Factors limiting larval dispersal that would impact the distribution of adult populations of the red-jointed fiddler crab (Uca minax Leconte, 1855) within tidal freshwater habitats of a river dominated estuary

Many estuarine species with relatively immobile adult life histories have pelagic larval life stages that increase their dispersal capabilities. Limitations to the successful recruitment of postlarvae and juveniles back to conspecific adult habitats is dependant on the physiological and developmental constraints on the larvae, biotic interactions (i.e. predation, prey availability, competition), cue recognition and response and physical factors (i.e. physiography of the estuary, tidal amplitude, river discharge, salinity, density gradients, wind).;We developed an empirical one-dimensional flow model for the freshwater, tidal portion of the Pee Dee River that discharges into Winyah Bay, South Carolina. I chose Uca minax as our model organism due to its ability to successfully inhabit brackish and freshwater habitats throughout Winyah Bay and its confluent tidal rivers. The coupled larval behavior-transport model is capable of predicting U. minax dispersal in the tidal freshwater reaches of the Pee Dee River for any combination of river discharge and tidal amplitude. I have recently begun to calibrate and ground-truth the model.;In the model, I assume that larvae and postlarvae behave as passive particles in the horizontal direction, but have the ability to move vertically in the water column. I have confirmed that megalopae of U. minax migrate toward the surface in response to flood currents and sink during ebb currents. Mean densities of U. minax burrows in the Pee Dee River were recorded along a longitudinal river transect and compared favorably with model predictions of expected rates of megalopae settlement. Metamorphosis and survivorship studies were conducted with U. minax megalopae to develop metamorphosis/survivorship function for the model. The results of these studies will be used to calibrate and validate our coupled larval behavior-transport model.