Researcher Shahriman Ghazali of Auckland University has discovered that fish communicate with each other in a secret language of grunts, growls, chirps and pops. Predators may even hunt out prey by intercepting fish talk, Ghazali said. “All fish can hear but not all can make sound — pops and other sounds made by vibrating their swim bladder, a muscle they can contract,” he said. He placed groups of fish into tanks in a laboratory, gave them a few weeks to settle in, and monitored them using an underwater microphone and instruments that detect water movement. It emerged that gurnard are among the most talkative, making distinctive grunts and keeping up a pattern of chatter throughout the day. Cod, on the other hand, stay mostly silent, except while spawning when they become very vocal.