Abstract
The method available for identifying spatially distributed fish populations is today different kind of neutral genetic markers. Due to the definition of neutral markers, they are not exposed to natural - or sexual selection. Hence, such markers can not be used to verify if a population has certain unique traits, i.e. being adapted to its local environment. Such knowledge is essential in fisheries management. However, it is difficult to study local adaptation in nature. In order to study whether local populations of sea trout are adapted to their environments, we launched the present Formas project (22.3/2001-1907) year 2002. We used a pedigree approach by fertilising eggs from known parents from five wild populations to study the within and between population variances for important quantitative traits e.g. growth survival morphology. We mixed the eyed eggs and placed them in four streams. The juveniles were caught and killed next autumn and measured for morphological traits. The parents of the offspring were identified based on microsatellite analyses. The preliminary results show that important life-history traits (survival, growth) have evolved mainly due to different selection pressures in their home streams. However, it seems as genetically based differences in morphological traits have evolved mainly a neutral manner. There is tendency for home/away effects, i.e. the populations tend to survive and grow better home than away.
Sweden