Harvesting is the final step in the culturing process. The harvesting is done by netting into the pond and getting the product out there Harvesting is done by after the desired count is available
Growth rate of the fish, market demand, desired market size, availability of seed and pond condition, are the major considerations for deciding on the time of harvesting.Generally the Shrimp culture will take from 90-120days and the Fish culture will take from 9-12months.
Usually the carp species attain marketable size within one year and hence the shorter rearing period of less than a year is not recommended unless there is an exceptional threat of flood or outbreak of disease, or for financial reasons. Post-flood stocking and pre-flood harvesting should be done in flood prone ponds while in seasonal ponds harvesting should be done before the water level falls below the critical level. In regions where seeds of desired cultivated species are available only during post-monsoon period, i.e. October/November, the stocking should normally be done during this period and the crop should be harvested by next October.
It has been experienced that even under the best management, Indian major carps on an average attain hardly 1 kg in size in a year, while Chinese carps reach over 2 kg or so. This kind of differential growth complicates the final harvesting programme and hence in such areas partial harvesting of marketable size fish is carried out.
Further, the market price of fish is directly related to its size. This factor should also be considered before deciding on the harvesting programme. Possibility of partial harvesting very much depends on the availability of fingerlings of desired carp species. In such cases the fish already reached the marketable size should be harvested and the stock should be replenished. Usually fish over 500 g should be harvested every 3 - 4 months with simultaneous stocking with fingerlings. Such partial harvesting programme should be synchronised with peak market demands depending on seasons, festivals, etc.
Complete harvesting can be carried out by draining the pond water through a bag net and hand picking. The average culture period required is around 120-150 days during which time the prawns will grow to 20-30 gm size (depending on the species). It is possible to get two crops in a year. Harvested shrimps can be kept between layers of crushed ice before transporting the consignment to market.
Two methods of harvesting are generally practiced on Shrimp farms. These are either by draining the pond and catching the shrimp in a bag net or by netting the shrimp within the pond. With either method, it is necessary to hand-pick the remaining shrimp in the pond, after the pond is drained. The harvested shrimp can be quickly killed by giving them a temperature shock (dip in iced water) to prevent damage and to improve storage.
The timing of harvesting depends on the condition of the shrimp in the pond and also the market price. Shrimps are sampled by a cast net from different areas of the pond to determine their average body weight and general condition. The proportion of soft shell shrimp should not be more than 5% at the time of harvest. This proportion could be obtained by scheduling the harvest halfway between two moultings. The time of moulting is indicated by the presence of exuviae in the pond. For example if the average body weight of the shrimp is 30 gm, then the harvest should be planned for 7-8 days after the exuviae are observed, as the next moulting cycle can be observed after 14-16 days. Harvested shrimp should be iced and transported to cold storage or processing plants in less than 10 hrs.