Rainbow Trout

Scientific name: Oncorhynchus mykiss (Walbaum, 1752)
Family: Salmonidae
Order: Salmoniformes
Class: Actinopterygii
Irish name: Breac Dea-dhathach
Irish record angling fish: Not recorded
Native species: No; Native to the Southwest Atlantic; Introduced in 1895;
Hybrids: No

Identifying features

Coloration variable according to habitat; in acid waters, greenish on the back, with a vivid rosy flush on the gill cover and along the side; in alkaline waters, rainbows are more silvery and the bar long the side is, at most, slightly pink; black spots only, absent from cheek and gill-cover and also, for the most part, along the mid-line of the sides; tailfin heavily spotted; sometimes faint spots on anal and pelvic fins also; in Irish waters, grows to about 4.5kg⁴ but much heavier fish are common at commercial put and take fisheries.

Environment and Habitat

Lake inhabitants; inhabit similar conditions to brown trout but are more tolerant of warmer, poorer quality waters; can grow to a large size if sufficient food such as Gammarus and Asellus are available.

European distribution

Widespread; introduced from US; 67°N - 32°N, 135°E - 117°W; stocked into specific  Irish lakes for angling ; three breeding populations became established in the wild from stocked fish but none are extant currently (Roche, pers. comm..).

Economic value in Ireland

Important species for angling tourism; freshwater and sea-reared rainbow trout are important commercial aquaculture species.

Red list status

Not evaluated.

Irish legislation status

1987 Irish Fisheries Amendment Act – expanded the term ‘salmonid’ to include Arctic char and rainbow trout and so protects rainbow trout spawning grounds, juvenile rainbows and designates a closed season.

EU legislation status

Unprotected.