructure, and they provide a design that can operate in more remote areas, and it is
suggested that these systems should continue to be an important part of Tanzania´s future aquaculture
portfolio.
8. FUTURE RESEARCH
Fish has for a long time been an important commodity, contributing to food security and livelihood in
Tanzania. This is because the country is endowed with various natural water bodies that used to supply
surplus quantities of the wild caught fish to a majority of the people. While the catches from the wild has
remained stagnant, fish demands have increased rapidly and expected to keep increasing due to a steady
growing human population. This thesis has shown the potential of increasing fish production through
adoption of integrated agriculture and aquaculture (IAA) systems in Tanzania. Based on the findings from
this study, it is suggested that the issues below would be interesting to be followed up with some further
research.
Few farmers in Tanzania currently practice integration of rice and fish, despite Tanzania being the second
largest rice producer in Eastern and Southern Africa (IRRI, 2020), involving an area of 1.1 million ha (URT
2019). Integrated rice-fish farming is not a new technology. It has been practiced successfully in tropical
Asia for centuries and provide to be an efficient way to produce both rice and fish (Xie et al. 2011). Thus,
future research should explore how rice-fish farming could be introduced for increased fish production in
Tanzania. Building on examples from Egypt, fish production from rice fields has been reported to contribute
significantly to the country’s total aquaculture production (Kalim and Sabi, 2020). Raising fish in rice fields
would minimize the investment costs for ponds, and could help the farmers to diversify their crop
production. In addition to providing animal protein, the fish would help to increase the rice yields and
control pests to the rice and vectors for human diseases that thrives in stagnant water (Xie et al. 2011).
Water availability is one of the most critical factors for the development of aquaculture sector. In this thesis,
it was found that water related problems mainly due long periods of drought, anthropogenic activities and
policy issues were among the most critical challenges facing fish farmers. Future research should be geared
to designing IAA systems that would optimize the water utilization efficiency for the production of both
fish and crops, considering the foreseen challenges from climate change. Example of such designs may
44
involve culturing of Nile tilapia and catfish in ponds and rice field integrated systems. These species are
known for their high tolerance to extreme conditions including high ammonium and nitrite concentrations
(El-Shafai et al., 2004; Schram, et al., 2010), thus requiring less frequent water exchange and pond
management. Thus, more research should be done on how IAA systems could help to design future
agriculture systems that are more resilient to environmental change, including climate change, and how
these systems can provide means to produce food more efficiently and at the same time contributing to
economic growth, social justices and environmental qualities.
The thesis found that women play a significant role in fish farming despite that almost all ponds are under
men ownership. Future research should thus also aim for a better understating of gender dimensions in
aquaculture in Tanzania, including issues confronting women, their participation in, and impact by,
aquaculture as well as ways through which gender equality could be improved in the aquaculture sector.
The thesis shows a potential to increase fish production from IAA, which is basically a small-scale type of
aquaculture, mainly practiced in rural areas. Since Tanzania has diverse agroecological and social settings,
future research should also focus on the development of other aquaculture systems in Tanzania, and how
these systems could strengthen and complement each other for an increased fish production. More
commercially oriented aquaculture systems are becoming increasingly popular in urban areas, and often
involve high inputs of resources (e.g. commercial diets and high technology), targeting middle- and high-
income consumers in densely populated cities like Dar es Salaam, Arusha and Mwanza. These systems
increase the availability of high-quality feeds, seeds and fish markets, which also could benefit small scale
farmers if well managed. Additionally, considering the presence of a number of water bodies including
Lake Victoria, Tanganyika, Nyasa and the Indian Ocean, there should also be more research on fish farming
using cage systems and their implication for socio-economic and environmental sustainability.
The overall vision of the Ministry of Livestock and Fisheries in Tanzania is to develop an aquaculture sector
that is commercially run, vibrant, diversified and sustainable using highly productive resources to ensure
food security and nutrition, employment and improved income for the households and nation at large while
conserving the environment (URT, 2015). If this vison is to be met future research should look into how
the future aquaculture systems (rural aquaculture vs urban aquaculture vs cage aquaculture) could
complement each other towards an increased sustainable production of fish.
9. ACKNOWLEDGEMENTS
I am very grateful to all people who have helped and supported me in many ways during the whole process
of accomplishing this thesis. First and foremost, I would like to express my sincere gratitude to my main
supervisor, Associate professor, Håkan Berg for all the help, encouragement and guidance through the
course of my PhD studies. His breadth of knowledge and experience has been very helpful in writing of
this thesis. Special thanks to my co-supervisors, Dr. Paul Onyango, Prof. Torbjörn Lundh and Dr. Rashid
Tamatamah for all the help. Their constructive ideas, comments and suggestions on study designs as well
as manuscripts writing were very valuable.
To Dr. Helle Skånes for assistance in various aspects at the Department of Physical Geography. To Dr.
Ingrid Stjernquist and Professor Stefan Wastegård for valuable comments on my Kappa. To Dr. Aviti
Mmochi from the Institute of Marine Science Zanzibar, for kindly accepting to be the examiner during my
45
halftime seminar. To my office mates here at Stockholm University, Baraka Nyangoko, Abhay Prakash and
Felicity Holmes, and all my fellow PhD students at the Department of Physical Geography, thank you for
your valuable support and kindness.
To Blandina Crescent, Martin Edbom, Lydiah Mwaipungu and Suzzane Macha for providing
accommodation during my different stays in Sweden.
