The diet of red‐breasted mergansers (<i>Mergus serrator</i>) during the smolt run in N.E. Scotland: the importance of salmon (<i>Salmo salar</i>) 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.