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Story Nine
Fishing for Clues
By MaryAlice Yakutchik
Lake Jesup -- Welaka was the first name for the St. Johns, a Seminole word meaning "River of Lakes." It's a picturesque descriptive, one I aim to expand upon by suggesting this: Think boa on a binge. If rivers are curvy and snake-like, then the St. Johns is a serpent that's swallowed a whole lot of things whole. The biggest bulge, in the belly region, is Lake George. Lakes Monroe and Jesup are prominent protuberances to its south.

These three freshwater lakes comprise a unique study area for Jim Gelseichter, a scientist from Mote Marine Laboratory in Sarasota whose research interest is not reptiles but elasmobranchs: an animal family that includes sharks, skates and rays. Unlike the bony bass these lakes are famous for, elasmobranch fish have skeletons of cartilage.

The St. Johns lays claim to the only elasmobranch in North America that lives permanently in fresh water.


Overall, elasmobranchs don't venture into freshwater. Some species do occasionally find their way up into the river, bull and tiger sharks among them, but they're casual visitors -- snowbirds -- not residents. However, the St. Johns lays claim to the only elasmobranch in North America that lives permanently in fresh water. It's an Atlantic stingray (Dasyatis sabina) -- the very same long-winged fish swimming along the coasts -- that has completely adapted to a river environment: It's born here; it reproduces here, giving live birth to several "pups" at a time; and it dies here.

This St. Johns population commands scientists' attention because it lives all its life in the St. Johns and it has retained the ability to still live in the ocean, an ability dependent upon salt-regulating cells in its gills; cells not so very different from those in human kidneys.

"They are as tough as you get," Jim says, openly admiring of the ability of St. Johns rays to live in a greater range of temperatures and salinity than any others. "They can survive fulltime in zero percent salinity and, despite that, they can re-adapt to salt water. They are one of a kind in that respect."

Having studied them in the field and lab for a handful of years, Jim is motivated by the secrets they can tell about the health of the river, and maybe even human health.

The focus of Jim's research is comparing the reproductivity of stingrays living at three different wide spots (aka lakes) in the St. Johns: George, Monroe and Jesup.

Then there's poor, algae-blanketed Jesup, afflicted by pesticides, sewage, fertilizers and industrial chemicals. It's the most polluted of the three, in fact one of the most polluted lakes in central Florida.


George, 72-square-miles of water, is flushed both by springs and by sea; it is the healthiest of the trio, partly because public lands around large parts of its periphery buffer it from agriculture and development. (When our houseboat is anchored overnight in Lake George, the tiki torches on our top deck are the brightest lights on the river as far as the eye can see; the only other light at all comes from a shooting star, the most dazzling I've ever seen.)

Monroe, smaller than George and more affected by agriculture and persistent development, is moderately polluted.

Then there's poor, algae-blanketed Jesup, afflicted by pesticides, sewage, fertilizers and industrial chemicals. It's the most polluted of the three, in fact one of the most polluted lakes in central Florida. That's where we are today, fishing for stingrays.

Jesup suffers because it has been amputated from the river proper. Once, there were two open mouths in Jesup on its northern edge, one gulping in water from the St. Johns and one spitting it back out; a healthy counter-clockwise flow from the river effectively flushed Jesup about every 30 days. Its plumbing troubles began with a canal in the 1930s and were compounded with a causeway in the 1950s. It takes about 300 days for Jesup's water to turn over.

"This system traps nutrients and pollutants," Jim says, motoring out to his collecting area. An filmy blue-green surface hides the fact that the lake bottom, just 8-feet-deep, is covered in organic-rich muck tainted with substances that have been banned for 30 years: DDT among them.

Jim studies a suite of 30 pesticides in the tissues of the stingrays he catches. Overall, he's collected 700 stingrays in the study -- and never once has been stung, he notes in tone of one who knows it's only a matter of time. He fishes for rays by attaching dozens of bits of shrimp to dozens of hooks intermittently spaced along a long line which he anchors to the lake bottom. And then he waits. And waits.

Rays are slow-moving bottom feeders, opportunistically crushing snails, insect larvae and small crabs with flat teeth. (Their "sting" comes from a neurotoxin produced by cells around the spine, and is strictly a defensive weapon, unleashed only if pressed or stepped on. Jim's first-aid advice if stung by a ray is first to flush the neurotoxin from the wound and then apply heat; heat kills the protein that makes up the toxin. Heating pad or hot liquid not handy? Fresh urine will also do the job.)

After an hour passes, Jim pulls up the line, winding it around a big spool. He usually finds at least a few rays dangling from the hooks. If he's lucky, he'll catch a female with fresh wounds; sometimes even one with a male still attached, biting her on her pectoral fin. (The mating ritual, Jim says, is "quite violent.")

His goal today is to collect five females for tissue sampling. Males will be tagged and released. There's not a one on any hook.

We motor closer to shore and Jim patiently re-baits all the hooks and then lays the line down again. It's slow going. We pass another hour, talking over the drone of traffic from a stretch of expressway that has bisected the lake since the early 1990s.

"The Jesup animals are reproducing quite well, but their hormone levels are higher than you find in George and Monroe; higher levels of testosterone and much higher levels of estrogen"


In all three lakes, Jim says, the female rays are producing eggs and pups year in and year out. The effects of pollution on the rays' reproductivity is subtle, he adds, but real.

"The Jesup animals are reproducing quite well, but their hormone levels are higher than you find in George and Monroe; higher levels of testosterone and much higher levels of estrogen," he says.

His latest data, from 2004, seem to indicate a problem with ovulation in the Jesup rays, Jim says. There's no clear cause, however.

Pesticides can mimic hormones, he explains, by turning on and off certain biological switches that cause physiological changes. Jim's wondering if the Jesup rays are compromised in their ability to rid themselves of hormones and pollutants, a job handled by the liver.

Whether or not human consumers of fish are similarly affected is an ongoing debate. No signs anywhere warn fisherman about potential health threats.

Would Jim eat fish from this lake? No, he says. He certainly would not.

Jim toils all day and catches just one ray. He'll be out again early tomorrow. His five-years worth of findings are hard-won. He hopes they're not ignored.

"Policymakers, when they're setting standards for the river, need to hear and consider these sub-lethal effects (of pollution)," he says, "subtle effects which, although they don't kill the animal, can impact its reproduction and growth."


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