Biologist is on a mission to preserve the terrapin

Eel pots, beach design endanger state reptile

May 29, 2002|By Heather Dewar | Heather Dewar,SUN STAFF

MECHANICSVILLE - Bundled up against a cold wind blowing across the Patuxent River, biologist Willem Roosenburg scoops up a fat croaker from a net intended to catch terrapins.

"Where are the turtles? Tell me where they are," Roosenburg croons light-heartedly, holding the fish's lips up to his ear. The answer is a loud, unhelpful grunt, and Roosenburg tosses the fish back into the water.

On this unseasonably chilly May morning, the diamondback terrapins he seeks lie out of sight on the muddy bottom of Persimmon Creek, lulled into listlessness by water temperatures hovering around the 60-degree mark.

The creek beds may be the one of the turtles' few havens, say experts like Roosenburg, who point to a long list of modern hazards threatening a creature that has roamed the brackish waters of the Atlantic Coast for at least 750,000 years.

Roosenburg, assistant professor of population biology at Ohio University, is working with other scientists to eliminate those hazards. The tally so far: one down, many more to go.

Maryland's state reptile may be in serious trouble, though no one can say for sure. There are no statewide studies of the animal. But all across their natural range, from Cape Cod to Texas' Galveston Bay, the signs point to a species in decline.

Sea walls are replacing the sandy beaches where they lay eggs. The marshes where young turtles shelter are yielding to waterfront homes. Hatchlings that survive to adulthood face the threats of being slashed by boat propellers and drowning in crab pots and eel traps.

Roosenburg, who grew up in Southern Maryland, has been studying terrapins for 16 years on the same stretch of Patuxent River shoreline. He has tagged more than 8,000 animals, most of them more than once, and has seen an as-yet-unexplained decline in the number of large adult females.

In 1999, Roosenburg's research helped persuade the Maryland Department of Natural Resources to require modification of recreational crab pots so that they let crabs in but keep turtles out.

Next on his agenda are eel pots, which like crab pots can pin the air-breathing terrapins underwater.

Fishermen catch eels as bait for crabs and fish, and for export to Europe and Asia, where they're considered a delicacy. State regulations allow watermen and recreational crabbers to set eel pots in open waters and in the shallows, where terrapins spend most of their time. Typically, the eel pots are baited with razor clams - terrapins' favorite food, Roosenburg said.

The biologist thinks some terrapins could be saved if the eel pots were equipped with rectangles made of heavy-gauge wire that fit around the traps' funnels and prevent them from opening large enough for a turtle. He calls the sleeves "bycatch reduction devices" or BRDs.

"We know the eel pots occasionally do take turtles. We need to quantify the amount," Roosenburg said. "And we need to show whether the BRD has any effect on the eel catch. If we have any hope of convincing commercial watermen to do something like that, you've got to be able to say, `Look, the data clearly show there's no effect.' "

To test the gadgets, Roosenburg and assistants Elizabeth Cook, Karena Fulton and Tom Radzio have become experimental eel fishermen.

Every other day, aboard a 22-foot skiff, the four biologists set 24 matched pairs of eel pots - one yellow and one orange - in the open Patuxent, along the river's shore and in its quiet creeks.

The scientists' yellow floats mark standard eel pots - cylinders made of rubber-coated wire mesh and divided by double-knit polyester funnels into two chambers. The pots marked by orange floats are the same, except that the entrances are equipped with the BRDs.

The work requires a deft hand at the boat's wheel and the same steady rhythm that watermen use, as the crew scoops up the pots and pours their silvery, slithery catch into mesh bags.

The study has been under way for a scant three weeks. Radzio, says the crew has caught 1,400 eels so far and only a couple of turtles, both in pots which lacked the excluders. The two types of pot seem equally good at catching eels, he says.

Most of the eels are youngsters known as "elvers" that have migrated here from the Sargasso Sea, a patch of open ocean beyond the West Indies. Scientists believe Atlantic Coasts eels originate in those tropical waters, then move into cooler regions' rivers and creeks. When they are old enough to reproduce, the eels apparently return to the Sargasso Sea to mate, spawn and die.

The terrapins' habits are quite different.

Most spend their entire lives, which can last 50 years or more, within a few miles of the beach where they were hatched, scientists believe.

Each female returns year after year to the same nest site, Roosenburg said. If the beach is covered by concrete or riprap, the turtle might not lay eggs. Or it might lay them below the high-water mark - where the hatchlings drown as they emerge - or higher up among beach grasses, which send roots into the eggs and prevent them from hatching.

Most nests fail, Roosenburg said. "The eggs are scavenged by raccoons and skunks, and the crows get the leavings. And the hatchlings are a smorgasbord for all kinds of fish."

Roosenberg thinks it should be possible to identify the characteristics of a good terrapin nesting beach and then persuade property owners to replace riprap or sea walls with more benign designs.

It's a goal shared by terrapin expert Marguerite Whilden at Maryland's DNR, who is trying to persuade waterfront residents to stop piling rocks on the shoreline and instead plant underwater grasses to protect beaches from erosion.

"We want to make the habitat better in places where terrapins are not that abundant," Whilden said. "I think it's an animal that, if we give it a little break, they'll come back."

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