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New Sea Turtle Challenges

After years of improving numbers, Kemp’s ridleys are on the decline again.

By Melissa Gaskill

After years of slow but steady improvement, the number of Kemp’s ridley sea turtles nesting on the Texas coast declined in 2013.

Donna Shaver, chief of sea turtle science and recovery at Padre Island National Seashore, documented 153 Kemp’s ridley nests statewide for the season. Contrast that with the 209 nests made in Texas by Kemp’s ridleys, an endangered species, in 2012 and numbers near 200 in 2011, 2009 and 2008.

“The 2013 season was a substantial drop,” says Shaver. “The Kemp’s ridley recovery plan calls for the population increasing 12 to 18 percent annually, and it isn’t anymore.”

Texas numbers are mirrored on a much larger scale on Mexico’s Gulf Coast, which for decades represented the only known ridley nesting beach and once hosted tens of thousands of nests annually. Pamela Plotkin, Texas Sea Grant director, points out that a Kemp’s ridley stock assessment prepared for the Gulf States Marine Fisheries Commission in June 2013 reports Mexico’s nest numbers increased exponentially from 1996 through 2009, when 19,163 nests were reported. Numbers dropped in 2010 but recovered the next two years. Then the number dropped again in 2013.

Sea turtles

It isn’t clear what’s behind the lower numbers, but there are several likely suspects. Shaver is involved in researching the 2010 Deepwater Horizon oil spill’s effects on the ridley population, but results (part of the federal Natural Resource Damage Assessment) remain confidential until legal actions from the spill are settled. Researchers know that the Louisiana coast, most heavily affected by the spill, is a migratory route for nesting turtles leaving Texas and an important foraging area for ridleys from Texas and Mexico. That is cause for concern for Carole Allen, Gulf office director for the nonprofit Sea Turtle Restoration Project.

“No one really knows what the oil spill did to ridleys,” Allen says. “We have no idea how many sea turtles were lost trying to migrate and forage across Louisiana during the spill.”

Another suspect, shrimp trawling, accounted for 76 percent of annual ridley deaths prior to regulations requiring use of “turtle excluder devices,” or TEDs, which allow turtles to escape trawl nets. Use of TEDs reduced that number drastically; in 2010, shrimp trawls accounted for only 4 percent of ridley mortality.

Plotkin suspects other factors are also in play, a sort of “perfect storm” including huge freshwater inflows following 2010 flooding along the Mississippi, which changed the temperature and salinity of Gulf waters, followed by drought that drastically reduced populations of blue crabs, key to the turtle’s diet. Recent red tide events could have played a part, too.

There is also good news for Texas sea turtles, though. Thirteen loggerheads nested in Texas in 2013, up from nine in 2010, and the 15 green sea turtle nests in 2013 represent a jump from the previous record of six. Grown green sea turtles, once abundant along our coast before commercial overharvesting and freezes, have again become a common sight. Their rising numbers here reflect robust increases in nesting across the U.S. and Mexico. In Florida, where Texas greens likely originate, there were 11,839 nests in 2013, twice as many as before.

“When I lived on the Texas coast in the late 1980s, I walked the jetties every day for four years and only once saw a green,” says Plotkin. “I returned to Texas two years ago, 25 years later, and there are juvenile greens all over. I counted 34 in just one hour last September. I never thought in my lifetime I would see recovery. The outlook was so bleak. It was just an amazing moment. I knew at that point all our efforts to protect and conserve sea turtles throughout the Gulf and Caribbean had really paid off.”

(Gaskill’s “A World-Wide Travel Guide to Sea Turtles” will be released by Texas A&M University Press this summer.)

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The Saga of the Kemp's Ridley Turtle

 

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