The review should be of interest to salmon farmers worldwide. It details how salmon behave and cope with their production environment and how farmers can best use this knowledge to improve production’ said lead author Dr Frode Oppedal.
Environments within sea-cages are typically highly variable in both space and time, with the greatest variation occurring with depth. Preferred swimming depths and densities of salmon are the result of salmon choosing their position in sea-cages in response to the environment, feed and perceived threats. These behavioral choices typically result in salmon schooling at specific depths within sea-cages at densities 1.5 to 5 times their stocked density, and up to 20 times in extreme cases.
‘Understanding how salmon farm environments vary and how salmon respond is essential for farmers to improve welfare outcomes, feeding regimes, artificial light management strategies and the success of sea-lice treatments.’ said Dr Oppedal.
Key recommendations of the review include:
- Measuring the farming environment (temperature, salinity and oxygen) continuously so farmers have the ability to adaptively manage the cage environment.
- Improving production and welfare by adjusting feed entry to the depths at which salmon prefer to swim rather that forcing salmon to the surface to feed. This should both improve fish welfare and production efficiency.
- Steering salmon to swim at depths away from the surface with artificial lights and/or submerged feeding during periods when levels of sea lice larvae are high in surface waters to reduce sea lice infestations.
- Developing a simple to use operational welfare index (OWI) based on the behaviours of salmon which farmers can use to detect abnormal behaviours which may be early warning signs of the development of disease.
The full scientific article ‘Environmental drivers of Atlantic salmon behaviour in sea-cages: a review’ can be accessed at the following web address: http://www.sciencedirect.com/science/journal/00448486