- Advances in evolutionary understanding have given researchers a deeper appreciation of a very sonorous underwater world.
- From finding a mate to defending their territory, fish employ a variety of innovative mechanisms to produce sounds, like vibrating their swim bladders or snapping their tendons.
- Researcher Aaron Rice says fish are much more dependent on sound for communication than we realize, given that sound production has evolved independently several times.
- The findings mean marine noise pollution presents a big potential threat to the health of marine and freshwater ecosystems.
It seems natural to assume that fish and other marine biodiversity live in a silent world; the idea that fish live in a noisy ecosystem seems bizarre. But a new study in Ichthyology & Herpetology finds that acoustic communication has independently evolved 33 times across ray-finned fishes, a class that contains more than 99% of known fish species alive today, or about 34,000 species.
In contrast, acoustic communication has only independently evolved six times in tetrapods, the group that includes all four-limbed animals such as amphibians, reptiles, birds, mammals and, of course, humans. This suggests that hearing and sound is much more important for fish than we may realize.
“The scientific study of fish has been biased by how humans perceive the world,” says study lead author Aaron Rice, a researcher at the K. Lisa Yang Center for Conservation Bioacoustics at the Cornell Lab of Ornithology. “When we go swimming, for example, we can’t smell underwater, so we think that there is no reason fish should be able to smell underwater as well — when in fact, many of them have a very well-developed sense of smell.”
This bias extends to how marine life “sees” the world too; many fish and even corals display wild ultraviolet color patterns invisible to the human eye. It’s the same with sound. While some seafloor-dwelling fish have fully lost the ability to see, there are no known cases of “deaf fish” — it seems that most, if not all, fish can hear.
While the idea of fish communicating with sound is definitely not new, advancements in genome sequencing and evolutionary phylogenetics allowed Rice and colleagues to analyze sound production patterns across 475 families of fish, focusing on the evolution of hearing.
The black drum makes drumming sounds using its pharyngeal teeth. Audio courtesy of Aaron Rice/Cornell Lab of Ornithology.
One of the first body parts on vertebrates to evolve was what would be known today as the modern ear, suggesting that the ability to hear sound has always been a major component of evolution, survival, and animal behavior, according to Rice.
The researchers posit that sound production in fish probably goes back at least 155 million years, given that this is when one of the most ancient families of fishes, the sturgeons, came on the scene. Sturgeons use their swim bladders to make sounds.
While the mechanism for receiving sound might be similar in both fish and land animals — i.e. ears — sound production is where fish get really innovative. The study has found that 60 fish families vibrate their swim bladders to make sounds, while others snap their tendons or grind their teeth. In other words, these creatures pretty much use any and all parts of their bodies to make noise.
But for what, exactly? Just like land animals, fish employ sound to find a mate, defend a resource or territory, or signal their presence.
Drum fishes produce sounds louder than a jackhammer and can dominate the soundscape of a coastal ecosystem for hours at a time. Catfish are known to make “agonistic” sounds, i.e. defensive or aggressive ones, to scare off predators. And Rice says toadfish are also quite noisy.
Vocalisations of a coral toadfish (Sanopus splendidus). Audio courtesy of Aaron Rice/Cornell Lab of Ornithology.
“While many people think toadfishes are ugly and sit at the bottom of the ocean doing nothing, they happen to have the fastest-contracting vertebrate skeletal muscles across the animal kingdom, and these are dedicated for sound production,” Rice says.
Rice and his team went through all the public sound records they could get their hands on. But he says one of the most challenging issues was pinpointing the sources of underwater sounds.
“With every coral reef or ocean ecosystem that we’ve recorded around the world, we’re always getting sounds back which we have no clue which fish they’re coming from,” he says.
This is where the scientific community has much to draw from Indigenous knowledge. Many fish are given common names after the sounds they make, such as the reef triggerfish (Rhinecanthus rectangulus), whose Hawaiian name is Humuhumunukunukuapua — “the fish that grunts like a pig.”
“There are native fishing communities in Southeast Asia and Alaska that listen for schools of fish to catch by … the sounds radiating through the hull of their boats. In some cases, they’ll put their oar into the water right up to their ears and listen to the vibration of the oars,” Rice says. “For generations and across thousands of years, fishermen have learned ways to listen for fish.”
The implications of this knowledge are spreading. Noise pollution is increasingly being recognized as among the human-driven factors impacting marine and freshwater ecosystems, alongside climate change, ocean acidification, coral bleaching, plastic pollution, oil spills, chemical runoff and other forms of pollution.
“Since we have so many fish that are depending on sound for communication — whether it’s for reproduction or social cohesion — how fish respond to increases in human-driven noise is a giant question mark,” Rice says. “So that fundamental question is, how can we use fish sounds as an indicator of the impacts humans are having on coastal ecosystems?”
Citations:
Johnston, C. E., & Phillips, C. T. (2003). Sound production in sturgeon Scaphirhynchus albus and S. platorynchus (Acipenseridae). Environmental Biology of Fishes, 68(1), 59-64. doi:10.1023/a:1026015912420
Rice, A. N., Farina, S. C., Makowski, A. J., Kaatz, I. M., Lobel, P. S., Bemis, W. E., & Bass, A. H. (2022). Evolutionary patterns in sound production across fishes. Ichthyology & Herpetology, 110(1), 1-12. doi:10.1643/i2020172
Banner image: Chromis Bonaire courtesy of Aaron Rice/Cornell Lab of Ornithology.
Related listening from Mongabay’s podcast: a conversation with Laurel Symes, assistant director of the K. Lisa Yang Center for Conservation Bioacoustics, listen here:
