Associations of demersal fish with sponge grounds on the continental slopes of the northwest Atlantic

Association of demersal fish taxa with Geodia-dominated temperate sponge grounds was examined in 104 research vessel survey trawl sets from 500 to 1500 m depth along the continental slopes of the Grand Banks and Flemish Cap, northwest Atlantic. The total number of fish taxa and their total biomass were negatively correlated with sponge biomass and catch depth, and sponge biomass increased with depth. ANOSIM identified significantly different fish communities (biomass and abundance composition) associated with 3 sponge catch weight classes, and multidimensional scaling plots showed separation of trawl sets labelled by this factor to be strongest for abundance. SIMPER analysis identified the fish assemblage associated with the sponge grounds (>= 250 kg km(-1)): roughhead grenadier Macrourus berglax, roundnose grenadier Coryphaenoides rupestris, blue hake Antimora rostrata, longnose eel Synaphobranchus kaupii, turbot Reinhardtius hippoglossoides, black dogfish Centroscyllium fabricii and deep-sea cat shark Apristurus profundorum. These contributed to 92 and 81% of the similarity (similar to 50%) among trawl set catches using biomass and abundance data, respectively. Four additional taxa contributed to 92% similarity in abundance: common grenadier Nezumia bairdii, shortnose snipe eel Serrivomer beanii, lantern-fish (Myctophidae) and goitre blacksmelts Bathylagus euryops. SIMPER dissimilarity identified 6 fish taxa with larger biomass in catches with high sponge catch weight: shortnose snipe eel, deep-sea cat shark, eelpout Lycodes spp., spinytail skate Bathyraja spinicauda, white skate Dipturus linteus and deepwater chimaeras Hydrolagus affinis. The first 3 species were also more abundant in those catches and are considered to be strongly associated with the sponge grounds. Future research focussing on these species identified as being associated with the sponge grounds may provide greater insight into the strength of the associations and the ecological linkages between these benthic and pelagic communities.