North America contains the highest diversity of aquatic species of any temperate region on Earth. Unfortunately, aquatic ecosystems in North America are experiencing ongoing human-induced impacts from land use transformations and climate change. Not surprisingly, aquatic species are some of the most threatened taxa in North America. Geographic information systems (GIS) facilitate the organization, manipulation, and analysis of biological and environmental data in a spatially explicit manner. The development and application of GIS techniques in aquatic systems offers a much needed framework to assess the impact of environmental variability on the distribution of aquatic organisms. The goal of this research is to develop GIS-based research tools to investigate the climatic and landscape characteristics regulating aquatic biodiversity at continental, regional, and local geographic scales. At the continental scale, GIS environmental data, including precipitation, temperature, and landcover, will be used to identify the factors regulating the distributions and diversity of all North American fish species. At the regional scale, climate data will be integrated with a hydrologic model to assess the influence of hydrologic variability on fish assemblages in Illinois and Alabama. At the local scale, fine-scale GIS data will be developed to examine the relationship between intra-annual habitat variability and fish abundance. The broader impacts of this work will be realized through the generation of data and techniques that facilitate an understanding of the impacts of climate variability and land use characteristics on the diversity and abundance of species in aquatic systems. In addition, annual workshops will be developed that provide GIS-based training to aquatic scientists from universities, government agencies, and non-profit organizations. The primary goals of these workshops include the enhancement of the technical and intellectual infrastructure for GIS-based studies of aquatic biodiversity, and the generation of a community of interactive scientists focused on GIS applications in aquatic sciences.