ELK LAKE — The research into a lake trout population living in Elk Lake started with a hunch.
In 2008, the Charlevoix Fisheries Research Station was doing a survey on Elk Lake, and the researchers ran into some lake trout that just looked different to fisheries biologist Jory Jonas. They were longer, more bullet-shaped and had a shorter jaw, she thought, than the lake trout now stocked into Lake Michigan.
Turns out, this population is different.
"We do know that we've run more genetic samples, and they're staying different from any of the fish we stock into Lake Michigan, and even in Lake Superior, though they're more related to those in Lake Superior," Jonas said.
Lake trout have been stocked into Lake Michigan since its native lake trout population was extirpated — went locally extinct — after the onset of sea lampreys and commercial over-fishing.
The researchers' next step is to compare the Elk Lake trout's genetics against historic Lake Michigan populations, which they will do with the help of geneticists and scale samples kept by old commercial fisheries.
Back when the native lake trout population was still robust, in the late 1800s or early 1900s, Jonas thinks a population moved into the chain of lakes that starts where Elk Lake meets Lake Michigan. There, in the early 1900s, a dam was constructed, blocking the lakes off from Lake Michigan — and the population of lake trout from commercial fishing and lampreys.
Now, Jonas is concentrating on learning as much as she can about these fish. Studying with her is Central Michigan University graduate student Laura Mathews.
"We know a little bit about the population, a little bit about where they're hanging out," said Jonas. "Now, let's figure out how they're sustaining themselves and how they're reproducing."
She and the DNR crews have netted and tagged 177 fish as of this spring, and 12 of those fish have been caught and reported by anglers. This helps the researchers get a population estimate of the fish. Though Jonas thinks the population is small, it has been sustaining itself under regular inland lake regulations for lake trout.
Mathews, along with fisheries technician Nathan Skop, is mapping the bottom of Elk Lake to see where the fish are spawning. And just like native lake trout in Lake Michigan, these fish seem to be spawning in deep water.
"They like to be in the 100-200 feet of water, and that in itself was a surprising thing," said Jonas.
It's surprising because the strain of lake trout now planted in Lake Michigan spawn on relatively shallow cobble reefs, near shore, where their eggs are vulnerable to invasive species such as rusty crayfish and round gobies.
Jonas, Mathews and Skop are netting during spawning season both to tag and release the fish and to take precise photos of the fish. Mathews uses the photos to measure the fish at 31 different landmarks, called a "truss analysis."
"For example, there are landmarks at the tip of the snout, above the eye, and at the insertion of the dorsal fin," she said.
Those measurement will help Mathews pin down the ways these fish differ from their stocked Lake Michigan counterparts.
"(Jonas) has a hunch that these look different, and I am just trying to show that these in fact are different," she said. "Anyone can say anything. I just have to prove it."
Elk Lake anglers who report the tagged fish through creel surveys and angler diaries can help the researchers assess how many lake trout make up the Elk Lake population. For more information and to request an angler diary, contact Jonas at email@example.com.
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What to do when you catch a tagged trout:
The Michigan Department of Natural Resources is tagging lake trout with a florescent green tag. Send the date, location of capture, length of the fish and tag if the fish is kept, or tag number if the fish is released to:
Michigan Department of Natural Resources
Charlevoix Great Lakes Station
96 Grand St.
Charlevoix, Mich. 49729
Or report information on the MDNR website at www.michigandnr.com/taggedfish/