The crucian carp (Carassius carassius) is a native freshwater fish in the UK, often found in still or slow-moving waters such as ponds, lakes and ditches. Known for its resilience to low oxygen levels, it is an important part of the aquatic ecosystem and supports biodiversity. however, hybridization with non-native species like goldfish and competition from other carp species have led to declines in its pure populations, making it a conservation priority in some areas.
