The recent revision of Italian legislation on nature conservation has highlighted the pressing necessity of elucidating the native distribution range of managed species. A recent study by Antognazza et al. (Current and Historical Genetic Variability of Native Brown Trout Populations in a Southern Alpine Ecosystem: Implications for Future Management. Fishes 2023, 8, 411) provides insights into the native status of brown trout in the Lombardy Prealps, northern Italy, and advocates urgent conservation measures. However, the possible effect of historical and recent anthropogenic impacts was dismissed in the paper. Here, we present how human-mediated activities plausibly might contribute to the observed distribution of population genetic variation, considering both the available literature and ongoing “Mediterranean trout” stocking activities in the region. Implementing management strategies without clear scientific evidence poses significant risks to native biodiversity conservation.

The current diversity and distribution of species and populations have been shaped by the major climatic oscillations during the Quaternary. The brown trout ( Salmo trutta ) is a striking example of the strong effect of past climate changes on the evolutionary history of species, in fact, the alternation of glacial/interglacial cycles has led to continuous phenomena of expansion and contraction of its distribution and, consequently, to the evolution of different genetic lineages. This phenomenon was also directly observed by the genetic analysis of S. trutta bones recovered from the archaeological assemblage of a coastal cave named ‘Grotta del Santuario Della Madonna’ (Southern Italy). In this study, additional S. trutta remains were morphologically and genetically analysed, and the genetic results were compared with those of modern samples caught from streams close to the cave locality. The analysis of S. trutta bones confirms that changes in abundance, body size and genetic diversity observed in different stratigraphic sections were determined by environmental changes caused by the Younger Dryas‐Holocene transition and by the ability of the species to perform anadromous migration, a behaviour that had disappeared at the end of the Pleistocene in the Mediterranean region. The comparison between ancient and modern samples highlights that extinctions and recolonizations due to past environmental changes affected also the current diversity and distribution of S. trutta in Southern Italian streams. Unfortunately, incorrect management policies related to sport fishing (i.e., stocking with alien brown trout strains) have been eroding millions of years of the trout evolution in just a few centuries.