Carassius carassius (Linnaeus, 1758)Carassius gibelio (Bloch, 1782)

Carassius carassius View in CoL View Figure

Common name. Crucian carp.

Diagnosis. Distinguished from non-native species of Caras- sius in West Asia by: ○ flank golden-green / ● last simple anal and dorsal rays weakly serrated / ● 23–33 gill rakers / ● 31–36 total lateral-line scales / ● free edge of dorsal convex / ● usually 6½ branched anal rays / ● peritoneum whitish. Size up to 550 mm SL.

Distribution. Locally in lower Sakarya (Akgöl), where it might be native,and in the upper Aras drainage (Lake Çıldır), where it may be non-native. Native to North, Baltic, White, Barents, northern Black, and Caspian Sea basins; Aegean Sea basin only in Maritza drainage; eastward to Kolyma drainage (Siberia); westward to Rhine and eastern drainages of England. Absent from North Sea basin in Sweden and Norway. In Baltic basin, north to about 66°N. Widely introduced to Italy, England, and France but possibly often con- fused with C. auratus .

Habitat. Usually restricted to densely vegetated backwaters and oxbows of lowland rivers. Also, in small, well-vegetated lakes and channels. Tolerates high summer temperatures and very low oxygen concentrations in summer and under ice cover. Able to survive in almost completely frozen water or almost-dry habitats by burying itself in mud. Spawns in dense submerged vegetation.

Biology. Lives about 10 years. Males reproduce for the first time at 3 years, females at 4 years in central and eastern Europe, at 2 years in southern Europe. Spawns in May–July at temperatures above 18°C. Individual females spawn with several males. Males follow ripe females, often with much splashing. Females spawn 3–5 times during a season. Eggs are sticky and are attached to water plants. Omnivorous, feeds all day but mostly at night on plankton, benthic inver- tebrates, plant material, and detritus. Seems to be a weak competitor, usually absent from waters with rich ichthyo- fauna and abundant predatory species. Very abundant in the absence of other fish species. High-bodied, fast-growing individuals in habitats with predatory fish more elongate in habitats without predatory fish.

Conservation status. LC.

Further reading. Szczerbowski & Szczerbowski, in Bănărescu & Paepke, 2002 (biology). Carassius gibelio View Figure

Common name. Prussian carp.

Diagnosis. Distinguished from C. carassius in West Asia by: ● flank silvery / ● last simple anal and dorsal rays strongly serrated/ ● 38–52gill rakers/ ○ 26–33total lateral-line scales / ● free edge of dorsal concave or straight / ● usually 5½ branched anal rays / ● peritoneum black. Size up to 350 mm SL.

Distribution. Mitochondria of this species are found throughout West Asia. Often considered native from Central Europe to Siberia.As there are no historical records from Europe or West Asia, considered non-native to region. Native to Amur drainage in Russia and China and introduced in Europe with fish imported from Amur. Introduced from Europe to North Africa, West Asia, and elsewhere.

Habitat. Identical to C. auratus .

Biology. Usually, diploid and tetraploid individuals of both sexes, often together with triploid females. Also, all-female populations where all individuals are triploids. Triploids reproduce by gynogenesis as sperm parasites of other species,such as Cyprinus carpio and various leuciscids.Lives about 10 years. Spawns first time at 3−4 years in central and eastern Europe,at 1−2 years in West Asia. Spawns May−July at temperatures above 14°C, with spawning most intensive in early morning. Older individuals spawn earlier in season than younger ones. Males move to spawning sites before females. Single female spawns with several males. Males follow mature female, often with much splashing. Female spawn up to three times per season.Sticky eggs are attached to water plants or other submerged objects. Feeding larvae and juveniles inhabit highly complex habitats such as reed beds. Omnivorous, feeding on plankton, benthic invertebrates, plant material, and detritus.

Conservation status. Non-native; introduced as a weed with stocked carp.

Further reading. Kottelat 1997 (systematics); Vasil’ev & Vasil’eva 2000 (genetics); Szczerbowski 2002 (biology; as C. auratus , in part); Hänfling et al. 2005 (genetics); Kottelat & Freyhof 2007 (distribution, biology); Yerli et al. 2014 (distribution).