FIRST it was fish vying for title of the world’s smallest vertebrate, now there’s a new fish record in the offing. A novel sonar technique has captured what is reputedly the largest massing of animals ever recorded.
A shoal of more than 20 million fish was imaged using low-frequency sonar by mechanical engineer Nicholas Makris and his team at the Massachusetts Institute of Technology. Fish are usually tracked using high-frequency sonar beams, but these dissipate within about 100 metres, meaning you can only monitor a small area around you.
Makris and his colleagues realised that because low-frequency sound waves travel…
