Declining sharks

The transformation of terrestrial and coastal ecosystems by humans is well known, but only recently have the impacts of anthropogenic forces in the open ocean been recognized. In particular, intense exploitation by industrial fisheries is rapidly changing oceanic ecosystems by drastically reducing populations of many marine species. For most oceanic species we lack a historical perspective.

In an important article to shortly appear in Ecology Letters, Baum and Myers demonstrate that the initial abundance of large apex predator populations, sharks, was enormously greater than is currently recognized. They estimate that since the onset of intense exploitation in the Gulf of Mexico in the 1950s, the pelagic shark assemblage has declined by over 80%, and the oceanic whitetip shark, initially the most common species, by over 99%. Remarkably, there is no conservation attention focused on this species. Rather it is all but forgotten in the Gulf of Mexico, with no recognition of its former prevalence in the ecosystem. That declines of this magnitude in these conspicuous species could go virtually unnoticed demonstrates how little we understand about the ocean.