Rainbow trout are now widespread in river and lake systems in the UK due to escaped fishery stock establishing populations. This species is now considered a game fish and are well-prized by anglers. Rainbow trout are capable of thriving in much poorer water systems than our native brown trout (Salmo trutta) and Atlantic salmon (Salmo salar) and thus has been introduced to every continent except Antarctica.
Individuals are predominantly silver in colouration with black spots; pink and blue bands from the head and down the body form the lateral line. Rainbow trout have black spotted tail fins contrasting the solid-coloured tail fins of native salmonids.
There are two forms of the species.
- The freshwater form has only one known population in the UK found in the River Wye, Derbyshire. This form is characterised by its self-sustaining nature; this population spawns in the spring and predate on the abundance of insect larvae, small fishes and flying insects found in summer. The River Wye population is confined to the 15 mile long river and thus poses little threat to the colonisation of nearby rivers. Elsewhere in the UK, freshwater fisheries are stocked with rainbow trout from hatcheries for recreational fishing. These individuals typically do not survive as well in the wild.
- The steelhead form is anadromous, living at sea and migrating up rivers to spawn. This form is generally declining due to migratory barriers that prevent access to spawning grounds.
eDNA analysis can be a useful tool for the management of rainbow trout including monitoring potential range expansion and determining stocking populations of fisheries.
