Invasion HistoryFirst Non-native North American Tidal Record: 1959
First Non-native West Coast Tidal Record: 1959
First Non-native East/Gulf Coast Tidal Record:
General Invasion History:
Pacifastacus leniusculus is native to northwestern North America from Oregon to British Columbia. The southern boundary of the native range is unclear. Museum specimens from the Klamath and Eel River drainages in Northern California are undated (Taylor et al. 1996; U.S. Museum of Natural History 2007). The Signal Crayfish was introduced to various watersheds in California, including the San Francisco Bay watershed and delta (Cohen and Carlton 1995).
North American Invasion History:
Invasion History on the West Coast:
Pacifastacus leniusculus was introduced to various California watersheds, possibly as early as 1898, in San Francisco. An official transplant was made in 1912 to hatcheries in Santa Cruz County, and in later years, they were introduced to the Sacramento-San Joaquin watershed. They were present in the Delta by 1959, and are now abundant (Riegel 1959). Other California locations include the Monterey Bay watershed, and upper reaches of the Sacramento watershed in the Sierras (USGS Nonindigenous Aquatic Species Program 2010). Two records near the coast were from the Carmel River and the Little Sur Rivers, south of Monterey Bay, two and one miles from the ocean, respectively (Riegel 1959).
In 2002, one specimen was caught in the Buskin River on Kodiak Island, Alaska (USGS Nonindigenous Aquatic Species Program 2011). This could have been a bait release.
Invasion History Elsewhere in the World:
In the 1860s, the fungus Aphanomyces astaci (Crayfish Plague) spread throughout Europe, killing the native crayfish (Astacus astacus) and other species. This disease was probably brought from North America with crayfish sold as food. Disease-resistant North American crayfish were stocked in many locations. Pacifastacus leniusculus was introduced to Sweden in 1959, and were widely transplanted into northern European freshwaters and are now present from Spain to Finland, with isolated populations in Greece (Holdich et al. 2009). It occurs in the Gulf of Bothnia, Baltic Sea (Olenin and Leppakoski 2000), but the extent to which it inhabits and disperses through estuarine waters is unclear (Holdich et al. 1997). Pacifiastcus leniusculus is established in the upper Danube drainage near Koszeg, Hungary (Puky et al. 2005). It also occurs in the Czech Republic and Austria, but has not been reported from the lower Danube or elsewhere in the Black Sea watershed.
Pacifastacus leniusculus stock from the Columbia River was introduced to Hokkaido and Honshu, Japan, between 1926 and 1930, and it is now widespread, especially in Hokkaido (Uso et al. 2007).
Male crayfish of the genus Pacifastacus (Signal Crayfish) lack hooks on the ischia (3rd segment) of the walking legs, while females lack the annulus ventralis (seminal receptacle), which in cambarid crayfish, is located between the 4th and 5th pairs of walking legs (Hobbs 1991). The margin of the rostrum in P. leniusculus is smooth. The Signal Crayfish matures at 60 mm and occasionally reaches 160 mm. The overall color of the animal is dark brown, but a turquoise and white patch at the base of the claw is distinctive (Riegel 1959; Taugbøl and Johnsen 2006).
Potamobius leniusculus (Ortmann, 1902)
Potentially Misidentified Species
Virile Crayfish, Midwest native, introduced to East Coast, West Coast, and Europe
Klamath Crayfish, native to Klamath and Eel basins, northern California and Oregon
Shasta Crayfish, California native, upper Sacramento basin
Life History- Freshwater crayfish mate by internal fertilization, with the male attaching spermatophores to the space between the 4th and 5th walking legs. The female curls her abdomen far forward, to create a chamber in which the eggs are driven by the pleopods. The mass of eggs becomes attached under the tail. Larval development takes place inside the egg and the young hatch as miniature adults (Barnes 1983).
Ecology- Pacifastacus leniusculus inhabits streams, ponds and lakes in a variety of habitats, including rocky, muddy, and vegetated areas (Taugbøl and Johnsen 2006). If soft sediment is present, it digs burrows. It is tolerant of salinities up to 28 PSU, but females with eggs have not been seen at salinities above 7 PSU (Holdich et al. 1997).
