A comparative study of the biomass-based and individual-based models of blue mussels

Abstract

The performance of a biomass-based model is compared with that of an individual-based model for a blue mussel Mytilus galloprovincialis. The mathematical models are developed to predict the environmental impacts of blue mussels, which adhere to the surface of coastal artificial structures and vary the surrounding material cycle with their feeding and respiratory activities. The existing biomass-based model is based on Scope for Growth (SFG) concept and allometric relations between body size and physiological rates. One problem of this approach is that it does not discriminate between fed and starved mussels in the mussel bed. However, mussels are usually attached to each other in several layers, with subsequent competition for food among them. Hence, some of the mussels are shoved to the inner layer of the mussel bed and must be starved due to their unfavorable position. They continue living by consuming the reserved materials little by little by means of standard respiration, therefore they does not contribute much to food ingestion and oxygen consumption rates of the mussel bed. In the present study, an individual-based model is developed to describe the dynamics of mussels as controlled by Competition for Space and Food (CSF) availability. The model consists of a physiological growth submodel based on Dynamic Energy Budget (DEB) concept and a competition submodel. Both the biomass-based and individual-based models are applied to the mussels growing on the artificial substrata suspended from the top of a pontoon type floating platform anchored in the head of Tokyo Bay in Japan. Then the observed results of growth and oxygen consumption rate of mussels are compared with the predicted results by means of both models. Consequently, the performance of the biomass-based model is sufficient when the mussel bed forms mono layer, however the performance of the individual-based model is better in the case when the mussel bed has several layers.