VICTORIA, British Columbia, Dec. 5 (UPI) -- Current fishing trends are making iconic marine predators such as sharks, tuna, swordfish and marlin increasingly rare, Canadian researchers say.
Half of the North Atlantic and North Pacific waters under national jurisdiction have experienced a 90 percent decrease in the populations of top predators since the 1950s, researchers from the University of British Columbia report in the journal Marine Ecological Progress Series.
Researchers from UBC's Fisheries Center modeled the impact of fishing around the world using global databases of fisheries catches from 1950 to 2006, a university release said Monday.
"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," UCB researcher Laura Tremblay-Boyer said. "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."
Exploitation of marine predators started in coastal areas of northern countries, and then expanded to the high seas and to the southern hemisphere, they said.
"After running out of predator fish in the north Atlantic and Pacific, rather than implementing strict management and enforcement, the fishing industry pointed its bows south," study co-author Daniel Pauly said. "The southern hemisphere predators are now on the same trajectory as the ones in the northern hemisphere. What happens next when we have nowhere left to turn?"