Fish sounds can help to preserve species



African News Agency


SUMMER is coming – at least to the northern hemisphere – and soon beaches will be full of the sounds of people having fun, splashing in waves, thwacking balls and thumping sand into castle shapes. If you can find a quieter spot of ocean and stick your ears under the water, you might hear many other sounds – made by fish. People have known that fish make sounds since ancient Greece; that’s why they gave some fish names like red drum, pig fish or croaker. “They’re based on the sounds these fish make,” said Audrey Looby, a fishsound researcher at the University of Florida in the US. So far, about 1 000 fish species have been recorded making sounds. You can listen to some of them at a website called FishSounds, to which Looby will soon contribute. Her favourite-sounding fish is the Gulf toadfish. Unlike birds, which make sounds in the same way, Looby said that fish evolved to make sounds many times during their existence. That means they make sounds in different ways. “Basically, they use whatever mechanism is easiest for them,” she said. Fish don’t have specialised vocal cords, larynxes or vocal folds. So one of the most common ways they make sound is through tribulation – rubbing two pieces of bony structure together, “like clicking their teeth or rubbing their pectoral fins against other structures to make cricket-like sounds,” said Looby. Many others make sounds with their swim bladders, which they use primarily to stay buoyant and level in the water. But, Looby said, “some fish have a sonic organ of some kind attached to this swim bladder, so they can bang on it and it resonates like a drum”. Scientists are unsure how many fish make sounds but some estimate that it might be as many as 22000 types, which is two-thirds of about 34000 known species. And those are just the sounds fish make on purpose – to call to mates, to let other fish know they’re in trouble or to communicate that “this is my area of the reef, listen to how tough I sound, so why don’t you just swim away,” Looby said. Fish also make passive sounds, such as chewing noises as they munch on sea grass or algae. According to Looby, active and passive sounds are important because they “convey a lot of information about what’s going on” to fish and to researchers. Chewing sounds, for example, let anyone who’s listening know that there’s a food source available. And the mating and warning noises of certain fish species tell scientists information such as “how much diversity is on a reef, where invasive species are located, where endangered species are located”, said Looby. With climate change making parts of the ocean heat up and become unlivable for fish in other ways, researchers say fish sounds could help them preserve and restore habitats. For example, there are projects looking into whether piping in the sounds of a healthy reef into one that is dying might encourage fish to come back and populate it. Learning about fish sounds “lets us learn about underwater environments and hopefully manage them at the same time,” Looby said. |