Fisheries management aims at improving the ecological quality of fish stocks. Therefore it is advisable to study the populationgenetics of those species which are of major importance for nature conservation to elucidate differences among populations. Apart from the much stocked pike (Esox lucius), the endangered species chub (Leusciscus cephalus) and brook trout (Salmo trutta)and the exterminated burbot (Lota lota) will be studied by means of restriction fragment length polymorphous (RFLP) of the mitochondrial genome. The results will be evaluated in a western European context.