Sockeye salmon, Kokanee / Invasive Species of Japan
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Oncorhynchus nerka

Basic information
Scientific name Oncorhynchus nerka (No picture)
Common names Sockeye salmon, Kokanee
Higher taxon Salmonidae, Salmoniformes, Actinopterygii
Natural range Freshwater in California, Canada, far eastern Russia, Chishima (Kuril) Islands, to Hokkaido, Japan, and N Pacific Ocean.
Habitat Lakes, rivers, and ocean.
Invasion information
Range in Japan Landlocked form (kokanee): Hokkaido (Shikotsuko and Toyako Lakes), Aomori (Towadako Lake), Tochigi (Chuzenjiko Lake), Kanagawa (Ashinoko Lake), Yamanashi (Saiko and Motosuko Lakes), and Nagano (Aokiko Lake) Prefs.
Anadromous form (sockeye): Hokkaido (Nishibetsu and Abira Rivers).
Range in Japan
Origin Within Japan. Shikotsuko Lake population was from Akanko Lake, Hokkaido. The almost other introduced populations were from Shikotsuko Lake or Etorofu Is., southern Chishima (Kuril) Islands.
Date Introduction from Akanko Lake to Shikotsuko Lake was in 1894.
Route Deliberate: As fishery resource
Impact Potentially: Predation on zooplankton. Competition with native fishes.
Affected organism: Native fishes and zooplankton.
Regulation in Japan Fishing of this species is prohibited by Hokkaido local government. In other lakes, fishing is prohibited in some season.
Introduced range in other countries New Zealand (from Canada).
Reference Notes
  • Froese & Pauly (eds) (2009) FishBase (Accessed on 2010-12-14) http://www.fishbase.org/
  • Kawanabe et al. (eds) (2002) Freshwater Fishes of Japan, 3rd ed.. Yama-kei Publishers, Tokyo (in Jpn)
  • Matsuzawa & Senou (2008) Alien fishes of Japan. Bun-ichi Sogo Shuppan, Tokyo (in Jpn)
  • Nakabo (2011) “Kunimasu” Oncorhynchus kawamurae (Pisces: Salmoidae), 70 years after extinction in Lake Tazawa, Akita Prefecture, Japan. TAXA. 30, 31-54 (in Jpn with English abst)
  • etc.
In Saiko Lake of Yamanashi Pref., another introduced salmon O. kawamurae was found in 2010. Oncorhynchus kawamurae, endemic to Tazawako Lake, Akita Pref., was assumed to be extinct in 1940s, and current living population is in Saiko Lake only. This species has sometimes been regarded as a subspecies of O. nerka.