Estimating Fish Abundance in the North Atlantic, 1950 to 2000

V. Christensen, S. Guenette, S. Heymans, C. J. Walters, R. Watson, D. Zeller, D. Pauly, (2001). “Estimating Fish Abundance in the North Atlantic, 1950 to 2000,” Fisheries Centre Research Reports No. 9 (Fisheries Centre, University of British Columbia, Vancouver, Canada biomass, saup, landings, Atlantic

We estimate the biomass of high trophic-level fish in the North Atlantic at a spatial scale of 1⁄2 degree latitude by 1⁄2 degree longitude over the time period from 1950 to 1999, based on 23 spatialized, ecosystem models, each constructed to represent a given year or short period from 1880 to 1998. We extract over 7800 data points that describe the abundance of high trophic-level fishes as a function of year, primary production, depth, temperature, latitude, ice cover, and catch composition. We then use a multiple linear regression to predict the spatial abundance for all North Atlantic spatial cells for each year from 1950 to 1999. The results indicate that the biomass of high trophic-level fishes has declined by two-thirds during the fifty-year period. Catches increased from 2.4 to 4.7 million tonnes annually in the late 1960s, and subsequently declined to below 2 million tonnes annually in the late 1990s. The fishing intensity for high trophic-level fishes tripled during the first half of the time period, and remained high during the last half of the time period. We estimate that the high trophic-level species contributed 53% to the value of total fish landings in 1950, and that this declined to 29% by the end of the century. Comparing the fishing intensity to similar measures from 35 assessments of high trophic-level fish populations from the North Atlantic, we conclude that the trends in the two data series are similar. Our results raise serious concern for the future of the North Atlantic as a diverse, healthy ecosystem, we may soon be left with only low trophic-level species in the sea.