ELISE R. IRWIN, Alabama Cooperative Fish and Wildlife Research Unit, 119 Swingle Hall, Auburn University, Alabama, USA

Historical rotenone data can be used to quantify temporal variation in fish communities. In 1951, the Tallapoosa River, Alabama, was free-flowing from its headwaters to Lake Martin (» 128 km) and a rotenone survey was conducted 8 km upstream of the lake. Harris Dam, a peaking hydropower facility, became operational in 1981 (72 km upstream of Lake Martin), causing daily stage fluctuations of 1.5 m at the historic rotenone site. Perceived declines in recreational harvest of catfishes, downstream of Harris Dam, was the impetus to repeat the 1951 rotenone survey. Changes in the fish community were measured by comparing the 1951 and 1996 data. Biomass declined from 51.8 kg/ha (N = 2,331) 1951 to 32.6 kg/ha (N = 366) in 1996. Composition shifted from a cyprinid/ictalurid (47/44%) dominated community (1951), to a centrarchid (73%) dominated community (1996). Cyprinids declined from 1,380/ha (1951) to 37/ha (1996), most representative of the overall decrease in fish abundance. Juvenile catfishes (< 150 mm) declined from 1,201/ha (1951) to 77/ha (1996), indicating recruitment may be impacted and realized in decreased harvest of adult catfishes. The shift to a centrarchid dominated community is consistent with the hypothesis that "generalist" species are more tolerant of disturbance regimes.