Shark Bay is a large inverse estuary, located in Western Australia. It has a number of unique habitats that support important species. The dynamics of circulation in Shark Bay have an influence on the species that inhabit the region, on small, local scales as well as on large Bay-wide scales. Numerical modeling and field data were used to examine small-scale dynamics in relation to an important recreational fish, pink snapper (Pagrus auratus). Icthyoplankton surveys collected and recorded egg density in regions where snapper are found. A barotropic three-dimensional hydrodynamic model was coupled with a two-dimensional Lagrangian particle-tracking program to simulate the passive transport of eggs through regions where spawning is known to occur. Circulation modeling results indicated residual flows on small scales that served to retain the eggs in the region where they were originally spawned. Results corroborate genetic work on adult snapper, which found no evidence intermixing of populations in Shark Bay. The numerical model was then further refined to run in a baroclinic mode. Simulations of salinity and temperature gradients were used to recreate frontal systems in Shark Bay. Frontal regions divide the Bay into a northern and a southern section as well as separate it from the ocean. Application of an analytical method for calculating front locations was consistent with the observed results and indicated that the primary forces determining frontal locations in the Bay are tides and gravitational circulation. Winds are a secondary influence, and solar heating is minimal in influence