Arctic Grayling Thymallus arcticus were extirpated from Michigan in 1936. Several factors led to their demise including over-fishing, habitat destruction from large-scale logging, and introductions of 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 their historic home waters in Michigan were unsuccessful. Recent advances in the understanding of Grayling have led to successful reintroductions in Montana, particularly through the use of remote site incubators. These successes have renewed interest in restoring naturally reproducing populations to Michigan, but many unknowns need to be addressed for such efforts to succeed. Determination of the timing of imprinting and the potential for recognition and preference of familiar water are key to determining the time at which Grayling are to be stocked into receiving waters. Predation and competition with resident trout may be two of the greatest challenges to overcome in re-establishing a self-sustaining population of Arctic Grayling in Michigan’s cold and cool water streams. This study addresses these key factors through examination of plasma thyroxine levels in sub-yearling Grayling, water choice trials, predation trials with age-1 Brook and Brown trout, and competition trials with Brook and Brown trout of the same year class. Grayling were incubated in East Lansing, Michigan from eyed eggs, provided by Ruth Burnett Sport Fish Hatchery in Fairbanks, Alaska. Grayling were found to have a peak in plasma thyroxine levels corresponding to the eyed-egg life stage, indicative of a time of potential olfactory imprinting. Predation did not differ between predator species and was found to decline over time as Grayling develop and increase in biomass. Brown Trout were found to have a significant competitive effect on Grayling resulting in decreased growth and high mortality while Brook trout did not affect Grayling growth or mortality. These data will help determine the time at which Grayling are to be stocked into receiving waters and to guide suitable streams for reintroduction, thus increasing the likelihood of a successful reintroduction.
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