Aimee Jones reports on how many fish communicate with one another, and that now we can hear their voices.
Photo by Luis Vidal
Although we have known for many years that fish can make sounds, it was assumed that they primarily rely on other means of communication, such as colour signals, body language, and electricity. However, when 34,000 species of ray-finned Actinopterygii were studied, 66% of the fish families were found to communicate via sound.
The Nature of Fish ‘Voices’
For most fish, the swim bladder produces the many sounds they make. The ‘purr’, ‘croak’, and ‘popping’ sounds are some of the most common we record from fish. The sonic muscle relaxes and contracts and, in turn, makes the swim bladder vibrate and produces sound as a result. Alternatively, sounds may be produced by tough parts of the body hitting one another, such as bones and teeth. Robert McCauley conducted a study in Perth over an 18-month period to research the nature of these underwater sounds.
Acoustic communication amongst fish has evolved approximately 33 times due to habitual diversity over 150 million years. Therefore, McCauley found that two fish from the same species may have difficulty understanding one another based on regional accents. For example, the ‘boops’, ‘honks’, and ‘hoots’ used amongst three-spinned toadfish would resemble more the croaking of a frog, where midshipman fish emit a low hum. Most of his recordings depicted a solo fish. But when the specific calls of fish overlap, they form a chorus - a primary mode of group communication.
McCauley discovered seven distinct choruses, which sounded at dawn and dusk, that were unusually similar to sounds expected from birds. However, these sounds are believed to share a similarity to human communication, ranging from interactions concerning sexual, nutritional, or territorial desires. Despite regional differences, though, there is something more malicious that affects the communication between our underwater friends.
Too Loud for Water?
Human noise pollution, from practices like commercial fishing, shipping, and military sonar, has been found to interfere with the fish's health and the way in which they communicate. Over 21 species of fish rely on sound in order to thrive, so intervention from man-made infrastructures has not only made oceans noisier, but has believed to drown out communication between fish. Ecologist, Ben Haplern, has iterated that:
“The landscape of sound – or soundscape – is such a powerful indicator of the health of an environment. […] Like we have done in our cities on land, we have replaced the sounds of nature throughout the ocean with those of humans” - Ben Haplern, YaleEnvironment360.
This kind of noise can dramatically impact acoustic communication between fish, not only causing them a great deal of stress but can even force fish to leave their habitats. Their ability to navigate their surroundings, communicate with one another, locate their prey, escape their predators, and even finding a mate, are all disturbed.
Letting Nature Be Heard
Aurore Morin, a marine conservation campaigner for International Fund for Animal Welfare (IFAW), states that only 1 in 5 people know what ocean noise pollution is. A lack of education on what acoustic communication is and how it has been negatively affected is a product of the matter not being considered ‘urgent’. However, IFAW have arguably given fish a voice. Across six continents, IFAW have saved more than 200,000 animals who have been harmed by human intervention, although this is only a fraction of the true number of animals living in distress.
Researcher Aaron Rice believes that more studies researching and capturing the complex acoustic environment will help connect people with life under the water and, ultimately, encourage them to speak out against industries that invertedly harm marine ecosystems. As both inhabitants of the earth, we should not be complicit in harming the lives of fish. It is our job to preserve them.
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