Many commercially important species of shellfish are managed by a periodic input of hatchery-reared juveniles which supplement natural recruitment, if any. Demographic models for such populations must include this recruitment subsidy to accurately characterize the population’s condition. An additional consideration is that many, if not all, commercially important shellfish populations are metapopulations, with distinct patches connected by larval exchange. Managers must allocate subsidies and harvesting among these patches and could therefore benefit from a model that can be used to compare different management strategies.
Results/Conclusions

Here, we build up a subsidized model including stage structure, recruitment subsidy, seasonal periodicity, harvest, and spatial structure. The sensitivity analysis of such a model has been impossible until now. We use matrix calculus to derive the sensitivity and elasticity of equilibrium abundance, stage distribution, patch abundance, or other measures of metapopulation status to the parameters defining both the life history (demography and dispersal) and management (harvest, subsidy). As an example of its use, we parameterize the model using data for the softshell clam, Mya arenaria, an important bivalve for New England fisheries. We use matrix calculus to derive sensitivity and elasticity of the equilibrium abundance (and therefore the harvestable abundance) to different seed clam distribution scenarios. Our model formulation is generally useful for management and conservation where subsidy is used to increase abundance.