Rising man-made noise pollution levels threatening fish

London, June 2 (ANI): Rising levels of man-made noise pollution are threatening fish, according to scientists.

The researchers 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 said.

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," the BBC quoted biologist Dr Hans Slabbekoorn of Leiden University, The Netherlands, as saying.

But, 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.

Generally fish hear best within 30-1000Hz, though species with special adaptations can detect sounds up to 3000-5000Hz.

Some exceptional species are sensitive to ultrasound, while others such as the European eel, a freshwater species that spawns at sea, are sensitive to infrasound.

That means human-generated underwater noise has the potential to affect fish just as traffic noise affects terrestrial animals such as birds, say the researchers.

"The level and distribution of underwater noise is growing at a global scale but receives very little attention," said Slabbekoorn.

Noise pollution might severely affect the distribution of fish, and their ability to reproduce, communicate and avoid predators.

For example, some studies have reported that Atlantic herring, cod and blue-fin tuna flee sounds and school less coherently in noisy environments.

That could mean that fish distributions are being affected, as fish avoid places polluted by man-made noise.

Noise pollution could significantly impact communication between fish- so far over 800 species of fish from 109 families are known to produce sounds, generally broadband signals at less than 500Hz.

Noise pollution could also interrupt their reproduction, by causing stress or restricting their ability to find a mate or keep them from preferred spawning sites.

It could also prevent fish from hearing each other and communicating effectively, and affect their ability to detect noisy prey, or hear oncoming predators.

The study was published in the journal Trends in Ecology and Evolution. (ANI)