Modelling mussel shell and flesh growth using a dynamic net production approach

Understanding and modelling bivalve growth dynamics under variable environmental conditions are crucial for the development of management and sustainability aquaculture plans. This work proposes a new dynamic bivalve growth model that combines net production Dynamic Energy Budget (DEB) theory and the species-specific growth dynamics of the Ecophysiological Model for Mussels (EMMY). In our approach, the assimilated energy is first used for metabolic requirements, and the surplus partitioned between shell formation, somatic growth, reserves and reproduction. We also incorporate site-specific estimates for feeding and spawning. We compare the performance of our model with a standard DEB model for the simulation of mussel growth in a low seston environment (Ría de Ares-Betanzos, NW Spain). Our model provides realistic estimations of shell and soft tissue growth, while the standard DEB model overestimates soft tissue growth. Indeed the Relative Mean Square Error (RMSE), which measures the discrepancy between field and simulated shell-soft tissue relationships, of our model is below 10% of that obtained with the standard DEB. Our model also captures the different effects of environmental variability on shell and flesh growth.