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Pacifastacus nigrescens

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA ARTHROPODA MALACOSTRACA DECAPODA ASTACIDAE

Scientific Name: Pacifastacus nigrescens
Species Authority: (Stimpson, 1857)
Common Name(s):
English Sooty Crayfish

Assessment Information [top]

Red List Category & Criteria: Extinct ver 3.1
Year Published: 2010
Date Assessed: 2010-06-01
Assessor(s): Schuster, G.A., Taylor, C.A. & Cordeiro, J.
Reviewer(s): Collen, B. & Richman, N.
Contributor(s): Livingston, F., Livingston, F., Soulsby, A.-M., Batchelor, A., Dyer, E., Whitton, F., Milligan, H.T., Smith, J., Lutz, M.L., De Silva, R., McGuinness, S., Kasthala, G., Jopling, B., Sullivan, K. & Cryer, G.
Justification:
Pacifastacus nigrescens has been assessed as Extinct. Despite targeted surveys for this species, no collections have been made in the 20th century.
History:
1996 Critically Endangered
1994 Extinct? (Groombridge 1994)
1990 Extinct? (IUCN 1990)
1988 Extinct? (IUCN Conservation Monitoring Centre 1988)
1986 Extinct? (IUCN Conservation Monitoring Centre 1986)

Geographic Range [top]

Range Description: Pacifastacus nigrescens was originally described from the vicinity of San Francisco, and reported from the hills on the north side of San Francisco Bay. This species was once common in the creeks surrounding the San Francisco bay; however, it has not been observed since the Signal Crayfish (Pacifastacus leniusculus) was introduced to California (probably 1800s- Bouchard 1977) and is believed to be Extinct (Rogers 2005). There have been no authenticated collections in 20th Century. Specific searches by Riegel (1959) and Bouchard (1977) found no extant populations. In 1980 and 1981 searches by McGriff also found no extant populations. All localities had populations of either Pacifastacus leniusculus or Procambarus clarkii (both implicated in the extinction of this species) and the habitat was greatly modified especially by urban development in the last hundred years (J. Cordeiro pers. comm. 2010). 

Countries:
Regionally extinct:
United States (California)
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: Specific searches by Riegel (1959) and Bouchard (1977) found no extant populations. In 1980 and 1981 searches by McGriff also found no extant populations. All localities had populations of either Pacifastacus leniusculus or Procambarus clarkii (both implicated in the extinction of this species) and the habitat was greatly modified especially by urban development in the last hundred years. This species is now thought to be Extinct (NatureServe 2009).
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: Pacifastacus nigrescens was found in streams (NatureServe 2009).
Systems: Freshwater

Threats [top]

Major Threat(s): Pacifastacus nigrescens is restricted to the San Francisco Bay region of northern California, but has disappeared as a result of urbanization and interactions with introduced crayfish species such as the Signal Crayfish (Pacifastacus leniusculus) and Procambarus clarkii (NatureServe 2009).

Conservation Actions [top]

Conservation Actions: This species has been assigned a Global Heritage Status Rank of GX by NatureServe (2009) and 'endangered possibly extinct' by the American Fisheries Society (Taylor et al. 2007).

Citation: Schuster, G.A., Taylor, C.A. & Cordeiro, J. 2010. Pacifastacus nigrescens. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 28 November 2014.
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