FORAGING MOVEMENTS IN RELATION TO MORPHOLOGY, WATER-COLUMN USE, AND DIET FOR RECENTLY EMERGED BROOK TROUT (SALVELINUS-FONTINALIS) IN STILL-WATER POOLS

Recently emerged brook trout (Salvelinus fontinalis) foraging is still-water pools varied considerably in the proportion of time they spent moving, speed while moving, and distance travelled during pursuit of prey. Trout that exhibited a high proportion of time spent moving, fast speeds while moving, and long pursuit distances directed more foraging attempts toward the upper portion of the water column, ate more insect prey and fewer crustaceans, and made more foraging attempts per minute than trout that exhibited a low proportion of time spent moving, slow speeds while moving, and short pursuit distances. The variation in movement was related less strongly to spatial heterogeneity in the locations (pool sizes, water depths) where individuals were observed. It was not significantly related to measures of temporal variation in the environment (date, time-of-day, water temperature), body size and shape, or hunger (the amount of food in the stomach). In these clear, shallow pools, differences in the spatial distribution and behaviour of prey types apparently facilitate divergent foraging behaviour and diet among the trout. Our findings are valuable for understanding the development and maintenance of the individual specializations in water-column use and diet reported previously for several salmonids.