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Salmo marmoratus
Conservation status
Vulnerable  (IUCN 3.1)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Salmoniformes
Family:	Salmonidae
Genus:	Salmo
Species:	S. marmoratus
Binomial name
Salmo marmoratus G. Cuvier, 1829

Salmo marmoratus, the marble trout, is a species of freshwater fish in the family Salmonidae. It is characterized by a distinctive marbled color pattern and high growth capacity. The marble trout is found in only a handful of drainages and rivers of the Adriatic basin in (going from north to south) Italy, Slovenia, Croatia, Bosnia and Herzegovina, and Montenegro, while in Albania, the species is considered most likely extirpated.

Distribution

In Italy, marble trout inhabits left tributaries of the upper northwestern reaches of the Po River, and Italian northeastern sub-Alpine region's direct Adriatic watersheds, namely the Adige, the Brenta, the Piave, the Tagliamento, and the Livenza; in shared Slovenia and Italy drainage of the Soča with Natisone; in shared Bosnia and Herzegovina and Croatia drainage of the Neretva river, and in shared Montenegro and Albania drainage of the Morača with Zeta river, and the tributary Cem (Cijevna). While once present in the Drin river basin in Albania, with White Drin in Kosovo and Black Drin in North Macedonia and Albania (as well as the Zalli i Bulqizes and the Okshtuni tributaries), and the Aoos river basin in Albania and Greece (as well as the Sarantaporos and the Drino tributaries), the fish is almost certainly extirpated there.

Appearance, biology, and ecology

The marble trout has a long, cylindrical body, slightly compressed laterally, with a large head (22–25% of the body length), which is why it is also known as glavatica (glava = head) in Bosnian. The most obvious characteristic of the marble trout is its marble pattern. The intensity of colour varies considerably upon the surroundings. Some marble trout have red spots that merge with the rest of the pigment, always only along the lateral line.

Its typical size is 30–70 cm. The largest specimen in Slovenia was a 117-cm, 24-kg female (found dead), largest living specimen caught was 120 cm and 22.5 kg. Individuals weighing up to 30 kg have been reported. The largest specimens were found in Bosnia and Herzegovina, inhabiting the Neretva River from below town of Konjic downstream to town of Čapljina, mostly in canyon section from town of Jablanica to city of Mostar, and later after construction of Jablanica Dam on the Neretva River in Jablaničko Lake. Trout become sexually mature at the age 3+ years (males) and 4+ years (females), and 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 15 °C (59 °F). It suffers numerous threats to its existence throughout its range, these include hybridisation with foreign trout species stocked for angling, water extraction, and pollution. In Bosnia and Herzegovina, its main threats are habitat loss (habitat destruction) due to construction of five large dams on the Neretva Rriver 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.

Marmorated trout

Adding to the confusion of salmonid taxonomy, other trout have marble patterns beside S. 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 nonmarble brown trout from the same river. This is an example of intrapopulational polymorphism.

References

1. Crivelli, A.J. (2024). "Salmo marmoratus". IUCN Red List of Threatened Species. 2024: e.T226403752A137328476. doi:10.2305/IUCN.UK.2024.RLTS.T226403752A137328476.en. Retrieved 14 November 2021.
2. "Fish Database - Save the Blue Heart of Europe". balkanrivers.net. Retrieved 1 July 2019.
3. "Marble trout (Salmo marmoratus)". Balkan Trout Restoration Group. Retrieved 2009-03-10.
4. S. MUHAMEDAGIĆ; H. M. GJOEN; M. VEGRA (2008). "Salmonids of the Neretva river basin - p" (PDF). EIFAC FAO Fisheries and Aqauculture Report No. 871. European Inland Fisheries Advisory Commission (EIFAC): 224–233. Retrieved 6 January 2014.
5. Snoj, Aleš; Marić, Saša; Berrebi, Patrick; Crivelli, Alain J.; Shumka, Spase; Sušnik, Simona (2 February 2009). "Genetic architecture of trout from Albania as revealed by mtDNA control region variation". Genetics Selection Evolution. 41 (1): 22. doi:10.1186/1297-9686-41-22. ISSN 1297-9686. PMC 3225828. PMID 19284692.
6. ^ Povž M; Jesenšek D; Berrebi P; Crivelli AJ (1996). The Marble Trout Salmo trutta marmoratus, Cuvier 1817 In the Soca River basin, Slovenia (PDF).
7. Pintar L (1991). "Najtežja soška postrv je končala pod peskom". Ribič. 50 (1–2): 16.
8. "Soca (19) – Ribiška družina Tolmin".
9. Mateš, Antun (2004). The Enchanted Angler. Zagreb: J&B d.o.o. ISBN 953-99019-3-6.
10. Fumagalli L; Snoj A; Jesenšek D; Balloux F; Jug T; Duron O; Brossier F; Crivelli AJ; Berrebi P (2002). "Extreme genetic differentiation among the remnant populations of marble trout (Salmo marmoratus) in Slovenia" (PDF). Mol. Ecol. 11 (12): 2711–2716. Bibcode:2002MolEc..11.2711F. doi:10.1046/j.1365-294X.2002.01648.x. PMID 12453253. S2CID 23810662.
11. Fish farming
12. Skaala O; Solberg G (1997). "Biochemical genetic variability and the taxonomic position of the marmorated trout in River Otra, Norway". Nord. J. Freshw. Res.
13. Crivelli, A.J. (2006). "Salmo marmoratus". IUCN Red List of Threatened Species. 2006. Retrieved 2020-05-28.

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Trout - Salmonidae
Trout of Europe and Atlantic basin Salmo	Adriatic trout Brown trout Fibreno trout Ferox trout Flathead trout Garda lake trout Gillaroo Isli trout Lake (lacustrine) trout Marble trout Mediterranean trout Ohrid trout Prespa trout River trout Sea trout Sevan trout Sonaghen
Trout of the Pacific basin Oncorhynchus	Apache trout Coastal cutthroat trout Cutthroat trout Gila trout Golden trout Mexican golden trout Rainbow trout Steelhead
True char Salvelinus	Arctic char Blunt-nosed Irish charr Brook trout Bull trout Cole's char Coomsaharn char Dolly Varden trout Haddy charr Kirikuchi char Lake char Lake trout Lough Melvin charr Orkney charr Silver trout Small-mouthed char Whitespotted char
Media related to Trout at Wikimedia Commons

• IUCN Red List vulnerable species
• Fish described in 1829
• Taxa named by Georges Cuvier
• Salmo
• Fish of Bosnia and Herzegovina
• Freshwater fish of Europe
• Endemic fish of the Neretva basin
• Morača
• Soča
• Species that are or were threatened by river-damming
• Habitats Directive species