Do Turtle Excluder Devices Work?
Sea turtles are protected by the Endangered Species Act and at least in the Gulf of Mexico, are showing signs of recovery. Shrimp fishing is big business in the Gulf of Mexico with over 7,000 commercial shrimp trawlers working year round. An unknown number of turtles are caught in shrimp trawlers' nets and drown. Since 1991 shrimp trawlers have been required to use turtle excluder devices (TEDs) to keep turtles from getting caught as bycatch in the shrimp fishery. The first few years TEDs seemed to be working and the numbers of turtles caught as bycatch declined. However, in 1994 the number of dead turtles washing up on the beach went up. If TEDs were decreasing the rate of bycatch then why are more turtles washing up on the shore? To answer this question Rebecca Lewison and her co-authors analyzed the stranding data for the last fifteen years. They found that TEDs were indeed effective at reducing turtle bycatch. Various lines of indirect evidence point to more turtles in the water as one of the reasons for the increasing number of dead turtles on the shore. The likelihood of a shrimper catching a turtle in their gear is small, but with so many boats in the water, even a low rate of mortality still has a big effect on the turtle populations. We spoke with Dr. Rebecca Lewison about her role in this important study.