When S. Hoyt Peckham first arrived in Baja California, Mexico, to study the foraging ecology of loggerhead turtles, he had a demoralizing surprise: The beaches were littered with the carcasses of the endangered reptiles. After interviewing local fishers, Peckham discovered that they were accidentally catching many of the turtles and then tossing them overboard. So Peckham, a graduate student at the University of California, Santa Cruz, changed the focus of his dissertation to this problem, called by-catch. Now, 6 years later, he and his colleagues are publishing another surprise.
In the 17 October issue of PLoS ONE, the team reports that just 80 small fishing skiffs in Baja have an enormous impact. In fact, they kill roughly the same number of loggerhead turtles as many hundreds of fishing vessels in the North Pacific combined--nearly 1000 turtles a year. "That number is shocking," says marine scientist Carl Safina of Stony Brook University in New York state. But during Peckham's fieldwork, he also cultivated relationships with fishers that are now paying off for turtle conservation.
Loggerhead turtles (Caretta caretta) live in the Atlantic, Pacific, and Indian oceans. Those in the Pacific nest on beaches in southern Japan, then as juveniles swim 12,000 kilometers to Baja where they feed on abundant crabs. It's a dangerous journey: Fishers kill an average of 1300 of the turtles a year in the North Pacific by snagging them on longlines barbed with thousands of hooks. Due to all these threats, the World Conservation Union considers the species endangered throughout its range. But local fishers in Baja had a hard time believing the official status of the loggerheads. Peckham recalls that when he talked with them, many would doubt him because they had caught so many. "I've heard that so many times: 'What do you mean they're endangered?'"
Peckham's first step was to figure out where the turtles were living. Starting in 1996, co-author Wallace Nichols of the California Academy of Sciences in San Francisco and others had begun outfitting loggerheads in Baja with telemetry devices. The team discovered that 26 of 30 loggerheads spent most of their time within the fishing grounds of a dozen small fleets, which typically use 6- to 9-meter-long boats called pangas.
Peckham and others also joined some of the fishers to measure how many turtles they were catching. In the summer of 2005, the researchers saw 11 loggerheads snared in gillnets during a 73-day period. Another 26 were hooked on longlines during seven trips. Extrapolating through the fishing season, Peckham's team estimates that the 80 boats in these two fleets caused a minimum of 979 turtles to die. "I would never have thought that a couple of guys in a panga could be having such a profound effect," Peckham says.
To lessen that impact, Peckham worked with a conservation group called Grupo Tortuguero in Baja California to educate the fishers. In August, one of the fleets agreed to give up its longlines and switch to using nets, which will spare hundreds of loggerheads a year. "I doubt I'll achieve a conservation action in my career that will be as important as that," Peckham says. The fishers also decided to declare part of the richest turtle waters a preserve. They and Peckham's team then asked the federal government to give it official status, which is being evaluated.
The findings "will help raise international attention to large by-catch problems in small-scale coastal fisheries," says Eric Gilman of the World Conservation Union, although he cautions that the sample size was small and the study not long term. Rebecca Lewison of San Diego State University in California calls the conservation steps in Baja "phenomenally successful" and says that the work is a model for lessening the ecological impact of small coastal fisheries.