In recent years, pollution and agricultural development have decimated California’s salmon population, so hopes for the acoustic barrier are high. It seems to be working so far, but nobody’s sure why. “We don’t know what a fish thinks or why it would respond to this,” says biologist Chuck Hanson, a consultant to the effort. “It’s a sound that the fish has never heard before. Whether that results in a fright response or whether they just want to avoid it, we don’t know.”
