Fishing with Sound

Scientists have adapted a low-frequency sonar system originally designed to survey seafloor geology to identify fish and zooplankton. The research team towed a low-frequency broadband imaging sonar near schools of fish. For comparison, they also collected sound data from a conventional high-frequency, hull-mounted fish-finding sonar system. Trawls collected fish for “ground truth”; that is, to see if the schools of fish shown by sonar matched the reality in the water. (Illustration by Jayne Doucette, Woods Hole Oceanographic Institution)