Marine Predators İn Trouble: UBC Researchers

Iconic marine predators such as sharks, tunas, swordfish, and marlins are becoming increasingly rare under current fishing trends, say University of British Columbia researchers. In half of the North Atlantic and North Pacific waters under national jurisdiction, fishing has led to a 90-per-cent decrease in top predators since the 1950s, and the impacts are now headed south of the Equator, according to a new study published online December 5 in the journal Marine Ecological progress Series.

Funded by the Pew Charitable Trusts, the Natural Sciences and Engineering Research Council of Canada (NSERC), and the French Consulate-General in Vancouver, researchers from UBC's Fisheries Centre modeled the impact of fishing around the world using global databases of fisheries catches from 1950 to 2006 and satellite images of phytoplankton, which are used to map where predators should be, based on food availability.

The scientists found that the exploitation of marine predators first occurred in coastal areas of northern countries, then expanded to the high seas and to the southern hemisphere. The decline of top-of-the-food-chain predators also means widespread and fundamental changes to both the structure and function of marine systems.

"Species such as tuna have been seriously exploited because of high market demand," says Laura Tremblay-Boyer, a PhD student at UBC Fisheries Centre and lead author of the study.

"A constant theme throughout our study of global marine ecosystems is that these top predators are today prey for human beings, assisted by some serious technology," says Tremblay-Boyer. "Top marine predators are more intrinsically vulnerable to the effects of fishing due to their life histories. Bluefin tuna, for instance, cannot reproduce until age nine."