Acoustics in fisheries research

And the story goes on…  |  The remarkable evolution of echo sounders and sonars  |  Frequency, amplitude, pressure, speed…  |  Echo sounders 
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Profileur acoustique de zooplancton

The propagation of sound through water is a phenomenon widely used by aquatic fauna to locate fellow individuals, prey and predators (the lateral line in fish, for example), to situate them precisely (dolphins, pilot whales) or even as a weapon to disorient prey (certain shrimp and mammals).
Historically, it seems that Leonardo da Vinci was the first to make use of the propagation of sound in water in 1490. At the time, he wrote, “If you cause your ship to stop and place the head of a long tube in the water and place the outer extremity to your ear, you will hear ships at a great distance from you.”
In 1870, Jules Verne as well brilliantly described this capacity in his book, 20,000 Leagues Beneath the Sea, “The slightest sounds were transmitted with a speed to which the ear is unaccustomed on the earth. Indeed, water is a better vehicle for sound than air, and it travels through it four times as quickly. […] Deep sounds, clearly transmitted by this liquid medium, reverberated majestically.”
This property was widely used during the First World War, simply by improving Leonardo da Vinci’s experiment, first by the use of a second tube at a distance from the first, sometimes directional, and placed near the other ear: the stereo effect allowed a rough approximation of the direction of origin of the sound. A bit later the system was improved upon once again by assembling two systems of a dozen tubes set to starboard and to port in the holds of ships: this system improved considerably the localization of sound sources, precise to the order of ½ a degree.

Écran de visualisation d'un sondeur pêche nouvelle génération SIMRAD ES 60