Ecology

Pelagic Predators Face Double Jeopardy, Too

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Science  15 Jul 2011:
Vol. 333, Issue 6040, pp. 268
DOI: 10.1126/science.333.6040.268-b

Swordfish

CREDIT: WERNER/ HISTOIRE NATURELLE DES POISSONS

Human impacts on terrestrial predators have not only decreased their abundance but also resulted in extirpation of populations and subsequent range contraction. Species in these conditions face “double jeopardy” because their populations are both smaller and found in fewer places. Pelagic predators have much greater mobility than terrestrial predators, suggesting, perhaps, that range contractions may not accompany reduced abundance in these species. Worm and Tittensor, however, found this not to be the case. Three large, global fisheries databases were used to quantify the presence or absence of 13 tuna and billfish species at 5° intervals over all the world's oceans, and across three decades. Nine out of 13 of these species have experienced significant range contractions, and those with the greatest decreases in abundance have had the greatest reductions in their range. For example, Atlantic blue fin tuna has experienced a 46% decrease in range size. Such contractions remove apex consumers from many regions where they were previously present—a factor that could have a large impact on the marine ecosystem.

Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1102353108 (2011).

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