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The world below the surface of the water is a noisy place

Geoff CarpentierI try to follow the news every day, even though it is often quite distressing. However, on some days, something interesting really catches my eye: for example, articles such as: “Many promises but little action at COP15” or “Earth’s core may be slowing down – should we be alarmed?” “Extinct giant birds from Australia baffle scientists.” “How heat domes indicate we need to change wildfire fighting strategies.” “Interesting noises fish make.”

Wait – what?

We all know that seals and whales make lots of neat sounds to communicate, look for mates, report on where food is and warn of danger, but fish?

Well, the reality is that the world below the surface of the water is a noisy place. Hundreds of species of fish make sounds, such as growls, pops, barks, purrs, clicks, whistles, groans and hums. They make these noises for the same reason other animals do: to scare predators, find mates, warn of danger, or mark territory.

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Because most of us have our heads (and ears) in the air, we seldom listen to what’s happening underwater. But intuitively, it makes sense. Why else would we have fish called drums, croakers or squeakers?

Squeakers, a type of catfish, produce sounds by a process called stridulation, in which hard body parts, like teeth or bones, hit each other to make sounds. In one species, the spines located in their pectoral fins are pushed into grooves on their shoulders. Now that I think of it, I do recall some strange ‘squeaky’ noises that catfish made when I caught them as a youth.

Inside the abdominal cavity of most types of fish is a gas-filled sac called a swim bladder. A fish uses this sac to control its buoyancy. When gas is added to the swim bladder, the fish is more buoyant, and when gas is removed, the fish sinks in the water.

In the Drum fish, a muscle attached to the swim bladder (the sonic muscle) contracts and relaxes in a rapid sequence, which causes the swim bladder to vibrate and produce a low-pitched drumming sound.

In toadfish, they go one step further: the bladder has two sonic nerves, each of which can generate a different sound at the same time.

Plainfin midshipman fish are found off the west coast of North America. During the mating season, the male hums by hitting his swim bladder with his sonic muscle to attract a female.

Seahorses produce clicking sounds by rubbing parts of their skull together, and herring communicate with each other by gulping air from the water’s surface and then storing it in the swim bladder. At the right moment, they forcibly expel the gas from the anal area, producing bubbles and a high-pitched sound. Hmmm – I think this action has another name?!?

A new database has been created called FishSounds. In their own words, this is what it’s about: “FishSounds presents a compilation of acoustic recordings and published information on sound production across [many] fish species globally. We hope this information can be used to advance research into fish behaviour, passive acoustic monitoring, and human impacts on underwater soundscapes as well as serve as a public resource for anyone interested in learning more about fish sounds.”

The data presented on the website is based on published, peer-reviewed articles, reports, conference proceedings, books, theses and dissertations. At the time I researched this column, 1,214 species were represented, but not all have recordings associated with them.

The work on the website is the product of an international collaboration between researchers and developers from five organizations – the University of Victoria, University of Florida, Universidad de São Paulo, Meridian and FishBase.

Another interesting website to explore is Discovery of Sound in the Sea which has information on the noises fish and other marine animals make.

In closing, I was in Ecuador many years ago and recall going out to look for ‘singing bass’ at night. Really? No, it’s true. These fish cause vibrations in the water that could actually be felt through the sides of our small wooden boats. I didn’t realize that, years later, that small adventure would be part of this nature column.

Who knew?

Geoff Carpentier is a published author, expedition guide and environmental consultant.

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