Relating groundfish diversity and biomass to deepsea corals and sponges using trawl survey catch data

Abstract

Deep-sea corals and sponges (DSCS) inhabit the world’s oceans and are often associated with high fish abundance. However, the precise nature and extent of any association is difficult to quantify and remains poorly understood. We investigated associations between DSCS and demersal fish using data from the Northwest Fisheries Science Center’s bottom trawl survey (2003-2015). General linear mixed models showed that average species density of groundfish was slightly higher and groundfish biomass slightly lower in tows with DSCS. Multivariate analyses were used to examine relationships among fish community structure, DSCS biomass, and environmental parameters (depth, latitude, bottom temperature). No strong correlations occurred between the community structure of groundfish and DSCS biomass; instead, bottom temperature and depth were the primary drivers of community composition. However, indicator species analysis also showed various species-specific associations with DSCS. Specifically, some flatfish species exhibited relationships with coral and sea pen biomass, whereas some rockfishes were associated with high sponge biomass. Our results provide information on the broad-scale associations among DSCS and demersal fishes that may be useful for developing studies focused on the functional value of DSCS as essential fish habitat and the role they play in groundfish life history and ecology.