Reared Atlantic salmon, Salmo salar L., in the catches of a salmon fishery on the western coast of Scotland

Abstract. Atlantic salmon, Salmo salar L., of reared origin were distinguished from putative wild fish In the catch of a single salmon fishery in western Scotland. Fish in seven day-catches made in 1990 totalling 403 individuals were assessed formally for the presence of residual fin damage resulting from culture. Fifty-eight (22%) were classed as being of reared origin, on the basis of previously established criteria. Additional examination of 54 of these fish showed the pigment canthaxanthin to be detectable in the tissues of 35 (65%), which were therefore classed as having escaped from sea cages. Among the fish in which canthaxanthin could not be detected, a further 17 individuals (31% of the total) were classed as having escaped from sea cages on the basis of scale growth patterns. Scale growth patterns in the remaining two fish (4% of the total) were consistent with their having grown in a hatchery before escape or release.