Arctic Grayling, scared to death: Are Brown Trout an impediment to Arctic Grayling reintroduction success in Michigan?

Introduction:

Arctic Grayling Thymallus arcticus were extirpated from Michigan in 1936. Their demise was caused by over-fishing, habitat destruction from large-scale logging, and Brook Trout Salvelinus fontinalis and Brown Trout Salmo trutta. Subsequently, Brook and Brown trout have become the dominant salmonid species in Michigan streams. Past attempts to restore Grayling to Michigan have been unsuccessful perhaps due to competition with these now resident salmonids.

Objective:

To determine the impacts of competition between age-0 Arctic Grayling and age-0 Brook and Brown Trout on Grayling growth and survival.

Methods:

Competition trials were performed in experimental streams, lasting two months, across three years, with three treatment types: the control, 10 Grayling with 10 Grayling; the Brook Trout treatment, 10 Grayling with 10 Brook Trout; and the Brown Trout treatment, 10 Grayling with 10 Brown Trout. 

Results: Brown Trout had a significant effect on Arctic Grayling growth and mortality, while Brook Trout had no effect on Arctic Grayling growth or mortality.

Conclusion: 

Age-0 Brown Trout negatively impacted growth, condition, and survival of age-0 Arctic Grayling, while the impacts of age-0 Brook Trout or conspecifics were negligible. This suggests reintroduction of Arctic Grayling may be more successful in streams with few or no Brown Trout.