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Marine Ecology Progress Series

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MEPS 442:169-185 (2011)  -  DOI:

Modelling the effects of fishing on the biomass of the world’s oceans from 1950 to 2006

Laura Tremblay-Boyer1,*, Didier Gascuel2, Reg Watson1, Villy Christensen1, Daniel Pauly1

1Fisheries Centre, Aquatic Ecosystem Resource Laboratory, University of British Columbia, 2202 Main Mall, Vancouver, BC V6T 1Z4, Canada
2Université Européenne de Bretagne, UMR Agrocampus Ouest / INRA Ecologie et Santé des Ecosystèmes, 65 rue de Saint-Brieuc, CS 84215, 35042 Rennes Cedex, France

ABSTRACT: Marine fisheries have endured for centuries but the last 50 yr have seen a drastic increase in their reach and intensity. We generated global estimates of biomass for marine ecosystems and evaluated the effects that fisheries have had on ocean biomass since the 1950s. A simple and versatile ecosystem model was used to represent ecosystems as a function of energy fluxes through trophic levels (TLs). Using primary production, sea surface temperature, transfer efficiency, fisheries catch and TL of species, the model was applied on a half-degree spatial grid covering all oceans. Estimates of biomass by TLs were derived for marine ecosystems in an unexploited state, as well as for all decades since the 1950s. Trends in the decline of marine biomass from the unexploited state were analyzed with a special emphasis on predator species as they are highly vulnerable to overexploitation. This study highlights 3 main trends in the global effects of fishing: (1) predators are more affected than organisms at lower TLs; (2) declines in ecosystem biomass are stronger along coastlines than in the High Seas; and (3) the extent of fishing and its impacts have expanded from north temperate to equatorial and southern waters in the last 50 yr. More specifically, this modelling work shows that many oceans historically exploited by humans have seen a drastic decline in their predator biomass, with approximately half of the coastal areas of the North Atlantic and North Pacific showing a decline in predator biomass of more than 90%.

KEY WORDS: Ecosystem modelling · Fisheries · Marine predators · Energy flow · Trophic level

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Cite this article as: Tremblay-Boyer L, Gascuel D, Watson R, Christensen V, Pauly D (2011) Modelling the effects of fishing on the biomass of the world’s oceans from 1950 to 2006. Mar Ecol Prog Ser 442:169-185.

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