POPULATION-LEVEL ANALYSIS AND VALIDATION OF AN INDIVIDUAL-BASED CUTTHROAT TROUT MODEL

An individual‐based model of stream trout is analyzed by testing its ability to reproduce patterns of population‐level behavior observed in real trout: (1) “self‐thinning,” a negative power relation between weight and abundance; (2) a “critical period” of density‐dependent mortality in young‐of‐the‐year; (3) high and age‐specific inter‐annual variability in abundance; (4) density dependence in growth; and (5) fewer large trout when pool habitat is eliminated. The trout model successfully reproduced these patterns and was useful for evaluating their theoretical basis. The model analyses produced new explanations for some field observations and indicated that some patterns are less general than field studies indicate. The model did not reproduce field‐observed patterns of population variability by age class, discrepancies potentially explained by site differences, predation mortality being more stochastic than the model assumes, or uncertainty in the field study's age estimates.