Research Document - 2010/039

Associations of Demersal Fish with Sponge Grounds in the Northwest Atlantic Fisheries Organization Regulatory Area and Adjacent Canadian Waters

By E. Kenchington, D. Power and M. Koen-Alonso

Abstract

The association of demersal fish taxa with Geodia-dominated sponge grounds was examined using data collected from 104 research vessel survey trawl sets of 500 to 1500 m depth along a portion of the continental slopes of the Grand Banks (NAFO [Northwest Atlantic Fisheries Organization] Divisions 3KLNO) and Flemish Cap (NAFO Division 3M). The total number of taxa and their total biomass were negatively correlated with both depth and sponge biomass in the catch, and sponge biomass increased with depth. Species composition was evaluated by analysis of similarity (ANOSIM), similarity of percent contribution (SIMPER) and multidimensional scaling (MDS) using log-transformed abundance and biomass of individual taxa. These analyses identified a small number of fish taxa as being more abundant and contributing to a significantly distinct faunal assemblage on the high density sponge grounds than elsewhere. Most other taxa showed the reverse, that is, lower abundance on the high density sponge grounds, or else a neutral response. The three taxa which contribute most to the community dissimilarity in biomass between the low and high sponge catch trawl sets are Black Dogfish (Centroscyllium fabricii), Blue Hake (Antimora rostrata) and the Longnose Eel (Synaphobranchus kaupii). The three taxa which contribute most to the community dissimilarity in abundance between the low and high sponge catch trawls are Lanternfish (Myctophidae), Common Grenadier (Nezumia bairdii) and Roundnose Grenadier (Coryphaenoides rupestris). All of these fish had higher biomass/abundance in the catches with low sponge by-catch. Six fish taxa had larger biomass in catches with high sponge: Shortnose Snipe Eel (Serrivomer beanii), Deepsea Cat Shark (Apristurus profundorum), Eelpout (Lycodes spp.), Spinytail Skate (Bathyraja spinicauda), White Skate (Dipturus linteus) and Deepwater Chimaeras (Hydrolagus affinis). The first three were also more abundant in those catches and are considered to be most strongly associated with the sponge grounds. Five fish taxa were never caught in the same sets with high sponge catches: Deepwater Redfish (Sebastes mentella), American Plaice (Hippoglossoides platessoides), Witch Flounder (Glyptocephalus cynoglossus), Vahl’s Eelpout (Lycodes vahlii) and Thorny Skate (Amblyraja radiata) and this may be explained by depth or substrate preferences. Determining the active or passive nature of the association of these taxa with the sponge grounds requires further research.

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