Rise in dead fish is linked to weather
Written by Detroit Free Press   
Monday, 01 May 2006 17:36

Fishing sites on the Internet are abuzz with dark rumors of chemical spills, pesticide poisoning and government cover-ups after a large number of dead fish were found in southern Michigan lakes and rivers.

But biologists say the recent fish kills -- mostly in southeast Michigan and the Ohio waters of Lake Erie -- are the result of unusually high water temperatures and spawning stress.

Tony Zain of Roseville guides for bass and walleyes on the Detroit River or Lake St. Clair almost daily from April to November.

Zain said he saw "a lot of dead fish on St. Clair" near the end of the April. "There were carp and drum and muskellunge" dead, "but no walleyes or smallmouths.

"There's a lot of rumors floating around about how people think the DNR had something to do with it, but to me, it looks like something natural. You always see some dead fish in spring. There's just more of them this year, and that's probably because of the warm water."

Another angler who fishes on the Detroit River for walleyes almost daily is Nick Homayed of Dearborn Heights. He was surprised by the number of dead fish he saw and by the refusal of seagulls to eat them.

"There were dozens of them out there a few days ago, and mostly muskies," Homayed said last week. "The gulls would go over and look at them, but they wouldn't touch them. That's why a lot of people think it must have something to do with pollution."

Anglers on the Detroit River have seen large numbers of dead muskellunge, many 4 feet or longer. Gary Towns, a research biologist for the state Department of Natural Resources, said the fish probably were victims of spawning stress, which kills many muskellunge every spring.

The higher number of dead fish reported this year likely is the result of one of the warmest winters on record, Towns said.

Water temperatures increased about 15 degrees in two weeks in early April, kicking up the metabolism of the fish when relatively little food was available and they were using large amounts of energy.

Each winter muskellunge spend much of their energy building new reproductive systems.

The higher stress is on the females, who must create masses of eggs. Anglers report that a high percentage of the dead muskellunge were very big fish, and those almost always are females.

Towns said spawning stress makes fish more susceptible to disease. Most of the muskellunge floating on the Detroit River had been dead for some time, making it impossible to tell what killed them, "but we got a fresh one the other day, a 50- or 51-incher, and ran it to the Michigan State University lab to see if we can find any disease organisms," Towns said.

Some anglers said on Internet blogs that they were suspicious of a cover-up because seagulls wouldn't eat the dead fish, which they said was an indication that pollutants had poisoned the fish.

"The seagulls don't eat them because most of the fish have been dead for weeks, and they're rotting and covered with fungus," Towns said. "They lie on the bottom and then float to the surface after they bloat.

"Seagulls won't feed on rotten fish when there's fresh fish available."

Besides the Detroit River and Lake St. Clair, numerous dead fish also have been found on Kent Lake at Kensington Metropark and on Lake Macatawa, just off Lake Michigan near Holland.

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