ZEBA MUSSELS UP IN MISSISSIPPI

PEORIA, Ill. -- The number of zebra mussels is decreasing in the Illinois River, but experts have found more of the pesky shellfish along the Mississippi.

The tiny parasitic mollusks wreak havoc on water intake pipes and on native freshwater mussels, which are exported to Japan where they are used as the seed to produce cultured pearls in oysters.

Many of the mussels in the Illinois River died in the last two years, said Doug Blodgett, a biologist with the state Natural History Survey.

"Originally, when (zebra mussels) first arrived, it looked like they were here to stay, but in 1994 and 1995, they haven't persisted," he said.

Native to the icy Baltic Sea, the zebra mussels were introduced into the Great Lakes in ballast water from ocean-going vessels. They began showing up in large numbers in area rivers and streams in the late 1980s.

High sediment levels as well as warmer water kept them from spreading.

Illinois River samples once showed more than 70 million zebra mussel larvae per second floating downstream near Havana, but October testing showed dramatically lower numbers.

Fisheries biologist Fred Cronin said his studies of the Mississippi River have shown the number of zebras mussels increasing but not as quickly as they did in the Illinois River in 1993.