1National Research Institute of Fisheries Engineering, Ebidai, Hasaki, Kashima, Ibaraki 314-0421, 2Tohoku National Fisheries Research Institute, Hachinohe, Aomori, 031-0841, Japan
A deep-sea video monitoring system on a towed sledge (DVMSTS) was used in Tohoku waters (Pacific coastal of northern Japan) at depths ranging from 440 to 700meters to estimate the population density of kichiji rockfish Sebastolobus macrochir. Thirty observations were completed at 24 survey sites in daytime during May and July in 2001. A seafloor area of 86,160m2 was surveyed, and 253 kichiji rockfish were observed. These fish stayed on the seafloor as solitary individuals. Most fish showed no behavioral response to the DVMSTS. Population densities ranged from 0 to 11fish/1,000m2 (mean, 2.9fish/1,000m2). The method of estimating the population density of kichji rockfish using DVMSTS is effective for stock assessment.