Rainbow trout

Rainbow trout

Oncorhynchus mykiss

Common name:

Rainbow trout

Scientific name:

Oncorhynchus mykiss

Alternative common names:


Rainbow trout are found in cold, well oxygenated water. They are listed under NEMBA as a Category 2 invasive species, meaning that this species is restricted by activity. Rainbow trout have been linked to the decline of some indigenous fish species.

Additional Information

Where does this species come from?

North America.

What is its invasive status in South Africa?

NEMBA Category – Not currently listed in accordance with Government Notice 115 of 24 February 2021.

Where in South Africa is it a problem?

Western Cape and highland regions of Gauteng, Mpumalanga, KwaZulu-Natal and Limpopo Province.

How does it spread?

They spread by swimming and establishing themselves in cold water rivers and under suitable conditions females will breed producing 2 000 to 3 000 eggs.

Why is it a problem?

Trout are efficient predators which prey on smaller fish species and threaten indigenous fish. They also feed on amphibians and invertebrates, leading to local declines.

What does it look like?

Description: Dark-olive in colour, shading to silvery-white on the underside with a heavily speckled body. A pink-red stripe is often present along their sides. This becomes most pronounced during the breeding season. The body profile is oblong and streamlined. In dams they can reach almost 70cm in length with a weight of 6kg, but in shallower rivers they seldom exceed 50cm and weigh around 1.5kg.

Habitat: Found in fast-flowing, well oxygenated rivers and highland dams. They have a preference for clear, cold water.

Breeding: Females produce 2 000 to 3 000 eggs. The eggs fall onto the gravel and between pebbles where they complete their development.

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