To my lovely wife Christina John (Mama D) and my daughter Davina and my son Daniel for their
encouragement, understanding as well as patience all the times I had to leave them alone while in Sweden.
To my sisters Kokuberwa, Kafura, Kahumbya and, brothers Rwebembera and Mujuni. For the
encouragement and comfort, for always being there whenever I needed you. To my aunt Jeremetrida
Babwanga for hosting me several times when I stayed in Dar es Salaam.
To Michael Stewart (Aquaculture technician, Kunduchi Fisheries College, UDSM), Muhidin Abdallah,
Babu Athuman, Babu Hashim, Yoakim Komba and other staff at Pangani-Mariculture Centre, Institute of
Marine Sciences, for their support during the field experiments.
To my fellow PhD students Christa Simon, Francis Mmanda, Moses Mbiru, John Mapunda and Dr. Levinus
Mapenzi (Post Doc) for all the company during our stay at Pangani.
To the Director General of the Tanzania Fisheries Research Institute (TAFIRI) for authorizing my PhD
study leave. Thanks also to the administration of TAFIRI Dar es Salaam Centre for providing their fish
ponds which were used in one of my field experiments. To the administration of the Institute of Marine
Sciences, Zanzibar, for providing all the necessary logistics when I was in Tanzania.
To all the fish farmers for taking their time to respond to the questionnaires and district fisheries officers
who helped in data collection.
Last but not least, I would like to thank GOD the ALMIGHTY, who gave me all the strength and health
during my PhD study.
9.1 Financial support
This PhD program was funded by the Swedish International Development Cooperation Agency (Sida)
through the Bilateral Marine Science Program of 2015-2020, between Sweden and Tanzania and through a
project grant (SWE-2010-194).
46
10. REFERENCES
Abdul-Rahman, S., Saoud, I. P., Owaied, M., Holail, H., Farajalla, N., Haidar, M. and Ghanawi, J. (2011).
Improving Water Use Efficiency in Semi-Arid Regions through Integrated Aquaculture-Agriculture.
Journal of Applied Aquaculture, 23:212–230. https://doi.org/10.1080/10454438.2011.600629
Adeleke, B., Robertson-Andersson, D., Moodley, G. and Taylor, S. (2020). Aquaculture in Africa: A
Comparative Review of Egypt, Nigeria, and Uganda Vis-À-Vis South Africa. Reviews in Fisheries
Science and Aquaculture, DOI:10.1080/23308249.2020.1795615.
Aguilar-Manjarrez, J. and Nath, S. S. (1998). A strategic reassessment of fish farming potential in Africa.
CIFA Technical paper. 32, FAO, Rome. http: www.fao.org:docrep:w8522e:w8522e00.htm.
Ahmed, N., Ward, J. D. and Saint, C. P. (2014). Can integrated aquaculture-agriculture (IAA) produce
“more crop per drop”?. Food Security, 6:767–779. DOI 10.1007/s12571-014-0394-9.
Ahmed, M. and Lorica, M. H. (2002). Improving developing country food security through aquaculture
development – lessons from Asia. Food Policy, 27(2):125–141. doi:10.1016/S0306-9192(02)00007-
6.
AOAC. (1990). Official Methods of Analysis: Association of Official Analytical Chemists (K. Helrich
(ed.); 15th ed., Vol. 1). Association of Official Analytical Chemists.
AOAC. (1999). Official Methods of Analysis of the Official Association of Analytical Chemists, 16th ed.;
AOAC Arlington: Washington, DC, USA.
APHA. (2005). Standard Methods for Examination of Water and Wastewater, 21st ed.; American Public
Health Association; American Water Works Association; Water Pollution Control Federation: New
York, NY, USA, 2005.
Baitilwake, M. A., De Bolle, S., Salomez, J., Mrema, J. P. and De Neve, S. (2012). Effect of organic
fertilizers on nitrate accumulation in vegetables and mineral nitrogen in tropical soils of Morogoro,
Tanzania. Experimental Agriculture, 48: 111–126. doi:10.1017/S0014479711000810
Balarin, J. (1985). National review for aquaculture development in Africa. FAO Fish Circ. 770. Rome:
Food and Agricultural Organization of the United Nations.
Barghouti, S., S. Kane, K. Sorby, and M. Ali. (2004). Agricultural Diversification for the Poor. Guidelines
for Practitioners. The International Bank for Reconstruction and Development. Agriculture and Rural
Development Department. Washington, D.C., 20433.
Berg, H. (2002). Rice monoculture and integrated rice-fish farming in the Mekong Delta, Vietnam
economic and ecological considerations. Ecological Economics, 41:95-107. Doi: 10.1016/S0921-
8009(02)00027-7
Berg, H., Soderholm, A. E., Soderstrom, A. S. and Tam, N. T. (2017). Recognizing wetland ecosystem
services for sustainable rice farming in the Mekong Delta, Vietnam. Sustainability Science,
12(1):137–154. doi:10.1007/s11625-016-0409-x.
Bosma, R. H. (2007). Using fuzzy logic models to reveal farmers’ motives to integrate livestock, fish, and
crops. Ph.D. thesis, Wageningen University, Wageningen.
Bosma, R. H., Udo, H. M. J., Verreth, J. A. J., Visser, L. E. and Nam, C. Q. (2007). Agriculture
diversification in the Mekong Delta: farmers’ motives and contributions to livelihoods. Asian Journal
of Agriculture and Development, 2(1-2):49–66.
Boyd, C. E. (2005). Water use in aquaculture. World Aquaculture, 13-15.
