Factors Influencing the Spatial Distribution of Age-0 Lake Trout at Two Spawning Shoals in Lake Superior

Age-0 lake trout are distributed heterogeneously on and near spawning shoals, but factors have not been evaluated that might explain these patchy distributions.  We surveyed two lake trout spawning areas, Gull Island Shoal and Sand Cut Shoals in Lake Superior, to determine the primary variables influencing monthly variability in the spatial distribution of age-0 lake trout.  We evaluated the effects of sculpin abundance, mysid abundance, temperature, foraging potential, and bioenergetic growth rate potential using spatially-discrete modeling techniques and compared these models with the distribution of age-0 lake trout determined from trawl data.  The most significant variable influencing age-0 lake trout distribution was bioenergetic growth rate potential based on a foraging model that estimated proportion of maximum consumption per minute.  A classification tree model based on this variable predicted the presence of age-0 lake trout in trawl data with 82% and 61% accuracy at Gull Island Shoal and Sand Cut Shoals, respectively.  Bioenergetic growth rate potential can be calculated using estimates of prey abundance and measurements of temperature, so this model is potentially useful to fishery managers who are attempting to identify high quality spawning habitat, both for rehabilitation in the Laurentian Great Lakes and for suppression in the western lakes.