Large fish in world's oceans disappearing, study says

By ALANNA MITCHELL
Globe and Mail Update

Every single species of large wild fish from the tropics to the poles has been fished so systematically over the past 50 years that just 10 per cent of each type remains, according to the first scientific study to assess the fish left in the global ocean.

And those left in the sea are roughly half the size they were before industrialized fishing began in about 1950, says the study which appears on the cover of Thursday's issue of the scientific journal Nature.

The study by marine biologists Ransom Myers of Dalhousie University in Halifax and Boris Worm of the Institute for Marine Science in Kiel, Germany, catalogues biological destruction that is unprecedented in this geological era in its global scope and rapidity.

"We have to quit thinking about the ocean as a blue frontier," said Dr. Myers, who is Killam Chair of Ocean Studies at Dalhousie. "What we have is a remnant."

Dr. Worm, who is the Emmy-Noether Fellow in Marine Ecology at the German Institute, was more blunt. The entire global ocean, which makes up 70 per cent of the Earth's surface, is no longer even close to its natural state.

"It is now a man-made system," he said, adding that it may be less stable and is probably less predictable as a stablizing force of the planet.

"We are tampering with the life-support system of the planet and that's not a good thing to do," Dr. Worm said.

The fish hit hardest are at the top of the ocean's food chain, and their loss has a profound effect on the whole ecosystem of the global ocean. It is akin to cutting off the head of a whole ecosystem, Dr. Myers said.

Some species are perilously close to the point of no return, the study found. The ocean's large sharks will die out unless the fishery catch in the planet's open ocean falls by 50 to 60 per cent, Dr. Myers said. And many other species are also in peril.

The fate of the Atlantic cod, whose population has been cut down to 1 per cent of its pre-1950 numbers, is unknown, one of the scariest signals of how unpredictable biological destruction on this level can be, Dr. Myers said. And the Pacific sardines are showing no signs of recovery either, he said.

But other species may be able to recover if strong measures to cut levels of fishing are taken immediately, Dr. Worm said. He drew comparisons with large land predators such as lions and tigers. Without aggressive measures 40 or 50 years ago, they would be extinct now.

The two scientists said that the critical next step is to fish dramatically less and set up reserves for some of the most important marine breeding areas. Now, 99.9 per cent of the world's oceans are open for fishing.