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
1500 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).
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