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Effect of longlining on pelagic fish
stocks - tuna scientists reject conclusions of Nature article
John
Hampton, John R. Sibert, and Pierre Kleiber
29/05/2003
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[View the document]
(pdf 346k)
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Introduction. Myers
and Worm (2003) present an analysis of Japanese longline and trawl fishery
catch and effort data 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 aggregate
CPUE so obtained as a time-series measure of “community biomass”.
Rapid declines in CPUE during the 1950s and 1960s were observed, leading
the authors to suggest 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, these conclusions are fundamentally flawed.
This note reviews the conclusions of Myers and Worm in relation to
available data for the Pacific, concentrating on the region west of 150°W
(referred to as the western and central Pacific). The comments are grouped
under headings that deal with the main issues of concern with the Myers
and Worm analysis.
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