EVALUATION OF VIDEO AND ACOUSTIC INDEX METHODS FOR ASSESSING REEF-FISH POPULATIONS

Since 1991, the National Marine Fisheries Service (NMFS) has used a vi deo camera/trap system to assess the relative abundance of reef fishes in the Gulf of Mexico occurring on natural hard-bottom substrata at d epths between 9 m and 110 m. The relative index of reef-fish abundance resulting from these annual Gulf-wide surveys is based on counts of f ish recorded during a 1 h set of a video camera on the bottom. During the 1993 reef-fish survey, a total of 115 reef sites were sampled with a video camera and fisheries acoustic system. Video data were used to identify fish species distributed above the bottom. Off-bottom fish i ncluded snappers (Lutjanidae), groupers (Serranidae), and amberjacks ( Seriola spp.), species of interest to commercial and recreational fish eries. Correlation between total off-bottom taxa abundance and volume backscatter was low (r=0.41, n=115). The low correlation may be caused by differences in the area sampled by the video camera and acoustic s ystems al each site. The low correlation limits the use of acoustic da ta as an auxiliary variable in a combined video-acoustic estimator. (C ) 1996 International Council for the Exploration of the Sea.