The Northern River Basins study was initiated in 1991 to understand and characterize the cumulative effects of development on the water and aquatic environment of the Peace, Slave, and Athabasca Rivers. Extensive uranium mine-mill operations were in place around Lake Athabasca from the 1950s to the 1980s and some mining continues today. Residents of the area are concerned that tailings from these mines may enter Lake Athabasca causing radioisotope contamination of the fish. The study performed radiochemical analysis and biological examinations of northern pike, suckers, and lake whitefish collected in February 1993 from Lake Athabasca near Bustard Island and Hook Point. A complete analysis for all the major, naturally occurring radioisotopes was conducted and the fish were examined for abnormal growth problems or diseases. This report describes the results of the analysis.