Boyd, C. E. and Tucker, C. S. (1998). Pond Aquaculture Water Quality Management; Kluwer Academic
Publishers: Norwell, MA, USA.
47
Brummett, R. E. (1999). Integrated aquaculture in sub-Saharan Africa. Environment, Development and
Sustainability, 1:315–321.
Brummett, R. E. and Williams, M. J. (2000). The evolution of aquaculture in African rural and economic
development. Ecological Economics, 33(2):193–203. doi:10.1016/S0921-8009(99)00142-1.
Brummett. R. E., Lazard, J. and Moehl, J. (2008). African aquaculture: Realizing the potential. Food Policy,
33: 371–385. doi: 10.1016/j.foodpol.2008.01.005
Butnariu, M. and Butu, A. (2014). Chemical composition of vegetables and their products, handbook of
food chemistry in: Cheung, P. (eds). Handbook of Food Chemistry. Springer, Berlin, Heidelberg.
https://doi.org/10.1007/978-3-642-41609-5_17-1
Chan, C. Y., Tran, N., Dao, C. D., Sulser, T. B., Phillips, M. J., Batka, M., Wiebe, K. and Preston, N.
(2017). Fish to 2050 in the ASEAN region. Penang, Malaysia: WorldFish and Washington DC, USA:
International Food Policy Research Institute (IFPRI). Working Paper: 2017-01.
Chan, C. Y., Tran, N., Pethiyagoda, S., Crissman, C. C., Sulser, T. B. and Phillips, M. J. (2019). Prospects
and challenges of fish for food security in Africa. Global Food Security, 20: 17–25. doi:
org/10.1016/j.gfs.2018.12.002.
Chenyambuga, S. W., Mwandya, A., Lamtane, H. A. and Madalla, N. A. (2014). Productivity and marketing
of Nile tilapia (Oreochromis niloticus) cultured in ponds of small-scale farmers in Mvomero and
Mbarali districts. Tanzania. Livestock Research for Development, 26 (3), 1–13.
Chopin, T., Troell, M., Reid, G. K., Knowler, D., Robinson, S. M. C., Neori, A., Buschmann, A. H., Pang,
S. J. and Fang, J. (2010). Integrated multi-trophic aquaculture. In: Advancing the aquaculture
Agenda: workshop proceedings. OECD, Paris, pp 195–218,
http://www.sourceoecd.org/agriculture/9789264088719
Costello, C., Ovando, D., Clavelle, T., Strauss, C. K., Hilborn, R., Melnychuk, M. C., Branch, T. A., Gaines,
S. D., Szuwalski, C. S., Cabral, R. B., Rader, D. N. and Leland, A. (2016). Global fishery prospects
under contrasting management regimes. PNAS, 113(18): 5125–5129.
Da, C. T., Phuoc, L. H., Duc, H. N., Troell, M., Berg, H. (2015). Use of wastewater from striped catfish
(Pangasianodon hypophthalmus) pond culture for integrated rice–fish–vegetable farming systems in
the Mekong Delta, Vietnam. Agroecology and Sustainable Food Systems, 39: 580–597.
http://dx.doi.org/10.1080/21683565.2015.1013241
Devendra, C. and D. Thomas. (2002). “Crop-Animal Systems in Asia: Importance of livestock and
Characterization of Agro-Ecological Zones”. Agriculture Systems, 71: 5-15.
https://doi.org/10.1016/S0308-521X(01)00032-4
Dey, M. M., Kambewa, P., Prein, M., Jamu, D., Paraguas, F. J., Pemsl, D. E. and Briones, R. M. (2006).
Impact of Development and Dissemination of Integrated Aquaculture-Agriculture (IAA)
Technologies in Malawi. NAGA, WorldFish Center Quarterly Vol. 29 No. 1 & 2.
Dey, M. M., Paraguas, F. J., Kambewa, P., Pemsl, D. E. (2010). The impact of integrated aquaculture–
agriculture on small-scale farms in Southern Malawi. Agricultural Economics, 41: 67–79. DOI:
10.1111/j.1574-0862.2009.00426.x
Duc, N. M. (2008). Farmers’ satisfaction with aquaculture – a logistic model in Vietnam. Ecological
Economics, 68:525–531. doi:10.1016/j.ecolecon.2008.05.009.
Duc, N. M. (2009). Economic contribution of fish culture to farm income in Southeast Vietnam.
Aquaculture International, 17:15–29. doi:10.1007/s10499-008-9176-8.
48
Duponchellé, F., Cecchi, P. H., Corbin, D., Nuñeï, J. and Legendré, M. (2000). Variations in fecundity and
egg size of female Nile tilapia, Oreochromis niloticus, from man-made lakes of Côte d’ivoire.
Environmental Biology of Fishes, 57:155–170.
Edwards P (1998) A systems approach for the promotion of integrated aquaculture. Aquaculture Economics
and Management, 2(1):1–12. https://doi.org/10.1080/13657309809380209
Edwards, P. (2008). From integrated carp polyculture to intensive monoculture in the Pearl River Delta,
South China. Aquaculture Asia Magazine, 13(2):3–7.
Edwards, P., Pullin, R. S. V. and Gartner, J. A. (1988). “Research and Education for the Development of
Integrated Crop-Livestock-Fish Farming Systems in the Tropics”. ICLARM Study Review 16, 53 p.
Edwards, P., Lin, C. K. and Yakupitiyage, A. (2000). Semi-intensive pond aquaculture. In: Beveridge
M.C.M., McAndrew B.J. (eds) Tilapias: Biology and Exploitation. Fish and Fisheries Series, vol 25.
Springer, Dordrecht. https://doi.org/10.1007/978-94-011-4008-9_10
El-Shafai, S. A., El-Gohary, F. A., Nasra, F. A., van der Steen, N. P. and Gijzen, H. J. (2004). Chronic
ammonia toxicity to duckweed-fed tilapia (Oreochromis niloticus). Aquaculture, 232: 117–127.
https://doi.org/10.1016/S0044-8486(03)00516-7
Erenstein, O. (2006). "Intensification or Extensification? Factors Affecting Technology Use in Peri-Urban
Lowlands along an Agro-ecological Gradient in West Africa". Agricultural Systems, 90 (1-3): 132-
158. doi:10.1016/j.agsy.2005.12.005
FAO (2000). The State of World Fisheries and Aquaculture 2000. Rome.
http://www.fao.org/documents/card/en/c/d7f3287e-b826-5876-9d59-0428c722f30f/
FAO (2012). FAO fisheries and aquaculture - national aquaculture sector overview – United Republic of
Tanzania. Retrieved November 5, 2018, from
http://www.fao.org/fishery/countrysector/naso_tanzania/en
FAO. (2018). The State of World Fisheries and Aquaculture 2018 - Meeting the sustainable development
goals. Food and agriculture organization of the United nations, Rome, Italy.
http://www.fao.org/state-of-fisheries-aquaculture/2018/en
FAO. 2020. The State of World Fisheries and Aquaculture 2020. Sustainability in action. Rome.
https://doi.org/10.4060/ca9229en.
Genschick, S., Marinda, P., Tembo, G., Kaminski, A. M. and Thilsted, S. H. (2018). Fish consumption in
urban Lusaka: The need for aquaculture to improve targeting of the poor. Aquaculture, 492:280–289.
https://doi.org/10.1016/j.aquaculture.2018.03.052
Green, B. W., Nagdy, Z. L. and Hebicha, H. (2002). Evaluation of Nile tilapia pond management strategies
in Egypt. Aquaculture Research, 33:1037-1048.
Hall, S. J., Delaporte, A., Phillips, M. J., Beveridge, M. and O’Keefe, M. (2011). Blue frontiers: managing
the environmental costs of aquaculture. Penang: The WorldFish Center.
Halwart, M. (2020). Fish farming high on the global food system agenda in 2020. FAO Aquaculture
Newsletter. 61: II–III.
Hezron, L., Madalla, N. and Chenyambuga, S. W. (2019). Mass production of maggots for fish feed using
naturally occurring adult houseflies (Musca domestica). Livestock Research for Rural Development,
31(4). http://www.lrrd.org/lrrd31/4/lhlut31057.html
Hishamunda, N. and Ridler, N. B. (2006). Farming fish for profits: a small step towards food security in
sub-Saharan Africa. Food Policy, 31:401–414. https://doi.org/10.1016/j.foodpol.2005.12.004
49
Huong, N. V., Cuong, T. H., Thu, T. T. N. and Lebailly, P. (2018). Efficiency of Different Integrated
Agriculture Aquaculture Systems in the Red River Delta of Vietnam. Sustainability,10, 493;
doi:10.3390/su10020493.
IRRI, (2020). International Rice Research Institute. Tanzania. https://www.irri.org/where-we-
work/countries/tanzania
Irz, X., Stevenson, J. R., Tanoy, A., Villarante, P. and Morissens, P. (2007). The equity and poverty impacts
of aquaculture: insights from the Philippines. Development Policy Review, 25(4):495–516.
Jha, S., Kaechele, H., Lana, M., Amjath-Babu, T. S. and Sieber, S. (2020). Exploring Farmers’ Perceptions
of Agricultural Technologies: A Case Study from Tanzania. Sustainability, 12, 998;
doi:10.3390/su12030998
Kaleem, O and Sabi A. F. B. S. (2020). Overview of aquaculture systems in Egypt and Nigeria, prospects,
potentials, and constraints. Aquaculture and Fisheries. Article in Press.
https://doi.org/10.1016/j.aaf.2020.07.017
Kaliba, A. R., Osewe, K. O., Senkondo, E. M., Mnembuka, B. V. and Quagrainie K. K. (2006). Economic
analysis of Nile tilapia (Oreochromis niloticus) production in Tanzania. Journal of the World
Aquaculture Society, 37: 464–473.
Kaminski, A. M., Genschick, S., Kefi, A. S. and Kruijssen F. (2018). Commercialization and upgrading in
the aquaculture value chain in Zambia. Aquculture, 493:355-364
https://doi.org/10.1016/j.aquaculture.2017.12.010
Kapetsky, J. M. (1994). A strategic assessment of warm-water fish farming potential in Africa. CIFA
Technical Paper 27. Food and Agriculture Organization of the United Nations, Rome, Italy.
Karim M., Little D. C., Kabir, M. S., Verdegem, M. J. C., Telfer, T. and Wahab M. A. (2011). Enhancing
benefits from polycultures including tilapia (Oreochromis niloticus) within integrated pond-dike
systems: a participatory trial with households of varying socio-economic level in rural and peri-urban
areas of Bangladesh. Aquaculture, 314: 225–235.
Kassam, L. and Dorward, A. (2017). A comparative assessment of the poverty impacts of pond and cage
aquaculture in Ghana. Aquaculture, 470: 110–122. doi:10.1016/j.aquaculture. 2016.12.017.
