Marmorated Trouts
Adding to the confusion of salmonid taxonomy, there are other trout with marble pattern beside Salmo marmoratus. One is trout from the river Otra, Norway. A certain percentage of brown trout (Salmo trutta) from that river has marble pattern. In all other aspects, these trout are identical to the non-marble brown trout from the same river. This is an example of intrapopulational polymorphism.
Recent studies also imply that marble trout from the in Neretva river of Bosnia and Herzegovina and Zeta river in Montenegro are not closely related to Salmo marmoratus of Northern Adriatic. The colour pattern probably evolved in geographically remote regions independently. In addition, genetic studies revealed that marble trout from Neretva is genetically indistinct from Salmo dentex.
Read more about this topic: Salmo Marmoratus