By Emmanuel A. Frimpong, Jian Huang, and Yu Liang
Fish occurrence data to support high-resolution distribution models and test various community and macroecological hypotheses have not been available at the national scale. We present IchthyMaps, a high-resolution database of historical freshwater fish occurrences throughout the conterminous United States. Designed on the principles of metacommunity ecology, IchthyMaps is a large compilation of fish presence records collected through approximately 1990, digitized from regional atlases, appended to 1:100,000 National Hydrography Dataset plus version 2 (NHDPlusV2) interconfluence stream segments, and readily aggregated within hierarchically coarser units (e.g., 8-digit and 12-digit U. S. Geological Survey [USGS] hydrologic units). IchthyMaps contains 606,550 presence records for 1,038 species and subspecies, spatially joined to 224,305 NHDPlusV2 interconfluence stream segments, representing more than 10% average sampling intensity consid- ering all the NHDPlusV2 segments as the sampling frame. IchthyMaps is freely and publicly accessible through the USGS ScienceBase web portal. It offers new opportunities for both basic and applied research and conservation programs in areas such as modeling species distributions, community ecology, gap analysis, and assessments of impacts of land use, species invasions, climate change, conservation biogeography, and fisheries management.