Salmo Marmoratus.
Species description.
Salmo Marmoratus or marble trout is a large growing trout species which can be recognised by its marbled pattern and its large head which takes up about 22-25% of its total length. These magnificent fish can grow to over 1m in length with a record fish being caught at 120cm and 22.5kg. Although typically, fish are caught between 30 and 70 cm as these fish are still eating insects, flies and larva. Above the 70cm mark they become almost pure piscivorous. their appearance can vary greatly as you can see in the pictures. The waters these fish inhabit rarely exceed 15 degrees Celsius and the fish start reproduction at 3+ year for males and 4+ year for females and the spawn in November and December.
Behaviour.
In a river marble trout can be recognised by there behaviour, they inhabit faster flowing water the you might expect. In these faster flowing waters, they lay on the bottom with their chin on a rock and they only move a little for food going past them. this in combination with their marble pattern they can be very hard to spot in a river and you might think there is no fish in a stretch of water. But when the circumstances are right, they also feed on fly's, beetles, ants and other insects on the water surface. marble trout are very shy fish and they can be easily spooked. Especially wild fish are very aware of their surroundings and when they are spooked, they will sometimes hide for a few hours before they start feeding again. Marble trout will always stay in places where they have hiding spots nearby. these are mostly bigger rocks with overhang or holes where they can hide in. Even the bigger fish which only eat fish and are the true rulers of the river still use hiding spot.
History.
Throughout History marble trout ruled the rivers of the Adriatic river’s river basin. But with the hunger crisis during the world wars, fish numbers decreased and people started stocking the rivers with the more common brown trout. These stocked trout started to hybridise with de marble trout which were left in the rivers. For long pure marble trout were thought to be extinct but in 1985 a pure population was found in the Zadlascica river. Finding these trout in this hardly accessible river, gave researchers the drive to find more pure populations, and in the years after a total of 8 genetically unique populations were found. Sadley researchers monitoring the populations saw 2 unique populations go extinct and other populations decrease to only a few fish. One of the locations, a 340m long head water which was separated by a waterfall which prevented stocked fish to move up and spawn with the marble trout. Was altered by logging and land slides filling the riverbed with gravel and sand and it is unclear if any fish survived. Researchers started using sanctuary streams to expand and safeguard the remaining strains and their habitat has been increased by 40%. Also, the species has been given a protected status and the species is being bred in fish farms. These farms stock one year old fingerlings, and in places with easier access and more fishing pressure larger 3- to 4-year-old fish are being released. This make that nowadays the waters managed by the fisheries research institute of Slovenia (zzrs), and the waters managed by the tolmin angeling club (ribiska druzina tolmin), are once again ruled by pure strain marble trout, and the hybrid and brown trout are becoming rarer.
Threats.
The biggest threats for marble trout are climate change, building of new dams which breaks up their habitat and make spawning grounds impossible to reach. Next to that there is still the hybridisation although with the conservation in the Soca valley this species is protected quite well. In the future we hope other watersheds are restored as well.
Distribution.
The native range of the marble trout is the Adriatic rivers river basin, which are rivers that flow into the Adriatic Sea. These rivers are found in Italy, Switzerland, Slovenia, Croatia, Bosnia and Herzegovina, Montenegro, Albania and Greece. In parts of Albania and in Greece the species is probably extinct. Nowadays only Slovenia and Italy have rivers with genetically pure marble trout, other countries still have marble trout but they are mostly hybridised. for more detailed information about river systems check the country pages.
Impresion photo's from contenders