Kawarazuka, N. and Béné, C. (2011). The potential role of small fish species in improving micronutrient
deficiencies in developing countries: Building evidence. Public Health Nutrition, 14:1927–1938.
doi:10.1017/S1368980011000814
Kinkela, P. M., Mutiaka, B. K., Dogot, T., Dochain, D., Rollin, X., Mvubu, R. N., Kinkela, C., Mafwila, J.
and Bindelle, J. (2017). Diversity of farming systems integrating fish pond aquaculture in the
province of Kinshasa in the Democratic Republic of the Congo. Journal of Agriculture and Rural
Development in the Tropics and Subtropics, 18(1), 149–160.
Kinkela, P. M., Mutiaka, B. K., Dochain, D., Rollin, X., Mafwila, J. and Bindelle, J. (2019). Smallholders'
Practices of Integrated Agriculture Aquaculture System in Peri-urban and Rural Areas in Sub
Saharan Africa. Tropicultura, 37(4): 2295-8010. DOI: 10.25518/2295-8010.1396
Koroleff, F. (1970a). Bestfimning av totalnitrogen i naturliga vatten genom persulfatoxidation.
International Council for the Exploration of the Sea, ICES. Council meeting 1969, Paper C:8, revised
version 1970.
Koroleff, F. (1970b). Direct determination of ammonia in neutral waters as indophenol blue. Conseil
international pour l'exploration de la mer. Service hydrographique. Information on techniques and
methods for sea water analyses. Charlottenlunds slott. Interlaboratory report no 3, 19-22.
50
Koroleff, F. (1976). Determination of phosphorus. In Methods of sea-water analyses. Grasshoff K (ed.), pp
117-126. Verlag Chemie, Veiheim, New York.
Lazard, J., Baruthio, A., Math´e, S., Rey-Valette, H., Chia, E., Cl´ement, O., Aubin, J., Morissens, P.,
Mikolasek, O., Legendre, M., Levang, P., Blancheton, J-P and Ren´e, F. (2010). Aquaculture system
diversity and sustainable development: fish farms and their representation. Aquatic Living Resources,
23:187–193. doi:10.1051/alr/2010018
Limbu, S. M., Shoko, A. P., Lamtane, H. A., Kishe-Machumu, M. A., Joram, M. C., Mbonde, A. S., Mgana,
H. F. and Mgaya, Y. D. (2017). Fish polyculture systems integrated with vegetable improves yield
and economic benefits on small scale farmers. Aquaculture Research, 48(7): 3631–3641.
doi:10.1111/are.13188.
Limbu, S. M. (2019). The effects of on-farm produced feeds on growth, survival, yield and feed cost of
juvenile African sharptooth catfish (Clarias gariepinus). Aquaculture and Fisheries, 5(1):58-64.
https://doi.org/10.1016/j.aaf.2019.07.002
Madalla. N., Agbo, N. W. and Jauncey, K. (2016). Evaluation of Ground - Sundried Cassava Leaf Meal as
Protein Source for Nile Tilapia Oreochromis niloticus (L) Juvenile’s Diet. Tanzania Journal of
Agricultural Sciences, 15(1), 1–12. https://www.ajol.info/index.php/tjags/article/view/164863
Mbwambo, N., Nandonde, S., Ndomba, C. and Desta, S. (2016). Assessment of animal feed resources in
Tanzania. Nairobi, Kenya: Tanzania ministry of agriculture, livestock and fisheries and international
livestock research institute (ILRI). pp 1-32.
Melaku, S. and Natarajan, P. (2019). Status of integrated aquaculture - Agriculture systems in Africa.
International Journal of Fisheries and Aquatic Studies, 7(4): 263-269.
Mmanda, F. P., Lundh, T., Haldén, A. N., Mtolera, M. S. P., Kitula, R. and Lindberg, J. E. (2020). Replacing
fish meal with locally available feed ingredients to reduce feed costs in cultured Nile tilapia
(Oreochromis niloticus). Livestock Research for Rural Development, 32 (11).
http://www.lrrd.org/lrrd32/11/torbj32178.html
Mohan, C. V. (2007). Seed quality in freshwater fish production. pp. 499–517. In: M.G. Bondad-Reantaso
(ed.). Assessment of freshwater fish seed resources for sustainable aquaculture. FAO Fisheries
Technical Paper. No. 501. Rome, FAO. 2007. 628p.
Molina-Poveda, C., Cardenas, R. and Jover, M. (2017). Evaluation of amaranth (Amaranthus caudatus L.)
and quinoa (Chenopodium quinoa) protein sources as partial substitutes for fish meal in Litopenaeus
vannamei grow-outdiets. Aquaculture Research, 48:822–835. doi:10.1111/are.12926
Morris, A. W and Riley, J. P. (1963). The determination of nitrate in sea water. Analytica Chimica Acta,
29: 272-279. doi: 10.1016/s0003-2670(00)88614-6.
Mosha, T. C., Gaga, H. E., Pace, R. D., Laswai, H. S., Mtebe, K. (1995). Effect of blanching on the content
of antinutritional factors in selected vegetables. Plant Foods for Human Nutrition, 47: 361–367. DOI:
10.1007/BF01088275
Mulandana, N. S., Mamadi, N. E., Du-Plooy, C. P. and Beletse, Y. G. (2009). Effect of spacing and
transplanting time on amaranths yield. African Crop Science conference proceedings, 9: 243–246.
