SCIENCE: Try, for a moment, to be a fish. As you swim through dim waters, you see shapes moving past and watch for threats. You hear other animals calling or producing rasps and crackles by scraping together rigid body parts. The water is a tapestry of smells that reveals predators and potential mates, food, and the route home.

Now, imagine that nothing makes sense—the tapestry has unraveled. Smells still reach you, but their meanings are muddled. You listen for calls from your kin, but all you hear is the roar of a passing boat. You can’t tell whether that looming shadow is a friend or foe.

When many people think of threats to the world’s fish, overfishing or vanishing reefs might leap to mind. Increasingly, however, scientists also worry about a subtler danger: how human activities might interfere with the senses fish use to perceive the world. Noise from ships and construction, murkier waters caused by pollution, and rising ocean acidification from the buildup of atmospheric carbon dioxide (CO2) are all possible culprits. In laboratories and in the wild, scientists study exactly how those factors might affect a fish’s ability to communicate, navigate, and survive. Read more.