It's one of the more comprehensive studies in recent memory, said Department of Natural Resources fisheries biologist Patrick Hanchin.
By the end of 2013, the DNR, the Little Traverse Bay Bands of Odawa Indians and Michigan State University researchers hope to have a more distinct idea of not only how many walleye live in the Inland Waterway, but what they eat, how successfully they reproduce, and where they move within the system of lakes and rivers.
The waterway begins just east of Petoskey, in Crooked Lake, and stretches through Crooked River, Burt Lake, Indian River through Mullett Lake and out the Cheboygan River. Pickerel Lake connects to Crooked Lake, and the Sturgeon River dumps into Burt; both of those bodies of water are considered in the study.
"The study initially came out of a discussion with the tribes," said Hanchin, after the DNR and the tribe had done a population estimate on Mullett Lake in 2009.
That population estimate showed walleye abundance lower — way lower — than a similar study performed in 1998.
"We started talking together and asking questions (about the smaller population). A lot we knew, but there were other things we didn't know," said Hanchin.
Some of those question marks included how often fish moved within the system, what they were eating and where they were reproducing.
Zebra mussels might explain the walleye population dip in Mullet in 2009, said Hanchin. A similar study in New York found that the invasive mussels were sieving out plankton walleye fry fed on.
But the two organizations were more curious about what was going on in their backyard.
"We wanted to see how those non-native fish species (zebra mussels, round goby, alewife and some rainbow smelt in Mullett) are influencing the food web or whether or not they were contributing to walleye foraging," said Michigan State graduate research assistant Seth Herbst.
Herbst expected to find that yellow perch were a major component of walleye diet across the lakes, but he found more of a mixed forage bag.
In Burt Lake, for example, anglers submitted 249 stomachs for Herbst to study. Of those, 173 stomachs were full, at almost 70 percent capacity. While yellow perch comprised most of the stomach content -- 32 percent of it — mayfly larvae comprised 26 percent, and round goby made up 20 percent.
In Mullett Lake, though, round goby comprised 52 percent of walleye stomach content, while unknown fish 16 percent and crayfish 10 percent.
But Herbst is quick to stress the low sample sizes of all of the lakes, particularly Mullett, which can skew his results.
And what the researchers have found so far is a double-edged sword: while walleyes are feeding on round goby, round goby has the potential to feed on walleye — or, rather, the eggs of walleye.
"We didn't expect round goby to be as abundant as what they were, but walleye were definitely feeding on goby quite a bit. Typically, they feed on yellow perch," said Herbst. "I anticipated a lot of yellow perch and mayfly larvae, but it makes sense walleye would be eating goby. Walleye are bottom, or benthic, predators, and that's where round goby live."
Goby, said Hanchin, are a high-energy food for walleye. But goby also live near gravelly cobble, where fish spawn and lay eggs, potentially skimming an easy meal off the cobbles.
Right now, according to fellow Michigan State student Ryan MacWilliams's research, walleye are best reproducing in the Sturgeon River, the Black River, Burt Lake and parts of Mullett Lake.
And the fish move, too, said Hanchin.
"We've seen significant movement between some of the lakes — Crooked and Pickerel have a significant exchange between them," said Hanchin.
Walleye, too, move between Burt and Mullett, and there is some movement between Burt, Crooked and Pickerel, though that movement is minor. The researchers are tracking walleye movement by electroshocking fish and placing jaw tags on them, which tell the researchers if and how far walleye have traveled when they've been caught by anglers. Some walleye have also been tagged with acoustic transmitters, which researchers can track both with passive receivers throughout the river system and by active tracking from a boat.
Helping track the movement of these fish — and what they're feeding on — is where angler participation is important.
"The other point we try to hammer home is, we're really relying on anglers to help with tag returns and getting stomachs from walleyes," said Hanchin, citing the importance of the study. "When you think about how many lakes we have in Michigan, it's just thousands and thousands of lakes. We generally might get to a lake once every 10 years, or more often we survey some larger lakes. But getting to one and doing a three-year comprehensive study that is that detailed, that might not happen for 50 or 100 years."
How you can help
The Department of Natural Resources, the Natural Resources Department of the Little Traverse Bay Bands of Odawa Indians and Michigan State University need angler participation to effectively study walleye within the Inland Waterway. If you catch a walleye, take the following steps:
— After the legal harvest of a walleye, make sure to keep the fish cold after it is caught to slow the digestion rate of the stomach contents.
— Freeze the fish's internal organs in a bag.
— Mark the bag with the date, approximate depth, length, location at which you caught it and your name.
— Drop the bag at the nearest DNR service center during working hours, including the DNR field offices at Indian River and Cheboygan, as well as the Charlevoix Fisheries Research Center in Charlevoix and the Gaylord Operation Service Center.
— If you should catch a walleye with a jaw tag whether with intention to harvest or to release, remove the jaw tag and submit it to the DNR by using the tag return form you can find at www.michigandnr.com/taggedfish.
For more information, contact the chair of the Northern Inland Lakes Citizens Fishery Advisory Committee Frank Krist by email at firstname.lastname@example.org, or by phone at (989) 734-3100 or (989) 351-2053. Contact DNR fisheries biologist Tim Cwalinski by email at email@example.com or by phone at (989) 732-3541, ext. 5072.
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