The name of the trout: considerations on the taxonomic status of the Salmo trutta L., 1758 complex (Osteichthyes: Salmonidae) in Italy

Abstract

The systematic status of the Italian trout in the Salmo trutta L., 1758 complex (including marble, Mediterranean and lacustrine trout), has long been -and is still todaysubject of controversies among ichthyologists. The specific name and the taxonomic rank changed several times in the last years, and the natural occurrence of this salmonid fish in some Italian areas was debated due to spread of alien strains. The main difficulty with the taxonomy of the Italian trout stems from the impossibility of disentangling it "on paper" or, even worse, trying to face this systematic issue considering only a very limited (local/national scale) part of the brown trout range. The taxonomy of the Italian trout population is inextricably linked to the necessity of clarifying first phylogeny and phylogeography in an overall Mediterranean context. The opportunity of a non "self-referential" taxonomy is even more fundamental for a vulnerable salmonid like the Italian brown trout, for which there is a very conflicting management problem related to sport fishing and, at the same time, the urgent need for effective conservation measures. It is however necessary to emphasize that conservation is independent from taxonomy but must start from the level of the local population. In fact, management units need stability and they cannot, therefore, coincide with entitiesthe Linnean speciesrequiring continuous taxonomic revisions. Modern molecular methods are the best tools for defining these units of management and conservation in an evolutionary perspective.

Genotyping of Two Mediterranean Trout Populations in Central-Southern Italy for Conservation Purposes Using a Rainbow-Trout-Derived SNP Array

“…In Italy, although the taxonomy is still controversial, the Mediterranean trout is referred to as Salmo cettii syn. Salmo macrostigma [ 3 , 4 , 5 , 6 , 7 , 8 ] and, unfortunately, it is one of the most highly threatened freshwater fish at risk of extinction [ 3 , 7 , 9 ]. Its biodiversity is declining rapidly due to a complex pattern of climatic and anthropogenic pressures [ 10 , 11 ], and it is currently listed in the Italian IUCN Red List as ‘critically endangered’ ( , accessed on: 31 March 2021).…”

Ethnoichthyology of freshwater fish in Europe: a review of vanishing traditional fisheries and their cultural significance in changing landscapes from the later medieval period with a focus on northern Europe

“…The introduction of trout from elsewhere to raise stocking levels can be deleterious to genetic integrity through interbreeding. Recent taxonomic studies in Italy [ 179 ] on trout of different ‘types’ in different habitats—defined as Mediterranean trout (Alps, Apennines and main islands), marbled trout (Po Valley) and the large ‘carpione’ trout (Lake Garda), have highlighted the problems of restocking by mixing these populations and importing ‘Atlantic’ trout from farther west weakening their unique genetic codes. Farmed trout in particular are a problem and most fisheries biologists now recommend farmed stock should be sterile.…”

Brown trout phylogenetics: A persistent mirage towards (too) many species

“…If a coherent phylogenetic frame is still missing, two other frames strongly cohabit in trout molecular studies: one concerns species definition, taxonomy and their associated revisions (supra and Fig. 2), while a second is sounded in conservation issuesoften crucial in troutand should be 'taxonomy independent' (Splendiani et al, 2019; see also Stanton et al, 2019). These two frames are generally considered fundamental to design efficient biodiversity conservation priorities and management strategies (Allendorf, 2012;Eizaguirre & Baltazar-Soares, 2014), but their uncoupling has been promoted by some agencies (e.g., Haig et al, 2006).…”