Biodiversity Loss in the Ocean: How Bad Is It? [research paper]
Science 1 June 2007:
Vol. 316 no. 5829 pp. 1281-1284
DOI: 10.1126/science.316.5829.1281b
The Research Article Impacts of biodiversity loss on ocean ecosystem services By B. Worm et al. (3 Nov. 2006, p. 787) projects that 100 of seafood-producing species stocks will collapse by 2048.
The projection is inaccurate and overly pessimistic.
Worm et al. define collapse as occurring when the current year’s catch is <10 of the highest observed in a stock’s time series. However, fish catch is rarely an adequate proxy for fish abundance, particularly for rebuilding stocks under management. A variety of biological, economic, and social factors and management decisions determine catches; low catches may occur even when stocks are high (e.g., due to low fish prices or the effects of restrictive management practices), and vice versa.
The inadequacy of Worm et al.‘s abundance proxy is illustrated by the time series of data for Georges Bank haddock (Melanogrammus aeglefinus). The highest catch for haddock occurred in 1965 at 150,362 tons (1). This catch occurred during a period of intense domestic and international fishing (1).
In 2003, haddock catch was 12,576 tons, or 8 of the time series maximum. Under the Wormet al. definition, the stock would be categorized as collapsed in 2003. However, stock assessment data (1) estimate the total magnitude of the spawning biomass in 2003 to be 91 of that in 1965. Comparing the estimate of spawning stock biomass in 2003 to the level producing maximum sustainable yield (MSY), the stock was not even being overfished in 2003 (2).
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