Evaluating potential fluvial habitat for arctic grayling (Thymallus arcticus) in Michigan using a landscape approach

Arctic grayling, once the dominant salmonid in Michigan’s Lower Peninsula rivers, have been extirpated from Michigan since 1936.  Since then, reintroductions have been attempted with sites selected based on location remoteness, their ability to support trout, and absence of predators.  All attempts failed, with a lack of suitable habitat suspected to be limiting within the state.  Recently, growing understanding of landscape influences on streams has allowed for evaluating habitat across large regions using natural and anthropogenic landscape characteristics.  We can use the landscape approach to support species conservation and management by considering how landscape factors may influence species-specific habitat requirements. Our project evaluates fluvial habitat in Michigan’s northern Lower and Upper Peninsulas to estimate habitat suitability for grayling.  Using established and modeled relationships between landscape factors and physical habitat variables and by incorporating river network connectivity, we developed a rating system for habitat conditions based on natural and anthropogenic conditions like land use and geology. Our work shows that suitable habitat remains within Michigan, with connectivity among spawning, feeding, and overwintering habitats key for potential grayling reintroductions.  This approach has utility to support introduction efforts of range-restricted or locally extinct species when habitat conditions must be compared across large regions.