Marine shrimp farming and genetic resources
Shrimp collectors in Sundarbans mangrove forest (Bangladesh). Collecting shrimp larvae for growout and wild broodstock for reproduction is a viable business in many rural areas
Importance of shrimp farming
Shrimp farming is very important in aquaculture today. In 1997, more than 941 000 metric tonnes of farmed shrimp valued over US$6.07 billion were produced (data from FAO Fishery Information, Data and Statistics Unit). Shrimp farming is a large foreign exchange earner. The developing countries engaged in this activity market most of their products in the developed world. This, together with supporting activities such as feed manufacture, shrimp processing and equipment manufacturing plays a substance economic role in countries such as Ecuador, Indonesia and Thailand.
Shrimp farming today relies heavily on natural genetic resources. Farmers in South and Central America such as the ones in Ecuador, Guatemala and parts of Mexico continue to use captured post-larvae to stock their production ponds. The collection of postlarvae has certainly impacted the wild populations of both the targeted species and the species that are caught incidentally. With respect to the collection of shrimp post-larvae, aquaculture differs little from those traditional fisheries that have no size regulations. Larvae of other crustaceans, fishes, and other animals of a wide diversity are caught and discarded as by-catch. However, wild shrimp post-larvae continue to be utilized because of their apparent hardiness and economical price. Depending on the method and location of the collection, at times, the by catch can be kept to a minimum when open sea collection of single species schooling post-larvae is done.
Viable shrimp hatcheries coexist in many of the shrimp farming regions of the Americas where collection of wild larvae occurs. However, these hatcheries also source their breeding stocks from the wild. Asia, which produces about 80 percent of the world's farmed shrimp (data from FAO Fishery Information, Data and Statistics Unit), relies primarily on the wild-caught brood stock, with exception of the Chinese White Shrimp (P. cinensis) which has closed its life cycle in captivity. The hatcheries, which produce hundreds of billions of post-larvae per year, capture small numbers of large adults or gravid female shrimp in order to produce post-larvae. Asian shrimp farming as a whole depends upon wild shrimp populations to provide all of its genetic resources. It is therefore, just as susceptible to fluctuations in the availability of wild resources as any capture fishery activity. Therefore, the conservation of wild genetic resources is invaluable to shrimp farming.
One of the most important issues in the use of wild stock, either for breeding or direct culture, is their uncontrolled movement by farmers. Beside the hazards of introduction of alien species either directly as shrimp or as incidental non-shrimp species when moving wild caught post-larvae, there are the dangers of introducing diseases. Wild brood stock of Pacific white shrimp (Penaeus vannamei) infected with Taura Syndrome Virus (TSV) and black tiger shrimp (P. monodon) infected with white spot disease (SEMBV) have been moved to previously disease-free regions (author's personal observation). Such introductions can rapidly affect wide geographical areas beyond the native ranges of shrimp species and of their diseases. This can have devastating consequences for both natural and cultured populations.