BANGOR (AP) – Scientists would kill possibly thousands of white perch under a project to help restore the ecological balance of East Pond in the Belgrade chain of lakes in central Maine.

East Pond has bloomed green with algae in seven of the past 10 years. If algae blooms continue unabated, they could sap the oxygen that fish and other organisms need to survive and transform the lake into a sterile one.

Camp owners have attempted to limit the algae blooms by reducing the runoff of phosphorus and other nutrients that can make their way into lakes from sewage systems, lawn fertilizer and household detergents.

But it hasn’t been enough, and researchers from the state, the University of Maine and Colby College are now investigating whether a process known as “biomanipulation” can re-establish the natural food web.

Scientists believe the algae are blooming because the zooplankton that feed on algae are themselves being eaten by a prolific population of white perch.

In a balanced system, the zooplankton – tiny creatures commonly known as water fleas -would graze on the algae, keeping its population under control, said Katherine Webster, an associate professor at the University of Maine.

“They’re very effective grazers. We call them the cows of lakes,” Webster said.

But young white perch eat zooplankton, and East Pond is estimated to have about 165,000 of the fish, said Richard Seaman, vice president of the local lake association.

During the coming year, researchers will study sediment cores, water samples and the contents of fish stomachs to develop a detailed picture of East Pond’s food network. They will use environmental monitoring equipment to study such factors as cloud cover, wind, temperature and humidity.

“I think we’re going to learn a lot about the lake and the way it works as time goes on,” said Melissa Evers, an environmental specialist with the Department of Environmental Protection who happens to have a home on East Pond.

If the data back up scientists’ suspicions, perch removal would likely start in 2006.

It’s not a sure thing that removing the perch would take care of the problem, but anecdotal evidence suggests it can make a difference.

At Sabattus Pond in Sabattus, Greene and Wales, once one of the most algae-clogged in the state, waters became clear after pike, anonnativee predator fish, were illegally introduced and began feeding on the perch, Evers said.

Introducing predators to East Pond is not an option -nonnativee fish introductions are illegal because they can create numerous biological problems – but researchers believe that killing the perch directly could have the same result.

Webster said it’s doubtful all the perch could be removed from the lake, but she believes the population can be kept low enough to keep the water clear.

State fisheries managers have few concerns about the project. Perch aren’t a popular game fish, and it’s unknown whether the fish are even native to East Pond.

If the project works, the process could be used in other ponds in New England.

“The more we get into the project, the more exciting it becomes. Potentially, we’re dealing with something much larger than East Pond,” Seaman said.


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