BIOSECURE SHRIMP FARMING TECHNOLOGY
In light of the devastating disease problems currently plaguing the global shrimp farming industry, water exchange has apparently become a risky management option for maintaining acceptable water quality. The biosecure shrimp farming system is an evolving culture practice which provides means to achieve a higher degree of biosecurity. Biosecurity in aquaculture is the sum of all procedures in place to protect living organisms from contracting, carrying, and spreading diseases and other non-desirable health conditions, with biotherapeutic agents like probiotics.
The Central Institute of Brackish water Aquaculture (CIBA) has developed a Bio secure Shrimp Farming Technology (BSFT) based on three years of study, which includes several yard experiments and two pond trials, involving investigations on utilization of bio therapeutic agents, water and sediment quality parameters in relation to modifications in culture practices. It differs from conventional farming with regard to practices on water utilization, biosecurity measures followed and in addressing disease concerns without the use of antibiotics and chemotherapeutics. In a way, this is a modification of the widely practiced zero water exchange system relying more on increased provisions of biosecured environment even in the absence of reservoir ponds. It is also advantageous over the existing zero water exchange system due to reduction in disease risks and input costs. The technology has been successfully tested in on-station field trials with improved productivity and feed conversion ratio (FCR) achieved by using defined biotherapeutic agents. This technology is more suitable for states like West Bengal, Orissa, Kerala, Karnataka, Goa and Maharashtra, since it takes advantage of good monsoon precipitation.
The biosecure shrimp farming technology can be applied to extensive, semi-intensive or intensive shrimp aquaculture. The salient features of this technology are:
• High scoring for biosecurity compared to conventional farming and zero water exchange systems
• Reduced operational costs (no use of antibiotics, chemicals, water exchange and related feed costs)
• Use of efficient biotherapeutic agents
• Reduced risk of disease outbreaks
• Growth and production performance at par or better than conventional farming and zero water exchange systems
• Better feed conversion efficiency as there is no loss of in situ nutrients
• Efficient water budgeting and utilization of harvested rainwater
• Better profitability and rate of return
The following gives the various steps to be followed with regard to site selection and pond design, bio security features, pond preparation, stocking, water and soil quality monitoring, feeding strategy, health management, harvesting and post harvest measures. These are steps unique for BSFT along with standard procedures followed in conventional farming.
Site selection and pond designing
➢ Good monsoon precipitation is one of the prerequisites for this farming to compensate evaporation or seepage loss throughout the culture period.
➢ Site must be free from pollution by industrial effluents and domestic discharge.
➢ Good quality brackishwater (salinity 10- 25 ppt, temperature 25-31o C) and optimum soil quality parameters are essential.
➢ Electricity and communication accessibility is indispensable as this technology requires heavy aeration throughout the production cycle.
➢ Rectangular pond with strong non porous high dykes is recommended.
➢ Sluice gate of the simple type with minimum cost compared to the heavy structural investment required in conventional system can be used.
➢ With minimal or zero water exchange a high degree of pathogen exclusion is maintained.
➢ Biosecurity barriers or fences around the pond, prevention of the carrier/vectors including birds, disinfection of intake water, avoidance of cross contamination, use of certified healthy seeds, quality feed, use of allowable chemotherapeutics, strict feeding management, water quality monitoring and overall hygiene including that of the equipment and personnel are some of the in-built features of this farming system.
➢ A key step in BSFT is the introduction of a defined microbial community in to the culture environment which can work synergistically to enhance the overall productivity of the shrimp ponds without resorting to commercial probiotics.
➢ Pond preparation is to be started with the drying of the pond bottom till it cracks and surface soil scraped to remove the black soil accumulated from the previous crop since it results in the deposition of considerable load of organic matter.
➢ Soil amendment measures like lime application must be practiced (depending on soil pH) similar to any other conventional shrimp farms.
➢ Water intake is to be done after proper screening and a higher depth of at least 1.5 m is maintained unlike conventional systems.
➢ Disinfection is recommended with application of Calcium hypochlorite (Ca (OCl) @ 60 ppm.
➢ Optimum natural productivity should be maintained using inorganic fertilizers (Urea: SSP: 2:1 @ 3 ppm) in frequent doses, if necessary; yeast based extract or some good biotherapeutic agents like Bacillus spp. can also be used for start up a good bloom.
➢ Ponds should be stocked with healthy seeds (postlarvae) from a certified hatchery.
➢ 12 nos./m2 postlarve is considered ideal for the BSFT system
➢ Proper acclimatization is to be done to avoid any kind of stress during stocking.
➢ The crop should be scheduled to take advantage of the monsoon rain.
➢ Maintain a stable environment with effective recycling of nutrients and other metabolites through the use of farm made probiotics.
➢ Good aeration is required for supporting the detritus food chain and effective mineralization of the higher level of organic matter in this closed system. .
➢ Parameters influencing productivity like alkalinity, pH and dissolved oxygen are to be maintained within optimum range.
➢ Nutrients like phosphate and nitrate are maintained at higher levels in the BSFT system throughout the culture, resulting in optimum levels of natural productivity.
➢ Feed requirement is to be appropriately estimated through regular sampling (growth and survival) and check tray observation.
➢ Over feeding should be avoided at any cost to prevent eutrophication and associated additional operational costs.
➢ During molting or any other stressful conditions, restricted feeding should be adopted.
➢ The pond bottom in the feeding area should be monitored periodically and if necessary bottom treatment including application of lime mixed with sand is to be adopted.
Health management
➢ Periodical health monitoring with due consideration to proper biosecurity measures is required.
➢ Beneficial microorganisms (such as Lactobacillus spp, Bacillus spp, Pseudomonas spp. and probiotic yeast Saccharomyces spp.) are to be applied as either in single/multi-strain for effectively controlling the pathogenic microorganisms and maintaining the water quality parameters in the optimum range.
➢ Best management practices (BMPs) like care for preventing pathogen carriers, pond bottom
managements, certified healthy seeds, quality feeds and non use of antibiotics /chemicals must be incorporated in the practices followed.
Harvesting and Post harvest measures
➢ There should be minimum stress during harvesting.
➢ After chill killing, the shrimps must be packed in good quality ice and must be transported to processing factory which adopts Hazard Analysis Critical Control Point (HACCP) principles.
Conclusion
This biosecure shrimp farming system is a better farming practice for the coastal ecosystem for its high scoring on biosecurity measures and avoidance of antibiotics and banned chemicals. Effective recycling of nutrients and other metabolites which results in a stable environment are features of this system. A reduced level of nitrogenous metabolites and better water quality could be maintained even with no water exchange. This BSFT system is amenable for control of disease through best management practices. This evolving farming practice with all its biosecurity features and effective utilisation of biotherapeutic agents can pay rich dividends with reduction in input cost coupled with higher level of production, besides its environment friendly features of utilising harvested rainwater.
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