EVALUATING THE POTENTIAL ENVIRONMENTAL FATE AND EFFECTS OF AQUACULTURE DRUG USE IN U.S. INTENSIVE AQUACULTURE

M.P. Gaikowski, L.J. Schmidt, Carol D. Lowenberg, and W.H. Gingerich, U.S. Geological Survey, Upper Midwest Environmental Sciences Center

U.S. Food and Drug Administration (FDA) approval is currently being sought for several waterborne or oral therapeutants for use in aquaculture to control mortality associated with a variety of bacterial or parasitic diseases of cultured freshwater fish. Each drug's potential environmental fate and effects following discharge after aquaculture use must be characterized prior to FDA approval. The risk characterization for a drug integrates available fate and degradation data with projected use and discharge patterns at U.S. aquaculture facilities to predict environmental introduction concentrations (EIC). These EIC estimates are then compared with available effects data to develop a probabilistic estimate of environmental risk of drug discharge. Risk ratios may indicate the need for further refinement of the available database (e.g. better degradation information, additional toxicity tests, improved discharge estimates). Previous U.S. Geological Survey (USGS) research focused on the development and validation of simple models to predict waterborne effluent concentrations following typical production raceway treatments and the development of hatchery survey information to characterize aquaculture drug use. Current USGS research is focused on the validation of existing dilution models in a broad spectrum of hatcheries and on the integration of national water chemistry databases into the risk assessment process. Expansion of existing dilution models to a broad spectrum of hatcheries will improve FDA's confidence in the EIC estimates generated during the environmental risk assessment - providing a more realistic estimate of exposure to the aquatic ecosystem. Improving these models will also provide information on realistic exposure durations if additional aquatic toxicity tests are required. The integration of water chemistry information into the environmental risk assessment will allow FDA reviewers to highlight those specific watersheds that may be particularly vulnerable to a drug based on the surface water pH, hardness, or other variable. By integrating actual hatchery locations with this water chemistry database, we can specifically identify those hatcheries whose discharge may result in unacceptable drug concentrations based on receiving water chemistry. Furthermore, the integration of these data sets into the regulatory decision making process may improve the protection of critical aquatic ecosystems that support threatened and endangered species (Figure 1) while still allowing hatcheries to use desperately needed pharmaceuticals to control disease in culture fish.

Figure 1. Average surface water pH and fish hatchery location relative to the habitat of the endangered winged mapleleaf mussel Quadrula fragosa in the St. Croix River.