Where did all the fish go?

And yet, even in the US where stocks are on balance in better condition than in other places, 41 of the 244 stocks for which the National Marine Fisheries Service (NMFS) has information are being fished at unsustainable levels, or overfished. Worldwide, one-quarter of fish stocks are overfished, says the FAO. Another 50 percent are fished to full capacity; they can sustain no more. According to one somewhat controversial analysis, if current fishing trends continue, all the world’s fisheries will have collapsed by mid-century.

What happened? Daniel Pauly, director of the Fisheries Centre at the University of British Columbia, Van­couver, calls the combined cultural, technological, and economic factors “the march of folly.”

It began with a long-held notion of the sea’s endless bounty.

Until relatively recently, fishermen, fishery managers, and scientists alike thought the sea was so vast, so teeming with life, that human activity simply couldn’t diminish it, Mr. Pauly says.

Until the advent of modern fishing technology in the 20th century, it couldn’t.

“The sea was very large compared to the means we had to exploit it,” Pauly says. But beginning with steam-powered trawlers more than 100 years ago, and ending with today’s global-positioning navigational systems, technology has improved fishermen’s reach and efficiency. “We essentially deployed our industrial armada against fish, and obviously we would win: It’s a war against fish,” says Pauly.

Technology made inaccessible fish accessible. Pristine areas used to constantly replenish adjacent areas that were fished, scientists hypothesize. But as technology let fleets fish in areas previously unfished due to remoteness or difficult undersea topography, this replenishment failed. Fish numbers fell, but better fishing technology concealed the trend. World catches remained stable or increased, suggesting healthy stocks.

Then, when local stocks began to collapse, fleets moved ever farther offshore, leading to what Robert Steneck, a professor of marine biology at the University of Maine, Orono, calls “roving banditry”: High-seas fleets fishing stocks to collapse, then moving on. Many countries also subsidized their fleets, increasing capacity far beyond what the seas could absorb. Worldwide, the FAO estimates that by the 1990s, subsidies had pushed fishing capacity some 30 to 50 percent above what the oceans could sustain. (It has since fallen.)

“When the biomass goes down because of fishing, in a sense the stock has a message…. ‘Leave me alone,’ ” says Pauly. “But subsidies, which contribute to the harvesting of fish, enable the fisher to ignore the signal of the stock.”

In the US, which actively developed its domestic fleet throughout the late 1970s and ’80s with low-interest loans and other programs, many thought that fishing overcapacity would self-correct. If fishermen were just another predator, once fish numbers dropped, fishers would, too. Equilibrium would be restored.

But the laws of economics led to a different outcome: “As stocks get rarer and rarer, their prices go up – the so-called ‘ratchet effect,’ ” says Steve Murawski, chief scientist at National Oceanic and Atmospheric Administration Fisheries in Silver Spring, Md. The incentive to catch the few remaining fish increases rather than decreases. “That wasn’t well understood,” he says.

Empty Oceans, a series on the state of the world's fisheries, will be appearing in the Monitor's environment section. For the full series, click here.

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