Líf- og umhverfisvísindastofnun

When is a fish stock collapsed?

Föstudagur, September 15, 2017 -
12:30 to 13:10
Nánari staðsetning: 

Will Butler, PhD student in MARICE, University of Iceland, will present his research:

Marine fish stock collapses are a principle concern for both scientists and society due to the high associated risks to biodiversity and food security. Although the public perception is that global fisheries are generally in a depleted state, high profile scientific reports on general trends in fish stock declines have been strongly contested, and the actual occurrence rate of stock collapses remains unclear. Here we propose a precise collapse definition to achieve clarity in the way fish stock status is assessed. Our study shows that existing criteria for stock collapse are numerous, and that a stock’s status is highly sensitive to changes in the collapse definition’s formulation. Unlike most existing definitions, our definition is process-based; it captures not only the decline event, but also the ensuing period of prolonged depletion and recovery potential. These attributes allow the definition to accurately distinguish a collapse from less severe depletions or natural fluctuations, identifying specific stocks that are in greatest need of reparatory measures. Through standardized use of species-specific generation times, the definition enables systematic evaluation of several ecologically and socioeconomically important fish stocks. Our study advocates the consistent use of definitions to promote co-operation across disciplines, and clear, accurate communication of science to both the public and policy-makers to ensure global healthy fish stocks in the future.


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