EL DORADO ? The state’s only known population of zebra mussels has increased dramatically, and a state biologist said El Dorado Lake’s infestation of the pesky mollusks was likely to get worse.

“The news isn’t good,” said Tom Mosher, an aquatic research biologist for the Kansas Department of Wildlife and Parks. “Zebra mussels are pretty much everywhere in the lake.”

Officials lowered the water level 3 1/2 feet in an effort to expose and kill the mussels, which were first found at the lake in late August. While the mussels exposed by the draw-down are dying, Mosher fears many more are thriving within the lake.

The mussels were living as far down as 17 feet this fall.

Last week, Mosher and a team of investigators found at least 200 mussels per square meter in many areas of the lake. In the summer, the concentration was about 55 per square meter and the mussels were largely confined to the southern parts of the lake.

One zebra mussel can produce up to 100,000 larvae, Mosher said.

“It’ll probably just keep getting worse and worse for the next five years or so; then they may start to die out,” he said. “It’s a new ballgame here; we just don’t know what we’re going to have happen.”

El Dorado’s zebra mussels are the first in Kansas. Populations have been found recently in two Oklahoma river systems.

The highly prolific mussels are known to out-compete native mussels and small fish for food in many waters. They’ve also caused millions of dollars of damage by clogging intake structures for water supply plants.

Biologists think that zebra mussels or their larvae are transported from place to place in water or vegetation hauled by ships, boats or boat trailers.