Stress may be factor in muskie deaths

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June 15, 2006 Eric Sharp

A large die off of muskellunge in Lake St. Clair and the Detroit River in May was attributed at first to above-average spawning mortality caused by unusually warm weather in April followed by unusually cold weather in May.

The Department of Natural Resources now says that the stress on the fish may have been exacerbated by a disease called viral hemorrhagic septicemia, which caused a huge die-off of freshwater drum and bluegills in Ohio waters of Lake Erie at about the same time.

"I know some people reported seeing 200 dead (muskies) in a day, but I think that was mostly because they all lay on the bottom until the water got warm, then they all filled with gas and floated to the surface at the same time," said Gary Towns, a DNR fisheries biologist.

"We did an aerial survey, and our best guess is that there were about 2,000 dead muskellunge. We know from other die-offs that only about half the fish usually float to the surface, so figure that total was maybe 4,000. That's still only about 1-to-3% of the muskies in the lake."

One muskellunge carcass has tested positive for the disease, and Gary Whelan, the DNR's fish production manager, said he hopes to get results on others in a few days and that the disease seems to have died off.