Chionoecetes bairdi Rathbun, 1893
Common name(s): Tanner crab, Southern tanner crab, snow crab, cobbler crab
|Synonyms: Chionoecetes opilio (those found south of Alaska)|
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)|
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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Lamb and Hanby, 2005
O'Clair and O'Clair, 1998
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
General Notes and Observations: Locations, abundances, unusual behaviors:
This closeup shows the rostrum, the spines on the anterolateral margins of the carapace, the chelipeds, and the eye pattern. Photo by Dave Cowles, July 2011.
A photo of another individual clearly shows the small spines lining the anterolateral carapace. Captured by Kirt Onthank by SCUBA at about 20 m depth at night in Burrows Bay. Photo by Dave Cowles, August 2015
|These images of the underside of a male show the shape of the abdomen and the specialized first pleopods underneath. Carapace width on this individual is 3.5 cm. Photos by Dave Cowles, August 2015|
|Ventral abdomen||Abdomen folded back to show pleopods|
A dorsal view of the same individual.
And the ventral side
This closeup of the chelae shows that the chelipeds are relatively short but with small spines and granules. The base (palm) of the propodus is swollen and slightly elongated. The fingers of the chelae are long and narrow and are serrated with sharp teeth.
A view of the mouth.