When I was growing up in the Carolina mountains, the older folk would often tell gullible young children stories about the time during WWII that a German U-Boat found it's way up the South Toe River. I never gave the story much credence (nor did I ever actually build any depth charges) but I am pleased to report that if it had been true our beautiful rainbow trout would have suffered no harm at the hands of the Jerry's sonar.
"This study, funded by the U.S. Navy, was designed to look at the effects on fish that might be exposed to low-frequency sonar from a Navy ship sailing nearby. The specific sonar system the team examined was the Surveillance Towed Array Sensor System (SURTASS) Low Frequency Active (LFA) sonar, which uses frequencies from 100 to 500 hertz, the range of best hearing of many fish species.
The tests were conducted on rainbow trout, at the U.S. Navy Sonar Test Facility in Seneca Lake, NY. While species of greatest concern are the endangered salmonids of the west coast, the rainbow trout has very similar ear structure to the salmonids and is not endangered. It is also found in Seneca Lake."
Link and photo via ScienceDaily.com