World's hot spots for large fish shrinking

[Metal Angler]

The diversity of tuna, marlin, swordfish and other ocean predators has dropped 50 per cent in the past 50 years, according to a new study.

Ecologists and oceanographers teamed up to build the first global map of hot spots for large predatory fish in the open ocean.


The recorded catch dropped 25 per cent in the Pacific and 50 per cent in the Atantic and Indian Oceans since 1952.
"If someone puts a fishing line in the ocean now he will catch only half as many species as 50 years before," said study co-author Boris Worm of Dalhousie University in Halifax.

Unlike previous research, the new study in Friday's issue of the journal Science looks at the effects of climate and fishing on a global scale.

Environmental effects like El Nino affect fish populations in the short term, but overfishing is the main force driving declines in the variety of big fish, the authors conclude.

Five hot spots remain and should be protected, said Worm, who has presented the data to the United Nations. He hopes the body will act to slow the silent, hidden collapse of the world's largest ecosystem.

The areas are:

East of Florida.
South of the Hawaiian Islands.
Southeast Pacific, particularly north of Easter Island.
East of Sri Lanka in the Indian Ocean.
East of the Great Barrier Reef in Australia.

The hot spots are mostly in warm waters with enough oxygen to support the zooplankton and small fish that larger fish feed on, the researchers found.

In fact, tuna show the same diversity pattern as zooplankton, said Steven D'Hondt, a zooplankton researcher who published the only other global study of ocean diversity.

The data suggests diversity declined by about 50 per cent on average in the Atlantic and Indian Oceans, and 25 per cent on average in the Pacific.




FROM MAY 14, 2003: Big fish disappearing from oceans

Two years ago, Worm and co-author Ransom Myers of Dalhousie found a decline in the number of fish. They concluded the world's oceans have lost 90 per cent of predatory fish that flourished 50 years ago.

Both papers used data from Japanese longline catches, using massive nets with thousands of hooks stretched across the ocean to catch everything in their path. The data set spans from 1952 to 1999.

The research was funded by the Sloan Foundation, German Research Council, Pew Charitable Trust and the Natural Sciences and Engineering Council of Canada.

World's hot spots for large fish shrinking
Last Updated Thu, 28 Jul 2005 22:00:25 EDT
CBC News