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Montana Field Guide

Montana Field Guides

Pilose Crayfish - Pacifastacus gambelii


Global Rank: G4G5
State Rank: SX

Agency Status
USFWS:
USFS:
BLM:


 

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General Description
Pigmented, eyes normal; rostrum with margins converging, at least 3 pr lateral marginal spines, acumen indistinct, median carina present; postorbital ridges lacking posterior spines or tubercles; cervical and hepatic spines absent; areola broad with 7-9 punctations in narrowest part, branchiocardiac groove interrupted so that distinct cephalic and caudal portions of areola evident; chela stout, dorsal surface of palm studded with minute tubercles, two conspicuous longitudinal clusters of setae on dorsal surface of palm; male lacking hooks and bosses on all pereiopods; male 1st pleopod lacking terminal elements, in form of tightly rolled tube, only distalmost 3-5% slightly attenuate; incisor region of mandible blade-like (Hobbs 1972).

Species Range
Montana Range

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Range Comments
Confirmed on the Pacific slope in California, Idaho, Nevada, Oregon, Utah, Washington, and Wyoming, and reported in the Missouri River drainages of Montana. It has been reported that this crayfish species inhabitated Montana waters of the Upper Missouri River drainages, but no museum records were ever located. Extensive searches (Gustafson 2004) have not turned up this crayfish species, so if it ever did exist in Montana it is presumed extirpated.

Habitat
This species is found in lentic & lotic habitats and is likely to breed during late-spring. This species is believed to be an opportunistic feeder and has a home range estimated to be no more than 50 meters (Wyoming Game and Fish Department 2000). The pilose crayfish is belived to be intollerable of warmer waters or of the warmer water fish populations (Johnson 1986).

Food Habits
This species is omnivorous and a scavenger, feeds by shredding large pieces of orangic materials and shredding them up.

Management
Probably extirpated from the state if it ever lived here.

Threats or Limiting Factors
Invasive and invading virile crayfish species, Orconectes virilis in the upper Missouri River drainages and water quality problems.

References
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Citation for data on this website:
Pilose Crayfish — Pacifastacus gambelii.  Montana Field Guide.  .  Retrieved on , from