EFFECTS OF SPATIAL SCALE AND FORAGING EFFICIENCY ON THE PREDICTIONS MADE BY SPATIALLY-EXPLICIT MODELS OF FISH GROWTH-RATE POTENTIAL

Spatially-explicit modeling of fish growth rate potential is a relativ ely new approach that uses physical and biological properties of aquat ic habitats to map spatial patterns of fish growth rate potential. Rec ent applications of spatially-explicit models have used an arbitrary s patial scale and have assumed a fixed foraging efficiency. We evaluate d the effects of spatial scale, predator foraging efficiency (combined probabilities of prey recognition, attack, capture, and ingestion), a nd predator spatial distribution on estimates of mean growth rate pote ntial of chinook salmon, Oncorhynchus tshawytscha. We used actual data on prey densities and water temperatures taken from Lake Ontario duri ng the summer, as well as, simulated data assuming binomial distributi on of prey. Results show that a predator can compensate for low foragi ng efficiency by inhabiting the most profitable environments (regions of high growth rate potential). Differences exist in predictions of gr owth rate potential across spatial scales of observation and a single scale may not be adequate for interpreting model results across season s. Continued refinements of this modeling approach must focus on the a ssumptions of stationary distributions of predator and prey population s and predator foraging tactics.