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

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

E.G. Dawe

Trends in prevalence of bitter crab disease caused by Hematodinium sp. in snow crab (Chionoecetes opilio) throughout the Newfoundland and Labrador Continental ShelfThis is part of Crabs in Cold Water Regions: Biology, Management, and Economics
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Description

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 was highest in mature females and intermediate-sized males, but there was 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 true prevalence in the population.

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