|Scientific Name:||Coregonus maraena|
|Species Authority:||(Bloch, 1779)|
|Taxonomic Notes:||This species is usually known as Coregonus lavaretus in Baltic Sea basin.|
|Red List Category & Criteria:||Vulnerable A2cd ver 3.1|
|Reviewer(s):||Kottelat, M. & Smith, K.|
This species is widespread in the Baltic basin. However, there are only few natural populations left. Most of the natural populations declined because of pollution, blocking of spawning rivers, and overfishing. Apparent abundance only reflects the massive stocking programmes in Germany, Poland and Scandinavia without which the populations would rapidly decline. In the Gulf of Bothnia alone, about six million juveniles were stocked annually (1995–1998) to support commercial fisheries. The major population crash of the wild population took place during major dam construction which ended more than 15 years ago, however there have still been some new dam constructions blocking the spawning grounds of Coregonus maraena (e.g., on the Kyrojnoki River in Finland which was constructed in 1993 (Himberg pers. comm.)) and there are still plans to construct more hydro-power dams in the Baltic basin. Even though the population has been in decline since before World War II, it is suspected that the wild native wild population has declined by more than 30% in the past three generations (15 years) as new dams have been built, and it is surviving at very low levels.
In the European Union 27 region, this species is also Vulnerable (VU A2cd), with the same rationale as above.
|Range Description:||The species occurs in the Baltic Sea area: Swedish coast (including Bothnian Gulf, missing in Gotland); in southern Baltic, German coast, extending from River Schlei to Gulf of Finland. Southeastern North Sea basin: Ems, Weser and Elbe drainages and small rivers of Schleswig-Holstein and Denmark. Landlocked populations also occur in Lake Miedwie (former Madüsee) and other lakes in Poland, Lakes Vättern, Vänern, Mälaren, Siljan (Sweden), Ladoga (Russia) and others. It has been introduced and transplanted in many drainages within its native range and outside westward to Rhine drainage.|
Native:Denmark; Estonia; Finland; Germany; Latvia; Lithuania; Netherlands; Norway; Poland; Russian Federation; Sweden
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||Populations have declined across most of the species range. In Germany and Poland, since World War II, all populations have been extirpated except one, and there is only one population remaining in Denmark. In Sweden and Finland the populations have also massively declined.|
|Habitat and Ecology:||
This fish forages along coasts and spawns in freshened parts of estuaries or in lower stretches of rivers. It also occurs in deep, oligo-mesotrophic lakes. Spawning occurs in shallow water, in rapids or small rivers or over firm sediments in lowland rivers and estuaries. In Lake Vänern, it spawns at 8–20 m depth, over firm bottom.
The species has both anadromous and landlocked populations. It spawns for the first time at 3–5 years. Adults enters rivers in June–October (northern Baltic) until November (southern Baltic), when the temperature falls below 10°C. In the River Tornionjoki (Finland), individuals ascending from sea in June–August can be distinguished by DNA markers from fish ascending in September. It spawns in October–November (Finland) until November–December (Poland), when the temperature falls below 6°C. Spawners overwinter in rivers or at sea very close to estuaries. Eggs hatch in early spring (March–April in Odra) and drift to sea or to estuarine bays. Juveniles migrate to sea in June–August (Odra). It may migrate up to 700 km from the spawning river to forage at sea (Bothnian Bay). Northernmost stocks undertake the longest migrations between spawning and foraging grounds. Some females spawn every second year. The species feeds on benthic prey (crustaceans, molluscs, large insect larvae, small fish).
|Use and Trade:||It is harvested for human consumption.|
|Major Threat(s):||Water pollution, impoundment of rivers and overfishing.|
|Conservation Actions:||The species is ranched in all of its range states. In Gulf of Bothnia alone, about six million juveniles were stocked annually in 1995–1998 to support commercial fisheries.|
|Citation:||Freyhof, J. 2013. Coregonus maraena. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 04 September 2015.|
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