BIOLOGIYA MORYA, 2016, Vol. 42, No. 5, pp. 349-353

Bitter crab syndrome in commercial crabs in the western part of the Bering and Chukchi seas

© 2016 T. V. Ryazanova¹, P. A. Fedotov², V. I. Harlamenko³

¹Kamchatka Research Institute of Fisheries and Oceanography (KamchatNIRO), Petropavlovsk-Kamchatski 683000;
²Pacific Research Fisheries Center (TINRO-Center), Vladivostok 690091;
³A.V. Zhirmunsky Institute of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok 690041

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We studied the distribution of the bitter crab syndrome, the disease caused by a parasitic dinoflagellate Hematodinium sp., in eight commercial species of crabs in the west of the Bering and Chukchi seas. The crabs (25 388 ind.) were sampled during bottom trawl surveys in July-September 2010 and in October-November 2012. The disease was first identified visually by color change of the exoskeleton and the hemolymph of the animals, and then using microscope analysis of hemolymph samples. Infestation was detected in crabs of three species, Chionoecetes opilio, C. bairdi, and Paralithodes platypus. The prevalence of the disease (percent of infested relative to all examined individuals) in C. bairdi and P. platypus was very low, 0.1 and 0.3%, respectively. Infestation was widespread among C. opilio, its peak in the Bering Sea was in the fall. The average prevalence of crab disease in various areas of the Bering Sea ranged from 0.8 to 10.8%. High rates of crab infestation were recorded in Korfa Bay. In the Chukchi Sea, the average prevalence was 2%. Infestation by Hematodinium sp. was not revealed in deep-sea snow crabs Chionoecetes tanneri and C. angulatus, and in three species of lithodid crabs, Paralithodes camtschaticus, P. brevipes, and Lithodes couesi. This can be explained by a small sample volume and/or ecology of these species, since the disease was registered in four of them in other areas.

Key words: Bering Sea, Chukchi Sea, crabs, parasitic dinoflagellates, prevalence, Hematodinium.