THE PROBLEM OF SAMPLING FAMILIES RATHER THAN POPULATIONS - RELATEDNESS AMONG INDIVIDUALS IN SAMPLES OF JUVENILE BROWN TROUT SALMO-TRUTTA L

In species exhibiting a nonrandom distribution of closely related indi viduals, sampling of a few families may lead to biased estimates of al lele frequencies in populations. This problem was studied in two brown trout populations, based on analysis of mtDNA and microsatellites. In both samples mtDNA haplotype frequencies differed significantly betwe en age classes, and in one sample 17 out of 18 individuals less than 1 year of age shared one particular mtDNA haplotype. Estimates of relat edness showed that these individuals most likely represented only thre e full-sib families. Older trout exhibiting the same haplotypes genera lly were not closely related.