Experts puzzled by appearance of dead turtles

Scientists unsure why nearly 2 dozen washed up along coast in past 10 days

`The numbers are high'

Hurricane-related change to current may be factor

September 11, 2004|By Chris Guy | Chris Guy,SUN STAFF

Nearly two dozen dead sea turtles - huge loggerheads and leatherbacks - have washed up on Maryland and Delaware beaches in the past 10 days, including one that startled visitors near 47th Street in Ocean City over Labor Day weekend.

At least nine of the animals, which are among six endangered turtle species protected by U.S. law, have been found on Assateague Island and in Ocean City since Sept. 1. In Delaware, marine stranding response teams have examined 17 of the reptiles in a week.

So far, scientists say, they have few clues as to why the turtles died. They have found no evidence that they were ill or fell victim to some environmental hazard they encountered in the deep waters off the Atlantic coast. As another hurricane churns into the Gulf of Mexico, some researchers speculated that violent weather in recent weeks might have created new or altered currents that have pushed the turtle carcasses onto area beaches.

Many of the turtles have been too decomposed for laboratory analysis. Testing on animals that were nearly intact has not been completed.

"At this point, we have nine confirmed: two leatherbacks and seven loggerheads," said Julianna Brush, a member of Maryland's Department of Natural Resources turtle and marine mammal response team, which investigates reports of dead turtles.

"At least two of them showed evidence of boat strikes. One was entangled in a commercial buoy line," said Brush, who is based at the University of Maryland's Cooperative Oxford Laboratory. "The numbers are high, especially for leatherbacks. Normally we would average maybe two a year."

In Delaware, researchers from the Marine Education, Research and Rehabilitation Institute are concerned because 10 of 17 sea turtles they have examined have been leatherbacks, which is unusual.

"I don't think this is any kind of epidemic out there, but normally we'd have 10 leatherbacks in 10 years," said Suzanne Thurman, MERR's executive director. "It's horrifying to think there might normally be this many, but I'd say it's likely that abnormal currents and tides brought them here."

Large numbers of Atlantic croakers washed ashore this summer at beaches from Delaware to Virginia and in Florida, but experts see no link to the turtle deaths.

Specialists from the Virginia Institute of Marine Science in Gloucester Point have logged four beached turtles since last month, including the remains of one loggerhead found on Virginia's Eastern Shore last weekend, said research assistant Meredith Fagan.

"These turtles have started their annual migration south," Fagan said. "During this time of year, we would typically see more strandings."

Researchers know little about the animals, which are thought to have a life span of 50 years or more. Leatherback turtles, the largest living turtles, roam the depths of the Atlantic and, sometimes, the northern Pacific. They can grow to 7 feet and can weigh 1,400 pounds. They feed primarily on jellyfish, a diet that sometimes brings the creatures into the Chesapeake Bay.

Loggerheads, the most common sea turtle in the southeastern United States, can grow to 4 feet long and weigh as much as 400 pounds. The creatures frequent underwater structures and reefs, eating jellyfish, crabs and mollusks.

David Schofield, who heads the marine animal rescue program at the National Aquarium in Baltimore said recent months have brought an unusually high number of strandings of marine mammals such as dolphins and whales from Maryland to South Carolina. During the first three weeks of last month his team was called to handle a bottlenose dolphin, a minke whale and a common dolphin.

"There do seem to have been a lot this year," Schofield said. "Ninety percent of sea turtle deaths come from ingesting plastic, becoming entangled in fishing gear or being struck by boats. But it is a disturbing trend if you think of these animals as sentinels of ocean health."

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