Big fish return to Mexican marine park

Most effects of overharvesting reversed within a decade

Within 14 years of a national marine park in Mexico’s Gulf of California closing its borders to fishing, the total mass of its denizens more than quintupled, a new study finds. Over the same period, the share of top predators — sentinels of a healthy ecosystem — also soared. Both trends countered those for fish in unprotected regions of the Gulf.

A 1.2-meter-long gulf grouper (Mycteroperca jordani) is among the large predators that have returned to Cabo Pulmo National Marine Park after a fishing ban. Octavio Aburto/iLCP

A group of bigeye trevally (Caranx sexfasciatus) forms a spawning aggregation. Such populations have returned to the waters of the Cabo Pulmo National Marine Park after a fishing ban. Octavio Aburto/iLCP

“People who object to marine protected areas, especially to strong protection like here, often say there is no proof that they work,” says Elliott Norse of the Marine Conservation Biology Institute in Bellevue, Wash., who was not involved in the new study. “Well, this is the proof.”

The 71-square-kilometer Cabo Pulmo National Marine Park sits close to where the Gulf opens into the Pacific. Its coral reef makes it a tourist destination for diving and snorkeling. Since 1995, 35 percent of the park’s waters have been off limits to fishing, but local communities informally extended the no-take zone to the rest of the park, says Octavio Aburto-Oropeza of the Scripps Institution of Oceanography in La Jolla, Calif. He and his colleagues surveyed the reef’s fish populations in 1999 and again in 2009. They report the results of those surveys August 12 in PLoS ONE.

Fishers typically first target meaty predators such as giant groupers and snappers. Absent in 1999, such big fish — some a meter or more long — again inhabit Cabo Pulmo, Aburto-Oropeza says. He even witnessed Pacific tunas visiting to dine on the park’s reef fish.

Sharks remain notable for their virtual absence. Owing to heavy exploitation for the fin trade and slow rates of reproduction, this family of predators remains rare inside Cabo Pulmo and out, Aburto-Oropeza says.

Norse says there’s no reason to believe that the new study’s findings should prove unique to the Gulf of California. “I suspect that what they found would occur anywhere people who fish exercise the admirable restraint that the people have at Cabo Pulmo.”

Janet Raloff

Janet Raloff is the editor of Science News for Students, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer.

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