Sing Like Fish: How Sound Rules Life Under Water
Amorina Kingdon
Crown, New York, 324 pages.
I saw Jacques Cousteau’s film The Silent World many moons ago when I was a little ankle-biter; all I remember about it is that everything under the water is silent. This belief has since become generally accepted, although Cousteau himself countered this stereotype in a subsequent movie.
The marine world is never truly silent, as Kingdon writes:
“… the ocean rumbles with Earth’s seismic mumblings: mudslides in subsea canyons, rock groans as mid-ocean ridges spread, undersea volcanoes roar…Coral reef sound travels dozens of kilometres underwater before it fades. Shrimp snap their claws. Parrotfish teeth crunch through coral as they graze on algae. Fish drum their swim bladders and pop their jaws.”
All the above is without the contribution of man-made sound, which, as we shall see, is a source of growing concern for researchers.
Interest in underwater sound and the perception thereof has a long history. Aristotle, around 350 BCE, wrote that sound is heard less distinctly under the surface, and Kingdon spends quite a few pages discussing the physics of how sound travels underwater: four and a half times faster than in air and under the right circumstances it can cross an ocean. The speed of sound in oceans depends on the temperature and has been extensively researched. An ocean layer with special sound-conducting qualities was soon discovered, dubbed the SOFAR channel (Sound Fixing and Range). Naturally it was soon employed for military use with listening stations all over the world.
Kingdon investigates the physics of underwater sound in some detail, I suspect that some readers may find this less than interesting. This section could certainly have been pruned.
For quite a long time people were unsure whether fish could hear, and when that problem was solved, the generally accepted opinion was that marine invertebrates such as crabs and corals could not perceive sound. Comparative anatomy and physiology showed that these animals in their adult form do indeed have organs which can respond to sound.
Interestingly enough, even some marine animals without known auditory apparatus respond to sound – the larvae of corals and crabs orient themselves about the origin of a sound wave. In 1950 the Cambridge biologist Richard Pumphrey wrote a widely acclaimed paper addressing the sense of hearing, making it clear that hearing and responding to gravity are inextricably intertwined.
That whales communicate by sound is by now well known and Kingdon devotes a number of pages to this interesting and in fact rather engaging habit – one which may well describe whale songs as a form of culture.
Unfortunately, man-made underwater sound is progressively interfering with their songs – and not only the lives of whales are disrupted in this manner, but many other marine creatures as well, even plankton is killed off in some circumstances.
Sing Like Fish gives a very interesting look at a part of our world which has never really come to the general reader’s attention and is well worth a few hours in an armchair.
