Costa Rican longline fisheries are killing thousands of sea turtles and sharks, catching more turtles than some commercial fish species, a study found. Writing in the Journal of Experimental Marine Biology and Ecology, researchers say Costa Rican longline fishery represents a major threat to the survival of eastern Pacific populations of sea turtles as well as sharks.
The researchers from Drexel University, the Costa Rican non-profit conservation organization Pretoma and a U.S. non-profit working in Costa Rica, The Leatherback Trust, urge time and area closures for the fisheries to protect these animals as well as to maintain the health of the commercial fishery.
Although the most commonly targeted fish, mahi mahi, was the most common species caught in the Costa Rican longline fishery, olive ridley turtles, internationally classified as vulnerable, were the second-most-common species caught, they said.
They estimate more than 699,000 olive ridley and 23,000 green turtles were caught during the study period, 1999 to 2010, and while around 80 percent of captured sea turtles are released from longlines and survive the experience, the long-term impacts are unknown.
"It is common to see sea turtles hooked on longlines along the coast of Guanacaste in Costa Rica. We can set some free but cannot free them all," Drexel environmental scientist James Spotila said. "The effect of the rusty hooks may be to give the turtles a good dose of disease. No one knows because no one holds the turtle to see if its gets sick."