By Matt Walker
Editor, Earth News
Sound matters to cichlids
Fish are being threatened by rising levels of man-made noise pollution.
So say scientists who have reviewed the impact on fish species around the world of noises made by oil and gas rigs, ships, boats and sonar.
Rather than live in a silent world, most fish hear well and sound plays an active part in their lives, they say.
Increasing noise levels may therefore severely affect the distribution of fish, and their ability to reproduce, communicate and avoid predators.
"People always just assumed that the fish world was a silent one," says biologist Dr Hans Slabbekoorn of Leiden University, The Netherlands.
But in the journal Trends in Ecology and Evolution, Dr Slabbekoorn and colleagues in The Netherlands, Germany and US report how the underwater environment is anything but quiet.
So far, all fish studied to date are able to hear sounds, either by an inner ear or a lateral line that runs along a fish's side.
Different fish vary in the sensitivity of their hearing.
For example, Atlantic cod have "average" hearing abilities, say the authors, while freshwater goldfish can hear at higher frequencies.
Generally fish hear best within 30