Trout become sexually mature at the age 3+ years (males) and 4+ years (females), they spawn during November and December. The marble trout is piscivorous, feed mainly on smaller fish and benthic invertebrates. Its natural habitat is rivers with a summer temperature of . It suffers numerous threats to its existence throughout its range, these include hybridisation with foreign trout species stocked for angling and water extraction and pollution. In Bosnia and Herzegovina main threats are habitat loss (habitat destruction) due to construction of five large dams on the Neretva river and plans for construction of several new dams on the upper course of the Neretva, water pollution, overfishing (sportfishing, food, including poaching) and hybridisation with introduced species of trout. All eight remaining genetically pure marble trout populations were found in remote streams of the River Soča basin. From these populations the Tolmin Angler's Society launched a reintroduction programme. Adding to the confusion of salmonid taxonomy, there are other trout with marble patterns beside "Salmo marmoratus". One is trout from the river Otra, Norway. A certain percentage of brown trout ("Salmo trutta") from that river have a 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.