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Ecological Approaches to Better Sustainability of Shrimp Culture in China YUAN Derun Network of Aquaculture Centres in Asia-Pacific JW Marriott, Bangkok, Thailand, 13 November 2019
Ecological Approaches to Better Sustainability of Shrimp Culture in China
YUAN Derun
Network of Aquaculture Centres in Asia-Pacific
JW Marriott, Bangkok, Thai land, 13 November 2019
INTRODUCTION1
3
(modified from Funge-Smith and Briggs, 1998)
23% feed N retained
4
12% feed P retained
Low nutrient conversion efficiency by single species is a common feature in typical intensive shrimp culture systems
24 – 35 % N and 8 -12% P retained (FCR 1.1 – 1.9)
Excessive waste nutrients in the system is the main culprit for:
Accumulation of hazardous substances in water
column and sediments
Opportunistic growth of pathogenic organisms
Stress to shrimp
Diseases
Environmental impacts
Technological options (1)
RAS:Minimal perterbation with surrounding natural
environmentHigh and precision control of production process Capacity of waste treatment
5 – 12 kg/m2
Technological options (2)
Ecological approachesOld practices with continuous evolution and adaptation
Low cost option for majority of small scale farms
ECOLOGICAL APPROACHES: PRINCIPLES AND COMMON SYSTEMS IN PRACTICE2
NH4+
NO3-
NO2- H2S
pHO2
TN
TPSediments
Basic principles
Recognize the interactions between an aquaculture farm and the external environment
Multiple species in the same culture system that occupy different nutritional and spatial niches
Mutually beneficial to each other with ecological synergy
Create an eco-system that favor shrimp survival, growth, and waste removal
Some systems
Polyculture
Integrated aquaculture
Multi-trophic aquaculture
Agro-aquaculture integration etc…
POLYCULTURE OF SHRIMP AND FISH3
Consume dead shrimp, small crustacean, break down disease transmission routes
Break down life cycle of pathogens
Inhibit growth of Vibros
Disease control
Consume uneaten shrimp feed, reduce nutrient leach
Selectively feed on certain species of plankton, maintain good water qualityPossibly increase oxygen level in sediments, re-suspend nutrients in sediment back to water column
Ecological benefit
Improve overall FCR
Reduce use of chemicals
Economic benefit
Increase productivity
Improve shrimp survival
Possible beneficial effects of fish as the secondary species in shrimp-fish polyculture systems
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Critical control point 1: Adjust environmental factors to reduce shrimp stress to prevent latent infection from turning into acute infection
Critical control point 2: Eliminate the opportunity for healthy shrimp to eat dead shrimp, break down the virus transmission route
(modified from He et al. 2018)
The epidemiological characteristic of WSS
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No biological control
We tested more than 30 species of fish to evaluate their predatory behaviors in shrimp ponds
We also studied the ingest selectivity of each fish species for health shrimp, diseased shrimp and dead shrimp
We determined the fish species, fish size and fish quantity available for WSS biological control in shrimp ponds
Fish as a biological control factor
WSS transmission is directly related to loss of biological diversity
(modified from He et al. 2018)
Some polyculture models
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Watersalinity
Shrimp Fish (/ha) Production
< 6 45 – > 200 pl/m2 Clarias catfish: 600 – 900/ha; 150 -500 gStocked 2-3 weeks later
Fish production may be insignificant but fish provide biological control to diseases esp. WSSManagement - dependent on shrimp density
< 8 45 – >200 pl/m2 Grass carp: 300/ha; 0.3-0.3 kgClarias: 300/ha; 0.3-0.5 kgTilapia: 150/ha; 0.2 kgBig head: 150/ha; 0.2 kgFish stocked 2-3 weeks later
Fish production insignificant but provide biological control to diseases esp. WSSManagement and production - dependent onshrimp density
< 20 45 pl/m2 All male tilapia: 1.5 fish/m2 ; 2 cmStock fish 10 -20 days after stocking shrimp
120 days; feed both shrimp and fishFish fed first, about half hour later, feed shrimpShrimp: about 2.75 tons/ha; 30 pc/kgTilapia: 7 tons/ha; 0.5 kg
Tilapia – a star
Omnivore; salinity tolerance
Low nutrient requirements
Fast growth
Quality flesh
Adaptation to various systems
Low feed cost
Relatively high productivity
Fit into various market niches
Tilapia as a secondary species in shrimp-fish polyculture
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Feed shrimp half hour after feeding tilapia
Observe shrimp feeding condition to
adjust feeding rate
Ensure sufficient aeration
Evolving treatment of pond sediment, fertilization to produce nature food in pond preparation
Close monitoring of feeding condition and control of excessive feed input
OTHER CULTURE SYSTEMS WITH ECOLOGICAL APPROACHES4
Co-culture of shrimp and plants
The plants absorb nutrientsPrevent algae from excessive growing and
reduce risk of shrimp AHPND/EMS
Rotation farming between shrimp and plants
Nutrients in soil of the shrimp culturing pond taken out by vegetables
Improve soil conditions for shrimp culture
Earthen pond based recirculation system
Reservoir for water storage and pond for water supply Pond designed with sludge sump usually located in the center of a
pond: so-called shrimp toilet Effluent from shrimp colure ponds flows through
Sediment compartment Biological treatment compartments (using filter fish, plants,
bivalves etc.) Water recirculate back to supply poind before reused in culture
unit May involve phasing of culture cycle (nursing, grow-out, partial
harvest) Tendency of using larger areas of water treatment (3:7)
