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  3. Pacifastacus leniusculus

Pacifastacus leniusculus

Basic information
Scientific name Pacifastacus leniusculus

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Major synonym Pacifastacus trowbridgii
Common names Signal crayfish
Higher taxon Astacidae, Decapoda, Malacostraca, Arthropoda
Natural range North America.
Habitat Lake or pond, stream. Brackish in Columbia River (native range).
Invasion information
Range in Japan Hokkaido, Fukushima, Shiga, Nagano, Tochigi and Chiba Prefs. Range in Japan
Origin From Portland, Oregon, USA
Date 1926—1930 (5 times). The first record in Chiba Pref. was in Sep 2009.
Route Deliberate introduction (for food). At first from Portland to Lake Mashu, Hokkaido, and after from Lake Mashu to other region of Japan.
Impact Predation, competition against native species. Acompaniment of crayfish pest. Destruction of freshwater vegetation.
Native organism(s) affected: Freshwater native species of amphibians, fishes, benthos (crayfish, crab, snail), and aquatic plants (e.g., spherical moss).
Regulation in Japan Import, transport and keeping are legally restricted in Japan. Worst 100 invasive species of Japan
Introduced range in other countries Europe
Reference Notes
  • DECO (ed) (2006) Dictionary of Alien Species. Tokyo-Shoseki. (in Jpn)
  • Ecol Soc Japan (ed) (2002) Handbook of Alien Species in Japan. Chijin-Shokan. (in Jpn)
  • JWRC (ed) (2008) A Photographic Guide to the Invasive Alien Species in Japan. Heibonsha. (in Jpn)
  • Usio et al. (2001) Species displacement between an introduced and a ‘vulnerable’ crayfish: the role of aggressive interactions and shelter competition. Biological Invasions 3:179-185.
  • Usio et al. (2006) Alien vs. endemic crayfish: roles of species identity in ecosystem functioning. Archiv fur Hydrobiologie 166:1-21.
  • etc.