The First Diets of Postemergent Brook Trout (Salvelinus fontinalis) and Atlantic Salmon (Salmo salar) Alevins in a Quebec River

In the Matamek River, Quebec, brook trout (Salvelinus fontinalis) and Atlantic salmon (Salmo salar) coexist. The trout alevins emerge from the redds in early June and the salmon ~1 mo later. The first diet of the trout consists primarily of small- to medium-sized invertebrates passing in the water column. Among the most common items are blackfly larvae and zooplankton derived from an upstream lake. The alevins also feed at the water surface and take considerable numbers of emerging adults of orthocladine chironomids. There appears to be diel variation in the importance of various dietary species. The salmon alevins hold station in faster water and tend to feed more from the substrate on medium- to large-sized invertebrates. Their first meals include large stonefly nymphs, chironomid pupae, and larval dytiscid beetles. The salmon also feed extensively on adult chironomids and caddisflies as they emerge at the water surface. All of these items are important in the diet of the older brook trout at this time. The concept of food availability is discussed.Key words: brook trout, Atlantic salmon, alevins, feeding behavior, invertebrates, drift