Talking fish: Wide variety of sounds discovered

Creative chatter
The butterflyfish might have coupled their swim bladders with their lateral line because "they don't have a mechanism to make loud sounds," Tricas speculated. "They can only generate these weak signals."

"We also know butterflyfish swim very close together," Tricas said. "What we think might be happening is they are essentially whispering, and have to swim close together to listen."

A fish that other scientists have recently investigated is the pearlfish. Curiously, these dwell inside living sea stars or tubular creatures known as sea cucumbers.

While a number of fish, such as the toadfish, communicate with their swim bladders by rapidly twitching it back and forth with muscles, the pearlfish instead use a much slower muscle that generates strong, low frequency sounds which pearlfish may use to speak with others, advertising their presence even from inside their homes.

"Think of the pearlfish swim bladder as a bongo drum. If you could grab its skin and let it go like a rubber band to go thunk, that's what the pearlfish is doing, some four to 20 times per second," Tricas said. "It's a highly novel system that I've never heard of anything like before."

Studying fish sounds could help shed light on the evolution of communication and hearing, as well as related behaviors, such as finding of mates or defending of territory, Tricas said. For instance, the fact that butterflyfish can effectively only whisper "may help explain the evolution of their pairing behavior, why the fish appear so social, and why almost all butterflyfish affiliate with one another so often."

Currently the purposes of some fish sounds remain complete mysteries. "There were early claims that seahorse clicking increased in intensity during courtship, but no evidence has been found to support that. It's a tantalizing question for scientists to work on," said marine conservationist Amanda Vincent, director of Project Seahorse in Vancouver

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