Significance of Mature Male Parr in a Small Population of Atlantic Salmon (Salmo salar)

Abstract

The spawning population of Atlantic salmon, Salmo salar, (mature male parr and adults (anadromous salmon)) were assessed in the River Baevra, central Norway, when the river was treated with rotenone in November 1986. The spawning population of adults consisted of 15 males and 19 females. The spawning population of males consisted of 167 mature male parr per adult male. The effective population size of adults was small; Na = 33.5 individuals. The presence of mature male parr theoretically increased the effective population size to Na = 71.7 individuals. This increase indicated that mature male parr brought the effective population size above a recommended minimum (Na = 50) to ensure long term viability.