| There are more fish in the “twilight” zone near the Antarctic than we thought | |
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Credit: Tracey Dornan |
There’s plenty of fish in the sea… but how many, exactly? How do you go about counting the number of fish in the sea, especially in remote areas like the “twilight” zone (200-1000 meters below sea level) of the Southern Ocean, close to Antarctica? Obviously, going at it one by one is not an efficient approach. So instead, researchers try something else: echo sounding |
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An echosounder sends out an acoustic pulse and when the pulse encounters something with different physical properties than the space around it, it is reflected back to the receiver. The fishes’ swim bladders, the gas-filled organs they use for buoyancy, are particularly sensitive to these pulses and offer very good reflectors. |
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