Mulokozi, D. P., Mtolera, M. S. P. and Mmochi, A. J. (2019). Spirulina (Arthrospira fusiformis) as a
potential protein source in practical diets for fry mariculture of Rufiji tilapia (Oreochromis urolepis
urolepis). WIO Journal of Marine Science, 18 (2) 57-67. http://dx.doi.org/10.4314/wiojms.v18i2.6
Mulokozi, D. P., Mmanda, F. P., Onyango, P., Lundh, T. and Berg, H. (2020a). Rural aquaculture:
Assessment of its contribution to household income and farmers’ perception in selected districts,
51
Tanzania. Aquaculture Economics and Management 0(0), 1–19.
https://doi.org/10.1080/13657305.2020.1725687
Mulokozi, D. P., Berg, H. and Lundh, T. (2020b). An Ecological and Economical Assessment of Integrated
Amaranth (Amaranthus hybridus) and Nile Tilapia (Oreochromis niloticus) Farming in Dar es
Salaam, Tanzania. Fishes, 5. 30. doi:10.3390/fishes5030030.
Murshed-e-Jahan, K., Ahmed, M. and Belton, B. (2010). The impacts of aquaculture development on food
security: lessons from Bangladesh. Aquaculture Research, 41:481–495. doi:10.1111/j.1365-
2109.2009.02337.x.
Mwaijande, F. A. and P. Lugendo. (2015). Fish-farming value chain analysis: Policy implications for
transformations and robust growth in Tanzania. The Journal of Rural and Community Development,
10 (12):47–62.
Naylor, R. L. and Burke, M. (2005). Aquaculture and ocean resources: raising tigers of the sea. Annual
Review of Environment and Resources, 30:185–218. doi:
10.1146/annurev.energy.30.081804.121034
Naylor, R. L., Hardy, R. W., Bureau, D. P., Chiu, A., Elliott, M., Farrell, A. P., Forster, I., Gatlin, D. M.,
Goldburg, R. J., Hua, K and Nichols, P. D. (2009). Feeding aquaculture in an era of finite resources.
Proceedings of National Academy of Sciences of the United States of America, 106(36):15103–
15110. doi:10.1073/pnas.0905235106.
NBS (2018). National Bureau of Statistics. National Environmental Statistics Report (NESR, 2017).
Tanzania, Mainland.
Nhan, D. K., Phong, L. T., Verdegem, M. J. C., Duong, L. T., Bosma, R. H., Little, D. C. (2007). Integrated
freshwater aquaculture, crop and livestock production in the Mekong delta, Vietnam: determinants
and the role of the pond. Agricultural Systems, 94:445–458. doi:10.1016/j.agsy.2006.11.017
Nilsson, H. and Wetengere, K. (1993). Adoption and viability criteria for semi-intensive fish farming: A
report on a socio-economic study in Ruvuma and Mbeya regions, Tanzania. Retrieved June 17, 2019,
from Aquaculture for Local Community Development Programme -FAO website.
http://www.fao.org/3/ad001e/AD001E00 htm#TOC.
Nobre, A. M. Robertson-Andersson, D., Neori A. and Sankar, K. (2010). Ecological economic assessment
of aquaculture options: comparison between abalone monoculture and integrated multi-trophic
aquaculture of abalone and seaweeds. Aquaculture, 306:116–126.
doi:10.1016/j.aquaculture.2010.06.002
Nzevu, J. M., Amwata, D. A. and Mutua, A. K. (2018). The contribution of fish farming to household
wellbeing of fish farmers in Kitui central sub-county, Kitui county. Journal of Agriculture and
Veterinary Science, 11: 69–76. DOI: 10.9790/2380-1101016976
Odhav. B., Beekrum, S., Akula, Us. and Baijnath, H. (2007). Preliminary assessment of nutritional value
of traditional leafy vegetables in KwaZulu-Natal, South Africa. Journal of Food Composition and
Analysis, 20(5): 430-435. https://doi.org/10.1016/j.jfca.2006.04.015
OECD-FAO (2019). Chapter 8. Fish and seafood in the OECD-FAO Agricultural Outlook 2019-2028.
Poot-López, G. R., Hernández, J. M. and Gasca-Leyva, E.U. (2009). Input management in integrated
agriculture—Aquaculture systems in Yucatan: Tree spinach leaves as a dietary supplement in tilapia
culture. Agricultural Systems, 103: 98–104. https://doi.org/10.1016/j.agsy.2009.11.003
Prein M. (2002). Integration of aquaculture into crop-animal systems in Asia. Agricultural Systems, 71:
127–146.
52
Putter, H., Koesveld, M. J. and Visser, C. L. M. (2007). Overview of the Vegetable Sector in Tanzania.
AfriVeg Report; Wageningen University and Research: Wageningen, The Netherlands.
Rahman, M. M., Jo, Q., Gong, Y. G., Miller, S. A., Hossai, M. Y. (2008). A comparative study of common
carp (Cyprinus carpio L.) and calbasu (Labeo calbasu Hamilton) on bottom soil resuspension, water
quality, nutrient accumulations, food intake and growth of fish in simulated rohu (Labeorohita
Hamilton) ponds. Aquaculture, 285(1–4):78–83. doi:10.1016/j.aquaculture.2008.08.002.
Rahman, S. M. A., Haque, A. and Rahman, S. M. A. (2011). Impact of fish farming on household income:
A case study from Mymensingh District. Journal of Social Sciences, 7 (2): 127–131.
doi:10.3844/jssp.2011.127.131
Rice, A. M., Mmochi, J. A., Zuberi, L. and Savoie, M. R. (2006). Aquaculture in Tanzania. World
aquaculture, 37.4: 50-57.
