Suitability Modeling of Lake Sturgeon Habitat in Five Northern Lake Michigan Tributaries: Implications for Population Rehabilitation

The availability of lotic spawning, staging, and nursery habitats is considered a major factor limiting the recovery of Lake sturgeon (Acipenser fulvescens) in Lake Michigan. Despite efforts to better understand the population biology and habitat use of remnant Lake sturgeon stocks, little information exists on the quantity, quality, and spatial distribution of habitats for riverine life stages. We applied georeferenced habitat information on substrate, water depth, and stream gradient to a Lake sturgeon habitat suitability index in a geographic information system to produce spatially explicit models of life stage-specific habitat characteristics in the Menominee River, Michigan-Wisconsin; the Peshtigo, Oconto, and lower Fox rivers, Wisconsin; and the Manistique River, Michigan. High-quality Lake sturgeon spawning habitat associated with coarse substrates (>= 2.1 mm) and moderate- to high-stream gradients (>= 0.6 m/km) comprised 1-6% of the available habitat in each system. Staging habitat characterized by water depths greater that 2 m located near potential spawning habitat comprised an additional 17-41%. However, access to a majority of these habitat types (range 30-100%) by Lake sturgeon from Lake Michigan is currently impeded by dams. High-quality juvenile Lake sturgeon habitat associated with finer substrates, lower stream gradients, and a broad range of water depths (i.e., 0.5-8 m) was relatively ubiquitous throughout each system and comprised 69-100% of the available habitat. Our study suggests that efforts to rehabilitate Lake sturgeon populations should consider providing fish passage and creating supplemental spawning habitat to increase reproductive and recruitment potential.