Tagged tuna graphic by Nancy Hulbirt, SOEST Illustration.

Changes in the Biomass of Large Pelagic Predators

In a recent letter to Nature (423:280 - 283, May 15, 2003), Myers and Worm present an analysis of catch and effort data from various trawl fisheries and from the Japanese longline fishery for various ocean regions dating back to the beginning of industrial fisheries exploitation. Their analysis aggregates catch across species for each fishery type and interprets the resulting aggregate CPUE as a time-series measure of "community biomass". Rapid declines in CPUE during the 1950s and 1960s were observed, leading the authors to conclude that "industrialized fisheries typically reduced community biomass by 80% during the first 15 years of exploitation", and that "large predatory fish biomass today is only about 10% of pre-industrial levels". In the case of tuna fisheries, in particular the fisheries for tropical tunas, many tuna experts contend that these conclusions are fundamentally flawed. This web site hosts a number of critiques of this paper as well as other interpretations of longline CPUE from various ocean regions. The views presented below are those of the authors and do not reflect the views of their employers or funders of their research.

The Letter to Nature letter can be obtained from the link below (subscription or payment may be required): http://www.nature.com/nature/index.html

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