In-waterloggerhead study shows more juvenile turtles
Edition:FINAL, Section: LOCAL & STATE, Page B1
Amission off the coast has given researchers optimism about the futureof loggerhead sea turtles. But a day's work studying the animals offCharleston Harbor also offered a graphic illustration of the threatsthese animals face on a daily basis.
State Departmentof Natural Resources scientists have been conducting a two-weekin-water sea turtle study aboard a converted shrimp boat called theLady Lisa in a program funded
by the NationalMarine Fisheries Service. On Thursday, the Lady Lisa's haul was atrio of loggerhead sea turtles — two living and one veryrecently deceased.
According toresearch team leader Al Segars, the study is showing significantlyhigher numbers of turtles across Southeastern waters and adjacent tothe Charleston shipping channel — an area that was last studiedfrom 1991 to 1992.
That study beganshortly after area shrimpers were mandated to begin using turtleexclusion devices, or TED's, on their nets to prevent the creaturesfrom drowning if they were unintentionally netted.
"We're seeing alot more juvenile turtles," Segars said.
DNR biologistMike Arendt said that during the 1991 study, researchers caught 53 or54 loggerheads between central Florida and Georgetown. Today, theyare catching that many in two weeks.
"When we startedthe program in 2000, people said, 'You go out looking for turtles inthe open ocean and you're not going to catch squat,' " he said. "Butwe caught over 300."
According toSegars, an at-sea study has enormous benefits compared with observingfemales as they heave their massive bodies up on the beach to laytheir eggs.
"All themanagement decisions in the past have been determined by studies ofnesting females," he said. "Nobody sees the males. Once they hatch,we don't know what's going on with them because they never return tothe beach."
In addition tobeing able to catch, tag and release males at sea,
researchers havebeen tracking
the creatureswith remarkably compact satellite transmitters that are fastened toshells with a
harmless epoxy.When the animals surface, the transmitter indicates location, lengthof dives, number of dives and water temperature. One animal taggedlast May has been tracked off Dewees Island lately.
Brought on deckwith the Lady Lisa's old shrimp rigging, a pair of near 100-poundturtles were measured for length, weighed and had blood samples andbarnacles on their backs taken for testing. The barnacles go to aCitadel scientist who can tell what part of the world they came fromthrough genetic tests.
The researchersdecided to name one of their turtles David and
fitted him with asatellite transponder. After having his skin poked with needles and aspot on his shell scraped clean of barnacles, a
hissing David wasclearly not amused. But placed atop an old tire that was once caughtin the Lady Lisa's nets, he was helpless to escape.
Among thefindings from five consecutive years of in-water studies has been thediscovery that loggerheads can thrive in a far colder ocean than themid-60 degree waters they were thought to find uncomfortable. Theyhave been found in offshore waters as cold as the mid-50s.
It was alsothought that turtles regularly migrated all over the Atlantic. Butsatellite data has shown that while some do indeed roam far and wide,many prefer to stay within a few hundred miles of the coast wherethey hatched. In one case, transponders have shown turtles severalhundred miles apart making beelines for Charleston waters astemperatures rise.
AroundCharleston, it has also been widely assumed that turtles typicallyfeast on blue and horseshoe crabs, but according to Arendt, a largeturtle on Wednesday "threw up about two gallons of jellyfish," whenit was propped upside down for a blood sample.
In addition tomeasuring levels of toxins such as mercury, pesticides and PCBs,blood tests reveal the sex of juvenile turtles. The sex of embryonicturtles is determined by the temperature of the sand in which theireggs are buried. Segars and Arendt said that an inordinate number offemales could arise from a warming climate or even beachrenourishment, which often places darker, more heat-absorbing sand onthe beach.
As the Lady Lisamade her last haul, the crew was initially excited to see a turtleshell in the net. But excitement soon turned to shock when it becameevident that the 100-pound, decade-old animal had been slicedcompletely in half — apparently by the propeller of an enormouscontainer ship that had passed a few minutes earlier. Though theturtle was dead, its rear flippers still moved as its body waslowered onto the deck. Several on board said they had occasionallyseen animals that had been cut in two by ships, but they had neverseen both halves together, or one so recently killed.
"It actuallyamazes me that this doesn't happen more often than it does," Segarssaid. "If we're to point fingers, we have to point them at ourselvessince we buy the products that come in on container ships, or hitturtles with our own small boats. When wildlife and humans interact,it's the wildlife that often ends up losing."
Reach Chris Dixonat 745-5855 or. email@example.com.
On the Web
Track the movementsof David and other satellite-tagged turtles at www.seaturtle.org.