Bitter crab disease: a fatal dinoflagellate infection and marketing problem for Alaskan tanner crabs Chionoecetes bairdi

A systemic dinoflagellate disease was discovered in Tanner crabs Chionoecetes bairdi harvested from two-thirds of the major production areas in the northern southeast panhandle of Alaska during 1985 and 1986. Processed meats from infected crabs were unmarketable as a results of a bitter flavor imparted by the causative agent. The disease is chronic but lethal, causing 100% mortality in naturally infected crabs when maintained in flowing seawater during a 5 mo period. Feral Tanner crabs in at least one harvest area had a parasite prevalence of 95% regardless of sex or age class. Disease pathogenesis and parasite description, probable life history, distribution and management implications are discussed.