LAUSR

Abstract The interaction between local hydrodynamics conditions and salmon cages are important in disease transmission and in the transport of waste products generated by aquaculture. We propose a modeling methodology to assess the hydrodynamic effects of a salmon farm in a Patagonian channel. The method is based on the coupling between a Coastal and Regional Ocean COmmunity model (CROCO) and a high resolution Large Eddy Simulation (LES) model. A salmon farm located in the Estero Elefantes Channel (45°39′16.50″S–73°35′59.40″W) was used as a study case. The physical coherence of the results was validated by comparison with field current velocities measured with an Acoustic Doppler Current Profiler (ADCP). The model predictions were capable of reproducing the tendencies of the variation although there were some differences in magnitude. The results showed that the hydrodynamics of the Estero Elefantes Channel is dominated by two circulation modes depending on the current direction in the adjacent Moraleda channel. Both circulation modes are characterized by a highly unstable shear flow composed by turbulent structures that interact with the salmon cages. Therefore it is not possible to select a local control volume with arbitrarily defined inlets, outlets and impermeable walls to evaluate hydrodynamic processes relevant to the salmon farms. The presence of the cages modifies the natural hydrodynamics of the channel, attenuating the intensity of the local velocity magnitude and generating recirculation and retention zones near them. However, their effect is not confined locally because the perturbations introduced by the presence of cages are propagated far from them. The transport of material discharged inside the cages was also analyzed. This information should prove useful both for producers and the aquaculture management authority.