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| Location of hatchery :
The hatchery should be located in place where good quality water is ensured for maintenance of broodstock, spawning, larval rearing, phytoplankton culture and all other hatchery activities Water treatment Disinfect the seawater with calcium hypochlorite (20-30 ppm) or sodium hypochlorite (150 ppm) for 1-2 days ensuring thorough mixing to eliminate pathogenic microorganisms. Remove excess chlorine from the seawater by neutralising with sodium thiosulphate. Filter the seawater and preferably sterilize by UV treatment. Cleanliness of hatchery facilities The tanks used for broodstock, spawning, larval rearing, etc. should be kept thoroughly clean by scrubbing, disinfecting and thorough rinsing. Treatment of broodstock The brood shrimps should be treated with 2ml/100 l formalin (20 ppm) and oxytetracycline (10 ppm) for 30 minutes before stocking in broodstock tanks to reduce the population of epibiotic microflora Care at the time of spawning Remove the scum formed after spawning. Stocking of nauplii Stock only healthy nauplii at an optimal stocking density. The nauplii may be disinfected by dip treatment in 20-30 ml formalin/100 l (200-300 ppm) or 0.1 ppm iodophore. Care during larval rearing Remove the unused feed, sediments, debris, algal growth and wastes accumulated at the bottom or sides of the tank routinely by siphoning and scrubbing as these waste encourage bacterial proliferation. Feeding : Feed the larvae with optimal amount of good quality balanced feed as the defence mechanism of the larvae depends upon their nutritional status. Use of chemicals and antibiotics The antibiotics should be used carefully at right doses, only after ascertaining in-vitro sensitivity of the pathogens. Low dose of antibiotics leads to development of antibiotics resistant mutants of bacteria and higher doses may be toxic to the shrimp larvae. Monitoring of larval health and water quality Examine the larvae every morning before changing water for any visual abnormality, and microscopically for fouling protozoa, filamentous bacteria, fungal infection, and presence of swarming bacteria within the haemocoel. Wet mount preparations of hepatopancreas should be examined from time to time for viral infections. Observe rearing water and shrimp larvae in dark for bioluminescence. This help in understanding the status of health of the shrimp larvae and thereby take appropriate remedial measures as needed. Monitor the water quality to maintain important parameters at optimal levels (Temp 27-30 C, Salinity 27-31 ppt, DO > 5 ppm, pH 7.8 - 8.5; Ammonia N: <0.5 ppm, Nitrite-N: <0.02 ppm) Since treatment of viral diseases of shrimps in not known, disease outbreak due to viral infection may be avoided by quarantine measures and destroying carriers and contaminated animals. Once viral infection is detected in hatchery, all activities should be stopped and all the contaminated facilities should be thoroughly disinfected before restarting hatchery activities. |
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