VANCOUVER - Overfishing is taking a heavy toll on marine predators such as sharks, tuna and swordfish, says a new study by scientists at the University of British Columbia.
The study, published online Monday in the journal Marine Ecology Progress Series, says predator species in north Pacific and Atlantic waters have dropped by more than 90 per cent since the 1950s.
The study found that predator species are also experiencing a dramatic decline in the south seas as those species are caught and sent to northern markets for consumption.
"It's important because fish are the last food we harvest from the wild at any type of scale," said lead author Laura Tremblay-Boyer. "When you eat fish, it's usually a predator fish. Whether it's a fish stick or you're at the restaurant, it most likely comes from another country."
Tremblay-Boyer, now a PhD student at UBC, said she conducted the research while finishing her master's degree.
Because it's impossible to count fish in the world's oceans, Tremblay-Boyer and her fellow researchers developed a model that analyzed data such as ocean temperature, the presence of algae, and the distance in the food chain that predator species were to the algae, much like a food pyramid.
The scientists also used a global database of fisheries catches between 1950 and 2006.
Tremblay-Boyer said the results were much like checking a bank account balance for the world's oceans.
"The global overview we have is most definitely not showing a great account balance," she said. "It's going down."
She also said fishing is a huge driving force in the deterioration of the marine ecosystem, noting that the removal of fish from the ocean can be compared to clearcuts in the Amazon.