The findings suggest that while turbulent conditions initially affect salmon behavior and growth, the fish are capable of adapting without long-term negative impacts on their well-being.
Photo: Frode Oppedal/HI.
Scientists at Norway's Institute of Marine Research (Havforskingsinstituttet - HI) have conducted a study to explore how farmed salmon adapt to living in environments with significant wave activity - an important contribution to knowledge on salmon farming, given the surge in interest in developing offshore aquaculture.
"It is very difficult to test the effect of large ocean waves on fish in a laboratory, and there are also no ocean locations where such tests can be carried out," said lead scientist Malthe Hvas, in an HI news release.
To solve this problem, the scientists constructed a "wave machine" to simulate turbulent ocean conditions in a controlled laboratory setting.
Over an eight-week period, salmon were exposed to simulated waves for most of the day, with a calm period only during feeding. A control group experienced calm water throughout.
Initially, salmon exposed to turbulence showed a decrease in appetite, eating 17% less than the control group, but this difference diminished after two weeks, with both groups eventually consuming similar amounts.
The control fish grew slightly larger by the end of the experiment, however the researchers believe that the difference between the two groups would have likely equalised over time, based on other studies.
Behaviourally, the turbulence-exposed salmon initially displayed more chaotic movements and experienced more collisions, which could potentially harm fish welfare.
However, researchers found that over time, these fish adapted, showing organized behavior and no significant differences in stress levels or welfare compared to the control group. X-ray analyses also confirmed there was no increase in injuries to the fish.
The study also debunked the notion that swimming in turbulent conditions could enhance the physical fitness of the salmon.
A "swimming competition" comparing the two groups of fish at the end of the experiment revealed no improvement in the wave-exposed fish's ability to maintain position against increasing water flow.
The experiment, part of a master's thesis by Erasmus Mundus student Emma Barbier, was conducted at the Institute of Marine Research's experimental station and supported by the Research Council of Norway through the SusOffAqua project.
The findings suggest that while turbulent conditions initially affect salmon behavior and growth, the fish are capable of adapting without long-term negative impacts on their well-being.
