A model of renewable resources and limitation of deposit-feeding benthic populations.

1. The renewal rate of resources exploited by a population influences carrying capacity and competitive interaction. A model of resource renewal is proposed where P is the fraction of the resource exploited at any given time, p the fraction exploited per day, and a the fraction remaining per day. At equilibrium, P=p/(1-a), and resource is always available if pü1-a. A logistic model of recovery is also proposed for living resources that are themselves limited by nutrients or space. 2. The models are used to predict carrying capacities of populations of the mud snail Hydrobia. The snail does not reingest its own fecal pellets until they have broken down. Pellet breakdown rate may therefore be a limiting factor to population size. Measured pelletization rates and fecal pellet breakdown rates predict densities within the range of natural Hydrobia populations. Pellet breakdown in this case is the renewable resource. As many natural sediments with deposit-feeders are completely pelletized we conclude that pellet breakdown rate is an important limiting factor to deposit-feeder density and that coprophagy may be avoided in deposit-feeding mollusks.