Fish stock

Fish stocks are subpopulations of a Particular species of fish , for qui 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.

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 with other species. In marine environments May this be less obvious than it land Because there are Fewer topographical 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 discrete population structure which has a degree of reproductive isolation from each other in space, in time, or in both. This isolation is reflected in the development between subpopulations of genetic differences, morphological variations and exposure to different chemical regimes and parasitic species. Sub-populations also respond to fishing in such a way that the population on the population dynamics of a neighboring population.

The present accepted definition of a stock in fisheries science, is that of Begg et al. (1999), “… [a” stock “] describes characteristics of semi-discrete groups of fish with some definable attributes which are of interest to fishery managers .

Stock identification is a field of fisheries science which aims to identify these subpopulations, based on a number of techniques.

Straddling stock

The United Nations defines straddling stocks as “stocks of fish such as pollock , which migrate between, or occur in, the economic exclusion zone (EEZ) of one or more states and the high seas “. [1] Sovereign responsibility must be worked out in collaboration with neighboring coastal states and fishing entities. Usually this is done through the medium of an intergovernmental regional organization set up for the purpose of coordinating the management of that stock.

Straddling stocks are usually pelagic , rather than demersal . 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. Pelagic fish are capelin , herring , whiting , mackerel and redfish , There are, however, a few demersal species that are straddling, such as the Greenland halibut migrates in feeding / spawning migrations to Greenland in the west and to the Faeroes in the east . [2]

Straddling stock can be compared with transboundary stock . Straddling stock ranks both within an EEZ 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. [3]

Stock assessment

See also: Stock assessment

In fisheries science and ecology , stock assessment is an important tool in fisheries management .

In Particular, to Ensure continued, healthy fish stocks, measurements of the Spawning Stock Biomass (the stock of population able Reproducing) Allows sensitive conservation strategies to be Developed and maintained through the implementation of sustainable fishing quotas . [4]

The World Wildlife Fund and the Zoological Society of London Jointly Issued their “Living Blue Planet Report” on 16 September 2015 qui states That There Was a dramatic fall of 74% in world-wide stocks of the major scombridae fish Such as mackerel , tuna and bonitos between 1970 and 2010, and the overall overall “population sizes of mammals, birds, reptiles, amphibians and fish fell in half an average of just 40 years.” [5]

Stock fluctuations

The stocks for individual marine species can “boom and bust” in linked and compensatory ways. For example, in billfish longline fisheries, the Atlantic catch of blue marlin declined in the 1960s. This is 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 wrestling. As a result, the overall billfish catch is fairly stable. At Georges Bank , the decline in cod during the 1960s was accompanied by a rise in flatfish, and more recently, with the collapse of the cod Atlantic predatory, lobster catches in Maine have boomed. [6]

Notes

  1. Jump up^ Straddling stocks
  2. Jump up^ Pelagic and straddling stocks
  3. Jump up^ FAO(2007)Report of the FAO workshop on vulnerable ecosystems and destructive fishing in deep sea fisheriesRome, Fisheries Report No. 829.
  4. Jump up^ International Council for the Exploration of the Sea (ICES) website
  5. Jump up^ . http://awsassets.wwf.org.au/downloads/mo038_living_blue_planet_report_16sep15.pdf
  6. Jump up^ Duffy, J. Emmett (2008)Marine biodiversity and food security Encyclopedia of Earth. Updated 25 July 2008.

See also

  • Lake Pohjalampi (in Finland)
  • List of harvested aquatic animals by weight
  • overfishing

References

  • Begg GA, Friedland KD and Pearce JB (1999) “Stock identification and its role in stock assessment and fisheries management: an overview.” Fisheries Research , 43 : 1-8.
  • Booke HE (1999) “The stock concept revisited: perspectives on its history in fisheries” Fisheries Research , 43 (1-3): 9-11. doi : 10.1016 / S0165-7836 (99) 00063-6
  • Cadrin SX, Friedland KD and Waldman JR (2004) Stock Identification Methods: Applications in Fishery Science. ISBN  0-12-154351-X
  • Pintassilgo, P. and Lindroos, M. Management of Straddling Fish Stocks: A Bioeconomic Approach ” In: Encyclopedia of Life Support Systems – Volume 5 , UNESCO.

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