Phosphorus to blame for Lake Erie dead zones

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CLEVELAND (AP) -- Melting snow carrying phosphorus from northern Ohio's farms contributes to so-called "dead zones" in Lake Erie where the oxygen is low, researchers say.

Storms flush phosphorus, a common farm nutrient, into drainpipes, creeks, then rivers and finally into Lake Erie. Once there, phosphorus causes extreme plant growth and algae, which suck oxygen from the water when they decompose.

Anglers had been reporting thousands of yellow perch floating off Cleveland and Lorain in recent days. This die-off follows a recent die-off of tens of thousands of sheepshead. "At first we thought the perch kill may have been a by-catch 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."

The Cleveland Plain Dealer reports the majority of the dead perch are in the 6- to 8-inch range, members of a large 2003 year class. 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.

"We always knew weather was important, but were not able to document it," said Gerald Matisoff of Case Western Reserve University, who headed a U.S. team of Lake Erie researchers. "Now we're seeing a connection."

The findings were presented at a Great Lakes conference in Windsor, Ontario where the International Association of Great Lakes Researchers had convened for their annual conference.

"Dead zones" create an area devoid of fish, worms and clams on the bottom of the lake, hurting commercial and recreational fishing. Researchers estimate that two-thirds or more of the phosphorus entering Lake Erie comes from runoff during storms.

While summer storms also wash fertilizer into the lake, big winter snowmelts can be worse. Four of the 10 snowiest winters to hit the region have occurred since 2000. "We will need to focus some of our land management issues toward trying to keep the soil on the land and the nutrients on the land," Matisoff said.

Fish kills have become common this year. The Michigan DNR 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.