The signal crayfish is one of two species of crayfish reported from British Columbia. It is a blue-brown to red-brown crayfish that reaches lengths of 15 (16) cm (males), 12 cm (females), with robust, smooth claws. The common name of the species is derived from the white to pale blue-green patch located near the claw hinge. The Global Invasive Species Database (2010) describes this species as follows: “The cephalothorax is smooth with two pairs of post-orbital ridges, the anterior pair with an apical spine; and no spines on shoulders of the carapace behind cervical groove...the areola between branchiocardiac grooves is obvious. The rostrum sides are smooth and more or less parallel until the apex; the acumen is very pointed with prominent shoulders; and a simple median carina down whole length...adult males are massive either lengthways or in width... weight is typically 60 and 110g at 50 and 70mm carapace length.”
There are three subspecies in BC which may be separated based on morphology: Pacifastacus leniusculus klamathensis, Pacifastacus leniusculus leniusculus, and Pacifastacus leniusculus trowbridgii.
This species tolerates a range of temperatures (up to 33C), but prefers temperatures of less than 25C (Bondar et al. 2005).
There is a lot of variation among populations of the signal crayfish in Canada, the US and in Europe (Bondar et al. 2005). In Europe and North America, mating and egg laying in this species is reported in the autumn, when 100 to 400 eggs are laid (Bondar et al. 2005). Eggs are carried for approx. 7 months, with hatching in April/May (Bondar et al. 2005). Hatchlings begin to forage independently after 1-2 months (Bondar et al. 2005).
The signal crayfish is omnivorous and will eat a variety of foods from decaying roots and leaves to meat, including smaller crayfish and fish (Wikipedia 2010). Juveniles and young of the year are reported as primarily carnivorous on benthic insects (Bondar et al. 2005).
This is a solitary species. It actively moves up and down rivers as well as overland, which aids dispersal (Global Invasive Species Database 2010). Originally, this was considered a non-burrowing species, but introduced populations in Europe construct burrows under rocks and along river and lake banks (Global Invasive Species Database 2010).
This is a hardy cool-temperate species that is found in small streams, rivers and lakes, including subalpine lakes. This species is tolerant of brackish water; salinities of up to 21 % have been reported (Bondar et al. 2005). It is sensitive to pH levels, preferring water above pH 6.0. As with most crayfish species, calcium levels above 5 mg/L is needed for re-calcification of the exoskeleton following moulting (Bondar et al. 2005). Adults and juveniles show different habitat selections (ontogenetic shifts in spatial distribution), with juveniles preferring boulder/cobble areas, and adults preferring sandy, silty areas in deeper water (Bondar et al. 2005).
The signal crayfish is endemic to the northwestern USA and southwestern Canada, and is introduced in some southern states, and Europe and Japan where it is considered invasive. It is found from British Columbia south to northern California, and east to parts of Utah and Montana (Bondar et al. 2005).
Distribution in British Columbia
The signal crayfish is known from the southern part of BC: Vancouver Island, the Lower Mainland, east to the Kootenays, and as far north as Okanagan Lake (Bondar et al. 2006). Specifically, Bondar et al. (2005) report the northern range limit in BC as approximately at latitude 51°N, and the eastern range limit as near longitude 118°W”. There is speculation that the species was introduced to Vancouver Island as there are no records for its presence prior to the 20th century (Bondar et al. 2005).
This species has been commercially harvested in the province.
Three subspecies are found in BC, however the range of these in the province is not well known (Bondar et al. 2005) :
1) Pacifastacus lensuculus klamathensis (Stimpson, 1857): British Columbia and Idaho south to Central California (Fetzner 2004-2006)
2) Pacifastacus lensuculus lensuculus (Dana, 1852): British Columbia, California, Idaho, Nevada, Oregon, Utah, and Washington. Introduced into Sweden (Svardson, 1965:92) and Japan (Global Invasive Database 2011) (Fetzner 2004-2006). Also introduced in Finland.
3) Pacifastacus lensuculus trowbridgi (Stimpson, 1857): British Columbia, California, Idaho, Oregon, Nevada and Washington. Introduced into Japan (Fetzner 2004-2006).
Bondar, C.A., Zhang, Y. and Richardson, J.S. 2005. The conservation status of the freshwater crayfish, Pacifastacus leniusculus, in British Columbia, Canada. Ministry of Land, Water and Air Protection Management Report 117. Available online..
Fetzner, James W. Jr. 2004-2010. The Crayfsh and Lobster Taxonomy Browser. Available online.
Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2021. E-Fauna BC:
Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab
for Advanced Spatial Analysis, Department of Geography, University of British
Columbia, Vancouver. [Accessed:
2022-09-28 2:48:54 AM]
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