Mystery Disease Kills Michigan Fish

MUSKEGON, Mich. — A mysterious ailment has killed more than 1 million newly hatched Lake Michigan coho salmon this year, potentially threatening a $1-billion recreational fishery.

As a result of the ailment, in which the stricken fish stop growing and die, there will be far fewer coho available for anglers to catch when the fish mature in 1995, said state Department of Natural Resources officials.

The cause of the fish loss, affecting six hatcheries in Michigan, Illinois, Indiana and Wisconsin, remains a mystery. But government researchers are studying possible causes including disease and viruses, toxic contaminants in the lake, genetic problems and potential nutritional deficiencies caused by exotic species like the zebra mussel and spiny water flea.

The ailment, called “dropout syndrome,” killed 90% of the fish being raised earlier this year at the Platte River Fish Hatchery, near Interlochen in northwest Michigan.

Coho is the second species of Lake Michigan salmon to be ravaged by a mysterious ailment. A bacterial kidney disease discovered in 1988 has devastated a once-thriving chinook salmon fishery.