The world's fishing stocks will collapse before mid-century, devastating food supplies, if overfishing and other human impacts continue at their current pace, according to a global study by scientists in five countries.

Already, nearly one-third of fished species — including bluefin tuna, Atlantic cod, Alaskan king crab and Pacific salmon — have collapsed and the pace is accelerating, the report says.

If that trend continues, the study predicts that "100 percent of (fished) species will collapse by the year 2048 or around that," said marine biologist Boris Worm, who led the research team. A fishery is considered collapsed if catches fall to 10 percent of historic highs.

Without more protection, the world's ocean ecosystems won't be able to rebound from the shrinking populations of so many fish and other sea creatures, the scientists reported today in the journal Science.

In recent years, marine scientists have warned of the toll of overfishing in many regions, but the new report, global in scope, offers one of the grimmest predictions for the future of the world's fisheries.

Yet there is hope, the scientists concluded: "Available data suggest that at this point, these trends are reversible."

If more protections are put into place, such as new marine reserves and better managed commercial fisheries, seafood supplies would surge and the oceans could recover, they said.

"The good news is that it is not too late to turn things around," said Worm, an assistant professor of marine conservation biology at Dalhousie University in Halifax, Nova Scotia. "It can be done, but it must be done soon."

The authors are 14 marine scientists, and funding came from the National Science Foundation, the University of California, Berkeley, and University of California, Santa Barbara.

GLOBAL ANALYSIS

The scientists spent four years analyzing 32 controlled experiments, other studies from 48 marine protected areas and global catch data from the U.N. Food and Agriculture Organization's database of all fish and invertebrates worldwide from 1950 to 2003.

The scientists also looked at a 1,000-year time series for 12 coastal regions, drawing on data from archives, fishery records, sediment cores and archaeological data.

The National Fisheries Institute, a U.S. fishing industry group, disputed the findings, saying that fishermen and government already have acted and that federal data "show more than 80 percent of fish stocks are sustainable and will provide seafood now and for future generations."

"Fish stocks naturally fluctuate in population. Fisheries scientists around the world actively manage stocks and rebuild fisheries with a low sustainable population," the institute said.

The group said that for the past 25 years, catches have been steady, with wild fisheries providing 85 million to 100 million metric tons annually, and aquaculture — fish farming — helping to fill the growing demand.

The scientists, however, said they are confident of their predictions because they found "consistent agreement of theory, experiments and observations across widely different scales and ecosystems."

Delving into recent catch data around the world as well as a thousand years of historical archives in regions such as San Francisco Bay, the team reported that estuaries, coral reefs, wetlands and oceanic fish are all "rapidly losing populations, species or entire functional groups."

'SABOTAGES STABILITY'

Scarcity of a highly nutritious food supply for the world's growing human population will be the most visible effect of declining ocean species. But the scientists said other disruptions also are occurring as ocean ecosystems unravel.

Biologists have long debated the lasting effect of removing a few species from oceans. The authors of the new report conclude that it "sabotages their stability" and recovery from stresses.

Water quality is worsening, and fish kills, toxic algal blooms, dead zones, invasive exotic species, beach closures and coastal floods are increasing, as wetlands, reefs and the animals and plants that filter pollutants disappear. Climate change also is altering marine ecosystems.

"Our analyses suggest that business as usual would foreshadow serious threats to global food security, coastal water quality and ecosystem stability, affecting current and future generations," the report says.

FOOD CHAIN SUFFERS

Other creatures are in danger of food shortages, too, biologists say.

"Animals like seals, dolphins and killer whales eat fish. If we strip the ocean of these kinds of species, other animals are going to suffer," said co-author Stephen Palumbi of Stanford, who specializes in marine evolution and population biology.

Many scientists not involved in the study echoed its findings yesterday, saying they are witnessing symptoms of crashing fish populations. P. Dee Boersma, a University of Washington scientist who has observed Argentina's depleted penguin populations travel farther in search of food, said "this message of collapse and long-term damage is an important one."

In Maine, marine scientist Robert Steneck said depletion of cod and other fish triggered an imbalance that caused lobster populations to surge and left the region with a fragile and unsustainable "monoculture that is the direct result of the overfishing Worm and others describe."

The strength of the new report "lies in the breadth of the array of information the authors used for their analysis," said Andrew Sugden, Science's international managing editor.