Genetic assessment of dispersal rates for wild and hatchery lake sturgeon and occupancy of riverine habitats during non-spawning periods

Reproductive isolation resulting from natal philopatry often results in genetically distinct populations in fishes, as exhibited by Great Lakes populations of lake sturgeon. Little is known regarding inter-population movement of wild and hatchery-reared individuals or habitat use during prolonged non-spawning periods. Identification of habitats used by lake sturgeon of different ages and from different populations during spawning and non-spawning periods is a fundamental requisite for management and recovery. Data on occupancy of riverine habitats during non-spawning periods will enable managers to minimize uncertainty when estimating population-specific impacts of exploitation or of environmental disruption. Mixed stock analysis and individual assignment tests based on 12 microsatellite loci were used to estimate rates of dispersal and to provide compositional estimates of population contributions to near-shore habitats during non-spawning periods. Dispersal by naturally reproduced lake sturgeon was non-random and in certain cases directional. In Lake Michigan, individuals  were commonly found near natal rivers during non-spawning periods but also frequented off-shore habitats and non-natal rivers. No dispersal of hatchery-reared individuals was documented into investigated Lake Superior tributaries. We will discuss results of assessments of movement propensities as a function of distance, population size, and temporally across seasons and years.