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Science 30 March 2007:
Vol. 315. no. 5820, p. 1764
DOI: 10.1126/science.315.5820.1764i
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The loss of large predators from ecosystems, often caused by human activities, can have effects that cascade through the rest of the food chain. Myers et al. (p. 1846) quantitatively assess the ecosystem consequences of the functional elimination of top predators from a northwest Atlantic marine environment. The loss of 11 species of large sharks, with numerical declines during a 35-year period of up to >99%, resulted in population increases in 12 out of 13 species of smaller sharks, rays, and skates eaten almost exclusively by large sharks. One of these, the cownose ray, has increased 20-fold since 1970. Its prey, bivalve mollusks, have been reduced to levels where commercial shellfisheries have suffered and where the water-filtering service of their remnant populations has been compromised.




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Science. ISSN 0036-8075 (print), 1095-9203 (online)