Comparative analysis of fjord- and farm-scale models in bivalve aquaculture: implications of spatial and temporal resolution

Mathematical models play a crucial role in bivalve aquaculture research and management, facilitating the optimization of coastal aquaculture. These models vary in complexity and can be applied at different spatial and temporal scales and resolutions, which have implications for the research question and the required computational power. This study examined the performance of fjord- and farm-scale models in simulating bivalve growth and farm productivity, focusing on the effects of spatial and temporal resolution under a range of environmental conditions in the Hardangerfjord, Norway. We relied on 2 previously published models: a fjord-scale model (NORWECOM.E2E), which has been recently coupled to a dynamic energy budget (DEB) model to simulate mussel bioenergetics, and a farm-scale model that simulates the effect of the suspended canopy, defined as the floating infrastructure and crop, on local hydrodynamics to predict mussel growth using DEB. A series of numerical experiments revealed that the characterization of water currents in relation to the orientation of the farm is challenging and can lead to uncertainty in farm-scale models. Further, the discrepancies between modelling approaches were strongly dependent on the stocking biomass, with low biomass scenarios minimizing these discrepancies. Based on the results of these experiments, the NORWECOM.E2E-DEB fjord-scale model can be used to explore site selection and aquaculture-environment interactions without impacting the estimations of farm production to a critical level. The study underscores the potential of combining both modelling approaches for holistic coastal and farm management, providing valuable insights for future aquaculture development.