Crucian Carp (Carassius carassius)
photo by Viridiflavus
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). 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. 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, such as the goldfish, which are not native to the British Isles. These 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, and to other native aquatic animals.
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 (FAO 2005).
The shape of a Crucian carp can be very high. The fish get an almost perfect disc shape with well rounded fins. If no predators like 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.
Many sources will claim that crucian carp are the wild version of the goldfish (Carassius auratus auratus). The wild form of the goldfish is however Carassius auratus gibelio, or rather Carassius gibelio with auratus as the subspecies. While they are certainly closely related, they are different species which can be identified by the following characteristics:
- C. auratus has a more pointed snout while the snout of a crucian carp is well rounded.
- The wild form of the Goldfish C. auratus gibelio or C. gibelio often has a grey/greenish color, while crucian carps are always golden bronze.
- Juvenile crucian carp (and tench) have a black spot on the base of the tail which disappears with age. In C. auratus this tail spot is never present.
- C. auratus have fewer than 31 scales along the lateral line while crucian carp have 33 scales or more.