Occurrence, Abundance, and Diversity of Gill Fouling Organisms in Snow Crab, Chionoecetes opilio (O. Fabricius, 1788), (Decapoda, Brachyura, and Oregoniidae) in the Northwestern Atlantic Ocean, Canada

Gill fouling organisms (GFO) in snow crab ( Chionoecetes opilio ) were identified and grouped into 10 taxons, representing 7 phyla. An unknown harpacticoid copepod species ( Coullia sp.) was described and the presence of a kinorhyncha species ( Echinoderes sp.) was first observed. GFO were present in nearly every snow crab examined, suggesting a near‐universal condition in terminal molt crab. The most frequent taxon groups in terms of abundance were Echinoderes sp. , Coullia sp., and nematoda, while the occurrence was highest for nematoda (92.3%), Tisbe sp. (71.2%), and Coullia sp. (59.7%). The occurrence, abundance, and diversity of GFO within the branchial chamber of snow crab were also compared among different demographics, sampling periods, and locations. Abundance of GFO varied strongly among crab demographic groups and locations, with additional influences of carapace size and condition. Large legal males generally had higher GFO abundances, suggesting more surface area for GFO colonization. Taxonomic richness increased from early to late sampling periods and likely reflects differences in environmental conditions. GFO abundance and richness were highest for snow crab from the Scotian Shelf, suggesting more favorable oceanographic conditions for the types of organisms inhabiting snow crab gills. The relationship between the host and GFO remains unknown although higher abundances of GFO may have physiological impacts on crab.