Deep-Sea Fish Fauna on the Seamounts of Southern Japan with Taxonomic Notes on the Observed Species

Keita Koeda,Shinji Tsuchida,Takehisa Yamakita,Yoshihiro Fujiwara,Soutarou Takashima

doi:10.3390/jmse9111294

Abstract

Several volcanic islands and submarine volcanoes exist in the sea connecting the Izu-Bonin Islands with the Mariana Islands, with trenches and islands formed by the submergence of the Pacific Plate under the Philippine Sea Plate. Although designated as a Marine Protected Area (MPA) in December 2020, the seamounts’ biodiversity has not been sufficiently researched. Therefore, direct observations and specimen sampling were conducted on four seamounts in this area using a remotely operated vehicle (ROV), autonomous underwater vehicle (AUV), and baited cameras (BCs). The ROV survey was conducted for 2–4 days on each seamount and divided into shallow and deep areas. During the expedition, 20 orders and 51 families of 81 deep-sea fish species were observed, including several potentially undescribed species, new genus or species records from Japanese waters, new depth records, new ecological information, and several rare fishes. The fish fauna and biodiversity abundance clearly differed among the seamounts; the seamount with a hydrothermal vent had the lowest diversity among the four seamounts. In shallow water, 23, 7, and 12 species were recorded only by ROV, AUV, and BC, respectively, indicating that combining these methods is beneficial for understanding the fish fauna of seamounts.

Highlights

In this study, direct observations and specimen sampling expeditions were performed at four seamounts in the area using a remotely operated vehicle (ROV), autonomous underwater vehicle (AUV), and baited camera (BCs) operated from aboard the Research Vessel (R/V) Kaimei
The cruise to study the four seamounts was undertaken at the end of 2020 (November 25 to December 12) using R/V Kaimei, a research vessel belonging to the Japan Agency for MarineEarth Science and Technology (JAMSTEC, Kanagawa, Japan)
The presence of a total of 82 fish species belonging to 51 families in 20 orders was confirmed around the four seamounts based on observations for a combined time of 138.4 h (ROV 52.2 h; AUV 9.2 h; baited cameras (BCs) 77 h) during the expedition

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Okamura et al [4] conducted one of the largest expeditions targeted at the seamounts in Japan and reported on the fish fauna of the Kyushu-Palau Ridge, which is located south of the Hyuga Sea, from southeastern Kyushu to Palau. They recorded 239 fish species from 92 families collected using a bottom trawl net and included midwater and pelagic fishes. Eng. 2021, 9, 1294 fauna, the Nishi-Shichito Ridge and Central and Western Mariana ridges in the area were designated as a marine protected area (MPA), and were cataloged as Offshore Seabed. In this study, direct observations and specimen sampling expeditions were performed at four seamounts in the area using a remotely operated vehicle (ROV), autonomous underwater vehicle (AUV), and baited camera (BCs) operated from aboard the Research Vessel (R/V) Kaimei

Study Area

Observation and Collection Methods

Species List

Results and Discussions

Underwater photographs of deep-sea fishes seamounts

Underwater