Main stocks in capture fisheries
Definitions
The FAO Glossary for Responsible Fisheries indicates, inter alia, that from a pragmatic point of view, a stock is "the part of a fish population which is under consideration from the point of view of actual or potential utilization". In more biological terms, it is also "a group of individuals in a species occupying a well defined spatial range independent of other stocks of the same species. A stock can be affected by random dispersal movements and directed migrations due to seasonal or reproductive activity. It can be regarded as an entity for management or assessment purposes. A unit stock comprises all the individuals of fish in an area, which are part of the same reproductive process. It is self-contained, with no emigration or immigration of individuals from or to the stock. On practical grounds, however, a fraction of the unit stock may be considered as a "stock" (or as a management unit) for management purposes as long as the results of the assessments and management remain close enough to what they would be on the unit stock".
Stocks present a wide range of characteristics that affect the fisheries exploiting them: they can consist of fish, shrimp, clams, etc. and can be a multispecies stock. It can be highly migratory, straddling or shared; global, ocean-wide, regional, national and local - attributes that often have different implications for management. Stocks are units generally defined by scientists for assessment purpose and their indicators intend to describe their size, potential, health status and trends. An example of a straddling or shared stock of sardine is found in the links below.
The term "resources" is also often used when referring to vaguely defined "stocks". The FAO Glossary for Responsible Fisheries indicates that aquatic resources are "biotic elements of the aquatic ecosystem, including genetic resources, organisms or parts thereof, populations, etc. with actual or potential use or value (sensu lato) for humanity. Fishery resources are therefore those aquatic resources of value to fisheries". Just like a stock, a fishery resource is defined in space and its geographical demarcation and often has a political or jurisdictional connotation (e.g. Moroccan resources; EEZ or high seas resources). Potential or actual catch is a typical resources indicator reflecting the notions of use or value attached to the resource's concept. It could be local, national (e.g. the shrimp resource of Ghana), regional (e.g. Atlantic tuna) or global (cephalopod resources of the world).
Stocks vary greatly in composition, size and other characteristics. They can include one or many species and be very large (e.g. Alaska Pollock) or rather small (e.g. the South African abalone or the precious red coral of the Mediterranean). The total number of entities identified as "stocks" in the world in not known and no comprehensive classification exists. FAO has started compiling a catalogue.
The Peruvian anchoveta, Eastern Pacific yellowfin tuna, Pacific Southern bluefin tuna, North Sea plaice, Canadian cod, Gulf of Mexico menhaden, Alaska Pollack, Atlanto-Scandian herring, New Zealand orange roughy; Antarctic minke whale, Mauritanian black hake; etc. are example of well known stocks. It can however be assumed that the largest majority of the world stocks have hardly been mentioned in available literature. More than 1 500 stocks and their population dynamic parameters are identified in FAO's POPDYN database but more comprehensive and detailed fact sheets will be made available in its Fisheries Global Information System (FIGIS).