Abiotic Habitat Assessment for Arctic Grayling in a Portion of the Big Manistee River, Michigan

Abstract Arctic Grayling Thymallus arcticus were once the dominant salmonid in the Big Manistee River, Michigan, but were extirpated from the watershed around 1900 and from the state of Michigan by 1936, likely due to overfishing, biotic interactions with introduced fish species, and habitat loss occurring largely around the turn of the 20th century. An interest in reestablishing native species by the Little River Band of Ottawa Indians led to an assessment of environmental conditions in a portion of the watershed encompassing 21 km of the Big Manistee River to determine whether suitable Arctic Grayling habitat remains. During summer in 2011–2013, abiotic habitat metrics, including water characteristics, substrate composition, channel profile, channel geomorphic unit, and stream velocity, were assessed across eight tributaries within the watershed. To assess whether abiotic conditions in these tributaries might support Arctic Grayling, the environmental conditions were compared to literature values from rivers where current or historical Arctic Grayling populations have been reported. This comparison, in conjunction with an assessment using a habitat suitability index for Arctic Grayling, indicated that important abiotic conditions were within ranges consistent with those associated with current and past populations of Arctic Grayling in North America. The results of this study will guide potential future reintroductions and indicate that suitable Arctic Grayling habitat does exist in portions of the Big Manistee River watershed, an assessment that will be further refined when coupled with biotic features of the environment. Received September 6, 2016; accepted February 28, 2017 Published online May 9, 2017