Sonar Data (IMAGE) NOAA National Marine Fisheries Service Caption The bottom-mounted sonars produce high-quality data. This image shows the abundance of pollock as viewed by the upward-looking sonar at a spawning site on March 15th, 2015. The colors in the image represent the strength of sound reflected from fish, with a strong echo from the sea surface visible at the top of the image. Credit NOAA Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.