Stocking techniques for increased production
Collecting fry for stocking
Management of inland fisheries
As an enhancement technique, stocking is one of the most widespread measures for management of inland fisheries in use today. As more conventional approaches to management by control of the fishery have proved incapable of limiting effort, compensation for shortfalls in recruitment caused by overfishing and environmental damage has been sought through the addition of young fish to the natural waters. The following major types of stocking can be identified:
FAO and ASFA
Ninety-four countries have reported stocking to FAO as part of their fishery statistics. Examination of the scientific literature produces some 4847 references extracted from ASFA (1978 - 1996) dealing with stocking of finfish, molluscs or crustaceans into inland or marine habitats.
Commonly stocked species
The most commonly stocked freshwater species are common carp (Cyprinus carpio) worldwide, rainbow trout (Oncorhynchus mykiss) in Europe, North America South America Africa and Asia, Atlantic salmon (Salmo salar) in Europe and North America, brook trout/sea trout (Salmo trutta) in Europe and North America, Nile tilapia (Oreochromis niloticus) in Africa, Latin America and North America, pike (Esox lucius) in Europe and North America, grass carp (Ctenopharyngodon idella) in North America and Asia, silver carp (Hypophthalmichthys molitrix) in Asia and Europe, pikeperch (Stizostedion lucioperca) in Europe, North America and Asia as well as Mozambique tilapia (Oreochromis mossambicus) in Africa, Asia and North America.
Atlantic salmon (Salmo salar) is typically stocked in Europe and North America
Stocks of coregonids, perch and zander are maintained in many alpine and northern European lakes in support of commercial as well as recreational fisheries. The transfer of coregonids and vendace has been practised for centuries, which considerably extended the distribution area of coregonids in Europe. Hatchery operations began in the mid-1800s and spread throughout Europe and North America. Similarly, stocking is one of the measures to maintain fisheries in lowland reservoirs and lakes in Poland and the countries of the former Soviet Union. In Russian reservoirs yields were considered to be far higher when managed.
Stocking programmes are also widely used throughout the USA and Canada where the emphasis is on management for balanced populations for recreational fisheries. Stocking is widespread in Latin America where the greatest development has been achieved in Cuba, Mexico and parts of Brazil. In general, stocking programmes aim at supporting commercial fisheries. In Brazil, stocking was a statutory requirement for mitigation of effects of dams. As regards Asia, successful stocking programmes are reported from India and China. Variable results are reported from Southeast Asia where it has been possible to raise catch levels from 20 to 100 kg/ha in some waters in Thailand, Indonesia, the Philippines and Malaysia. Data for Africa are rather scarce although this continent has fisheries that are supported by stocking.
There are two main sources of seed material for stocking, i.e. extraction of the products of natural spawning from rivers, lakes and coastal waters, and production from aquaculture installations. The latter option is usually involving higher costs.