Fishing ban brings species back to Mexico park. But can it rebuild a fishery?

You can sunbathe, go kayaking or windsurfing, or try your hand at diving. No fishing. Period.

That, in effect, is the dictum residents of the tiny village of Cabo Pulmo, at the tip of Baja California, have enforced throughout a 27-square-mile patch of ocean that a decade ago was severely over-fished.

The patch is a national marine park that Cabo Pulmo's residents help oversee. And according to a new study of the impact of that no-fishing policy, fish populations have rebounded beyond anyone's wildest dreams.

The researchers conducting the work say they hope the results will do more than build momentum for more effective enforcement of marine reserves elsewhere in the Sea of Cortez. The research, they say, also highlights the positive effect that residents in comparable areas around the world can have when they buy into the concept of a ban on fishing.

Between 1999 and 2009, total fish biomass – an aggregate figure that accounts for the number and size of fish – grew by more than 460 percent, from roughly 600 pounds per acre to 3,392 pounds per acre, according to a study published recently in the on-line journal PLoS One, an on-line journal of the Public Library of Science.

And species – from top predators to tiny fish that feed on plankton and marine plants – have returned in proportions that resemble those found in ocean ecosystems that have escaped overfishing, signaling a biologically vibrant ecosystem, according to Octavio Aburto-Oropeza, leader of the team that conducted the study.

The only other marine reserve known to have experienced a comparable recovery is Cabo de Polas off of Spain.

For many marine scientists, the concept that no fishing in an overfished area gives stocks a chance to rebuild is a no-brainer, acknowledges Dr. Aburto-Oropeza, a scientist at the Scripps Institution of Oceanography in La Jolla, Calif. But he and his colleagues, whose results were posted Friday on the PLoS website, were stunned at how quickly the recovery took place.

The group did not expect it to happen in a decade, he explains. "It's amazing."

The results are definitely above average, notes Ray Hilborn, a marine ecologist at the University of Washington in Seattle, who was not part of the research team.

He notes that protected marine areas whose fishing restrictions are well enforced typically see stocks rebound by two to three times their pre-protection level.

"The particularly high increase here indicates both that it was severely over-fished" before the no-take zone was set up, and that the enforcement "was particularly good," he writes in an email.

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