3D visualization for pelagic fisheries research and assessment

Traditional acoustic approaches to the estimation of fish biomass have relied upon single-beam echo sounders that sample a relatively small volume of the water column within the survey area. Mean transect values, after bottom removal, are extrapolated to provide an estimate of number or biomass within a survey area. Over the past 20 years, many multibeam sonars have been developed but these systems which are commonly employed to collect detailed bathymetric and seafloor-type data, have been designed to remove mid-water returns. Only recently has a multibeam sonar been developed that allows for continuous digital recording of mid-water returns. For fisheries acoustics, the movement from single-beam to multibeam surveys provides a mechanism to greatly enhance the area and volume of coverage. The large volume of data generated by these systems, however, presents serious challenges for analysis and interpretation. This paper describes initial studies related to the transition from single to multibeam applications including the types of equipment investigated, the limitations of several acoustic systems examined, and how geomatics and 3D visualization can be used to enhance our knowledge of pelagic fish schools. Early results indicate that multibeam sonars, in conjunction with 3D visualization software can be powerful tools for assessing fish stocks, investigating fish school behavior, for exploring habitat preferences and for addressing questions related to vessel avoidance. As the technology improves so will the capability to investigate and to incorporate additional multiparameter data such as water column properties and bottom type and as calibration techniques are developed for multibeam sonars estimates of biomass may also be possible.