“As silent as a fish”
– A saying from ancient Greece
In 1953, Jacques Cousteau co-authored a book titled The Silent World: A Story of Undersea Discovery and Adventure. It was long assumed that the ocean was a quiet world, empty of sound. But we have since discovered that this is far from the truth. The seas that surround us are filled with a vast array of sounds.
“The underwater soundscape can be as noisy as any rainforest”
– Kate Stafford
Underwater sound is generated by a variety of natural sources, such as breaking waves, rain, the sound of bubbles popping and of volcanoes erupting at the bottom of the ocean. There is the creaking and cracking of ice, screeching and popping and groaning. The noise from ships at the surface and the sound of the earth quaking. And of course, the sounds of marine life.
Because sound travels five times faster through water than through air it is a useful tool for aquatic animals. Especially given that sight and smell are less effective underwater. All it takes is a bit of murky water and your vision is severely restricted but sound can travel for thousands of miles in the ocean.
Animals use sound to study habitat (echolocation) and to detect predators and prey. Sound is used for communicating about reproduction and territory and some animals even use sound to stun their prey, such as the pistol shrimps.
Whales and dophins
Probably the most well known sound from the sea is probably that of the whale song. The haunting, eerie moans gave the whale a voice and in doing so, probably aided conservation efforts. Whale song is now part of human culture and helps us feel connected to these mysterious creatures.
The humpback whale has the loudest voice in the animal kingdom, carrying for miles. And it is thought that they may have one of the most complex songs in the animal kingdom. Their songs are sung by the males and the songs are always changing although whales from one area sing the same song, whales from different areas sing different songs. Almost like they have accents.
In contrast to the melancholic songs of the whale, we find the excited pips of dolphins who use high pitched beeps to paint a picture of the world around them. Their language of squeaks and chirps lets them communicate with each other and whistles are used in a similar way to names, they are unique to each dolphin and seem to be a sort of greeting, an announcement that you’re there.
Apparently, dolphins are also able to mimic sounds and one scientific paper suggest they may even sleep talk in whale song.
We have long been fascinated by dolphins, ancient Greek mariners listened to them through the hulls of their ships and according to Aristotle in about 344 BC, they even heard dolphins snoring! NB, there doesn’t seem to be any evidence that they do actually snore…
The term crustaceans covers a vast array of marine species including crabs, lobsters, shrimp and barnacles. They are united by their exoskeleton and some use this to produce sound.
For example, the snapping shrimp are rather noisy creatures, especially given their size. They produce a crackling, sizzling sound by clicking their claws. They do this to stun prey,deter predators, and to communicate with others.
Hermit crabs make a noise by rubbing its body parts together or rubbing against the inside of their shell and do so as a sign of aggression. Male fiddler and ghost crabs use acoustical signals to call to females during breeding season and are apparently unique amongst crustaceans in doing so. Other species use sound once they’ve found a potential mate but not to call out.
Spiny lobsters make a rasping sound by rubbing a piece of soft tissue, called a plectrum, against a smooth, stuff file near their eye. Essentially they move the plectrum over the file in the way that a bow is moved over the strings of a violin.
We tend to think of fish as silent, except for the occasional little noise of their mouths opening and closing but this isn’t the case. They produce sound using their swim bladders and their teeth that include grunts, croaks, clicks and snaps.
When it comes to mating, it is usually the male that makes the sound. Some fish come together in large groups to ‘sing’ and may continue for hours, dominating the local soundscape. Fish, such as the oyster toadfish, that live in murky water, need to make use of sound to find a mate as vision is limited.
The other key reason that fish make noise is when they are threatened, want to show aggression or need to defend their territory.
For some fish, instead of producing sound, it is listening that is crucial. Many coral reef fish have a stage in their life where they go away from the reef, returning at a later time to mature. These fish, such as the clownfish, need to know how to return and it’s thought the song of the reef provides a road map.
The song of the reef
A healthy coral reef is not a quiet place. When they are teeming with life, they are one of the noisiest places in the ocean, making a sound like crackling popcorn thanks to the snapping shrimp.
The sound landscape changes throughout the day, with a rhythm like birds on land. Fish have dawn and dusk songs and different creatures call at night than during the day.
Sea urchins are one of the contributors to the evening chorus. Kina sea urchins dominate New Zealand waters with the sound of their eating. And that specific local flavour to the music of the ocean is important for our little critters which are searching for home, or for a healthy reef to start new life on.
The song of the ocean is not a static one, it is not a consistent one. It changes as the day passes, it changes by season and by locality and it changes based on the health of the sea.
There are many recordings of ocean music and of particular species but these are two I found helpful: