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Image: Greenpeace / Institute of Marine Research / FIS
Wind turbines attract cod larvae
(NORWAY, 4/13/2023)
Cod larvae were attracted to the sound of wind turbines and swam against the noise.
Photo: Institute of Marine Research
When the turbines are running, it creates a continuous, low-frequency underwater noise that spreads outwards from the offshore wind farm.
"We already know that fish and other animals in the sea are sensitive to sounds, and that some species react to low-frequency underwater noise", says marine researcher Alessandro Cresci at the Institute of Marine Research (HI).
"What we do not know, however, is how fish, and especially early in life, such as larvae, react to sound from offshore wind turbines. This is a new industry, especially here in Norway."
Filmed larvae in floating cages
Cod is one of the species that is sensitive to low-frequency sounds.
In order to find out how the cod in the North Sea might react to the offshore wind farms that are planned to be developed, the researchers got down to business: they recreated the situation in a fjord, albeit on a smaller scale.
"We filmed cod larvae drifting naturally in the water inside transparent acrylic cages with mesh walls. While the cages were floating in the water, we used a loudspeaker to emit a continuous, low-frequency sound at 100 Hz. We wanted to see if the sound caused the larvae to change their behaviour", Cresci explains.
Changed direction towards the sound source
Around 90 cod larvae were tested in the water - half were exposed to noise, while the others were allowed to swim in peace and quiet.
When the larvae were allowed to swim in peace, they oriented themselves clearly to the northwest. When the sound came, the cod larvae instead turned towards the sound source.
"This is an experiment on a small scale, but our results show that cod larvae drifting with the ocean currents past or near an offshore wind farm can be attracted by the underwater noise from the turbines", says the HI researcher.
Photo: Institute of Marine Research
The struggle to survive from larva to adult cod is very tough. Therefore, even small changes in the spawning and rearing areas can affect the population, and it is useful to know how different activities affect the fish.
Will test several species
Now the researchers plan to test out other commercially and ecologically important species in the same way.
"It is important to learn more about how a new industry, such as offshore wind, can affect fish and the ecosystem."
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(NORWAY, 4/13/2023)
"What we do not know, however, is how fish, and especially early in life, such as larvae, react to sound from offshore wind turbines. This is a new industry, especially here in Norway."
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