Fish and Shellfish Stocks: 2013

Information on the state of fish and shellfish stocks of commercial importance to the Scottish fleet, inclduing Total Allowable Catches (TACs) for each stock.

Introduction to fisheries management in Scotland

Fisheries management involves a number of political and scientific processes that aim to provide a sustainable supply of fish. Each year Marine Scotland Science ( MSS) carries out the scientific work to support fisheries management. Monitoring and research is undertaken at MSS to understand the biology and the state of commercially important fish stocks. Management is generally applied at the level of these biological units known as stocks. MSS investigates the life history of each stock, for example when the fish spawn, how long they live, and what they eat. Staff also research how changes in the marine environment may affect fish stocks.

The state of the stock refers to the numbers of fish in the population or their total weight, known as the stock biomass. The aim is to provide fishery managers - the Government and the European Commission - with information on the state of stocks. They can then make decisions on exploitation rates to sustain the stocks and the management actions necessary to achieve them.

Many of the stocks of interest to Scotland are shared with other nations. In general, scientific advice is based on a pool of information provided by several European fishery nations. In a process known as stock assessment, scientists estimate the past and current state of the stocks. Four main measures are considered in the determination of the health of exploited fish populations:

  • Fishing Mortality (F) - A measure of the rate at which fish are removed from the stock. This can be related to the proportion of the stock taken out each year by fishing.The figure below illustrates this relationship
  • Spawning Stock Biomass ( SSB) - The total weight of mature fish (capable of spawning) in the population
  • Recruitment - The number of young fish produced each year which survive from spawning to enter the adult stock and the fishery.
  • Landings - The total annual tonnage of fish taken from the stock and landed by the fishing fleet.

Every year scientists at MSS, as well as other members of the International Council for the Exploration of the Sea ( ICES), look at the changes in these characteristics and forecast what is likely to happen in the future. This information underpins the basis of fisheries advice and subsequent management action.

How fishing mortality rates (F) translate into annual removal rates

How fishing mortality rates (F) translate into annual removal rates


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