Fish stocks are subpopulations of a particular

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

, for which intrinsic parameters (growth, recruitment, mortality and fishing mortality) are traditionally regarded as the significant factors determining the stock's population dynamics, while extrinsic factors (immigration and emigration) are traditionally ignored. Stocks fished within biologically sustainable levels decreased from 90% in 1974 to 62.3% in 2021.

Concepts

The stock concept

All species have geographic limits to their distribution, which are determined by their tolerance to environmental conditions, and their ability to

compete Competition is a rivalry where two or more parties strive for a common goal which cannot be shared: where one's gain is the other's loss (an example of which is a zero-sum game). Competition can arise between entities such as organisms, individ ...

successfully with other species. In marine environments this may be less evident than on land because there are fewer

topographical Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the landforms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary scienc ...

boundaries, however, discontinuities still exist, produced for example by mesoscale and sub-mesoscale circulations that minimize long-distance dispersal of fish larvae. For fish, it is rare for an individual to reproduce randomly with all other individuals of that species within its biological range. There is a tendency to form a structured series of discrete populations which have a degree of reproductive isolation from each other in space, in time, or in both. This isolation is reflected in the development between sub-populations of

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

tic differences, morphological variations and exposure to different

chemical A chemical substance is a unique form of matter with constant chemical composition and characteristic properties. Chemical substances may take the form of a single element or chemical compounds. If two or more chemical substances can be combin ...

regimes and

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The ent ...

species. Sub-populations also respond to fishing in such a way that fishing on one population appears to have no effect on the population dynamics of a neighbouring population. The currently accepted definition of a stock in fisheries science, is that of Begg et al. (1999), ''“… “stock”describes characteristics of semi-discrete groups of fish with some definable attributes which are of interest to fishery managers.”'' Fish-gf0d0932a6 1920

Stock identification is a field of

fisheries science Fisheries science is the academic discipline of managing and understanding fisheries. It is a multidisciplinary science, which draws on the disciplines of limnology, oceanography, freshwater biology, marine biology, meteorology, conservation, ...

which aims to identify these subpopulations, based on a number of techniques.This concept is applied in sustainable development goal 14 where target 14.4 is measured a fish stock sustainability indicator 14.4.1.

Straddling stock

The

United Nations The United Nations (UN) is the Earth, global intergovernmental organization established by the signing of the Charter of the United Nations, UN Charter on 26 June 1945 with the stated purpose of maintaining international peace and internationa ...

defines straddling stocks as "stocks of fish such as

pollock Pollock or pollack (pronounced ) is the common name used for either of the two species of North Atlantic ocean, marine fish in the genus ''Pollachius''. ''Pollachius pollachius'' is referred to as "pollock" in North America, Ireland and the Unit ...

, which migrate between, or occur in both, the economic exclusion zones (EEZ) of one or more states and the

high seas The terms international waters or transboundary waters apply where any of the following types of bodies of water (or their drainage basins) transcend international boundaries: oceans, large marine ecosystems, enclosed or semi-enclosed regiona ...

". Sovereign responsibility must be worked out in collaboration with neighbouring coastal states and fishing entities. Usually this is done through the medium of an intergovernmental regional organisation set up for the purpose of coordinating the management of that stock. Straddling stocks are usually

pelagic The pelagic zone consists of the water column of the open ocean and can be further divided into regions by depth. The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or water column between the sur ...

, rather than

demersal The demersal zone is the part of the sea or ocean (or deep lake) consisting of the part of the water column near to (and significantly affected by) the seabed and the benthos. The demersal zone is just above the benthic zone and forms a layer o ...

. Demersal species move less than pelagic species, since they tend to relate to bottom topography. Pelagic species are more mobile, their movements influenced by ocean temperatures and the availability of zooplankton as food. Example pelagic fish are capelin,

herring Herring are various species of forage fish, belonging to the Order (biology), order Clupeiformes. Herring often move in large Shoaling and schooling, schools around fishing banks and near the coast, found particularly in shallow, temperate wate ...

, whiting,

mackerel Mackerel is a common name applied to a number of different species of pelagic fish, mostly from the family Scombridae. They are found in both temperate and tropical seas, mostly living along the coast or offshore in the oceanic environment. ...

and redfish, There are, however, a few demersal species that are straddling, such as the

Greenland halibut The Greenland halibut or Greenland turbot (''Reinhardtius hippoglossoides'') belongs to the family Pleuronectidae (the right-eye flounders), and is the monotypic, only species of the genus ''Reinhardtius''. It is a predatory fish that mostly rang ...

migrates in feeding/spawning migrations to Greenland in the west and to the Faeroes in the east.Pelagic and straddling stocks
Straddling stock can be compared with transboundary stock. Straddling stock range both within an

EEZ An exclusive economic zone (EEZ), as prescribed by the 1982 United Nations Convention on the Law of the Sea, is an area of the sea in which a sovereign state has exclusive rights regarding the exploration and use of marine natural resource, reso ...

as well as in the high seas. Transboundary stock range in the EEZs of at least two countries. A stock can be both transboundary and straddling.

