Better management practices for shrimp farming – Part II
31. Water is a scarce and very precious natural resource. Try to maximize the efficiency of water utilization.
32. Exchange the water carefully. Do not frequently exchange or in-take the water.
33. During the first month, there should not be any water exchange. Starting the second month, if necessary, water exchange can be done but try to minimize it as much as possible.
34. Release the water when the plankton bloom is too thick i.e., dark green or dark brown water.
35. When releasing the water disturb the pond bottom near the water gate to release the black coloured organic waste from the pond.
36. Do not release or intake more than 15-30 cm depth of water in a day.
37. Take the water in only when there is no disease in the farming cluster.
38. Always use double layer water filter net of fine mesh size or 300-micron mesh size to filter the intake water.
39. Use agriculture lime after every water intake or exchange and after rain. Lime acts as a buffering agent for water.
40. If there is foam on the water surface or if the watercolour suddenly changes or becomes clear then exchange 5-10 cm of water and add agriculture lime at a rate of 200-300 kg per hectare.
41. Regularly check the water quality parameters.
42. pH of the water should be in the range of 7.5 to 8.5. To measure this, use a universal liquid indicator or litmus paper. If the pH is lower than 7.5 then apply shell lime to increase the pH. If the pH is higher than 8.5 then exchange the water to reduce the pH.
43. Ideal water salinity for shrimp is 10-25 ppt. The refractometer is used to measure the salinity.
44. Dissolved oxygen or DO concentration should be 5 to 6 ppm. Electronic DO meter can be used to measure the DO concentration in water. If oxygen level depletes in the pond, shrimp will start swimming near the water surface especially during early morning hours. DO concentration below 4 ppm is very stressful to shrimps. Therefore if it falls below 4 ppm especially during night and early morning period, then use paddlewheel aerators or water pump to aerate the water by spraying the water over the pond. If there is no disease outbreak in farming cluster then water can be exchanged to improve the DO level.
45. Watercolour should be green or brown colour indicating healthy plankton bloom. It should not be turbid or transparent or dark green or dark brown colour. This indicates either there is no plankton bloom or very dense plankton bloom, both the conditions are not desirable in the pond.
46. Alkalinity should be 100 ppm. Alkalinity instant test kit can be used to measure its concentration.
47. Ammonia should be less than 0.1 ppm. Ammonia instant test kit can be used to measure its concentration.
48. Hydrogen sulfide should be 0 ppm. Hydrogen sulfide instant test kit can be used to measure its concentration.
49. Remove the benthic algae as and when it develops in the pond. If not removed, it will decay in the pond bottom and release toxic gases stressful to shrimp.
50. Also, remove filamentous algae and hydrilla from the pond on regular basis. If not removed, the shrimp can get entangled in the algal filaments and die. Milkfish can be effectively used to remove algae.
51. Regularly monitor the shrimp for health and growth. This can be done on daily basis by collecting 10 to 15 shrimps from feed check trays or weekly basis by collecting shrimps using cast nets.
52. Shrimps should be clean with normal body colour and without loss of any legs or antennae. Gut should be full. If the shell or gills of shrimp are dirty then it means that the pond bottom where shrimp stays is not clean. As a remedy spread the feed to another cleaner bottom area in the pond and exchange about 10 cm of water and apply agriculture lime at a rate of 200 kg per hectare.
53. If white faeces or sick or dark shrimps are found on the surface water then check if they have dirty or black gills. If so, reduce the feed quantity and exchange 10 cm of water.
54. If there is a disease in the pond, on a daily basis record the number of diseased or dead shrimps. If the daily mortality remains low, say 5 shrimp per day, or subsidies, then there is no need to go for an emergency harvest. Testing the sick shrimps for disease using dot blot test kits like Shrimple helps in confirming the deadly white spot disease.
55. Remove the diseased and dead shrimp as and when it appears in the pond and bury them far away from the pond site. Do not throw away the dead and diseased shrimp in the water canal or on open places. Do not apply for any chemicals or medicines without advice from shrimp health specialists. There is no medicine to cure the viral diseases in shrimp.
56. If there is a rapid increase in mortality on a daily basis and with or without white spots on shrimps, combined with a rapid decrease in feed consumption, decide for emergency harvest. If mortalities rapidly reach 50 shrimp per day and pond records do not indicate an obvious environmental cause or the dot blot testing confirms the white spot disease, harvest the entire crop by cast net and retain water in the pond for at least one month. If shrimp are too small to harvest, retain them in the pond for at least one month. If there is urgency to prepare for another crop, then apply bleaching powder or calcium hypochlorite at a rate of 1000 kg per hectare to disinfect the pond water and after 15 days release the water in to the canal.
