A Comparison of Remotely Operated Vehicle （ROV）and Time Lapse Camera Techniques for Investigating Fish Fauna Around an Anchored Fish Aggregating Device （aFAD）

Abstract

Fish species composition was observed by using Remotely Operated Vehicle （ROV）and time lapse camera around an anchored fish aggregating device （aFAD）in Goto Islands, Nagasaki in summer 2018. A total of 10 families and 15 species were observed by both ROV and time lapse camera. The most frequently observed fish was largescale blackfish Girella punctata recorded by both techniques. More families and species were observed by the time lapse camera as compared to the ROV. However, Shannon’s diversity index was low for the time lapse camera compared to the ROV. Bray-Curtis similarity index between the ROV and the time lapse camera was 0.95 suggesting that the observation between the 2 techniques was different. This could have been attributed by the difference in mobility by both techniques, temporal and spatial distribution of aggregated fish around the aFAD. Therefore, researchers investigating artificial fish habitats including aFADs should understand such potential differences among visual observation techniques and utilize the advantages and disadvantages for better understanding of fish fauna around the habitats.