Assessing habitat utilization and rockfish ( Sebastes spp.) biomass on an isolated rocky ridge using acoustics and stereo image analysis

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Rooper, Christopher N., Hoff, Gerald R., De Robertis, Alex
• Other Authors: Jech, J. Michael
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2010
• Subjects: Bering Sea; Alaska
• Online Access: http://dx.doi.org/10.1139/f10-088; http://www.nrcresearchpress.com/doi/full-xml/10.1139/F10-088; http://www.nrcresearchpress.com/doi/pdf/10.1139/F10-088

For those marine fish species with specific habitat preferences, a habitat-based assessment may provide an alternative to traditional surveys. We conducted a habitat-based acoustic and stereo image stock assessment survey for rockfishes (Sebastes spp.) on a rocky ridge habitat in the eastern Bering Sea. Video analysis suggested that juvenile and adult rockfishes were more abundant on the seafloor in the rocky ridge area than on the surrounding sandy flats. Over the ridges, the distribution of rockfishes was uniformly low in the water column during nighttime surveys and higher during daytime surveys. The opposite pattern was observed in the video on the seafloor between night (high density) and day (lower density), indicating that fish in the water column during the day moved to the seafloor at night. Mean biomass of adult rockfishes for the rocky ridges was 1.54 × 10 4 tonnes based on acoustic data. The biomass of juvenile fish was estimated to be 9.2 × 10 2 tonnes. Utilization of similar survey methodologies on a larger scale might improve assessment of rockfishes not only in Alaska, but also throughout their range where fishery-independent biomass estimates have been difficult to obtain.