Wild fish catch hits limit

AFTER DECADES OF GROWTH, the reported global wild fish catch peaked in 2000 at 96,000,000 tons, then fell to 90,000,000 tons by 2003, the last year for which worldwide data are available. The catch per person dropped from an average of 17 kilograms in the late 1980s to 14 kilograms in 2003--the lowest figure since 1965.

As fishing fleets expanded through the late 1980s and fish-finding and harvesting technologies became more efficient, the world's fishers systematically have gone after their catch at greater depths and in more remote waters. Over the past 50 years, the number of large predatory fish in the oceans has dropped by a startling 90%. Catches of many popular food fish such as cod, tuna, flounder, and hake have been cut in half despite a tripling in fishing effort. According to the United Nations Food and Agriculture Organization, the 4,000,000 vessels scouring the world's waters are at, or exceeding, the sustainable yields of three-quarters of all oceanic fisheries.

The 10 most-fished species constitute 30% of the world's catch. Seven of these have reached their limits and are classified as fully exploited or overexploited throughout their entire ranges, meaning that we cannot expect to increase their harvests. Included in this group are two types of Peruvian anchoveta, Alaska pollock, Japanese anchovy, blue whiting in the northeast Atlantic, capelin in the North Atlantic, and Atlantic herring. The other three species--chub mackerel, skipjack tuna, and largehead hairtail--are overfished in parts of their ranges.

Interestingly, several of these species became fishing targets only after the stocks of more desirable fish were overharvested. After the collapse of the 500-year-old Canadian cod fishery in the early 1990s, blue whiting catches increased. In the northwest Pacific, the overfishing of Alaska pollock and Japanese sardine led fishers to focus on Japanese anchovy, largehead hairtail, and squid. Some scientists warn that continuing to "fish down the food web" will lead to harvests almost exclusively of bait fish and jellyfish.

The tendency to catch larger and older fish first, leaving those small enough to escape from nets to breed, has, over time, reduced the average size of those caught. The effect on large predators is striking. In the 1950s, for instance, an average blue shark weighed 52 kilograms; in the 1990s, 22 kilograms. In addition, fish that breed late in life sometimes are pulled out of the water before they can reproduce. When fish respond to overharvesting by reproducing at earlier ages, research shows that their populations are still hit hard because, for some species, the offspring of older fish have a better chance of survival than those of younger fish.

Although fishers generally target specific kinds of fish, they often bring in more than just the intended catch. Some eight percent of global landings are discarded, returned to the sea dead or dying. Shrimp trawlers, which drag enormous nets over the seafloor and destroy delicate ecosystems, are the most indiscriminate: some 62% of their catch is thrown back. Moreover, these tallies underestimate the true losses as they only include reported bycatch and do not consider any of the marine mammals or birds that become entangled in fishing gear. Longliners with thousands of hooks on central fishing lines of up to 60 miles are estimated to kill some 4,400,000 sharks, sea turtles, seabirds, billfish, and marine mammals in the Pacific each year.

Overall, 1,000,000,000 people around the world rely on fish as their primary source of protein. While annual consumption per person in the industrial countries (at 29 kilograms) is more than twice that of developing nations, three quarters of the fish caught in the wild (by weight) come from developing countries, which also supply nine out of 10 tanned fish.

While fish stocks historically have been monitored on a species-by-species basis, scientists now recognize the need for management of entire ecosystems. This includes setting aside marine reserves where fishing is prohibited altogether. There is no guarantee that a collapsed fishery can recover, but studies of protected areas around the world have shown that some exploited fish populations rebound taster and that individual fish grow larger in and around marine reserves than in unprotected areas. A global network of marine reserves protecting up to 30% of the world's oceans would cost around $13,000,000,000--far less than the subsidies that currently promote overfishing. Such a network also would create some 1,000,000 new jobs and bolster the number of fish that can be caught in nearby waters.

Creating sustainable fisheries also depends on strict fishing quotas and better enforcement to quash illegal fishing. Restricting the most damaging and indiscriminate types of fishing gear and adopting new bycatch-reducing technologies can stop the killing of incidental catch.

With oceanic ecosystems hitting their limits and demand for fish climbing, the farming of fish in pens and ponds supplies a growing share of the world's food fish. From less than 1,000,000 tons in 1950, global aquacultural production hit a high of 42,000,000 tons in 2003, making it the fastest-growing food production sector in the world.

Nonetheless, aquaculture will alleviate pressure on wild fish only if it is done wisely. The construction of offshore fish farms frequently requires the razing of sensitive wetlands. These farms also harbor diseases and concentrate fish wastes that can lead to harmful algal blooms and low-oxygen dead zones. Making matters worse, farmed carnivorous fish can eat several times their weight in wild fish, which only adds to pressure on such resources. Though salmon, trout, shrimp, and prawns currently account for just nine percent of world aquacultural output, production of these carnivorous fish is doubling almost every eight years, rapidly increasing demand on wild stocks.

Janet Larsen is a research associate at Earth Policy Institute, Washington, D.C.

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