September 15, 2011
Accidental Sea Turtle Deaths Down, But Still Too High
Some 4,600 sea turtles are accidentally caught and killed in U.S. fisheries every year, a 94 percent reduction since 1990, according to a new study published this month in the journal Biological Conservation.
However, the progress may not be enough to sustain turtle populations, according to researchers at Duke University's Project Global and Conservation International, who conducted the study.
The use of turtle-excluder devices (TEDs), or large holes that allow the sea turtles to escape from nets that nab smaller marine creatures, has resulted in a "dramatic reduction" in accidental sea turtle deaths, which surpassed 70,000 annually before such protective measures were put in place, the researchers said.
The study used data collected from 1990 to 2007 by the National Marine Fisheries Service (NMFS) to determine bycatch rates across more than 20 fisheries operating in Atlantic waters from the Gulf of Mexico to the Canadian border, and in the Pacific Ocean, along the West coast and around Hawaii.“¨“¨
The data revealed that overall turtle bycatch rates, including both fatal and nonfatal run-ins, have fallen about 60 percent since 1990.
Shrimp trawls in the Gulf of Mexico and southeastern U.S. accounted for up to 98 percent of all by-catch takes and deaths during the study period, the researchers said.
All six marine turtle species in U.S. waters -- loggerheads, leatherbacks, hawksbills, olive ridleys, Kemp's ridleys and green sea turtles -- are currently categorized as threatened or endangered.
Bycatch is an acute threat to sea turtle populations worldwide, and high bycatch rates can be indicative of unsustainable fishing practices that negatively impact the health of marine ecosystems. “¨“¨
"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 report.
"Our findings show that there are effective tools available for policymakers and fishing industries to reduce sea turtle bycatch, as long as they are implemented properly and consistently."
Among the mitigation strategies that have helped reduce bycatch are the use of circle hooks and dehooking equipment in longline fisheries, to reduce the severity of turtle injuries, the use of turtle excluder devices (TEDs) in shrimp trawl nets to allow captured sea turtles to escape and the implementation of time-area closures to restrict fishing activities at times and places turtles are most likely to be present in the highest numbers.
Piecemeal regulation remains a problem, the researchers said. Sea turtles are currently managed on a fishery-by-fishery basis, meaning bycatch limits are set for each fishery without accounting for the overall population impacts of all the takes added together. Such a fragmented approach leads to total allowed takes that exceed what sea turtle populations can sustain.
"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," said study co-author Bryan Wallace, director of science for Conservation International's Marine Flagship Species Program.
Actual bycatch rates are likely higher than what the study reports because in many fisheries, particularly the shrimp trawl fishery, the number of on-board observers who document bycatch on fishing vessels is low relative to the sheer volume of fishing that is occurring, the researchers said.
"This paper provides a baseline to examine what is working and what can be improved in preventing sea turtle bycatch," Finkbeiner said.
"It (makes) a strong case for the need for increased observer coverage and bycatch reporting."
The study was published online August 26, 2011 in the journal Biological Conservation.
On the Net:
- Duke University Project Global
- Conservation International
- National Marine Fisheries Service
- Study Abstract