57. Drive away animals and birds from disease-affected ponds. Do not move farm workers or exchange farm utensils from diseased ponds to other ponds.
58. It is important to carefully harvest, handle and preserve the shrimps in order to maintain the freshness and quality of shrimps.
59. Coordinate the harvest with other farmers in the farming cluster. Make sure the neighbouring farmers are informed about the harvest. Three to four days before harvest apply agriculture lime at a rate of 200 kg per hectare to the pond especially to the corners and trench area, this helps in cleaning the shell surface. Avoid harvest during the molting period i.e., full moon or new moon period. Two days before harvest check if there are any molted shrimp, if newly molted shrimp are more than 10% of the population, delay the harvest by a day or two. Do not exchange water or reduce water level 3 to 4 days before harvest. Harvest between 6 o’clock in the evening and 6 o’clock in the morning. Avoid harvesting and packing shrimp during hot time of day. Do not feed the shrimp 6 hours prior to harvesting to keep the gut empty and improve the shelf life of shrimp. Complete the harvesting process within 6 to 8 hours. Use more water pumps if necessary to complete the harvesting in time and to catch most of the shrimp with bag net. Avoid using cast nets for harvesting when the water depth is too shallow. If normal draining of pond water is difficult, use artificial gates made up of bamboo sticks or fish nets inside the pond in a corner at deeper side of pond for fixing the bag net and to harvest shrimps. Separate hand-picked shrimps from bag net harvested shrimp.
Thoroughly wash the shrimps in clean water and dip the shrimps in slurry of ice for about 15 minutes for chill killing. This practice improves the freshness of shrimp. All the time do not use pond water or any other dirty water in these process of washing and chill killing. Do not use any chemicals while washing the shrimp or chill killing. Make sure good quality ice is used during chill killing and packing. Use equal quantity of shrimp and crushed ice with proper mixing in transportation insulated tubs. Before stacking the packed boxes one above the other, make sure bottom of the boxes are clean. Always maintain cleanliness.
60. Keeping daily record book for pond management is important. It helps to analyse the crop results, possible cause of disease etc. Also it helps to keep a check on crop-related expenditures and income thus to improve the economic efficiency of the crop management by farmer. It is a pre-requisite for traceable shrimps in the market. The pond daily record consists information on pond preparation details, seed source, quality and stocking details, treatments given to soil and water, water exchanges, feed type and quantity, water quality parameters, information on health status of shrimps, harvest information, expenditure and income details.
61. For achieving the better efficiencies in marketing, organizing the small-scale farmers in groups at farming cluster level is the only way forward. Farmer groups can easily facilitate the purchase of the quality farm inputs at cheaper prices thus reducing the cost of production. Several village level farmer groups can join together to market the farmed shrimps for better prices. Certified shrimps are in demand in international market. This can give edge to farmers in highly competitive international market not only to successfully sell their product but also to sell at premium prices. Responsible and successful farmer groups are attractive to the banking and insurance sectors to extend credits and crop insurance. This will reduce the financial burden and risk on farmers.
Consumers are increasingly concerned about the food quality and safety issues due to its impact on human health. Importing countries have banned chemically contaminated shrimps especially with antibiotics, pesticides and other harmful chemical residues. These chemical contaminants could be from shrimp hatcheries, nurseries, farms and processing plants. Hence these chemicals must not be used in any part of production and supply chain. Also, there could be contamination of shrimps with harmful microorganisms or bacteria like Salmonella, E. coli, Vibrio cholerae. This microbial contamination could be due to unhygienic conditions in farming areas like open toilets on source water canals, use of untreated/wet organic manures like cow dung, poultry manure etc. Also, it could be from the poor harvest and post-harvest handling practices, unhygienic processing and packing conditions. This microbial contamination can be prevented by using hygienic toilets in the farming areas, treating the water in farm reservoirs, improved harvest and post-harvest handling practices, implementation of HACCP programmes in the processing and packing factories. The freshness of shrimps is another quality aspect. Quick processing and preservation of shrimps immediately after harvest is key to preserve the freshness of shrimp.
Source: Indonesian Aquaculture