June 30, 2011

Walleye fishing has always been a popular sport on northern Michigan's Mullet Lake. A 2009 Department of Natural Resources fisheries survey of Mullet Lake raised eyebrows when it produced an estimate of the walleye population that was low according to historical standards. Both recreational anglers and tribal fishermen - who have a right to fish the lake under the Treaty of 1836 - had concerns about the estimate.

The Fisheries Division's response was twofold. It immediately tightened recreational harvest regulations, by decreasing the creel limit and pushing the opening date of walleye back from the last Saturday in April to May 15. And it committed to teaming up with the Little Traverse Band of Odawa Indians to survey the entire inland waterway system in 2011, because the dynamics of walleye movement throughout the system -- which includes Burt, Mullet, Crooked and Pickerel lakes as well as the Sturgeon, Maple, Crooked, Cheboygan, Black, Indian and Pigeon rivers -- are not well understood.

"We saw these changes in Mullet Lake," explained DNR fisheries research biologist Patrick Hanchin. "The walleye population was not what it was when we last surveyed it in 1998. But we had not surveyed the other lakes in the system since 2001, so we couldn't tell if similar changes occurred in those lakes, too."

The systemwide survey was a Herculean task, said DNR fisheries biologist Tim Cwalinski of Gaylord, who sought help from Fisheries Division staffers all over the state.

"We had three net boats on Burt, two on Mullet and one on Pickerel," Cwalinski explained. "Meanwhile, tribal personnel worked Crooked Lake. And we had two electro-fishing boats running rivers each day and some nights.

"We had boats running all the time."

The survey was complicated by a lingering winter and bad weather as fisheries technicians and biologists rushed to complete the work.

"The idea was to mark as many fish as possible up to the peak of spawning," Hanchin explained.

Using trap nets, fyke nets and electro-fishing boats, survey personnel were able to tag 7,323 walleyes. More than half the fish came from Burt Lake and its immediate tributaries (Sturgeon, Maple and Crooked rivers). Only 1,112 were tagged on Mullet Lake and its immediate tributaries (Cheboygan, Black, Indian and Pigeon rivers).

Hanchin said he formed several immediate impressions.

"The Burt Lake population looked real good as we thought it would," he said. "Mullet Lake looked like it did in 2009; there are not a lot of walleyes there. That tells us that the 2009 population estimate was probably on target."

Time will tell whether the data reinforce those perceptions. Because it's a tag-and-recapture study, biologists will continue to collect data for a number of years. Tag returns will not only provide a basis for making a population estimate, but it will help biologists better understand the movement patterns of the walleyes among the various lakes and rivers.

"Tag returns are already rolling in," Hanchin said. "But we've got to look at tag returns for more than a year to see where and when fish move. We've only got a small piece of the puzzle so far."

Fisheries biologists are beginning to collect some clues about the how the fish use some of the waterway. For instance, the DNR surveyed the lower Black River in 2009 and fin-clipped walleyes there. Electro-fishing on the Black this spring turned up a lot of walleyes with clipped fins. Meanwhile, creel census surveys on Mullet Lake the last couple of years - which will continue -- failed to turn up many fin-clipped walleyes.

"That makes us think those fish stay there in the Black River," Hanchin said. "We'll go back there next spring and look with electro-fishing gear and see if we catch many of those fish we tagged this year."

In order for the DNR to come to valid conclusions, it will need the cooperation of the state's recreational anglers. Hanchin hopes anglers will turn in the tags from any walleyes they catch in the system. (On that note, about half the tags carry a $10 reward for anglers returning them.)

"That's a big part of the study, getting the tags returned so we can determine movement," Hanchin said.

In addition to the tag-and-recapture study, Michigan State University is looking for larval walleye - to try to better define reproductive success - and conducting some walleye stomach contents analysis as part of a forage-fish study. Anglers can help out there, too, Hanchin said.

"If you catch a walleye, freeze the guts and return them to us with information on the lake, the date, and the depth of where the fish was caught, and bring them to the nearest DNR service center," Hanchin said.

The surveys have helped biologists better understand other aspects of the system's fishery, too, Hanchin said.

"Burt and Mullet are tremendous trout waters," he said. "The number of browns and steelhead we saw was impressive. We don't think a lot of people are taking advantage of that fishery. They are tremendous populations and they reproduce naturally in that system."

But the main focus of the study remains the walleye population.

We still don't know what portion of the population heads out to Lake Huron," Hanchin said. "That's something we're going to try to figure out.

"This was a monumental effort to put this together. The planners in our unit had been nervous about this - there are a lot of things that could go wrong - aside from weather, which wasn't pretty. We hauled every boat we could get our hands on from around the state and in one night we electro-fished Burt, Mullet and the Cheboygan River.

"In the end, we were pleased with marking as many fish as we did," Hanchin said. "I think we did a pretty good job."

Learn more about the DNR's efforts to sustain a healthy state fishery at www.michigan.gov/fisheries.