It is native to the rivers of North America that flow into the Pacific, from Alaska to California, where it has migratory populations and sedentary populations in freshwater, which are very different from each other.
Its body is greenish-brown, dotted with numerous rounded black spots, as are its dorsal and caudal fins. A pink or red band runs along its sides, becoming more intensely colored during the breeding season in males, whose lower jaws take on a hooked shape. It can exceed 70 cm in length and weigh 7 kg. In Trentino, in the few streams where it has acclimated, it rarely exceeds 30 cm.
It lives in both flowing and lake waters, but with cool temperatures (below 20-22°C) and well-oxygenated conditions. Strains raised over many generations in fish farms are less demanding on environmental quality, easily surviving even in habitats that would be unsuitable for the original strains.
The diet is essentially carnivorous, consisting of aquatic invertebrates and small fish. A crustacean-based diet gives the meat a salmon-like color, which can also be achieved with appropriate feed in fish farming.
The breeding season usually runs from October to March, but some strains acclimated to mountain streams breed in May. Reproduction is essentially similar to that of native trout. Sexual maturity is reached between the second and third year. Each female produces 1,000 and over 3,000 eggs per kg of body weight. The eggs are 3.5–5 mm in diameter and require approximately 350 degrees per day for hatching.
Rainbow trout arrived in Trentino in 1885, imported from the Torbole Artificial Fish Farm. Farming began immediately, and is still thriving and of considerable economic importance: there are about sixty fish farms raising it in the province of Trento. Supported by abundant stockings since the beginning of the last century, the rainbow trout's presence in public waters is now quite limited. The species has rarely managed to acclimatize, and its release is increasingly prohibited because it can cause health problems, such as the disappearance of Arctic char in high-altitude lakes. The meat, especially of specimens raised in natural conditions, is excellent.
Dialect: iridea .
G. TOMASI, 2004 - The Three Hundred Lakes of Trentino. Ed. Artimedia – Temi, Trento, 535 pp.
