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 chi nook salmon, Oncorhynchus tshawytscha, and lake trout, Salvelinus nama ycush, in Lakes Michigan and Ontario. This grid-based approach predict s a predator's physiological growth response, growth rate potential, f rom 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 fora ging model defined predator consumption rates from prey data. A bioene rgetics model calculated growth rate potential based on consumption ra tes and prevailing thermal conditions. We compared habitat quality bet ween lakes using both the mean growth rate potential and the volume (o r proportion) of water capable of supporting positive growth rates. Me an growth rate potential for both chinook salmon and lake trout was si milar between the lakes despite known differences in the prey species composition and abundance. However, Lake Michigan provided a greater v olume of water capable of supporting growth for both chinook salmon (2 6%) and lake trout (21%) compared with that for Lake Ontario (19% for both species). Our measure of habitat quality based on species-specifi c physiological requirements should provide a tool to compare ecosyste ms and quantify ecosystem change.