By Howard Meyerson

Saginaw, Mich. — Scientists studying walleyes in Saginaw Bay have long known that they migrate into Lake Huron during the summer months. But the results of new telemetry research using radio-tagged fish shows as many as 2 million walleyes – far more than expected – leave for open waters as early as June.

The hydro-acoustic sensors (red) mark the passage of walleye with tiny, implanted transmitters. Map courtesy of the Great Lakes Fishery Commission

“Previously, we had evidence that it was a July or August phenomenon,” said Dave Fielder, a Michigan DNR research biologist at the Alpena Fisheries Research Station. “Based on (previous) jaw-tag returns from anglers we thought 8 percent of the walleyes out-migrated. But we see it’s more like 50 percent.”

Fielder and other scientists do not know why they leave. It may be for cooler waters or for food. The radio-tagging study is providing information about where they go. Strategically placed acoustic sensors on the bottom of Lake Huron are helping researchers track the radio-implanted fish, according to Fielder. The data collected lets them know whether Saginaw Bay walleyes swim south to the St. Clair River or north to Drummond Island.

“Thunder Bay and Alpena anglers know there is (typically) a surge in walleye fishing in June and have said, ‘Oh the Saginaw Bay fish are here.’ I think they are right,” Fielder said. “The Saginaw Bay fish are coming to and through Thunder Bay.”

The preliminary 2011 information is the first take from the three-year study funded by the Great Lakes Restoration Initiative. To date, $5 million has been spent to set up a network of hydro-acoustic sensors. The 350 sensors installed so far are used for a variety of research projects like tracking walleye, sea lampreys, lake trout, Great Lakes sturgeon, and Asian carp, according to Marc Gaden, communications coordinator with the Great Lakes Fishery Commission.

The walleye study relies on approximately 160 sensors located on the bottom of Lake Huron, and bullet-size transmitters that have been surgically implanted in just over 400 walleye. Half of those fish come from the Tittabawassee River spawning run.

The other half comes from the Maumee River on Lake Erie.

“We know that walleye move around the Great Lakes and cover a wide geographic area,” Gaden said. “But does that movement relate to spawning and year-class recruitment, are they coming from Lake Erie, or do they spawn in the Tittibawassee River?”

That’s what scientists are trying to discover, according to Fielder. Chris Vandergoot, of the Ohio DNR, could not be reached for this story, but Fielder said his Ohio counterpart is using the technology to determine whether Lake Erie walleyes are migrating into Lake Huron.

Lake Erie has been home to an estimated 70 million walleye in past years, according to Fielder. Jaw-tagging studies showed 1.5 percent of that population migrated into Lake Huron.

“We know from those studies that there has been substantial movement,” Fielder said. “But it looks to us like there was no movement in 2011. So, that contribution to the Lake Huron population is declining.”

Knowing that, or how many may end up in commercial fishing nets down by Sarnia, helps Michigan fisheries officials determine appropriate management decisions, Fielder said.

“If we can get a network of these sensors established in the Great Lakes basin, any scientist could come to us and put a proposal forward to take advantage of the array. This is something that is widely used on the east coast and west coast of North America now,” Gaden said.

Anglers are being encouraged to help with the walleye project by returning any fish found with a transmitter and tag, which has numbers to contact. The reward is $100 for each.

“Of the original 400 walleye, we have 51 turned in by anglers so far,” Fielder said. “When we get them (the transmitters) back we redeploy them.”

Study details and maps showing walleye movement on Lake Huron can be found at www.glfc.org/telemetry/walleye.php.

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© 2012 Howard Meyerson

This story and more can be found at: Michigan Outdoor News