• Michigan is using genetic testing to determine whether stocked fish survive
• A pilot program in the Upper Peninsula found fish stocking is working in some lakes, but not others
• The DNR spent more than $11 million on fish stocking in 2024-25

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The Michigan Department of Natural Resources has begun using genetic testing to track the success of some of its fish-stocking operations. 

The goal is to find out if fish living in a particular water body descended from the parents of stocked fish. Doing so helps the DNR know if its multimillion-dollar stocking efforts are paying off by telling them if the stocked fish are living on in the waterway.

“Think about genetics (testing) like Ancestry.com, 23andMe,” Jen Johnson, senior fisheries management biologist for the DNR, told theMichigan Natural Resources Commission during itsmeeting Wednesday in Marquette. “Are you related? That’s the big question that we’re asking here.”

The DNR spends about a third of its annual budget on fish rearing and stocking. In the 2024-25 fiscal year, that totaled over $11 million. According to the department, past methods of tracking success have been limited or costly. 

Pilot research with the new method, known as parentage-based tracking, has been cost-effective, freed up staff time, and has shown some illuminating results.

“This tool is going to open up a lot of insights into what we do at the fish division,” said Randy Claramunt, fisheries chief for the DNR.

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It will allow the division to assess whether fish they catch were born naturally or from fish bred and stocked by the DNR ,which will give them a sense of which approach is working better.

The DNR breeds and stocks fish primarily to create new places for people to fish a certain species or to add numbers to struggling populations. The department can check to see if stocked fish are surviving in their introduced location by tagging the fish and then searching for them there at a later date. 

But tagging methods have been problematic. Using physical tags has meant individually tagging fish. Tags can get lost or an angler may fail to report when they reel in a tagged fish. 

Another method of tagging involves internally marking fish, but that method can only be verified on dead fish using a microscope, and it takes up a lot of staff time. It’s also more expensive than genetic testing.

Parentage-based tagging involves genetically analyzing the DNA of the parents of a brood of stocked fish. Researchers collect the parents’ DNA since their offspring are fragile when young. Doing so can also help them determine the qualities of the most successful parents. 

Later, when fish are caught in an area where stocking occurred, their DNA is sent to a lab at Michigan State University to find out if they were related to the parents of the stocked fish.

“It’s a really cool technique. But before we actually implemented this statewide, it was a wise idea to start a smaller pilot project to see if this is an actual effective technique,” Johnson said.

So she decided to use parentage-based tagging to evaluate the success of the DNR’s walleye stocking methods in Dickinson and Iron counties in the Upper Peninsula. 

Between 2024 and 2025, Johnson’s team collected fish from some waterbodies there and the results were pretty illuminating. 

Out of 25 fish caught in Lake Emily, 24 were found to be related to the stocked fish family. So stocking was working there. 

But the opposite was found in two other lakes. Out of 147 fish caught in Hargerman Lake, only two were related to the stocked fish. Out of 34 fish caught in Lake Ottawa, again just two were related to the stocked fish. 

Using further genetic analysis, Johnson determined that the walleye in Hagerman Lake were not related at all to the walleye found in Little Bay de Noc, which is where they had been getting the parents for recent walleye stocking reproduction efforts. 

However, they found that the walleye in Hagerman Lake were genetically indistinguishable from walleye found in Lake Gogebic, where the parents for fish stocking efforts of the 1980s were taken from. Efforts from that decade were successful, while the recent efforts in the lake were not.

“Stocking’s an expensive endeavor, and annoyingly, we’re trying to do stocking attempts that were largely ineffective,” Natural Resources Commissioner Brandon Fewens said.

“If I had my way, all 20 million fish we stocked would be tagged, so we could evaluate them,” responded Claramunt, the fisheries chief.

For this upcoming fiscal year, the DNR will take500 samples of stocked walleye from waterbodies across the state to have them genetically tested. Johnson said this “is going to help enable biologists with their stocking decisions.” For example, they will not continue to stock Hagerman Lake.

Expanding the program to other species in the future would “ultimately help us answer a lot of these management questions we have.”

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