Distribution and habitat association of benthic fish on the Condor seamount (NE Atlantic, Azores) from in situ observations

Distribution of fish assemblages and habitat associations of demersal fishes on the Condor seamount were investigated by analyzing in situ video imagery acquired by the Remotely-Operated Vehicles ROV SP 300 and Luso 6000. A total of 51 fish taxa from 32 families were inventoried. Zooplanktivores (10 species) were the most abundant group followed by carnivores (23 species) and benthivores (18 species). Non-metric multidimensional scaling (MDS) analyses were performed on dive segments to visualize the spatial relationships between species and habitat type, substrate type or depth, with depth being the most significant parameter influencing fish distribution. Four major fish groups were identified from their vertical distribution alone: summit species (generally to <300 m depth); broad ranging species (ca. from 200 to 800 m); intermediate ranging slope species (ca. from 400 m to 800–850 m); and deeper species (800–850–1100 m). The fish fauna observed at the summit is more abundant (15.2 fish/100 m2) and habitat-specialized than the fish observed along the seamount slope. Down the seamount slope, the summit fish assemblage is gradually replaced as depth increases, with an overall reduction in abundance. On the summit, three species (Callanthias ruber, Anthias anthias and Lappanella fasciata) had higher affinity to coral habitats compared to non-coral habitats. A coherent specialized fish assemblage associated to coral habitats could not be identified, because most species were observed also in non-coral areas. On the seamountʹs slope (300–1100 m), no relationship between fish and coral habitats could be identified, although these might occur at larger scales. This study shows that in situ video imagery complements traditional fishing surveys, by providing information on unknown or rarely seen species, being fundamental for the development of more comprehensive ecosystem-based management towards a sustainable use of the marine environment.