Harvesting and marketing
Methods of harvesting shrimps have been briefly described. Efficient harvesting has to be based on the habits of the particular species under culture and the culture procedures. Shrimps graze at night and are generally attracted by light. They also respond actively to water movements, especially when water is let into a pond or drained. Most Penaeid species are more active during the full moon and new moon, and the maximum activities are shortly after sunset and shortly before sunrise. These are the best times for harvest.
Total harvest is usually carried out at the end of each crop by draining and placing a bag net at the sluice gate to catch the shrimps as they swim from the pond. Partial harvesting can be done by seine nets after partial draining, from peripheral canals or from harvest basins. Some farmers catch the shrimps in large traps built in the outlet canals outside the sluice gates, as the pond is drained. In Taiwan, cast nets are some-times employed for partial harvesting, using sea snails as bait.
As mentioned, it is very profitable to sell shrimps alive in countries like Japan, and so the harvesting technique has to be adapted for capturing them without injury. The pound net used in Japan to trap shrimps is well-suited for this purpose. During cool seasons, when the shrimps do not move so actively at the bottom, a pump net or an electric shock is more effective (fig. 25.15). These methods are suitable for P. japonicus, which burrows at the bottom. Electric fishing is successfully employed in harvesting tiger shrimps in Taiwan. Harvesting is avoided when most of the shrimps are moulting, as soft-shelled shrimps will not stand handling. Live shrimps are transferred to containers placed in cold water tanks. Methods of packing and transport of live shrimps have been described.
Since shrimp culture in many developing countries is export-oriented, modern methods of chilling, freezing and packing are practised to meet the requirements and regulations of importing countries. Whole shrimps, shrimp tails or partially or completely shelled products are exported.