Behaviour of Mature Male Salmon Parr, Salmo salar juv L

Abstract

IN a recent account of early and normal sexual maturity in male salmon parr in the Welsh Dee¹, we directed attention to the possibility of these young mature males behaving differently in their river movements from other young parr of the same age, immature males and females. The absence of mature males from one tributary, Hirnant Brook, at the time of examination indicated that they might have migrated; but as the sample was a very small one consisting of eleven individuals, the discriminating behaviour of the mature male could only be regarded as a possibility. In November, however, significant information was obtained. Pure samples of mature male parr were found on November 14, 15 and 16—coincident with the ascent of the last batch of adult spawners up the River Alwen—to have collected in numbers (twelve, sixteen and twenty respectively) in the stream-like race or overflow from a set of salmon-keeping tanks built into the bank of the River Alwen at Pont Barcar Weir. The race runs alongside the river and is separated from it only by a revetment wall, around the lower end of which the race runs into the river with a fall of a few inches.