The River Neretva and its tributaries represent the main drainage system in the east Adriatic watershed and the foremost ichthyofaunal habitat of the region.
Salmonid fishes from the Neretva basin show considerable variation in morphology, ecology and behaviour. It is therefore not surprising that several species, i.e. Salmo trutta Linnaeus, 1758 (brown trout), Salmo marmoratus Cuvier, 1817 (marble trout), Salmo obtusirostris Heckel, 1851 (softmouth trout), Salmo farioides Karaman, 1937 and Salmo dentex Heckel, 1851 (no common name exists for the last two) were identified by early studies (Heckel, 1852; Karaman, 1937).
While some of these taxa have controversial histories, the existence of both Salmo trutta and Salmo marmoratus has been well accepted (Karaman, 1926; Vuković, 1982; Kosorić et al., 1983). Similarly, the marbled trout from the River Neretva has been assumed as Salmo marmoratus although no reliable analysis has ever been carried out to confirm its conspecificity with Salmo marmoratus stocks from the northern Adriatic watershed.
The status of Salmo dentex and Salmo farioides has always been questionable, mainly due to inadequate original descriptions and rare sightings.
On the basis of recent morphological study performed by Delling (2003), another new species that “in morphology appears intermediate between Salmo trutta and Salmo obtusirostris” has been described in the River Neretva and tentatively assigned as Salmo cf. montenigrinus (referring to Trutta montenigrina Karaman, 1933 from the River Morača, Montenegro).
Natural hybrids between Salmo obtusirostris × Salmo trutta and Salmo marmoratus × Salmo trutta have also been observed and reported in the Neretva basin (Vuković, 1982).