Chionoecetes bairdi Rathbun, 1893 

Common name(s):  Tanner crab, Southern tanner crab, snow crab, cobbler crab
Synonyms: Chionoecetes opilio (those found south of Alaska) Juvenile
Phylum Arthropoda
Subphylum Crustacea
Class Malacostraca
Subclass Eumalacostraca
Superorder Eucarida 
Order Decapoda
Family Oregoniidae (formerly in Family Majidae)
Chionoecetes juvenile captured at 250-300 foot depth in San Juan Channel.  Carapace width 2.75 cm.
(Photo by: Dave Cowles, July 2011)
Description:  This crab has a rostrum composed of two broad, flattened processes (photo) which project forward but are not turned dorsally.  Its carapace is slightly broader than long, and nearly oval in outline.  The carapace margins have spines on the anterolateral margins (photo) but are not expanded into winglike lobes.  The dorsal surface of the carapace has tubercles.  The walking legs are long, and longer than the chelipeds.  The merus of the walking legs is slightly inflated and flattened.  The margins of the merus and carpus of the walking legs have spines.  Color of adults is greenish-brown with red granules and orange lateral spines.  Pink on the ventral side.  Chelipeds have a golden iridescence, and have white fingers with red stripes and orange at the base..  The walking legs are brown, white, pink, and orange and have dorsal red stripes.  The dactyls are red.  Carapace width to 14 cm in males, 8.1 cm in females.

How to Distinguish from Similar Species: Chionoecetes tanneri (C. angulatus?) has a rostrum which turns dorsally.  It is mainly found at depths below 1000 m. style="font-style: italic;">C. opilio is an arctic species common near the Aleutian Islands, with carapace length and width nearly equal and less spines on the carapace.  Most other crabs from family Majidae, which look similar, have a carapace longer than wide (except for Mimulus foliatus, in which the carapace margins are expanded into winglike flanges).

Geographical Range: Northern Alaska to central Oregon

Depth Range:  6 to 475 m

Habitat: Subtidal, Sandy or muddy bottoms

Biology/Natural History: This crab is harvested commercially in Alaska as the snow crab, although that harvest is mostly of the relative C. opilio.  Predators include sea otters in Alaska.  The egg masses of this species may be parasitized by a tiny Nemertean worm Carcinonemertes regicides.  A leech, Notostomium cyclostoma, which feeds off fishes lays its eggs on the crab carapace.  The leeches do not appear to feed on the crab.  It may also be parasitized by the dinoflagellate Hematodinium.  This crab has a terminal molt.


 
 
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References:

Dichotomous Keys:
  Coffin, 1952
  Kozloff 1987, 1996
 
 

General References:
  Hart, 1982
  Lamb and Hanby, 2005
  O'Clair and O'Clair, 1998

Scientific Articles:
Myers, T.C.,  T.M. Botelho, T.M. Koeneman, S. Short, and K. Inamura, 1990.  Distribution of bitter crab dinoflagellate syndrome in southeast Alaskan Tanner Crabs Chionoecetes bairdi.  Dis. Aquat. Org. 9: pp. 37-43 

Web sites:

General Notes and Observations:  Locations, abundances, unusual behaviors:

Rostrum

This closeup shows the rostrum, the spines on the anterolateral margins of the carapace, the chelipeds, and the eye pattern.


Authors and Editors of Page:
Dave Cowles (2011):  Created original page
CSS coding for page developed by Jonathan Cowles (2007)