10 20 40 60 cm
mittakaava < 40 cm
© Copyright: Images:
Gösta Sundman: Suomen Kalat (Kansalliskirjasto, The National Library of Finland), Jouko Lehmuskallio, Lauri Urho. All rights reserved.
- Family: Carps and minnows – Cyprinidae
- Similar species: carp, prussian carp
- Size: Lake form usually 20-35 cm, max. around 40 cm and 1 kg, seldom over 2 kg. Pond form 5-15 cm.
- Appearance: The faster-growing form of the Crucian carp, which is found in rich lakes and sea inlets, is a sturdy, deep-bodied fish with prominent scales. Distinguished from other deep-bodied fish of the carp family by the rounded tips to the large caudal fin. Only the common carp, which has been introduced in a few places in Finland, has a similar tail fin. There can be no confusion between the two, as the common carp has barbels around the mouth. The fish most closely resembling the Crucian carp is its near relation the Prussian carp, a recent introduction into Finland. However, the two differ not just in their colour but also in the size of the scales, the Crucian carp usually having 31-35 along the lateral line while the Prussian carp’s scales are slightly larger, with only 27-32. The slower-growing pond form of the Crucian carp has a larger head in relation to its body and is not as deep bodied as the lake form. The body shape resembles that of the common carp, but in Finland the Crucian is always smaller, as common carp are planted at a size larger than that ever attained by the Crucian; neither does the Crucian have barbels. The pond form is often the only species found in shallow, nutrient-rich ponds. Depending on the feeding available, body shapes and proportions vary greatly between lake and pond forms.
- Colouring: Overall greyish when young, sides soon becoming golden. Older lake forms are a deep gold or copper colour. Reddish tinge to pelvic and anal fins. Prussian carp retain their silvery sides even when fully grown. A reliable distinction is provided by the colour of the membrane lining the abdominal cavity, which is whitish in the Crucian carp but black in the Prussian carp.
- Reproduction: Spawns in warm water in shallow reedy bays. Spawning may take place in several batches and last from late May until July. During dusk spawning Crucians sometimes splash noisily on the surface.
- Food: Benthic invertebrates, insects and plant material.
- Distribution and habitat: Crucian carp have been introduced into many waters, both intentionally and accidentally, as a bait fish. Its distribution is thus somewhat patchy. Most northerly occurrences are in Kittilä and Sodankylä in Lapland. More widespread in the nutrient-rich lakes of central and southern Finland. Also found in similarly rich bays of the Gulf of Finland and Gulf of Botnia as far north as Vaasa. Crucian carp do not compete well with other species, and in mixed fisheries its numbers are often small. Its strong point is its ability to tolerate low oxygen levels during winter. This allows it to survive in eutrophic waters repeatedly affected by oxygen depletion. It can even survive in ponds that freeze completely by burying itself in the bottom mud. It is therefore often the only species found in small nutrient-rich ponds.