An Uncertain Future for Kemp’s Ridley Turtles

A Kemp’s ridley sea turtle hatchling is released on the beach at Padre Island National Seashore, Texas.

At about 2 feet long and weighing up to 100 pounds, the Kemp's ridley turtle (Lepidochelys kempii) is one of the smallest sea turtles — and the world's most endangered. Kemp's ridleys live throughout the Gulf of Mexico and along the U.S. Atlantic coast. Some nest on Texas beaches, but most choose remote beaches in northern Mexico. While they are occasionally spotted off Florida's west coast and the Keys, adult Kemp's ridleys tend to spend their time in waters with muddy or sandy bottoms, so divers seldom encounter them.

An amateur video taken in 1947 shows a mass nesting, or arribada, of at least 40,000 individual Kemp's ridleys on a single day on Rancho Nuevo beach in Tamaulipas, Mexico. Unfortunately, the species later was listed under the Endangered Species Conservation Act of 1970, and by 1985 the only known Kemp's ridley nesting beach in Mexico was Rancho Nuevo, which then hosted fewer than 800 nests or about 300 nesting females.

In response to the Kemp's ridley's rapid decline, a group of scientists, government managers, conservationists and industry representatives gathered in October 1985 in Galveston, Texas, to determine how to save this endangered species. This First International Symposium on Kemp's Ridley Sea Turtle Biology, Conservation and Management spurred renewed efforts to reduce the number of sea turtles killed in fishing nets and shrimp trawls and resolved to continue support of nesting-beach protection efforts that Mexico initiated in 1966.

Symposium participants also renewed their commitment to a project begun in 1978 to re-establish nesting at Padre Island National Seashore off the coast of South Texas. The project involved collecting Kemp's ridley eggs from nesting sites in Mexico, incubating them in Padre Island sand and temporarily releasing the hatchlings on the national seashore's beaches with the hope of imprinting the turtles to the area so they would return there as adults to nest. For the first few years, the hatchlings were then captured in the Gulf of Mexico, reared in captivity for 9-11 months (until they were large enough to avoid most predators), tagged and then returned to the Gulf's waters.

Within a decade these efforts began paying off: The number of Kemp's ridley nests increased by 14 to 16 percent each year between 1995 and 2009, when it hit a peak of 21,000 (or about 8,000 nesting females) in Mexico and a then-record 197 nests in Texas. Those involved in the recovery project expected to record 25,000 nests (or 10,000 nesting females) in a season — the threshold for downlisting the species from endangered to threatened — within another decade. But in April 2010 BP's Deepwater Horizon oil rig exploded, discharging almost 5 million barrels of oil into the Gulf of Mexico.

The disaster occurred off the Louisiana coast in an important feeding area for Kemp's ridleys and a place where females were known to forage among Sargassum algae after nesting. According to aerial surveys conducted after the disaster, thousands of sea turtles, including Kemp's ridleys, encountered the oil. Recent ocean modeling has revealed that the Gulf of Mexico's currents bring juvenile sea turtles — typically too small to spot via aerial surveys — into the spill area in much larger numbers than previously thought. This makes it likely that many more sea turtles encountered oil than official statistics reflect.

Donna Shaver, Ph.D., documents a Kemp’s ridley sea turtle nesting on North Padre Island, Texas. Kemp’s ridleys typically nest during the day.

In 2010 the number of Kemp's ridley nests dropped by 35 percent. After slight upticks in 2011 and 2012, the number decreased significantly in 2013 and 2014. Scientists say that the pattern reflects either decreased reproduction or increased mortality, either of which could be attributed to the turtles' exposure to the oil. The species had once been poised for revival, now its future doesn't look so bright.

In November 2014 scientists organized the Second International Kemp's Ridley Sea Turtle Symposium in Brownsville, Texas, to discuss the precarious future of the endangered sea turtle. "My plan was to wait until 2015 and hold the second symposium 30 years after the first one," said Pamela Plotkin, Ph.D., director of Texas Sea Grant and one of the event's organizers. "But given the current status of the species, I felt it was important to gather as soon as possible to raise awareness of the problem and consider how to get Kemp's ridleys back on the road to recovery."

Scientists at the symposium presented a litany of grim statistics. Coincident with the BP oil spill Kemp's ridleys suffered a huge spike in mortality: The Kemp's Ridley Stock Assessment Project reported 65,505 total deaths in 2010, only 2,884 of which were due to shrimp trawls. High levels of strandings have continued every year since then — roughly 400 per year within the area affected by the spill. One reason for this rise in mortality relates to the spill's effect on blue crabs, the primary food source for adult Kemp's ridleys. Associated studies show that sea turtles have altered their foraging habits in the years following the spill.

Symposium participants did note at least one success story: Significantly fewer sea turtles die in shrimp trawls today thanks to turtle excluder devices (TEDs), which attach to trawl nets to help sea turtles escape rather than suffer injury or drown. "Shrimp trawl mortality is the lowest it's been in recorded history, in large part due to use of TEDs," reported Benny Gallaway, Ph.D., president of Texas-based LGL Ecological Research Associates.

A Kemp’s ridley sea turtle hatchling crawls toward the Gulf of Mexico after being released at Padre Island National Seashore.
Kemp's ridley sea turtles continue to face many of the threats that initially led to their endangered status, such as loss of nesting beach habitat, pollution, marine debris, incidental capture by fishing operations and the increased water temperatures and sea levels resulting from climate change. Drought and inland development also mean less fresh water flowing from Texas rivers into the bays and estuaries necessary for maintaining healthy blue crab populations.

"Overall, not enough time has passed since the spill, nor has enough data been collected, to fully understand its effects on sea turtles," said Selina Heppell, a marine fisheries ecologist at Oregon State University. Consequently, symposium participants called for continued funding of conservation efforts and research.

This is a critical time for conservation efforts. More than 90 percent of Kemp's ridleys make their nests in Mexico, and both Mexico and the United States have cooperated to protect those nesting beaches. For almost 40 years the U.S. Fish and Wildlife Service (FWS) provided funding for those efforts, but due to federal budget cuts the agency halved its support to only $50,000 in 2014 and announced "continued financial support will likely not be possible in fiscal year 2015 and beyond." Those involved in Kemp's ridley recovery efforts stress the importance of restoring this funding, noting that the value to the species is high relative to the amount of money needed.

"We are way ahead of where we were in 1985, so there's room for hope," said Patrick Burchfield, director of the Gladys Porter Zoo in Brownsville, Texas, and, as chairman of the U.S. Kemp's Ridley Sea Turtle Recovery Field Group for the FWS, part of the recovery project since its inception. "But we were so close, ready to say we'd recovered this species, and now we can't say that."

© Alert Diver — Q2 Spring 2015