Fish, including those in European rivers, are increasingly at risk due to man-made noise

2010 - 06 - 02
Fish, including those in European rivers, are increasingly at risk due to man-made noise

Fish are increasingly threatened by rising levels of human-induced noise pollution. This is claimed by the scientists asked to investigate the impacts of noise from underwater drilling rigs, ships, and sonars on the fish populations around the world.

Although fish are said to live in a world of silence, most of them hear well and sound plays an active role in their life, scientists say. “People always assumed that the fish world is silent,” says biologist Hans Slabbekoorn of Leiden University in the Netherlands. Scientists from the Netherlands, Germany, and USA argue that the underwater world may be characterised in various ways, but certainly cannot be described as silent.

So far, all the fish they have examined are able to hear sounds, either through their inner ear or so-called lateral lines. Various fish only differ in the sensitivity of their hearing. For example, the cod has “average” hearing abilities, while the freshwater goldfish hear well at higher frequencies.

In general, fish hear best in the frequency range of 30 to 1000 Hz, some species can detect sounds up to 3 to 5000 Hz. There are also species sensitive to ultrasound, while others, such as the European eel and other freshwater fish that spawn in the sea are sensitive to infrasound.

This means that man-made underwater noise may affect fish just as traffic noise affects terrestrial animals. The level and spread of noise under the sea level is increasing globally.

Rising noise levels may significantly affect fish distribution, reproduction capacity, communication, and the avoidance of predators. Noise may interrupt their reproduction, cause stress, and limit their ability to find a partner, or prevent them from staying at their preferred mating location. Noise may also prevent fish from hearing each other and communicating effectively, affecting their ability to notice noisy prey or to hear approaching predators.

For example, some studies suggest that the Atlantic herring, cod, and bluefin tuna are fleeing noise. This could mean that fish distribution will be increasingly affected by trying to avoid places with man-made noise.

Noise could also significantly affect communication among fish: so far, more than 800 fish species that can make sounds are known, typically signals with a bandwidth of less than 500 Hz. Fish make sounds as they fight for territory, compete for food, during spawning, and predator attacks.

“Noise has long been a neglected factor that negatively affects human health. The new scientific research shows that noise negatively impacts the animal kingdom as well. It is therefore in the interest of nature protection and health protection to very strictly tighten noise limits,” said Director Dalibor Dostal of the European Wildlife conservation organization.

Indeed, noise, together with overfishing, may be another risk factor for fish populations.

Photo: Petter Arvidson / Profimedia

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