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

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(modified from Funge-Smith and Briggs, 1998)

23% feed N retained

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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)

Thanks!yuan@enaca.org

NACA website: www.enaca.org

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