Abstract
A deep-sea video monitoring system on a towed sledge was used in Pacific coastal waters of northern Japan at depths ranging from 440 to 700 m to estimate the density and the spatial distribution of kichiji rockfish Sebastolobus macrochir. Thirty observations were completed at 24 survey sites in daytime during May and June in 2001. A seafloor area of 86,160 m2 was surveyed, and 253 kichiji rockfish were observed. Most of the fish showed no behavioral response to this system. Densities ranged from 0 to 11 fish/1,000 m2 (mean 2.94 fish/1,000 m2). Kichiji rockfish stayed on the seafloor as solitary individuals. Only 4.9% of kichiji rockfish was situated less than 5 m to other kichiji rockfish, 3.5% occurred between 5 and 10 m to other fish and the remaining 91.6% was more than 10 m away from other fish. Of the 253 kichiji rockfish, 209 were small (5-9.9 cm) and 44 were more than or equal to 10 cm. Most of the small fish were between one year and two years old. Kichiji rockfish would be distributed as solitary individuals at least from one year old. The method to estimate the density of the kichiji rockfish using this system is effective for stock assessment.