Ridha, M. T. (2005). Comparative study of growth performance of three strains of Nile tilapia, Oreochromis
Niloticus, L. at two stocking densities. Aquaculture Research, 37: 172–179.
https://doi.org/10.1111/j.1365-2109.2005.01415.x
Ridler, N. B. and Hishamunda, N. (2001). Promotion of sustainable commercial aquaculture in sub-Saharan
Africa. Policy framework Volume 1. Food and Agriculture Organization of the United Nations,
Rome, Italy.
Rivera-Ferr´e, M. G. (2009). Can export-oriented aquaculture in developing countries be sustainable and
promote sustainable development? The shrimp case. Journal of Agricultural and Environmental
Ethics, 22(4):301–321. doi:10.1007/s10806-009-9148-7.
Rothuis, A., Turenhout, M., van Duijn, A., Roem, A., Rurangwa, E., Katunzi, E., Shoko, A. and
Kabagambe, J. B. (2014). Aquaculture in East Africa; A regional approach. Wageningen, LEI
Wageningen UR (University and Research centre), LEI Report IMARES C153/14| LEI 14-120.54
pp.; 16 fig.; 8 tab.; 37.
Rukanda, J. J. (2016). Evaluation of aquaculture development in Tanzania. Nations University Fisheries
Training Programme, Iceland [final project].
http://www.unuftp.is/static/fellows/document/janeth16aprf.pdf.
Savci, S. (2012). Investigation of effect of chemical fertilizers on environment. APCBEE Procedia, 1: 287–
292. https://doi.org/10.1016/j.apcbee.2012.03.047
Schram, E., Roques, J. A., Abbink, W., Spanings, T., De Vries, P., Bierman, S., van de Vis, H. and Flik, G.
(2010). The impact of elevated water ammonia concentration on physiology, growth and feed intake
of African catfish (Clarias gariepinus). Aquaculture, 306, 108–115.
doi:10.1016/j.aquaculture.2010.06.005
Schreinemachers, P., Simmons, E. B. and Wopereis, M. C. S. (2018). Tapping the economic and nutritional
power of vegetables. Global Food Security, 16, 36-45. http://dx.doi.org/10.1016/j.gfs.2017.09.005
Sen, S., Lundh, T., Preston, T. R. and Borin, K. (2010). Effect of stocking densities and feed supplements
on the growth performance of tilapia (Oreochromis spp.) raised in ponds and in the paddy field.
Livestock Research for Rural Development, 22: 227.
Sheheli, S., Fatema, K. and Haque, S. M. (2014). Existing status and practices of fish farming in Trishal
Upazila of Mymensigh district. Progressive Agriculture, 24(1-2): 191–201. doi:10.3329/pa.v24i1-
2.19172
Shoko A. P., Getabu A., Mwayuli G. and Mgaya Y. D. (2011a). Growth performance, yields and economic
benefits of Nile tilapia Oreochromis niloticus and Kale Brassica oleracea cultured under vegetable-
fish culture integration. Tanzania Journal of Science, 37: 37–48.
53
Shoko, A. P., Lamtane, H. A., Wetengere, K., Kajitanus, O., Msuya, F. E., Mmochi, A. J., and Mgaya, Y.
D. (2011b). The status and development of aquaculture in Tanzania, East Africa. In P. Natarajan, L.
Wondimu, T. Boyossa, M. I. Zuberi, A. S. Nair, A. Beyeh, & E. Aga (Eds.), Technical Proceedings
of the International Conference on Ecosystem Conservation and Sustainable Development
(ECOCASD 2011) (pp. 85–97). Ambo, Ethiopia: Ambo University.
Shoko A. P., Limbu, S. M., Mrosso, H. D. J. and Mgaya Y. D. (2015). Reproductive biology of female Nile
Tilapia Oreochromis niloticus (Linnaeus) reared in monoculture and polyculture with African
sharptooth Catfish Clarias gariepinus (Burchell). Springerplus, 4(1): 275.
Shoko, A. P., Limbu, S. M., Lamtane, H. A., Kishe-Machumu, M. A., Sekadende, B., Ulotu, E. E., Masanja,
J. C. and Mgaya, Y. D. (2019). The role of fish-poultry integration on fish growth performance,
yields and economic benefits among smallholder farmers in sub-Saharan Africa, Tanzania. African
Journal of Aquatic Science, 44(1):15–24. doi:10.2989/16085914.2018.1555512.
Tacon, A. G. J., Metian, M., Turchini, G. M. and De Silva, S. S. (2010). Responsible aquaculture and
trophic level implications to global fish supply. Reviews in Fisheries Science, 18(1): 94–105. DOI:
10.1080/10641260903325680
Tipraqsa, P., Craswell, E. T., Noble, A. D. and Schmidt-Vogt, D. (2007). Resource integration for multiple
benefits: Multifunctionality of integrated farming systems in Northeast Thailand. Agricultural
Systems, 94: 694–703. doi:10.1016/j.agsy.2007.02.009
TMA (2019). Tanzania Metrological Authority. Statement on the Status of Tanzania Climate in 2019.
Toma, N. I., Mohiuddin, M., Alam, M. S. and Suravi, M. M. (2015). An economic study of small-scale
tilapia fish farming in Mymensingh district of Bangladesh. Journal of Agricultural Economics and
Rural Development, 2: 50-53.
