Challenges to preserving native brown trout diversity in the Western Balkans

Abstract

In the Western Balkans, fishery management and legislation do not recognize the high molecular diversity of native brown trout. For this reason, stocking of streams relies on brown trout of non-native origin. In recent years, there have been new findings about the life-history features, dispersal and molecular characterisation of nominal taxa of brown trout in the Western Balkans. This has prompted to a re-evaluation of their risk of invasiveness in the region. In this study, based on a screening of six non-native lineages of brown trout, four lineages were ranked as high risk and two as medium risk of invasiveness under current climate conditions, whereas one lineage was ranked as high risk and the other five as medium risk under predicted global warming scenarios. Variation in scores and risk outcomes were related to life-history traits differing among lineages, with most pronounced differences in dispersal mechanisms. The results of this study point to the need for improvement of relevant legislation in several sectors of fishery management. Management strategies should aim to mitigate the conflicts arising among stakeholders, which contribute to the deterioration of the native traits of brown trout stocks throughout the Western Balkans.