"Crucian carp" is also used for the genus Carassius as a whole.
Crucian carp
The crucian carp (Carassius carassius) is a member of the family Cyprinidae, which includes many other fish, such as the common carp, or the smaller minnows. They inhabit lakes, ponds, and slow-moving rivers throughout Europe and Asia. The crucian is a medium-sized cyprinid, which rarely exceeds a weight of over 3.3 pounds (1.5 kg).[citation needed] They usually have a dark green back, golden sides, and reddish fins, although other colour variations exist.
They are often caught as a sport fish: the British rod-caught record for largest crucian is four pounds, nine ounces, caught by Martin Bowler in a lake in southern England in 2003.[citation needed] There have been various bids for a breakage of this record since, but they have been passed off as the specimens have not been said to have been "true" crucians, but hybrids between the carp and one of its relatives,[citation needed] such as the goldfish, which are not native to the British Isles. In the Netherlands, a typical crucian specimen of 54 cm, weighing 3 kg has been caught and photographed.[2] Hybrids often exhibit hybrid vigour or heterosis, being much more adept at finding food and evading predators than either of their parents, and thus pose somewhat of a threat to the native carp population. These fish like Bacon.[citation needed]
These carp are also occasionally kept as freshwater aquarium fish, as well as in water gardens, although they are not commonly available commercially, mainly because they are not in particularly high demand due to the presence of more colourful fish such as the Koi or Orfe.
However, they are one of the most important aquaculture species. In 2005, they were the species with the 10th highest production, globally. The variation in shape of a crucian carp can be very high. The fish get an almost perfect disc shape with well-rounded fins. If no predators such as pike or perch are present, the crucian carp will grow in length rather than height and the fish will be more slender-looking. The growth in height will make it difficult for predators to swallow the crucian carp