Tran, N., Chu, L., Chan, C. Y., Genschick, S., Phillips, M. J. and Kefi, A. S. (2019). Fish supply and demand
for food security in Sub-Saharan Africa: An analysis of the Zambian fish sector. Marine Policy, 99:
343–350. https://doi.org/10.1016/j.marpol.2018.11.009
UN-DESA (2017). United Nations Department of Economic and Social Affairs. World Population
Prospects: The 2017 Revision, Key Findings and Advance Tables; UN-DESA: New York, NY, USA,
2017; Available online: https://esa.un.org/unpd/wpp/publications/files/wpp2017_keyfindings.pdf
(accessed on 6 October 2020).
UNDP. United Nations Development Program. Sustainable Development Goals. Goal 2: Zero hunger.
Available online at https://www.undp.org/content/undp/en/home/sustainable-development-
goals/goal-2-zero-hunger.html (accessed on 1 October 2020).
URT (2012). United republic of Tanzania. Basic Facts and Figures on Human Settlements, in Tanzania
Mainland. National Bureau of Statistics. Ministry of Finance.
URT. (2015). The United Republic of Tanzania Ministry of livestock and fisheries development, fisheries
sector. National fisheries policy of 2015.
URT (2016a). United Republic of Tanzania. The Tanzanian Fisheries Sector, Challenges and Opportunities.
URT (2016b). United Republic of Tanzania. Ministry of livestock and fisheries development, fisheries
sector. Aquaculture Development Division. Aquaculture production statistics 2015/2016.
URT (2017). United Republic of Tanzania. Agricultural Sector Development Programme II (ASDP-II).
URT. (2019). The United Republic of Tanzania. Ministry of agriculture. National rice development strategy
phase ii (NRDS ii) 2019-2030.
URT (2020a). United republic of Tanzania. Ministry of livestock and fisheries development (MLFD).
Annual budget speech 2020.
54
URT (2020b). United Republic of Tanzania. Ministry of livestock and fisheries development, fisheries
sector. Aquaculture Development Division. Aquaculture production statistics 2019/2020.
van der Heijden, P. G. M. (2012). Water Use at Integrated Aquaculture-Agriculture Farms: Experiences
With Limited Water Resources In Egypt. Global Aquaculture Advocate, 2012 (July-August), 28-31.
van der Heijden, P. G. M. and Shoko, A. P. (2018). Review and analysis of small-scale aquaculture
production in East Africa; Part 3. TANZANIA. Wageningen Centre for Development Innovation,
Wageningen University and Research. Report WCDI-18-020. Wageningen.
Vassiliou, V., Charalambides, M., Menicou, M., Chartosia, N., Tzen, E., Evagelos, B., Papadopoulos, P.
and Loucaides, A. (2015). Aquaculture and feed management system powered by renewable energy
sources: Investment justification. Aquaculture Economics and Management, 19: 423–443.
https://doi.org/10.1080/13657305.2015.1082115
Wetengere, K. (2011). Socio-economic factors critical for intensification of fish farming technology. A case
of selected villages in Morogoro and Dar es Salaam regions, Tanzania. Aquaculture International,
19:33–49. DOI 10.1007/s10499-010-9339-2.
Wetengere, K. and Kihongo, V. (2011). The Efficacy of Group Work in Rural Development: The Case of
Group-Owned Fish Ponds in Morogoro Region, Tanzania. Current Research Journal of Social
Sciences, 3(1):8-16.
Wilson, E., McInnes, R., Mbaga, D.P. and Ouedaogo, P., (2017). Ramsar Advisory Mission Report: United
Republic of Tanzania, Kilombero Valley; The Ramsar Convention Secretariat: Gland, Switzerland,
2017. Gland, Switzerland.
WorldBank. (2019). Rural population – Tanzania. https://www.worldbank.org/en/country/tanzania
WorldFish. (2020). The Big Facts on Aquatic Foods. WorldFish Research and Innovation Strategies 2030.
https://worldfishcenter.org/strategy-2030/
Wossink, A. and Boonsaeng, T. (2003). Farmers' Knowledge and Perceptions of Animal Waste
Management Technologies: An Explorative Study for North Carolina. ARE Report, No. 29.
Wu, Y., Han, H., Qin, J. and Wang, Y. (2015). Effect of feeding frequency on growth, feed utilization, body
composition and waste output of juvenile golden pompano (Trachinotus ovatus) reared in net pens.
Aquaculture Research, 46: 1436–1443. doi:10.1111/are.12297
Xie, J., Hu, L., Tang, J., Wu, X., Li, N., Yuan, Y., Yang, H., Zhang, J., Luo, S. and Chen, X. (2011).
Ecological mechanisms underlying the sustainability of the agricultural heritage rice-fish coculture
system. Proceedings of the National Academy of Sciences, 108 (50): E1381–7. DOI:
10.1073/pnas.1111043108
Yoo. K. H. and C. E. Boyd. (1992). Hydrology and water supply for pond aquaculture. Chapman and Hall.
New York.New York USA.
Zajdband A.D. (2011). Integrated agri-aquaculture systems. Genetics, Biofuels and Local Farming
Systems, pp.87–127. Springer, Dordrecht, the Netherlands. DOI: 10.1007/978-94-007-1521-9_4
Zeller, D. and Pauly D. (2005). Good news, bad news: global fisheries discards are declining, but so are
total catches. Fish and Fisheries, (6): 156–159.
