Carp dying in bay areas

Unusual numbers of fish found dead in Chesapeake rivers

`It's been a wild spring'

`Spawning stress,' water temperatures, bacteria are blamed

June 05, 2000|By Joel McCord | Joel McCord,SUN STAFF

Carp, those overgrown goldfish that root in the mud of upper Chesapeake Bay tributaries for dinner, are dying off in unprecedented numbers in creeks off the Bush, Bird, Middle, Elk, Sassafras and Choptank rivers.

Scientists blame a combination of see-sawing water temperatures, a bacteria they haven't identified and "spawning stress" -- male carps ram females to shake loose eggs, then fertilize them as they settle to the bottom.

"The ritual itself is very energetic," says Charles Poukish, who is tracking the deaths for the state Department of the Environment. "There are a whole lot of males competing for one female. It's basically a circus out there."

It's not unusual to see dead carp, worn out by the mating ritual, floating on the surface in the spring, "but only a few here and there," Poukish says.

"Most of these, we're getting 100 to 150 in a quarter-mile stretch. We're talking easily 5,000 fish, and it's probably a lot more than that we don't know about."

Carp, popular as food in Europe, were introduced to the United States in the 19th century and spread quickly through fresh and brackish waters with the help of a government-sponsored program. But they never caught on in this country, says Kent Mountford, senior scientist with the Environmental Protection Agency's Chesapeake Bay Program.

"Some people eat them, but it's mostly very poor people, subsistence fishermen," he said.

As a result, the carp population has outgrown its spawning territory, Poukish says.

"There are too many fish for the water available," he says. "The species is very prolific, it's widespread and it is not kept in check by natural predators. We know that Mother Nature will do this kind of thing on a cyclical scale."

MDE started getting reports of fish kills in mid-May, and the die-off continues, Poukish says. It is unclear whether it has peaked.

Debbie Haverly and her family were playing at the edge of the Magothy River in Anne Arundel County May 20 when they saw "fish floating up," she recalls.

"There must have been 50 to 100 of them."

Thomas G. McWilliam Jr., who lives near the mouth of Plum Creek in Cecil County, says he saw more dead fish Thursday.

"We noticed three large carp of spawning size dead on the beach," he says. "Occasionally a dead fish washes up, but I don't recall anything like this."

Meanwhile, MDE has collected samples of dead fish and sent tissues to laboratories for analyses. They haven't determined what killed the fish yet, but they have some ideas.

Water temperatures went from the 50s to the 70s "almost overnight" in early May, then dropped quickly during a rainy spell at the end of the month, putting stress on the fish beyond the usual rigors of spawning. In addition, some of the dead fish have damaged gills with brownish streaks and show signs of a secondary bacterial infection, Poukish says.

"Normally, the bacteria would not affect a fish unless it was weakened by other stresses," he says.

The die-off clearly demonstrates that nature "throws a lot of curves at creatures in the bay," says Mike Hirschfield, a vice president of the Chesapeake Bay Foundation.

"We need to make sure that we don't make things worse for them."

He compared the carp die-off to the "mahogany tide," an algal bloom that rose in the lower Chesapeake last month and has since dissipated.

"It's been a wild spring and the weather plays a role, in the case of the carp and the mahogany tide," Hirschfield says. "But then, so do we."

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