Distribution and bathymetric zonation of deep-sea brittle stars (Echinodermata: Ophiuroidea) off the Japanese Pacific coast

Abstract

The distribution and bathymetric zonation of deep-sea ophiuroids off the Japanese Pacific coast were analysed. Samples were collected using beam trawls between depths of 60 and 6382 m. In 154 samples, 139 ophiuroid species were found. Data were clustered based on Morisita–Horn similarity index and a dendrogram was constructed. The Japanese Pacific coast can be divided in two major zones. One in the northern part off the Japanese Pacific coast, and another in the region off the central Japanese Pacific coast. In the northern region, five bathymetrical zones were detected at depths of 130–250, 300–500, 500–650, 1100–1500, and 2000–3000 m. In the central region, eight bathymetrical zones were detected at 100–140, 150–250, 200–300, 220–300, 300–400, 400–500, 800–1000, and 1000–1500 m depth. Representative species for each bathymetrical zone are reported.