Wave-generated currents threaten aquaculture sites

• Measured wave and current data and their combined impact on the net pen on an exposed aquaculture site. • Wave-sheltering shoal unexpectedly triggers strong current jets during storms, posing a hazard to the aquaculture site. • Combined wave and current forces significantly reduce cage volume, surpassing the impact of currents alone. This study investigates the impact of wave-generated currents on fish farms, focusing on a novel exposed aquaculture site in the bay of Sandsvág, Faroe Islands. While shoals can attenuate wave height, our research reveals that breaking waves generate localized currents, which can intensify into powerful jets during severe storms. A strong correlation between wave height and current speed was established, demonstrating that these jets arise under specific conditions and can contribute to significant fish mortality. We analyze how currents interact with the cage structure, particularly reducing cage volume as the sinker tube is displaced sideways and lifted within the water column. Frequency analysis of cage deformation reveals dominant oscillatory behaviors linked to infragravity waves and current pulsations. The results indicate that slack generated during wave troughs allows these currents to reduce cage volume further, increasing fish density and the risk of collisions with the netting. These findings underscore the challenges of aquaculture in exposed locations and highlight the need for improved site selection strategies and cage designs. Furthermore, predictive modeling is essential for assessing the formation of jet currents, their impact on cage integrity, and the challenges of capturing extreme wave-current events through short-term measurements.