environmental stressors that predispose fish to development of lesions in the Great Wicomico River (GWR). The Pfiesteria Initiative Ecological Study (PIES) is an integrated, comprehensive field investigation of watershed and riverine processes and their relationship to environmental stressors.
Menhaden are intensively sampled from spring through fall to determine temporal and spatial variations in lesion prevalence. Histological and microbiological studies are performed to identify pathogens associated with lesions.
Physical and water quality parameters in feeder streams, groundwater, and the river are studied to determine how the watershed and groundwater influence nutrient and plankton dynamics in the river and development of hypoxic/anoxic conditions.
Water samples are collected and processed for determination of abundance and culture of heterotrophic dinoflagellates such as Pfiesteria and pathogens such as Aphanomyces.
Most fish kills occur as a result of hypoxia or low dissolved oxygen, especially for such aerobically active fish as menhaden. Unresolved fish kills are examined for a suite of potential causes.
Hydrodynamic and watershed models are in development to allow prediction of water quality, nutrient concentrations, and occurrence of environmental stressors in the GWR.