Researchers at the Norwegian Institute for Nature Research (NINA) and Sintef have found a new method that makes it possible to listen to the sounds salmon make underwater.
Quite how the sounds should be interpreted is not yet clear, but the researchers have observed clear changes in sound when the fish are hungry or stressed, reports Norway’s national broadcaster NRK.
This will likely become a useful tool to get a better picture of how the fish are doing, and thus achieve better fish welfare.
May reduce feed use
Scientists have listened carefully to the sound frequency when the fish should be fed. The result shows that a full salmon makes a different sound, or has a different frequency than a hungry salmon.
“This discovery can help to streamline the aquaculture industry since the expenditure on feed is one of the biggest costs. It is stupid to waste food that is not eaten,” said NINA’s Carolyn Rosten.
Here you can hear what the sound is like when salmon are calm.
Sound of stressed salmon
In another experiment, it appears that the frequency changes significantly when the salmon is stressed. The sound was measured before and after a school class entered the facility where the fish swam.
“A large group of children necessarily makes some noise. We measured marked differences in the frequency of the sound from the salmon before, in the meantime and after the children stood by the vessel,” Rosten said.
Here you can hear how salmon change frequency when the school class enters the room where the salmon stands.