Self-contamination of aquaculture cages in shallow water

Benthic foraminifera to assess ecological quality statuses: The case of salmon fish farming

“…Sediments directly below the cages are characterized by a moderated and localized increase in mud, organic carbon and nitrogen content (Kempf et al, 2002;Baux et al, 2017;Dauvin et al, 2020). Both the high hydrodynamic regime in the RdC and the acceleration of currents under the cages (Poizot et al, 2016) may often enhance the dispersion of excess organic waste from the salmon fish farm and limit long term accumulation of organic matter (OM). Hence, there are most likely a shift between periods of accumulation and then dispersion of the sediment under the cages.…”

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

“…Near the bottom, the growing speed of the current and the wavy morphology of the sea-bed are responsible of highly energetic turbulent structures of bigger sizes (> 0.25 m). Between these two areas, interactions cages-current generate turbulent vortex tied up to the wake effect as showed in Poizot et al (2016). These two latter interactions, i.e.…”

“…Discrepancies between simulated and measured data were due to an increased net solidity from cages deformed by the flow and a block effect from the fish inside the cage. Poizot et al (2016) showed that in spite of favourable environmental conditions (sea protection and tide currents which regularly refresh the water), periods of non-negligible fish mortalities can be observed to occur without clear evidence of their origin. They showed through turbidity measurements and numerical modelisation, that in some cases the flow acceleration under the cages can be at the origin of sediment re-suspensions and bio-deposits.…”

“…One of the main conclusions of the various works aiming to numerically model the transport of effluents linked to aquaculture in the marine environment is that the variability of water flows on the various temporal and spatial scales and their action on flexible cages leads to complex interactions (Klebert et al, 2015;Gansel et al, 2018;Poizot et al, 2016). In order to be able to model more precisely the dynamics of the structure of the water column and the dispersion of effluents from breeding cages, it appeared necessary that the numerical models have an accurate representation of transfers due to turbulent diffusion.…”