Models are important tools to address sustainability challenges associated with developing aquaculture at farm, regional and global scales1 . The objective of the MOCAA project (Modeling ecosystem assimilation capacity for a sustainable aquaculture ) is to develop a chain of modeling tools to assess the environmental impact of land-based and marine cage fish farm ing, in metropolitan France and overseas territories. The MOCAA decision-support tool considers the production systems characteristics (species, production, type and farm management , etc.) and the characteristics of the ecosystem (bathymetry, hydrodynamics, sensitivity of benthic ecosystems, etc.) to simulate the emission, the fate and the impact of aquaculture on the environment. The project involves aquaculture stakeholders to ensure that the tool will meet multi-stakeholder needs. The project is divided into three phases. For each phase, a review of existing tools has been realized, in order to integrate the most accurate existing ones. Workshops are organized in collaboration with fish farmers, public authorities and other stakeholders to present the approach, define needs and to co-construct the tool.
From 2021 to 2023, two modules have been developed and coupled: 1) a farm-scale module ( integrating a dynamic bioenergetics model2 and a farm management model) that simulate fish growth rates and emission of solid and dissolved waste for 7 marine fish species : Seabass (D. labrax), seabream (S. aurata), red drum (S. ocellatus), meagre (A. regius), trout (O. mykiss and S. trutta) and atlantic salmon (S. salar) and 2) a lagrangian dispersion model3 that simulate the dispersion a nd dilution of particulat e and dissolved waste in the water column. The dispersion module uses outputs of hydrodynamic models or measured water currents . In 2024, the validation of the growth model and farm model are carried out. Outputs of the growth model for each species have been confronted to published data (xx publications). M ean relative errors (MRE) depend on the fish species. The lowest MRE is observed for seabass with 0.14, indica ting good accuracy of the model, followed by sea bream and salmon species ( MREs of 0.21 and 0.29 respectively). In contrast, the trout species showed the highest MREs (0.44 and 0.39). Validation at farm scale is carried out in fish farms with in contrasted environment encompassing temperate (Brittany) and tropical (Martinique) conditions. T he rigor of the approach is ensured by taking into account all stakeholders from construction to transfer of the modelling tool.
1 Chary Killian, Brigolin Daniele, Callier Myriam (2022) Farm‐scale models in fish aquaculture – An overview of methods and applications. Reviews in Aquaculture 12695, 1-32
2 Kearney, M. R., & Porter, W. P. (2020). NicheMapR – an R package for biophysical modelling: The ectotherm and Dynamic Energy Budget models. Ecography, 43(1), 85–96. https://doi.org/10.1111/ecog.04680)
3 Delandmeter, P and E van Sebille (2019), Geoscientific Model Development, 12, 3571–3584
Funding information: French Ministry for Food and Agriculture; French Ministry of the Sea; Institut Français de Recherche pour l’Exploitation de la Mer.