High resolution characteristics of turbulence tied of a fish farm structure in a tidal environment.

• Vertical microstructure profiler is an accurate sensor for small vortices characterisation. • Aquaculture cages are responsible of turbulence generation and modification. • The anisotropy of vortices grows with the water velocity and along the production structures. • Wavelets are powerfull for both spatial and temporal turbulence analysis. Characterization of tidal flow variations and turbulence levels surrounding aquaculture infrastructures contribute to optimal fish production management and to a good environmental quality assessment. Such flow characterization was performed in Cherbourg Roadstead, France. An acoustic Doppler current profiler was used to measure flow velocities and a vertical microstructure profiler to assess turbulence levels and length scales in the vicinity of a commercial fish farm. Flow measurement results show that fish nets increase local turbulence level, impacting the flow and vorticity produced by the nets, contributing to more scouring of the ocean floor. A wavelet analysis allows to evaluate vortex sizes and where they are localized along the water column. Flow characterization shows these vortices are produced in the vicinity of fish nets and in their wake. Larger and more energetic turbulent structures are produced below aquaculture cages, which extend into the wake and onto the ocean floor. [ABSTRACT FROM AUTHOR]