By Shreya Dasgupta Underwater noise from ships is making it tough for killer whales, or orcas, to find and catch their favorite fish, a recent study has found. Orcas (Orcinus orca) rely heavily on sound to hunt. They emit ultrasonic echolocation clicks that bounce off objects. By listening for the echoes of these clicks, the orcas can identify objects that are around, including prey like salmon. Since orcas “see” with sound, researchers wanted to understand how ship noise in the Salish Sea, off the west coast of the U.S. and Canada, affects their hunting. So they tagged 25 orcas from two threa…