Fishing quotas are set politically, each year the Fisheries Ministers meet in December to set next year's fishing quotas, a ministerial meeting that attracts a lot of media attention. The Ministers shall take their decisions, inter alia: Based on an assessment of the number of fish in the sea and the risks associated with different future fishing quotas. This assessment takes place during the year and is coordinated through the International Council for the Sea (ICES). The studies and analyses are carried out by researchers employed by the national fisheries research institutes. In Denmark it is "Denmark's fisheries surveys" that are responsible for the Danish contribution to this international work.
Assessing how many fish are in the sea is a measuring task of the same nature as many other metrics (statistics) that we make every day. The basis is the amount of captive fish (not only from the quantities landed), broken down by species and size, samples of the trapped fish to determine the age distribution and fishing with sea-research vessels in order to obtain an assessment of the quantity of fish without the influence Fishing grounds are represented by fisheries. Fishing does not take a random sample of the population, but chooses its fishing grounds with high concentrations of fish in the sizes that have market value. It is therefore essential to correct the impact of fishing on selected seats in the assessment.
Proposal for a fishing quota shall be based on a forecast of 1) how the quota will affect the stock and 2) What impact the future expected stock level will have on the ability of the stock to continue to reproduce itself (sustainability). However, stock development is not only dependent on fishing, but also depends on many other factors, such as currents, temperature and oxygen conditions (survival of eggs and larvae), the amount of other fish (fish eat fish), diseases (which may be introduced by pollution), etc. Many of these factors are not foreseeable and therefore the influence of these factors as "noise" and the prognosis on probabilities, such as the likelihood of the stock falling below the limit of a particular fishery, must be addressed. Since fish are needed to ensure the reproduction and thus conserve the stock, we must put the fishing quota in such a way that the probability is very small for the Bestan to fall below the limit at which the reproduction can no longer be maintained. This means that the natural event which, in association with a certain fishing quota, could threaten the stock only occurs very rarely i.e. With very little probability. Loosely, we are talking about securing the stock against a collapse triggered by fisheries.
The calculation of probabilities (risks) for adverse events is based on our historical experience of how the systems behave. Such data may, for example, be the frequency of small vinings even in good condition. However, we have only systematically collected data since about 1880 and for many stocks we started around 1950 or even later collecting data systematically. Naturally, nature has many more possible incidents than we have experienced in this rather short period of time. You are therefore working to get data that goes much further back in time. This is not the usual data from the fisheries research industry, but instead is used for example tax reporting to the king.
See more at: http://www.ices.dk