Influence of structurally complex benthic habitats on fish distribution

Abstract

This study examined the relationship between demersal fish distributions and benthic habitats in the Traenadjupet marine protected area (MPA) on the Norwegian continental shelf. Using a towed video system, multiple pairs of plots with varying densities of cold-water coral mounds and sponges were examined, as well as control plots containing neither of these taxa. A total area of 130000 m2 was surveyed along 16 and 12 linear transects in 2009 and 2010 respectively. The most numerous demersal fish were Sebastes viviparus and Trisopterus esmarkii, followed by Brosme brosme, Chimaera monstrosa and Micromesistius poutassou. Analyses indicated that T. esmarkii and M. poutassou exhibited very general patterns of habitat selection whereas C. monstrosa, S. viviparus and B. brosme appeared to be more specialized in their selection of habitat. C. monstrosa was abundant in the sponge-beds and unstructured seabed, and ap - peared only rarely in the coral habitats. The occurrence of cold-water coral mounds and sponges seemed to mainly influence the distribution of S. viviparus and B. brosme, which were twice as abundant in areas with structurally complex sponge and coral habitats than in the unstructured flat seabed at all spatial scales examined (i.e. <3 m to 2 km). None of the fish species examined in Traenadjupet were confined to only one of the habitats examined, thus the study confirmed facultative use of cold-water corals and sponges as fish habitats on the Norwegian continental shelf.