The Role of Spatial Structure and Habitat Effects in the Dynamics of Coastal Fish Populations

Local habitat interventions are a potentially powerful tool to enhance coastal fish populations, but quantifying their effects remains challenging because population dynamics models typically do not resolve habitat effects. We developed a spatially explicit fish population model incorporating differential habitat use, movement and habitat-specific vital rates to investigate impacts of local habitat restoration. Habitat availability and quality can alter the local recruitment relationship and lead to spatial variation in sustainable harvesting. We applied our model to common snook (Centropomus undecimalis), a highly valued game fish, and investigated the contribution of habitat to the persistence of a local sub-population in Sarasota Bay on the Gulf coast of Florida. High quality mangrove habitat is sparsely distributed in Sarasota Bay and preliminary simulation results suggest that the local snook sub-population is recruitment limited and sustained in part by immigration of non-resident fish. Restoration of mangrove habitat is predicted to increase local fish abundance. We found that the spatial extent of habitat to be restored and assumptions about fish movement determine if predicted increases in local abundance are related to improved recruitment or spatial redistribution of fish. Thus the long-term benefit of habitat restoration depends on more detailed, spatially explicit monitoring of fish movements.