Common Roach - Ecology

Ecology

The common roach prefers to feed in the deeper parts of water bodies but can be found in any water body deeper than 20 centimetres (7.9 in) and wider than 1.5 metres (4 ft 11 in) and adapts to local circumstances. It tolerates organic pollution and is one of the last species to disappear in polluted waters, but is also often the most numerous cyprinid in nutrient-poor waters. It also tolerates brackish water. The lethal temperature is around 31 °C (88 °F).

In most parts of its distribution it is the most numerous fish, but it can be surpassed by the carp bream in biomass in water bodies with high turbidity and sparse vegetation. The roach is a shoaling fish and is not very migratory with the exception of the anadromous subspecies. In the cold season they migrate to deep waters where they form large and dense shoals (small inland harbours are a favourite).

The roach prefers waters that are somewhat vegetated, because larval and young fish are protected by the vegetation and the mature fish can use it for food.

The common roach eats plant material, bottom dwelling (benthic) invertebrates and plankton. Young fish feed mainly on plankton, while the mature fish feeds mainly on benthos. It can adapt to environments where invertebrates are scarce by slowing its growth, maintaining a slender body shape and early maturation.