90% of large fish in world's oceans gone, study says

The collapse of Atlantic cod stocks, far from being an unusual disaster, is typical of what's happening to large fish around the world, a major study has found.

Industrial fishing has cut populations of large fish in the oceans to a mere 10 per cent of 1950 levels, says the study, published today in Nature magazine.

The devastating decline affects open ocean species such as tuna, swordfish and marlin, and groundfish such as cod, halibut and flounder.

"Our analysis suggests that the global ocean has lost more than 90 per cent of large predatory fishes," study authors Ransom Myers and Boris Worm of Dalhousie University say.

Myers says the world is in "massive denial", spending its energy fighting over the few fish left instead of cutting harvests before it's too late.

"We have to understand how close to extinction some of these populations really are," he said in an interview.

"And we must act now before they reach the point of no return."

"We are in massive denial and continue to bicker over the last shrinking numbers of survivors, employing satellites and sensors to catch the last fish left," Myers said.

The researchers spent 10 years collecting data on large fish in four continental shelf and nine oceanic systems from the beginning of record-keeping to the present.

They concluded that industrial fishing, using sensors and satellites, takes only 15 years to reduce a new fish community to a tenth of its original size.

"The amazing thing is, all these data sources show almost identically the same pattern," Myers said in an interview.

Most managers have no idea how much depletion has occurred because they don't realize how abundant the resource once was, Worm said.

"The impact we have had on ocean ecosystems has been greatly underestimated."

Large fish are not only declining in numbers, they no longer attain the size they once did, the scientists say. The few blue marlin caught today weigh one-fifth of what they once did.

The depletion has occurred even in open ocean where untapped reservoirs of fish were presumed to exist. Japanese longline fishing, using lines with thousands of hooks, is a major factor.

Many fish are under such intense harvesting pressure they never get a chance to reproduce, the researchers say.

Myers dismisses the arguments of Newfoundland Premier Roger Grimes who has bitterly protested the federal closure of the Newfoundland cod fishery.

"This is absurd. They have these pictures and say, `Look at all these fish that are there.' They're baby fish! They can't catch the quota that they have. I view it as sheer idiocy."

He maintains that harvesting must be cut by at least 50 per cent, pointing to Alaska as a jurisdiction where sustainable fishing is practised successfully.

"We can, as a society or societies, decide to fish the sea in a rational fashion and obtain more benefit certainly than we are obtaining at the moment.

"It's not the technology, it's the lack of control over the technology. They have factory ships in Alaska and yet they have a sustainable fishery."