A SPATIALLY EXPLICIT BIOENERGETICS MEASURE OF HABITAT QUALITY FOR ADULT SALMONINES - COMPARISON BETWEEN LAKES MICHIGAN AND ONTARIO

We used spatially explicit modeling to compare habitat quality for chinook salmon, Oncorhynchus tshawytscha, and lake trout, Salvelinus namaycush, in Lakes Michigan and Ontario. This grid-based approach predicts a predator's physiological growth response, growth rate potential, from measured physical and biological environmental conditions and is a species-specific measure of habitat quality. Underwater acoustics was used to map prey spatial distributions, abundances, and sizes. A foraging model defined predator consumption rates from prey data. A bioenergetics model calculated growth rate potential based on consumption rates and prevailing thermal conditions. We compared habitat quality between lakes using both the mean growth rate potential and the volume (or proportion) of water capable of supporting positive growth rates. Mean growth rate potential for both chinook salmon and lake trout was similar between the lakes despite known differences in the prey species composition and abundance. However, Lake Michigan provided a greater volume of water capable of supporting growth for both chinook salmon (26%) and lake trout (21%) compared with that for Lake Ontario (19% for both species). Our measure of habitat quality based on species-specific physiological requirements should provide a tool to compare ecosystems and quantify ecosystem change.