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Previously collected fisheries data identified for entry into GIS were not entirely compatible with the three-level structure developed by the Bureau of Reclamation for the GCES/GIS data base (Werth et al., 1993). To allow for integration of fisheries information, a six-level structure was developed, ranging from level 1 as the most geographically accurate to level 6 as the least geographically accurate. Level 1 was survey information with sub-centimeter accuracy and included bathymetric maps developed from total survey station techniques and superhydro technology. Level 2 was primarily for information referenced to or mapped onto 1:2,400-scale orthophotos developed for the GCES projects, and included radiotelemetry tracking data accurate to the nearest 5 in, and gill and trammel net sample sites located to the nearest 10 in on uncorrected 1:1,200 aerial photographs. Level 3 was 1:1,200-scale maps, and included surficial habitat maps, current pattern maps, and shoreline habitat measurements located within 10 in, to provide an assessment of habitat conditions at different flow stages. Level 4 was 1:24,000-scale maps used for most of the fisheries data collected outside of the orthophoto areas. Level 5 was based on river mile referencing to the nearest 0.20 river mile, and was the least spatially accurate for quantitative fishery data. Level 6 provided a general location, and was used primarily for historic records and accounts with no specific spatial requirements. Discussion An integrated, centralized data base and GIS linkage is vital for providing comprehensive information on fisheries resources to managers of Glen Canyon Dam. Using GIS for fisheries information integration is a relatively new application of GIS technology. Traditional fisheries biology has not focused on relating fish locations to mapped information of large river resources. For many fisheries studies, the effort required to map actual river resources is not justified or planned. The increasing importance of the endangered and native fish requires decision makers to make better use of all available information. A GIS offers analytical capabilities in addition to query and viewing of archived fisheries information. Fisheries information in a GIS data base provides an inventory of endangered and native fish handled by biologists and all associated information, including scanned photographs (to be used for morphometric measurements and archival purposes), tag numbers, meristics, etc. These data can be used as important historic information for developing long-term monitoring to identify past collection sites for historic distribution and abundance, past and recent population demographics, and current research needs and data gaps. Specific locations of fishery-related data collections are documented to allow revisiting previous collection sites. The greatest long-term benefit of a GIS data base is the capability to share and exchange information between scientists and among managers that is linked both historically and spatially. To more fully understand the relationships between the various resources under study and Glen Canyon Dam operations, individual researchers need to be able to access and use other scientific data bases. An additional benefit of a GIS data base is the visual representation of fishery resources and sample locations. This representation facilitates evaluation of relationships between fisheries and other resources and enhances analysis capabilities for impact analyses and resource assessments. The GCES/GIS fisheries data base will provide a structure for a consolidated, centralized fisheries data base that will be accessible to managers and decision makers. With a formalized structure, data from current and future research can easily be incorporated into the data base to provide an ongoing information and retrieval system. This data base is unique in that it is geographically referenced, multi-temporal, multi-accuracy, and multi-media. It is currently 25