Trends in prevalence of bitter crab disease caused by Hematodinium sp. in snow crab (Chionoecetes opilio) throughout the Newfoundland shelf

Dawe, E.G.

Alaska Sea Grant Report, 02-01: 385-400

2002


Accession: 024009559

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Abstract
This paper describes the spatial distribution and prevalence of bitter crab disease (BCD) in snow crabs (Chionoecetes opilio) throughout the Newfoundland and southern Labrador continental shelf during 1996-2000. This disease or syndrome, caused by a hemo-parasitic dinoflagellate of the genus Hematodinium, occurs predominantly in recently molted (new-shelled) crabs of both sexes and is fatal to the snow crab host. Prevalence determination was based on macroscopic identification of chronic cases in crabs collected during annual fall bottom trawl surveys. Bitter crab disease was most prevalent within the center of the broad snow crab distribution and was rare in the southernmost area. Spatial and annual variations in both distribution and prevalence of BCD were considerable. Prevalence Highest in mature females and intermediate-sized males, but there annual and spatial variation in size ranges most affected. Relationships between catch rates and prevalence of BCD showed no clear evidence of either density dependence or an effect on natural mortality. It is unknown how well disease prevalence in trawl-caught samples represents prevalence in the population.