Michigan Wants Its Grayling Back. Brown Trout May Be Standing in the Way.

Arctic grayling disappeared from Michigan in 1936, and earlier attempts to bring them back have not worked. A new study run in a Michigan State University lab tested one possible reason: the trout that now live in the streams. Young brown trout hurt young grayling badly in the lab. Young brook trout did not.

Why anyone is testing this

The authors say past restoration attempts in Michigan were unsuccessful, perhaps because of competition with salmonids that now live there. So they set up a controlled test of how young grayling do alongside young brook trout and young brown trout.

What they found

In the authors' words, "Brown Trout had a significant effect on Arctic Grayling growth and mortality."

Survival is where it showed up most. Grayling survival differed between the groups, and it was significantly lower with brown trout (27%). Brook trout, by contrast, had no effect on grayling growth or mortality. In one of the three years, every grayling in the brown trout stream was dead before the eight weeks were up.

Biomass told the same story. Grayling biomass in the brown trout treatment fell from an average of 25.2 g at the start to 12.5 g at week 8 across all years. Fin damage differed significantly among the groups, and the researchers saw brown trout chasing and nipping grayling. Of ten chase events they logged, eight were brown trout chasing grayling. With brook trout, the two species fed together without signs of aggression.

The authors conclude that age-0 brown trout negatively affected growth, condition, and survival of age-0 grayling, and that reintroduction may be more successful in streams with few or no brown trout.

How the test was built

This was not a river. It was a set of experimental stream channels in the Michigan State University Animal Containment Laboratory. Trials ran 8 weeks and were repeated across three years (2018, 2019, and 2021). There were three setups: a grayling-only control, 10 grayling with 10 brook trout, and 10 grayling with 10 brown trout. All fish were age-0, meaning that first year of life. The grayling came from eyed eggs from an Alaska hatchery, and the trout were collected from two creeks by backpack electrofishing.

The catch

The authors name the big limitation themselves. The channels were closed systems, so the grayling had no way to get away from the pressure. They say this may have overestimated how much harm brown trout do in the real world. The feeding setup was also predictable enough that fish may have learned it. And the study covers only the first year of life, in a tank-sized stream, not a wild Michigan river with cover, side channels, and other fish.

One more thing. The paper has a few internal numbers that don't line up, such as two different control mortality figures in different sections, so I've stuck to the figures that are consistent. The brown trout result held up in every year of trials, and the authors point to that consistency. It's still one study, not a settled answer on grayling restoration.

My read: what this means for Michigan trout water

This part is my interpretation, not the study's.

I fish the family cabin lake in the Upper Peninsula, but I have never caught an Arctic grayling, and I haven't fished a grayling stream anywhere, so I can't tell you what a restored population would feel like on the water. What I can say is that the study's own suggestion is narrow: grayling may do better in streams with few or no brown trout. That's a question about which streams get picked, not a verdict on brown trout fishing.

If you fish a Michigan trout stream, expect restoration talk to come down to which streams get picked. Keep an eye on state DNR announcements and public comment periods, because the stream selection is the part that matters. [INTERNAL LINK: Michigan trout fishing guide]

Citation

Watson, N. M., Hayes, D. B., & Zorn, T. G. (2026). Arctic Grayling, scared to death: Are Brown Trout an impediment to Arctic Grayling reintroduction success in Michigan? North American Journal of Fisheries Management. https://doi.org/10.1093/najfmt/vqag083