Evaluation of video and acoustic index methods for assessing reef-fish populations

Abstract

Since 1991, the National Marine Fisheries Service (NMFS) has used a video camera/trap system to assess the relative abundance of reeffishes in the Gulf of Mexico occurring on natural hard-bottom substrata at depths 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 fish 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. OV-bottom fish included snappers (Lutjanidae), groupers (Serranidae), and amberjacks (Seriolaspp.), species of interest to commercial and recreational fisheries. Correlation between total oV-bottom taxa abundance and volume backscatter was low (r=0.41, n=115). The low correlation may be caused by diVerences in the area sampled by the video camera and acoustic systems at each site. The low correlation limits the use of acoustic data as an auxiliary variable in a combined video-acoustic estimator. ? 1996 International Council for the Exploration of the Sea