MUSMOD(C), A PRODUCTION-MODEL FOR BOTTOM CULTURE OF THE BLUE MUSSEL, MYTILUS-EDULIS L

A mussel production model, MUSMOD(C) was developed to seed bottom cult ure lease sites in Maine to their carrying capacity. The process of mo del development is demonstrated with three models: (a) an initial conc eptual model, (b) an aggregated model driven by the tidal exchange of food particles and (c) MUSMOD(C), the final model driven by food suppl ied in the tidal flow of water across a site. The final model predicts mussel production using the concentrations of phytoplankton and detri tus in the surface water, detritus quality, tidal current speed, water depth and temperature. Field measurements of several quantities (e.g. , clearance, respiration, growth rates for shell and meat, food concen tration gradient, and temporal feeding pattern, (Newell et al., 1997, Development of the mussel aquaculture lease site model, MUSMOD(C): a f ield program to calibrate model formulations, J. Exp. Mar. Biol. Ecol. , this volume) were obtained to evaluate and calibrate the final model . Model refinement using iterations of modeling and field work demonst rated the importance of food quantity and quality in explaining the ob served patterns of mussel growth. Food quantity explained the first-or der growth pattern, but it was necessary to account for the quality of the food to explain the second-order details of growth. Vertical mixi ng supplied the majority of new food particles, however, particles set tling over the mussel bed during slack water accounted for 33% of the phytoplankton and 45% of the detritus entering the feeding layer from above. A sensitivity analysis of the effects of seed density on mussel growth using MUSMOD(C) identified the optimum carrying capacity for t hree Maine lease sites. Seeding mussels during the optimum time period (May to early July) resulted in the harvest of marketable mussels fro m 40 mm seed in 8 months for a high food year and in 13 months when th e food supply was low. Characterizing the food supply using particulat e organic matter, POM, alone was not sufficient to explain mussel grow th in the detail necessary to answer many farm management questions. ( C) 1998 Elsevier Science B.V.