Individual Variation and Alternative Patterns of Foraging Movements in Recently-Emerged Brook Charr (Salvelinus Fontinalis)

Abstract

AbstractRecently-emerged juvenile brook charr foraging in relatively homogeneous, clear, still-water pools displayed significant interindividual variation in the proportion of search time spent moving, the average speed during search, the average speed during periods of moving search, and the distance moved during pursuit of prey. The frequency distribution for interindividual variation in the proportion of time spent moving was bimodal, but distributions for the other movement parameters were not. Thus, in the field, young charr tended to specialize at one of two alternative movement patterns differing primarily in the proportion of time spent moving. The movement parameters were all positively correlated, but correlations between the proportion of time spent moving, the speed while moving, and pursuit distance were small enough (r2's < 0.30) to suggest that different aspects of search mode may vary relatively independently. Our findings have three implications for studies of search mode. First, intraspecific variation in search mode need not be only a response to environmental change, but can occur in the same environment at the same time. Second, frequency distributions of movement parameters offer a more objective base than do arbitrary classifications for determining how many types of foragers are present. Third, studies using different movement parameters to distinguish between alternative search modes (e.g. sitting-and-waiting and actively searching) may not be directly comparable.