Quantitative Surveys of Fish Assemblage at a High-rise Artificial Fish Reef by Stationary Underwater Cameras

Abstract

Stationary underwater cameras were deployed to evaluate spatial and temporal distribution of fish assemblage inhabiting a high-rise artificial reef. The camera named FISCHOM has a stereo camera or a monaural camera on board and it can operate periodically by an arbitrary interval. We can acquire the information about fish fauna and fish size distribution and their time series of reef fish assemblages by the assessment using the FISCHOMs. Two surveys were conducted in the early summer and fall of 2005 at a high-rise artificial fish reef in the Sea of Japan. In both surveys, five FISCHOMs were fixed dispersedly on the reef and operated in an hour interval. As a result, we could evaluate the spatial and temporal distribution of the fish assemblage and their seasonal variations around the reef about 20 days. In total, 48 thousands of fish were counted in both surveys. Pearl-spot chromis Chromis notata notata, jack mackerel Trachurus japonicus, and rockfish Sebastes spp. were mainly observed. We confirmed these major species had stable diurnal cycles; they were observed in daytime and rarely observed in midnight The differences of the spatial distributions of the major species were found by comparing the results of each FISCHOMs. The folk lengths of the major species were estimated by stereo measurements.