09/14/2011 08:09 am ET Updated Dec 06, 2017

Fewer Sea Turtles Killed In U.S. Fisheries, But Still Too Many, Study Finds

Every year, 4,600 sea turtles are killed in U.S. fisheries, according to a new study.

Even though this number is a 90 percent reduction of turtles accidentally caught and killed since 1990, this may not be enough to sustain turtle populations, according to a study published in Biological Conservation this month, and conducted by Duke University's Project GloBAL and Conservation International.

“It is disgraceful that U.S. fisheries are allowed to kill 4,600 endangered and threatened sea turtles each year – and that is the best case scenario. This estimate also assumes that sea turtle protection measures are being followed in all U.S. fisheries. The actual number of sea turtles killed in U.S. fisheries is likely significantly higher," Oceana, an international advocacy group working to save the world's oceans said in a press release.

One of the authors of the report and Director of Science for Conservation International's marine flagship species program Dr. Bryan Wallace told The Huffington Post that while the reduction of turtles killed in fisheries was promising, more needed to be done to help their recovery.

"One of the problems is that we don't have that magic number that serves as a quota across all fisheries," he said. "Coming up with that number can determine the mortality rate that populations can sustain. Then we can work out how much bycatch is happening in each fishery, and added together, that should be lower than the ceiling set for sustainable numbers."

Bycatch is described by Conservation International as "the accidental capture and injury of marine animals in fishing gear that are not the target catch species."

Wallace said that even on a global scale, fisheries are one of the most serious and acute threats to turtle populations. He used loggerhead turtles as an example, which he said are "the most abundant sea turtle species in the U.S., but have declined 40 percent over the last 20 years."

A press release by Conservation International stated that although the "reductions in sea turtle bycatch are important, it is still unclear whether bycatch has been reduced enough to help sea turtles recover."

To achieve the reduction, the National Marine Fisheries Service implemented regulations for individual fisheries, including dehooking equipment that helps to reduce the severity of injuries to turtles, shrimp trawl nets with turtle excluder devices that allow captured sea turtles to escape, and time-area closures that aim to separate fishing activities and turtles in places and during times when there is likely to be high numbers of turtles.

However, the release says that due to a lack of observer coverage and inconsistent compliance with turtle excluder devices with shrimp trawlers, which account for 98 percent of sea turtle fatalities in the Gulf of Mexico, bycatch estimates may be higher than what the study reported.

Wallace said the tools were in place to save these sea turtles, but commitment to implementing them was needed to be successful in promoting sustainable fisheries.

"If we can address this, then maybe we can get them down to a sustainable level," he said.

An Oceana press release writes: "As few as 21 percent of shrimp trawl vessels are complying with sea turtle protection measures; mortality estimates in this study assume 100 percent compliance. Fishing gear technologies to reduce sea turtle interactions such as turtle excluder devices only save sea turtles when they are used properly."

According to Conservation International, all six sea turtles that are found in the U.S. are currently threatened or endangered on the U.S. Endangered Species List.