Lake Erie fish are unexpectedly dying, with anglers reporting thousands of yellow perch floating off Cleveland and Lorain in recent days. It follows a massive die-off of tens of thousands of sheepshead, or freshwater drum, along the Ohio shoreline in late April and early May.

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That fish kill was due to a viral infection, hemorrhagic septicemia or VHS, diagnosed by the U.S. Fish and Wildlife Service laboratory in La Crosse, Wis.

"At first we thought the perch kill may have been a bycatch issue from commercial trap nets, but it was too widespread," said Kevin Kayle, an ODNR Division of Wildlife fisheries biologist at the Fairport Harbor station. "The perch kill stretches from Lorain to Conneaut.

"It's important to know if this could be VHS spreading from freshwater drum, or perhaps a bacterial infection in perch like Ontario experienced last spring in the Western Basin [of Lake Erie]."

The majority of the dead perch are in the 6- to 8-inch range, members of a plentiful year class that hatched in 2003. Only a few thousand perch from a population in the millions has been affected so far, said Kayle. The most likely explanation is that those perch were stressed as the high-density year class spawned for the first time. Also stressing Lake Erie's fish stocks were last summer's abnormally hot weather followed by a mild winter with no ice cover, allowing winds to keep Lake Erie stirred up and muddy.

Fisheries biologists were on Lake Erie on Monday looking for perch. Only fish that are sick or have just died can be accurately sampled for a bacteria, virus or fungus. Perch brought in by sport anglers or caught in DOW survey nets have been in excellent shape.

Fish kills have become common this year. The Michigan Department of Natural Resources is still investigating a winter kill that claimed about 4,000 muskies in Lake St. Clair and the Detroit River. Michigan fisheries biologist Gary Towns said the muskie kill represented a small percentage of the Lake St. Clair population, and muskie fishing should again be excellent in 2006.