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How To Stop Fish From Shrinking

Individual fishing quotas have got to be one of the niftiest ideas in environmental economics—an attempt to deal with the fact that earlier methods of preventing overfishing—say, restricting equipment or limiting the length of the fishing season—have mostly backfired. The classic example, as discussed earlier, is the pre-1995 Alaskan halibut fishery, where fishing seasons were limited to as little as 24 hours, creating a dangerous race to catch fish as quickly as possible and causing fishing boats to sit idle the rest of the year. Individual fishing quotas, by giving each fisherman the right to a certain percentage of the catch that scientists determine a fishery can handle for the year, help eliminate the inefficiencies of other regulations—and give fishermen a financial interest in making sure the fishery stays healthy. A paper recently published in Science provides some evidence that they really do work: Of the 11,135 fisheries that the authors surveyed, only 14 percent of those with quota systems suffered population collapse, compared to 28 percent of other fisheries.

A separate question, though, is whether quota systems can help prevent certain evolutionary changes driven by fishing. As another recent Science paper revealed, many species of fish are starting to become smaller a result of heavy fishing pressure. Smaller fish, after all, are more likely to slip through fish nets, giving them a survival advantage that produces evolutionary change at a surprisingly speedy rate. Since smaller fish are less valuable for eating, this is a serious problem. It's a problem exacerbated by old regulations that—in the interest of preventing overfishing—require a minimum net mesh size to allow small fish to escape.

Switching to individual quota systems in fisheries that currently rely on mesh-size and season-length restrictions to prevent overfishing would alleviate some of this evolutionary pressure. But some areas will need to maintain their mesh-size restrictions in order to limit the catch of non-target species. And unless fishermen start trawling with cheesecloth, some small fish are always going to get away. That's why it's also important to establish no-fishing marine reserves that provide areas in which big fish can survive and pass on their genes. The good news is that fishermen who work under quota systems—unlike most other commercial fishermen—are surprisingly receptive to marine reserves. They're limited to a certain amount of fish each year, so as long as they're able to catch that limit, being shut out of a certain area isn't a big deal. Besides, they figure that marine reserves will improve the health of the fishery, meaning that they'll be allowed to catch more—and, as it turns out, bigger—fish in the future.

--Rob Inglis, High Country News