One of the most persistent myths in biology is that fish are silent. Your goldfish might be the quietest pet you’ll ever have, but out in the open ocean, there’s a legit cacophony of hoots, moans, barks, and chirps that our human ears aren’t capable of perceiving.
And now scientists have found evidence that certain species of fish actually sing together, in a chorus, each day at dawn and dusk. Yep, just like birds, fish sing together when the Sun rises and falls.
Over the past decade or so, researchers have been increasingly familiarising themselves with the vocalisations of fish.
According to Emily Anthes from the New Yorker, more than 800 species have so far been confirmed to make some sort of noise, and some even appear to engage in shouting matches in parts of the ocean that are particularly loud.
"Clownfish chirp and pop by gnashing their teeth together. Oyster toadfish hum and blare like foghorns by quickly contracting muscles attached to their swim bladders. Croaking gourami make their signature noise by snapping the tendons of their pectoral fins."
While it goes against our long-held assumption that birds and mammals are noisy but fish are our silent friends, it makes sense that fish vocalise just like everyone else.
In nature, shouting is probably the most effective way to get someone’s attention. Frogs croak to find mates, prairie dogs have a complex series of "yips" to alert each other of danger, and baby birds would really like to let you know how freaking hungry they are.
And now we have evidence that fish hoot and holler to each other to call on mates, settle territorial disputes, and find food.
"I’ve been listening to fish squawks, burble and pops for nearly 30 years now, and they still amaze me with their variety," Robert McCauley from Curtin University in Western Australia told Greta Keenan at New Scientist.
"We are only just beginning to appreciate the complexity involved, and still have only a crude idea of what is going on in the undersea acoustic environment."
McCauley and his team just completed an 18-month study of fish sounds in the coastal waters off Port Headland in Western Australia, and in that time, managed to identify seven distinct choruses, which rise up at both dawn and at dusk.
You can listen to three of the choruses here, which together sound like something Sebastian the Crab cooked up:
According to Keenan, that lone 'foghorn' sound is made by a black jewfish (Protonibea diacanthus), while the grunting call that the team compares to the "buzzer in the Operation board game" comes from a species of Terapontid - a family of fish known as grunters or tiger perches.
The softer "ba-ba-ba" chorus is being made by batfish.
The team recorded the sounds using two sea-noise loggers, located 21.5 km apart, at 8 and 18 metres deep. Over the 18-month period, the seven different fish choruses were recorded mainly through late spring and early autumn, and the team reports that there were 80 days when more than one chorus was being made at the same site
"When fish call en masse, producing a high level chorus over a defined, several-hour period, they can produce a continuous choruses," the researchers explain, adding that many of them matches their vocal behaviour to the solar and lunar cycles.
"As with other tropical waters, this area of Australia is diverse in the number of call types evident on the recordings."
So why listen in on what fish have to say?
Just as birds have been found to sing louder in cities so their prospective mates can hear them over all that urbanisation, the same thing is likely happening underwater, with all the acoustic pollution we're spreading around.
So far, McCauley's team couldn't find evidence that the Port Headland fish were particularly fazed by sound pollution in their patch of ocean, but it could be a different story elsewhere. Previous studies have already suggested that the ocean is getting too noisy for whales and dolphins.
"All seven choruses continued for many days despite significant anthropogenic noise within a similar frequency band, implying that, in the short term at least, the callers are not directly displaced by the elevated background noise," say the researchers.
The research has been published in Bioacoustics.