ALFISHES: A Size-Structured and Spatially-Explicit Model for Predicting the Impact of Hydrology on the Resident Fishes of the Everglades Mangrove Zone of Florida Bay

By: Jon C. Cline, Jerome Lorenz, and Donald L. DeAngelis

A model (ALFISH) for functional fish groups in fresh-water marshes in Greater Everglades area of Southern Florida is extended to create a new model (ALFISHES) to evaluate the spatial pattern of fish densities in the community of resident fishes of the Everglades mangrove zone of Florida Bay. Both the ALFISH and ALFISHES models were developed as part of the Across Trophic Level System Simulation (ATLSS) project. (The model simulates fish from a single functional group, small fish (< 110 mm in length). The model is size-structured and spatially-explicit. These fish constitute an important prey base for large fish, reptiles, and birds, which are important indicators of ecosystem health. The model combines field data assessing the impact of salinity of fish biomass with hydrology data from the USGS Southern Inland Coastal Systems (SICS) numerical model.

The estuarine landscape consists of a spatial grid of 500 x 500 meter cells across the coastal areas of the Florida Bay. Each cell is divided into two habitat types, flats, which are flooded only during the wet season, and creeks, which are always wet and serve as refugia during the dry season. Daily predictions of water level and salinity are obtained from the SICS model. As in the fresh-water model, the fish spread out into the flats during flooded conditions. As the cells dry out, the fish either retreat by moving into creeks, move to other spatial cells, or die if their cell dries out. The model output may be used to assess the impact of changes in hydrology on fish biomass and its availability to wading bird and other consumer populations.