aquatic plants, freshwater invertebrates, carrion
fishes, turtles, snakes, raccoons, otters, birds
Other crayfish species
|General Habitat||Fresh (nontidal) Marsh||None|
|General Habitat||Grass Bed||None|
|General Habitat||Coarse Woody Debris||None|
|General Habitat||Nontidal Freshwater||None|
|General Habitat||Tidal Fresh Marsh||None|
|Salinity Range||Limnetic||0-0.5 PSU|
|Salinity Range||Oligohaline||0.5-5 PSU|
|Salinity Range||Mesohaline||5-18 PSU|
|Salinity Range||Polyhaline||18-30 PSU|
Tolerances and Life History Parameters
|Minimum Temperature (ºC)||7.5||Westhoff and Rosenberger 2016|
|Maximum Temperature (ºC)||32||C. DALE BECKER, ROBERT G. GENOWAY, and J. A. MERRILL 1975, Resistance of a Northwestern Crayfish, Pacifastacus leniusculus (Dana), to Elevated Temperatures. Transactions of the American Fisheries Society 1975;104:374–387|
|Minimum Salinity (‰)||0||This a freshwater species.|
|Maximum Salinity (‰)||28||~60% survival over 9 weeks (Holdich et al. 1997)|
|Maximum Reproductive Salinity||7||Maximum salinity in which eggs on berried females hatched (Holdich et al. 1997)|
|Maximum Length (mm)||160||ISSG Global Invasive Species database 2011|
|Broad Temperature Range||None||Cold temperate-Warm temperate|
|Broad Salinity Range||None||Nontidal Limnetic-Polyhaline|
General ImpactsPacifastacus leniusculus (Signal Crayfish) has had a significant positive economic impact as a fisheries species, but it has had negative impacts as a competitor with native species in California, Europe and Japan. In Europe, it is also a vector for the spread of the crayfish plague (Cohen and Carlton 1995; Usio et al. 2007; Holdich et al. 2009). In Sweden, the estimated cost of impacts from the Signal Crayfish and the crayfish plague was estimated at about 53-88 million US dollars (Gren et al. 2009).
Fisheries- Pacifastacus leniusculus is the major crayfish species caught in the San Francisco Bay Delta, supporting a fishery of 250 tons annually (Cohen and Carlton 1995). Pacifastacus leniusculus supports substantial fisheries in Sweden and other northern European countries (Taugbøl and Johnsen 2006).
Competition- In the San Francisco Bay watershed, Pacifastacus leniusculus may have contributed to the extinction of a native crayfish (P. nigrescens, Sooty Crayfish), and is considered to be a competitor threatening the native crayfish P. fortis (Shasta Crayfish) (Cohen and Carlton 1995). Pacifastacus leniusculus displaced the native crayfishes (Astacus astacus, Austropotamobius pallipes) in Europe (Lowery and Holdich 1999; Holdich et al. 2010). In Japan, it is reported to compete and prey on the country's only native crayfish (Cambaroides japonicus) (Usio et al. 2007).
Disease Vector- Pacifastacus leniusculus is a major vector for the spread of the 'Crayfish Plague' fungus, Aphanomyces astaci, which has greatly reduced the abundance and range of native crayfishes in Europe (Lowery and Holdich 1989; Holdich et al. 2009).
Habitat Change- Burrowing by P. leniusculus has been reported to cause erosion at the rate of 1 m per year on the River Lark, England (Stancliffe-Vaughan, 2009, cited by Holdich et al. 2009).
|P090||San Francisco Bay||Economic Impact||Fisheries|
|Pacifastacus leniusculus is the major crayfish species caught in the San Francisco Bay Delta, supporting a fishery of 250 tons annually (Cohen and Carlton 1995).|
|P090||San Francisco Bay||Ecological Impact||Competition|
|Pacifastacus leniusculus may have contributed to the extinction of a native crayfish (P. nigrescens, Sooty Crayfish), and is considered to be a competitor threatening another native crayfish, P. fortis (Shasta Crayfish) (Cohen and Carlton 1995).|
|Pacifastacus leniusculus supports substantial fisheries in Sweden and other northern European countries. However, the native A. astacus is still preferred by many customers and sells for a higher price in Sweden and Finland (Holdich et al. 2009). Gren et al. (2009) estimated the loses for fisheries in Sweden due to the crayfish plague (Aphanomyces astaci) and the displacement of native crayfish by P. leniusculus at 365 to 598 million Swedish kroner (53-88 million US dollars).|
|Pacifastacus leniusculus has displaced the native Noble Crayfish (Astacus astacus) in Sweden and Finland (Holdich et al. 2009).|
|B-XIII||None||Ecological Impact||Parasite/Predator Vector|
|Disease Vector- Pacifastacus leniusculus is a major vector for the spread of the 'Crayfish Plague' fungus, Aphanomyces astaci, which has greatly reduced the abundance and range of native crayfish in Europe (Lowery and Holdich 1989).|
Regional Distribution Map
|Bioregion||Region Name||Year||Invasion Status||Population Status|
|P293||_CDA_P293 (Strait of Georgia)||0||Native||Estab|
|P090||San Francisco Bay||1959||Def||Estab|
|P093||_CDA_P093 (San Pablo Bay)||1959||Def||Estab|
|P073||_CDA_P073 (Central Coastal)||1959||Def||Estab|
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