FTV - A SONAR FOR TRACKING MACROZOOPLANKTON IN 3 DIMENSIONS

A three-dimensional sonar imaging system, Fish TV (FTV), was developed to observe the three-dimensional trajectories of macrozooplankton in situ. Consisting of two arrays of eight transducers, the sonar uses on e of the arrays as a projector and the other as a receiver. In this wa y, a combination of 8 x 8, or 64 beams, is constructed. Spatial resolu tion is approximately 2 degrees by 2 degrees and the range resolution is 3 cm. The sonar is capable of recording up to five images every sec ond. The data is stored digitally in a three-dimensional matrix which can be postprocessed. Tests performed in the lab with both test target s and freshwater shrimp indicate that the system has the sensitivity a nd accuracy to track euphausiids in the ocean. The system was deployed at sea on an ROV (Remote Operational Vehicle) and the tracks of eupha usiid sized objects were recorded.