Johnson

A few decades ago, when I was on a team mapping a proposed lake trout refuge, an old friend and mentor quipped: “Fish have tails and they use ’em. You had better make the refuge big”.

It seems I am reminded of fish tail power almost daily in my work with fish. If, for example, it’s July and you want to catch some of the Chinook salmon that had been stocked at Rogers City, you had better trailer your boat to Green Bay, Wisconsin, where most of those fish go to feed during summer. Another example: lake trout that spawn in Thunder Bay in November are chowing down in Saginaw Bay (that’s where the most food is) by late December. Almost all of the walleye caught in Thunder Bay and Presque Isle originated in Saginaw Bay.

Let’s focus on walleye and their nomadic tendencies. I used to see them as a bit sedentary as fish go. Wrong! Dr. David Fielder heads the DNR’s walleye research on Lake Huron at the Alpena Fishery Research Station and is a leader in fish telemetry (use of electronic tags to monitor fish movement) for Lake Huron. I had the chance to speak with Dave this week. He has stories that would take up a dozen of these columns. Here is just a sample. See the next installment for more of Dave’s discoveries.

Dave and his partners in research employ two kinds of tagging. Acoustic tagging involves inserting a tiny signal-emitting capsule into adult walleye; as the fish moves around, the signals are picked up by an array of receivers deployed all over Lake Huron. Each fish’s acoustic tag emits a unique, identifying signal. This allows mapping of daily movement paths for each tagged fish. These fish also receive the other type of tag – a plastic “spaghetti” external tag inserted near the dorsal fin with a number on it and DNR contact information. Some tagging involves only the spaghetti tags. Anglers catching fish with these external tags are asked to send the tag number and information about their catch to the DNR. The spaghetti tag returns from angler’s, science survey’s, and commercial fisher’s catches allow Dave to estimate harvest and annual survival rates as well as where walleye are being harvested.

So how and where are all these walleyes being tagged? This in itself is a spectacular story of recovery. Walleye were virtually annihilated from the Saginaw River system from pollution caused by logging, industrial, and municipal wastes. Center stage of this horror story was Midland downstream of Dow Chemical on the Tittabawassee River. Thanks to the Clean Water Act and other initiatives, one of the chief spawning sites for walleye is now, of all places, at Dow Dam on the grounds of Dow Chemical, representing an amazing turnaround. And Dow Dam is where the majority of walleye have been tagged since the mid-1980s. It so happens that walleyes are drawn to DC electrical current, thus walleyse are sampled using “electrofishing” boats. These boats are designed to attract fish, using electric currents, to where the boat crew can net them. The fish are then measured, and spine samples are taken for ageing the fish. (Age is determined

in the lab by sectioning the spines and reading annual rings much as foresters age trees.) Then the fish is tagged and released.

Both the acoustic and spaghetti-only tagged fish show up in Alpena – regularly. One female walleye set the speed record back in the 1990s, having been caught in Alpena just two weeks after it was tagged at Dow. That’s a distance of 130 miles and about 9 miles per day, if it took a direct route to Alpena with no detours.

Then there was the acoustic tagged walleye that not only migrated to Thunder Bay, but it also kept going to the Straits of Mackinaw and disappeared into Lake Michigan where there were no acoustic receivers. So, we don’t know how far into Lake Michigan it went. Then, just to prove a point, that same fish returned on a reverse route that fall, spawned again at Dow in early April, and repeated its trip up Lake Huron and into Lake Michigan a second time. Then, presumably, its battery ran out.

These fish are not exceptions. Dave, using computer models he has built over the last 30 years, estimated that approximately four million walleye born in Saginaw Bay area migrate to the north-central shore (Oscoda to Presque Isle) of Lake Huron every year.

If by now you have surmised that there are a lot of walleyes produced in Saginaw Bay, you would be right. Next time I will tell more of what Dr. Fielder and his cohorts have learned about this rising star of our Great Lakes fisheries – the Saginaw Bay Walleye Phenomenon.

Be sure to visit the new Besser Museum Fishery Heritage Exhibit this June, where you can learn more about our shared Great Lakes fishery heritage.