Great Fish Going the Way of the Dinosaurs

"From giant blue marlin to mighty bluefin tuna, and from tropical groupers to Antarctic cod, industrial fishing has scoured the global ocean. There is no blue frontier left," says lead author Ransom Myers, a fisheries biologist based at Dalhousie University in Canada. "This isn't about just about one species," he says. "The sustainability of fisheries is being severely compromised worldwide."

"The impact we have had on ocean ecosystems has been vastly underestimated," says coauthor Boris Worm of Dalhousie University and the University of Kiel in Germany. "These are the megafauna, the big predators of the sea, and the species we most value. Their depletion not only threatens the future of these fish and the fishers that depend on them, it could also bring about a complete reorganization of ocean ecosystems, with unknown global consequences."

Their 10 year long study based on data sets representing all major fisheries in the world, shows that industrial fisheries take only 10 to 15 years to reduce any new fish community they encounter to one tenth of what it was before. The research will be published as the cover story in tomorrow's issue of the international journal "Nature."

"Since 1950, with the onset of industrialized fisheries, we have rapidly reduced the resource base to less than 10 percent - not just in some areas, not just for some stocks, but for entire communities of these large fish species from the tropics to the poles," said Myers.

The authors constructed trajectories of biomass and composition of large predatory fish communities from four continental shelves and nine oceanic systems, from the beginning of exploitation to the present.

For shelf ecosystems they used data from standardized research trawl surveys to track the decline in the populations of large fishes.

To measure the decline in open ocean ecosystems, the researchers used Japanese longlining data. Pelagic longlines are the most widespread fishing gear, and the Japanese fleet is the most widespread longline operation, covering all oceans except the circumpolar seas.

Longlines catch a wide range of species in a consistent way over vast areas, but today the hooks are coming up empty more often than not. "Whereas longlines used to catch 10 fish per 100 hooks, now they are lucky to catch one," says Myers.

"The longlining data tell a story we have not heard before, says Daniel Pauly, a fisheries scientist from the University of British Columbia. "It shows how Japanese longlining has expanded globally. It is like a hole burning through paper. As the hole expands, the edge is where the fisheries concentrate until there is nowhere left to go."

Pauly says that because longlining technology has improved, the authors' estimates are "conservative," and "the declines are even greater than they are saying."

"We have forgotten what we used to have," says Jeremy Jackson of the Scripps Institution of Oceanography. "We had oceans full of heroic fish - literally sea monsters. People used to harpoon three meter (10 foot) long swordfish in rowboats. Hemingway's "Old Man and the Sea" was for real," he said, referring to Ernest Hemingway's novel.

"Where detailed data are available we see that the average size of these top predators is only one fifth to one half of what is used to be. The few blue marlin today reach one fifth of the weight they once had. In many cases, the fish caught today are under such intense fishing pressure, they never even have the chance to reproduce," says Myers.

ÒThe findings of the Nature study should be a wake-up call to fishery managers and regulators all over the world," said Dr. Michael Hirshfield, chief scientist of Oceana, an ocean conservation organization based in Washington, DC.

"Without immediate action," Hirshfield said, "fishery managers will not have anything left to manage -- and fishermen will have nothing left to catch. For years, the conservation community and responsible fishermen have argued that the ocean is not limitless, and have called for actions to prevent overfishing, reduce wasted catch, and limit the use of destructive fishing gear."

This year, Oceana started two campaigns to stop harmful fishing practices. The Stop DirtyFishing campaign is working to eliminate the approximate 44 billion pounds of fish -- an amount equal to 25 percent of the world catch -- that are wasted in the course of commercial fishing.

The Stop Bottom Trawling campaign is working to prohibit the use of bottom trawling fishing gear, a method of fishing that Hirshfield calls "the worldÕs damaging," because it causes "unselective and systematic destruction of the ocean."

Myers and Worm sent their findings to many of the top fisheries scientists in the world for review. They found acceptance of the overall pattern of rapid depletion of fish populations, but when it came to the current status of individual species, especially tuna, says Myers, some fisheries managers "find it very hard to accept."

Myers has dealt with this type of denial when he was a fisheries biologist with the Canadian Department of Fisheries and Oceans in Newfoundland during the 1980s. He fought to save the Atlantic cod, which were declared and endangered species by the Canadian government last week.

"No one understood how fast the decline happened at the end - it was only a couple of years," says Myers. "The quotas had been too high. They refused to slow down because they had seen lots of little fish coming in - a good year class. The little fish were caught and discarded and there was no future."

"This is extremely troubling news for anyone who cares about the health of the oceans," said Dr. Randy Kochevar, science communications manager at the Monterey Bay Aquarium and a principal investigator with the Tagging of Pacific Pelagics (TOPP) research project. TOPP is a collaboration among scientists from around the world to understand the migration patterns of large open ocean animals in the North Pacific Ocean.

"The magnitude of the threat is startling," Kochevar said. "Even if the authors' numbers are off by as much as 50 percent, this is a big, big problem. The trends they've identified have profound consequences for the future of ocean life."

At the World Summit on Sustainable Development in Johannesburg last summer, 192 nations called on the global community to restore world fisheries stocks to levels that can provide maximum sustainable yield by 2015. Myers and Worm say their results provide the "missing baseline" needed to restore fisheries and marine ecosystems to healthy levels.

The fishing nations must reduce quotas, reduce overall fishing effort, cut subsidies, reduce bycatch, and create networks of marine reserves, the scientists say.

Worldwide, 27 million tons of fish, mammals, turtles, birds and other marine life is discarded dead or dying into the sea each year as fishing "bycatch," according to the Pew Oceans Commission, based in Washington, DC.

"A minimum reduction of 50 percent of fishing mortality may be necessary to avoid further declines of particularly sensitive species," Myers says. "If stocks were restored to higher abundance, we could get just as much fish out of the ocean by putting in only 1/3 to 1/10 of the effort. It would be difficult for fishermen initially -- but they will see the gains in the long run," he said.

"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," warns Myers.

"We have to understand how close to extinction some of these populations really are. And we must act now, before they have reached the point of no return. I want there to be hammerhead sharks and bluefin tuna around when my five year old son grows up. If present fishing levels persist, these great fish will go the way of the dinosaurs."