Pelagic Fisheries Research Program
University of Hawaii at Manoa
Joint Institute for Marine & Atmospheric Research
1000 Pope Rd. MSB 312, Honolulu, HI 96822
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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):

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More recent postings listed at the end of this section:

Critique from Hampton, Sibert and Kleiber (PDF, 346 KB)
Send comments or questions to: John Hampton, John Sibert, Pierre Kleiber
The editors of Nature declined to print the following letter because it does not "take our
knowledge forward in some discernible way". The signers of this letter have the same opinion of the Myers and Worm letter.
Letter to the Editors of Nature (PDF, 10 KB)

The following letter was sent to U.S. Senator John McCain of the Senate Committee
on Commerce, Science and Transportation on the occasion of June 12, 2003.
Letter to Senator John McCain (PDF, 7 KB)

The record of the Commerce Committee hearing can be viewed at:

Can biomass time series be reliably assessed from CPUE time series data only? (PDF 189 KB)
Send comments or questions to: Francis Laloë,

Ecosimple: A new individual based model tool for application to ecosystem-based fishery
management. It includes real-time management intervention from the user, effects of research, marine reserves, habitat, realistic graphics, and sound effects, and it operates from the perspective of the fish. Anyone who succeeds in maintaining a balanced ecosystem should contact the PFRP and convey the text of the verification message. It may confer eligibility to publish in Nature. Development of this software was not supported by the Pew Charitable Trust or by anyone else we can get to admit to it.
Ecosimple Read Me file (PDF)
Ecosimple.exe file (1.3 MB)

We are not alone. Nature declined to print a critique of an article on the impacts of
aquaculture on wild fisheries. The critique was eventually published in the report of the ICES Working Group on Environmental Interactions of Mariculture. The associated web site is of interest:

Tuna Longline Catch Rates in the Indian Ocean (PDF, 212 KB)
Send comments and questions to: Tom Polacheck,
Are the Apparent Rapid Declines in Top Pelagic Predators Real? (PPT, 1.6 MB)
PowerPoint presentation to the Scripps Institution of Oceanography Ecology Seminar,
March 12, 2003, Mark Maunder, Shelton Harley, Mike Hinton et al. (PDF version, 679 KB)
Folly and fantasy in the analysis of spatial catch rate data. (PDF, 131 KB)
Carl Walters, Can. J. Fish. Aquat. Sci./J. Can. Sci. Halieut. Aquat. 60(12): 1433-1436 (2003)

Nature Stumbles (PDF, 79 KB) by Menachem Ben-Yami, World Fishing, 2003 (8):10
Comments and questions to Menakhem Ben-Yami,
Related commentary by Ben-Yami can be found at
Problems with interpreting catch-per-unit-of-effort data to assess the status of individual
stocks and communities: Is integrated stock assessment, ecosystem modeling, management strategy evaluation, or adaptive management the solution? (PPT, 1.7 MB)
PowerPoint presentation to the Fourth World Fisheries Congress, Vancouver, BC, Canada
May 2-6, 2004, Mark N. Maunder, John R. Sibert, Alain Fonteneau, John Hampton, Pierre
Kleiber, and Shelton J. Harley. (PDF version and additional notes)


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This page updated May 21, 2004