Overexploitation of stocks

06 Aug 2015

Worldwide global fishing fleets are two to three times larger than the oceans can sustainably support, says a new European Commission study published in the journal 'PLOS One'.

In the Mediterranean and Black Seas, several fish stocks have been reported as overexploited based on traditional assessment methods, such as data recorded by national authorities, regular stock assessments or scientific surveys.

The research was conducted because the traditional methods of stock assessment were designed to measure single species fisheries, not different species. This means that current surveys could be missing up to 80% of landed fish from the Mediterranean, according to some estimates.

This research aimed to address the problem by using a more comprehensive set of data to measure all stocks for which there is landing data, and to assess the degree of exploitation of fish stocks in the different subdivisions of the Mediterranean and Black seas between 1970 and 2010.

This included looking at the variability of total landings over time, the number of recorded stocks, the ‘trophic level’ of the catch and the ‘fishing-in-balance index’.

The results showed that overexploited and collapsed stocks were increasing at a rate of 44, 33, and 38 stocks per decade for the western, central, and eastern Mediterranean, respectively, and 13 stocks per decade for the Black Sea.

It also showed that the pattern of exploitation and the state of different fish stocks varied among the different subdivisions, with the eastern Mediterranean and Black Sea notably worse than the western and central Mediterranean, where the total percentage of overexploited and collapsed stocks exceeded 50% and growing populations were less than 10%.

Such data should be used to inform and improve marine management and policy, the authors say.

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