Forecasting spatial distributions of salmonines in Lake Michigan

Spatial arrangement of habitats of varying quality influences foraging, growth, mortality, and distribution of fishes. Spatially explicit models of growth rate potential (SEM-GRP) provide one measure of habitat quality, which integrates physical and biological habitat components (e.g., temperature, prey biomass, light level, etc) with the potential to predict fish spatial distributions. Most applications of SEM-GRP have been limited to a 2-dimensional plane due to lack of 3-dimensional (3-D) temperature data. However, recent advances in 3-D hydrodynamic models provide forecasts of temperature at depth in the Great Lakes, and enable forecasts of fish GRP and distributions in 3-D. We combined output from a calibrated 3-D temperature model with a SEM-GRP to predict salmonine GRP distributions in Lake Michigan in 1998. These forecasts were compared to fishery dependent (anglers) and independent (gillnet) indices of salmonine spatial distributions. Salmonine catch rates and GRP varied among depths, areas, seasons, and species. Further developments will compare SEM-GRP predictions to angler catch rates from 1998-2007, and provide higher resolution 3-D models to forecast potential salmonine spatial distributions.