Muskegon River spawns state's walleye supply
Written by Muskegon Chronicle   
Saturday, 04 April 2009 10:53
Rich O'Neal arrived at the Muskegon River's Pine Street boat launch earlier this week to find a small army of biologists engaged in the annual ritual of collecting walleye eggs from fish captured in the river.

"We've got a lot of hands here," said O'Neal, a fisheries biologist with the Michigan Department of Natural Resources. O'Neal has helped shepherd the recovery of the Muskegon's walleye fishery over the past three decades.

Since 1978, the Michigan Department of Natural Resources has collected millions of walleye eggs each year from fish in the Muskegon. The biological and economic significance of the process cannot be overstated -- the Muskegon River's fishery provides walleye for dozens of lakes and rivers across Michigan's Lower Peninsula.

This year's egg collection took on added significance as scientists from the DNR, Grand Valley State University's Annis Water Resources Institute and the National Oceanic and Atmospheric Administration were on hand to collect samples of walleye eggs, sperm and scales.

The scientists' work is part of a two-year study to answer one of the most vexing ecological mysteries in the Muskegon River: Why can't walleye successfully reproduce in one of Michigan's healthiest rivers?

"There are a number of potential causes, such as invasive species and water temperatures," O'Neal said. "We hope to figure out exactly what's happening."

Ed Rutherford, a NOAA research fisheries biologist, said the velocity of the river may destroy walleye eggs as they drift downstream. And he said walleye eggs that do hatch often become meals for alewives, a foreign fish species found in Muskegon Lake and Lake Michigan.

Rutherford said the walleye fishery in Lake Huron's Saginaw Bay, and the fish's ability to successfully reproduce on its own, flourished after alewives disappeared there in 2004.

The walleye's inability to sustain its species in the Muskegon without human assistance is not for a lack of trying. About 50,000 walleye migrate up the Muskegon every spring to spawn.

The problem is that the fertilized eggs do not survive to become mature fish. That failure to successfully reproduce is the missing link in the river's walleye fishery.

Absent the human intervention that takes place every spring -- when biologists squeeze millions of eggs and sperm out of fish and raise the fertilized eggs in a hatchery -- the Muskegon's walleye fishery likely would crash, O'Neal said.

"The Muskegon has historically had a natural run of walleye, but pollution (in the mid-1900s) in Muskegon Lake and Lake Michigan decimated the population," O'Neal said.

At the peak of the spawning run, in the 1930s and '40s, as many as 120,000 walleye migrated up the river annually, O'Neal said. Severe water pollution in Muskegon Lake and Lake Michigan disrupted the walleye's reproductive cycle -- by the 1950s, only about 300 walleye spawned in the river each year.

The state began collecting walleye eggs from the Muskegon River in 1978 and raising the fish in hatcheries. The two-inch-long fish are planted in the river after spending about eight weeks in a hatchery and ponds.

The DNR last year reduced walleye production after VHS, viral hemorrhagic septicemia, spread across much of the Great Lakes in 2007. The fish virus, which does not affect humans, has killed numerous fish from 28 different species in Lakes Michigan, Huron, Erie and Ontario.

In previous years, the DNR collected 13 million walleye eggs from the Muskegon River, Little Bay de Noc and the Tittabawassee River. The agency will collect six million eggs this year; eggs will not be collected from the Tittabawassee because that river flows into Lake Huron, where VHS has killed several types of fish.

VHS has never been found in Muskegon River fish or in fish caught on Michigan's side of Lake Michigan. The virus did kill round gobies in Wisconsin last year.

"So far, the fish we've tested from the Muskegon River look fine," O'Neal said.

To prevent VHS from infecting inland lakes or rivers, the state is not stocking walleye this year in lakes that are isolated from the Great Lakes, O'Neal said.

The DNR also will not stock walleye in rivers that are upstream of dams that block fish passage from the Great Lakes. That means walleye will not be stocked in the Muskegon River upstream of Croton Dam, or in the Manistee River upstream of Hardy Dam.

The end result, O'Neal said, is that anglers who have grown accustomed to catching walleye in Houghton Lake and other inland waters will see fewer of those fish this year.

O'Neal said the DNR hopes to resume its normal walleye production once procedures are developed to inoculate the fish eggs against VHS.

"As soon as we can get the appropriate testing done to see if we can treat walleye eggs, we can go back to stocking the fish in inland lakes," O'Neal said.

As DNR scientists search for ways to keep VHS from ravaging walleye, researchers from NOAA and GVSU will spend the next two years studying why walleye offspring can't survive in the Muskegon River. Rutherford said scientists hope to solve that ecological riddle by 2011.

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