Ide

(Leuciscus idus)

Order: Cypriniformes Family: Cyprinidae

Foto: Jussi Pennanen

Description: The ide is a relatively large brassy-flanked cyprinid with yellow eyes. The fins on the ventral side are red or reddish, and the anal fin has 11−13 fin rays. The ide resembles the roach but has smaller scales; it usually has 55 to 61 scales on the lateral line whereas the roach has 42−45.

Origin and distribution: The ide prefers large, clean and clear waters. The southern border of its range is marked by the Alps and Pyrenees. The species is lacking from the mountains of Norway and Sweden and from areas west of the Rhine. In the east, it occurs as far as the Lena drainage basin in Eastern Siberia and in Lake Baikal. In Finland, the ide occurs in all coastal brackish waters and in almost all the main watersheds. The northernmost ide populations are in the upper reaches of the rivers Kemijoki (Lokka reservoir), Ounasjoki and Tornionjoki. During the 20th century, it was translocated to new waters, sometimes to enhance a diminishing original stock.

Reproduction: Ide reach maturity at 5−8 years and at a length of 30−35 cm. They migrate to their spawning grounds in shallow streams soon after the ice cover has melted. From the sea, they run upstream to estuaries, rivers and even small brooks, but they also spawn in reed-covered coastal bays. Spawning usually lasts only a couple of days. The eggs adhere to vegetation or rocks. The incubation time of the embryos depends on the water temperature, usually lasting from 10 to 9 days. After hatching, the larvae stick to plants for a few days before starting to swim.

Diet, growth and migrations: Ide have a diverse diet. Larvae feed on zooplankton, whereas juveniles and adults favour benthic invertebrates. Large individuals also prey on other fish species. Growth is fastest during the first couple of years. At 10 years of age, ide weigh about 1 kg, and may sometimes live for over 20 years and weigh 3 kg or more. In spring, after spawning ide migrate from shallow coastal waters to the open waters of lakes and to the outer archipelago. In summer, they often move in shoals, and can be seen near the surface, especially when the water is calm. For the winter, ide move to deep waters.

Fishing and catches: The ide used to be a popular species for household use, but it has fallen into disfavour along with the general decrease in appreciation of cyprinids for human consumption. Some ide are still caught for the market in the Archipelago Sea and Gulf of Finland and in estuaries of the northern Gulf of Bothnia. In many freshwater areas, the ide is an occasional gillnets catch. It makes an interesting target for rod fishermen. In 2001, the estimated annual ide catch by recreational fishermen was 368 tonnes.

Vulnerability, threats and management: Ide stocks have been declining locally owing to eutrophication, dam building and water level regulation. Some have even vanished as a result of acidification. Conservation and rehabilitation of estuaries and brooks and the construction of fishways could enhance ide populations. Efforts have been made to revitalise some stocks by translocating brood fishes from other areas and releasing one-summer-old juveniles. In general, the species is a least concern species in Finland.

Comments: The orange form of ide, the golden orfe, is reared as an ornamental fish for ponds.

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