Tracking zooplankton at sea with a three‐dimensional acoustical imaging system

The Acoustical Imaging Group in the Marine Physical Laboratory, Scripps Institution of Oceanography, has developed a real time, high‐resolution three‐dimensional acoustical imaging system for use in the ocean. The system, called Fish TV (FTV) is designed for the observation of macrozooplankton and small fish. FTV can synoptically examine a 16° by 16° volume of seawater with a 1‐Hz frame rate. The sonar has recently been used at sea in two configurations. In the first experiment, the sonar was mounted 40 m deep, looking laterally from the research platform R/P FLIP. A video camera provided ground‐truthing. In the second experiment, the sonar was attached to a Phantom DS4 remotely operated vehicle and deployed, again with video ground‐truthing. Results indicate that the system can be used both to track animals in three dimensions and to estimate their density.