Spawning of escaped farmed Atlantic salmon,Salmo salarL., in western and northern Scottish rivers: egg deposition by females

摘要

Abstract.In 1991, the progeny of female Atlantic salmon,Salmo salarL., were sampled at emergence from sites in 16 rivers in western and northern Scotland. The progeny of farmed females that had escaped from sea‐cages were identified by detecting the presence of maternal canthaxanthin in the juveniles’ pigment load. Canthaxanthin was detected among fish sampled from 14 of the 16 rivers examined. Overall, 109 of the 2373 fry sampled carried canthaxanthin with an average frequency over all the rivers examined of 5·1. This value will underestimate the real frequency of occurrence of the progeny of escaped farmed salmon: some escapees do not contain canthaxanthin and male fish do not contribute to the pigment load of their pro