Model for growth and survival of mussels Mytilus edulis reared in Prince Edward Island, Canada

Abstract

Mathematical models of commercially important species enable one to integrate the diversity of information on these species, understand mechanisms responsible for observed population dynamics, and assess management scenarios. We present a population model for blue mussels Mytilus edulis grown in suspended culture in 2 bays in Prince Edward Island, Canada. The model incorporates a number of ecological processes, namely allometric growth of individual mussels, temperature-dependent growth rates (based on the Lassiter-Kearns equation), and survival of mussels based on self-thinning. Analysis of our model suggests that the optimal temperature for mussel growth is 15.8C. Also, survival does not depend on site or year, indicating that self-thinning is probably due to competition for space rather than food or other site-specific conditions. Based on sensitivity analyses, growth predictions are robust to changes in parameter values, while survival predictions are quite sensitive to changes in the strength of the effect of initial mussel density and of self-thinning. Evaluation of management scenarios over one grow-out period indicates that date of deployment strongly affects time for seeds to reach commercial size. Optimal initial mussel density depends on whether one wants to maximise the proportion of mussels surviving to harvest or the number of mussels available at harvest; this decision depends on whether seed availability or lease area is limiting.