Search

NOAA technical memorandum NMFS PIFSC ; 83

The results of the 2014 Underwater Camera Survey of the Eastern Bering Sea slope and outer shelf are presented here. The 2014 survey was the first comprehensive underwater camera survey of coral and sponge on the Bering Sea slope and outer shelf conducted by the National Marine Fisheries Service. Two-hundred fifty transects were successfully completed during the survey, which extended north from Bering Canyon to Pervenets Canyon. Transects were randomly selected between Unalaska Island and Pervenets Canyon. Each transect was assigned to one of eight geographical regions. Demersal populations of corals, sponges, sea whips, fishes, and crabs were sampled by drifting a stereo drop camera for 15 minutes at each transect. Survey results presented in this report include fish and crab composition and density, coral, sponge and sea whip density and height, and substrate composition for each transect. The Appendix lists start position, distance towed, swath, mean depth, and mean temperature for each transect completed.

This report describes a set of software programs that were developed by the Alaska Fisheries Science Center for analyzing stereo images. The main application is called SEBASTES, and is used to count, range, and measure fish using stereo-image algorithms. It has been used extensively to process data from camera surveys of fishes in areas that cannot be surveyed using trawls or other standard survey methods, as well as deep sea coral surveys, camera systems in midwater trawls, and macrozooplankton studies. Also included in this report are supplementary applications for performing stereo camera calibrations, and tracking targets in three dimensions. The report is meant as a resource for those using the software, as well as a technical reference for the methods used to extract quantitative data from stereo images.

We describe the application of two types of stereo camera systems in fisheries research, including the design, calibration, analysis techniques, and precision of the data obtained with these systems. The first is a stereo video system deployed by using a quick-responding winch with a live feed to provide species- and size- composition data adequate to produce acoustically based biomass estimates of rockfish. This system was tested on the eastern Bering Sea slope where rockfish were measured. Rockfish sizes were similar to those sampled with a bottom trawl and the relative error in multiple measurements of the same rockfish in multiple still-frame images was small. Measurement errors of up to 5.5% were found on a calibration target of known size. The second system consisted of a pair of still-image digital cameras mounted inside a midwater trawl. Processing of the stereo images allowed fish length, fish orientation in relation to the camera platform, and relative distance of the fish to the trawl netting to be determined. The video system was useful for surveying fish in Alaska, but it could also be used broadly in other situations where it is difficult to obtain species-composition or size-composition information. Likewise, the still-image system could be used for fisheries research to obtain data on size, position, and orientation of fish.