The diet of red‐breasted mergansers (Mergus serrator) during the smolt run in N.E. Scotland: the importance of salmon (Salmo salar) smolts and parr

Abstract

Salmon (Salmo salar) formed the largest proportion by mass offish found in the stomachs of red‐breasted mergansers (Mergus serrator) shot during the smolt run in north‐east Scotland. Salmon parr represented approximately two‐thirds by mass of juvenile salmon eaten, whilst smolts were present in a smaller proportion than previously predicted. The median lengths of parr and smolts eaten were 70 and 115 mm, respectively; the latter being significantly smaller than the smolt population sampled during annual production estimates on the river.