Waves and currents decrease the available space in a salmon cage

Area of Science:

• Aquaculture science
• Fish behavior
• Marine environmental science

Background:

• Increasing demand for salmon necessitates expansion into more exposed marine sites.
• Environmental constraints at established sites drive the need for new production areas.
• Understanding fish behavior in challenging conditions is vital for sustainable aquaculture.

Purpose of the Study:

• To investigate the effects of strong currents and waves on salmon behavior.
• To determine how salmon utilize available space in exposed aquaculture sites.
• To assess factors influencing salmon spatial preferences in sea cages.

Main Methods:

• Field observations conducted at a marine site characterized by strong tidal currents and well-mixed water.
• Utilized video cameras and echo sounders to monitor salmon movements and space utilization.
• Analyzed salmon distribution in response to varying environmental conditions, including currents, waves, and light.

Main Results:

• Salmon generally utilize the entire water column but restrict movement in response to cage deformation, waves, or daylight.
• A strong horizontal preference was observed, with salmon occupying areas exposed to currents.
• Waves induced dispersal from exposed cage areas to more sheltered locations, while strong currents did not deter salmon from exposed zones.

Conclusions:

• Salmon prioritize areas with strong currents, even when space is limited, suggesting good water exchange mitigates density aversion.
• Waves significantly influence salmon distribution, causing them to seek shelter.
• Ensuring adequate vertical space is recommended for improved salmon welfare, even in high-current environments.