Baby olive ridley sea turtle. Photo by Rhett Butler
The number of sea turtles accidentally caught and killed in United States coastal waters has declined by an estimated 90 percent since 1990, reports a new study published in the journal Biological Conservation. The authors, including researchers at Duke University and Duke University, say regulations to reduce bycatch are responsible for the decline.
The study, which analyzed bycatch data from the National Marine Fisheries Service (NMFS), estimates some 4,600 sea turtles are killed each year in U.S. coastal waters, down from 70,000 annually in 1990. Overall turtle bycatch, including all fatal and non-fatal captures, fell roughly 60 percent from 300,000 between 1990 and 2007.
The authors credit the implementation of regulations by the NMFS for the reduction. According to Conservation International, these included
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the use of circle hooks in longlines as well as dehooking equipment to reduce the severity of injuries to turtles; the implementation of turtle excluder devices (TEDs) in shrimp trawl nets to allow captured sea turtles the chance to escape; and time-area closures that keep fishing activities and turtles separate in places and during times that turtles are most likely to be present in highest numbers.
The authors say the results show that mitigation strategies could be effective in reducing sea turtle mortality in other countries.
“The reduction of bycatch and mortality shows important progress by NMFS, which serves as a model for reducing sea turtle bycatch in other parts of the world,” said Elena Finkbeiner, a PhD student at Duke and lead author of the paper. “Our findings show that there are effective tools available for policy makers and fishing industries to reduce sea turtle bycatch, as long as they are implemented properly and consistently.”
The authors did however highlight shortcomings in the NMFS’s current approach, noting that sea turtles are managed on a fishery-by-fishery basis without accounting for the impact on overall turtle populations.
“This piecemeal view and fragmented approach leads to total allowed takes that far exceed what sea turtle populations can sustain, in part because they are affected by multiple fisheries,” stated Conservation International in a press release. “So although these reductions in sea turtle bycatch are important, it is still unclear whether bycatch has been reduced enough to help sea turtles recover.”
The authors also noted inconsistent compliance in the Gulf of Mexico shrimp travel fishery, which accounts for the 98 percent of sea turtle deaths. They warned that insufficient on-board observer coverage made enforcing regulations difficult.
“We commend the successful efforts of fishers and NMFS managers to reduce sea turtle bycatch, but there is still important work to be done,” said Dr. Bryan Wallace, a co-author on the study and Director of Science for the Marine Flagship Species Program at Conservation International and Adjunct Faculty member at Duke University. “Bycatch limits must be set unilaterally across all U.S. fisheries with overall impacts to populations in mind, much as it’s done for marine mammals. This would ensure that these bycatch reductions are successful in recovering sea turtle populations.”
“We just have to commit to consistently implementing these tools in fisheries in U.S. waters and around the world to promote sustainable fisheries with reduced bycatch.”
All six species of turtle species found in U.S. waters — loggerheads, leatherbacks, hawksbills, olive ridleys, Kemp’s ridleys and green sea turtles — are currently categorized as Threatened or Endangered on the U.S. Endangered Species List.
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