Species Profile

 

 

 

Snow Crab (C. opilio)

The Snow crab populations are managed for maximum sustainable yield, and as such, are stable. The principle threat to Snow crab stocks in Alaska is Bitter Crab Disease (BCD).

By the 1984/1985 season, processors handling crab from the extreme north end of Southeast Alaska, notably Lynn Canal, were receiving complaints from consumers of bitter crab meat. Most management staff thought it was associated with a normal pre-molt condition in Snow crab. However, a few samples of crab blood collected during the 1985/1986 season revealed that the bitterness was closely correlated with presence and concentration of a systemic parasite - a highly specialized dinoflagellate of the genus Hematodinium.

Symptoms associated with BCD had been reported since at least the early 1980s, with some anecdotal references to off-tasting Snow crabs dating back to the mid-1970s. Fishermen have since reported incidence of BCD from most major fishing grounds in Southeast Alaska and sporadically from other areas as well. Its definitive identification in Bering Sea snow crab (C. opilio) stocks, with the economic implications, has accelerated research on Hematodinium.

Hematodinium infects all sizes and both sexes of Snow crab, and appears to kill them within one to 1.5 years. It severely reduces the vitality and reproductive capacity of crabs, with egg clutches of infected females being greatly reduced in size, but the mechanism and seasonal timing of transmission remains unknown. The disease may spread by free-living, infected spores released by dying crabs, or vegetative stage organisms passively transmitted during periods of crab aggregation, such as immediately before and during seasonal mating periods.

Crabs in later stages of infection cannot be marketed because of the astringent taste and soft, chalky texture of the meat. These crabs can be identified on the fishing grounds by external symptoms such as the abnormal pink or pale coloration of their abdomens and the ventral sides of their walking legs.

Text: Bishop, G. H., J. Rumble, and S. E. Merkouris, 2002, Report to the Board of Fisheries: Southeast Alaska Snow Crab Fisheries, Regional Information Report No. 1J02-14, Alaska Dept. of Fish and Game.