Identification

Recognising species of bream can often be a challenging task, especially if they resemble or live in the same aquatic environments. The crucian carp (Carassius carassius) has distinctive features that set it apart from other fish species....

How to distinguish our crucian carp from other fish species?

Basic characters

Mouth without barbels (versus common carp)
Dorsal fin significantly longer than the anal fin (compared to the bitterling)
Concave dorsal fin (gibel carp have it slightly bent inwards or straight; i.e. convex)
Spot in the base of caudal fin (up to a body size of approx. 10 cm, the gibel carp have it only very rarely)

The crucian carp - juvenile with a clearly visible black spot at the base of the caudal fin.

The gibel carp without spot at base of caudal fin. — Gibel carp without spot at the base of the caudal fin.

More detailed characters

The caudal fin is shallowly curved (in gibel carp and goldfish it is distinctly curved)
Toothing of the last hard ray of the unpaired fins

The dorsal margin of the crucian carp is serrated, the teeth in the dorsal fin are of the same size, usually 25 to 30 (gibel carp and goldfish have these teeth in varying numbers of 20 to 25, with the largest teeth being at the end of the ray - furthest from the body and having more pronounced dorsal and caudal fin rays).

Number of scales in the lateral line is usually 30-36 (compared to the gibel carp, which has 28-33)

However, there is a misconception that there is no overlap in this character.

Auxiliary features that distinguish it from the gibel carp. These features need to be looked at

Golden green colour
Smaller scales
Head shape is rounded
Mouth are small and point slightly upwards
Eye position is higher
Finer toothing of the last hard dorsal fin ray

(You may notice the more pronounced serration in the gibel carp when keeping it in a pen. Due to the large sawtooth teeth on the dorsal fin, it happens that they get caught on the netting of the keep net or the netting of the hand net).

crucian carp (left) vs. gibel carp (right)

Other signs - fish has to be dead for identification

Number of gill rakers on the first gill arch

Crucian carp - 23-33

Gibel carp and goldfish - 38-57

Peritoneal colouration (lining of the abdominal cavity)

The crucian carp - whitish to silvery

Other Carassius - dark

Note: Individuals of the three species mentioned above (gibel carp, goldfisf and ginbuna) are difficult to distinguish from each other and form a so-called species complex C. auratus, they can hybridize and all are widespread in the Czech Republic. For identification purposes (of this project), it is sufficient to distinguish between the crucian carp and one of these three non-native Carassius. Then just write the gibel carp.

Below you can see the subtle differences between the crucian carp and gibel carp. Even within a species there is a great variation in shape, so distinguishing between these species takes a bit of practice.