Sinking Whales

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Science  24 Oct 2003:
Vol. 302, Issue 5645, pp. 537
DOI: 10.1126/science.302.5645.537b

We tend to think that if only we stop human depredations on a wild animal population, it will then recover. A longer-term analysis by Springer et al. suggests the reverse.

These authors have traced the knock-on effects of industrial whaling since the 1940s in the North Pacific Ocean. They suggest that with the demise of the great whales, killer whales shifted their attentions to smaller sea mammals. A similar phenomenon seems to have occurred in the Southern Ocean, which was once home to vast whale populations. This “top down” effect, rather than the “bottom up” effect of a decrease in prey for the smaller mammal species, may explain the sudden decline in Steller sea lion populations, as well as those of several other seals and of sea otters, in the North Pacific since the 1980s. An added complication is that as whale populations increase, they are checked as they again become vulnerable to the adaptable killer whales. It seems that even if human beings cease implementing techniques for industrial-scale slaughter in the oceans, the disturbances to long-established ecosystems may be irreversible. — CA

Proc. Natl. Acad. Sci. U.S.A. 100, 12223 (2003).

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