FAO The Food and Agriculture Organization of the United Nations; . (FAO) is a List of specialized agencies of the United Nations, specialized agency of the United Nations that leads international efforts to defeat hunger and improve nutrition ...

(2007) tp://ftp.fao.org/docrep/fao/010/i0150e/i0150e00.pdf Report of the FAO workshop on vulnerable ecosystems and destructive fishing in deep sea fisheriesRome, Fisheries Report No. 829.

Assessments

and

ecology Ecology () is the natural science of the relationships among living organisms and their Natural environment, environment. Ecology considers organisms at the individual, population, community (ecology), community, ecosystem, and biosphere lev ...

stock assessment Stock assessments provide fisheries managers with the information that is used in the regulation of a fish stock. Biological and fisheries data are collected in a stock assessment. A wide array of biological data may be collected for an assess ...

is an important tool in

fisheries management The management of fisheries is broadly defined as the set of tasks which guide vested parties and managers in the optimal use of aquatic renewable resources, primarily fish. According to the Food and Agriculture Organization of the United Nation ...

. In particular, to ensure continued, healthy, fish stocks, measurements of the

Spawning Spawn is the Egg cell, eggs and Spermatozoa, sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of freely releasing eggs and sperm into a body of water (fresh or marine); the physical act is ...

Stock

Biomass Biomass is a term used in several contexts: in the context of ecology it means living organisms, and in the context of bioenergy it means matter from recently living (but now dead) organisms. In the latter context, there are variations in how ...

(the stock population capable of reproducing) allows sensible conservation strategies to be developed and maintained through the application of sustainable fishing quotas. The

World Wildlife Fund The World Wide Fund for Nature (WWF) is a Swiss-based international non-governmental organization founded in 1961 that works in the field of wilderness preservation and the reduction of human impact on the environment. It was formerly named the ...

and the

Zoological Society of London The Zoological Society of London (ZSL) is a charity and organization devoted to the worldwide animal conservation, conservation of animals and their habitat conservation, habitats. It was founded in 1826. Since 1828, it has maintained London Zo ...

jointly issued their "Living Blue Planet Report" on 16 September 2015 which states that there was a dramatic fall of 74% in world-wide stocks of the important scombridae fish such as

tuna A tuna (: tunas or tuna) is a saltwater fish that belongs to the tribe Thunnini, a subgrouping of the Scombridae ( mackerel) family. The Thunnini comprise 15 species across five genera, the sizes of which vary greatly, ranging from the bul ...

and

bonito Bonitos are a tribe of medium-sized, ray-finned, predatory fish in the family Scombridae, which it shares with the mackerel, tuna, and Spanish mackerel tribes, and also the butterfly kingfish. Also called the tribe Sardini, it consists of ...

s between 1970 and 2010, and the global overall "population sizes of mammals, birds, reptiles, amphibians and fish fell by half on average in just 40 years." It is hoped that global efforts like the United Nations Sustainable Development Goal 14 meets its targets aimed at reversing these trends. The UN

Food and Agriculture Organization The Food and Agriculture Organization of the United Nations; . (FAO) is a specialized agency of the United Nations that leads international efforts to defeat hunger and improve nutrition and food security. Its Latin motto, , translates ...

found that stocks fished within biologically sustainable levels decreased from 90% in 1974 to 62.3% in 2021..

Fluctuations

The stocks for individual marine species can "boom and bust" in linked and compensatory ways. For example, in

billfish The billfish are a group (Xiphioidea) of saltwater fish, saltwater predatory fish characterised by prominent pointed beak, bills (rostrum (anatomy), rostra), and by their large size; some are longer than . Extant billfish include sailfish and m ...

longline fisheries, the Atlantic catch of blue marlin declined in the 1960s. This was accompanied by an increase in sailfish catch. The sailfish catch then declined from the end of the 1970s to the end of the 1980s, compensated by an increase in swordfish catch. As a result, the overall billfish catch remained fairly stable. At Georges Bank, a decline in cod during the 1960s was accompanied by a rise in flatfish, and more recently, with the collapse of the predatory Atlantic cod, lobster catches in

Maine Maine ( ) is a U.S. state, state in the New England region of the United States, and the northeasternmost state in the Contiguous United States. It borders New Hampshire to the west, the Gulf of Maine to the southeast, and the Provinces and ...

have boomed.Duffy, J. Emmett (2008
Marine biodiversity and food security
''Encyclopedia of Earth''. Updated 25 July 2008.

Sources

References

External links

*
Identification of stocks of herring, ''Clupea harengus''FAO Fisheries Department
and it

addressing fish stocks {{fisheries and fishing Fisheries science