The spawning season and length at maturity were determined for female blue catfish in Kentucky Lake, Kentucky-Tennessee, where this species is commercially harvested. A gonosomatic index (GSI) was determined from 581 females of 3 length categories: 400-499 mm, 500-599 mm, 2:600 mm. The mean GSI for fish in the largest length category peaked at 3.72% during 1 May-15 May, when water temperature was 20.5° C, and rapidly dropped to 0.21% during 1 June-15 June. Spawning activity in 1986 peaked between 15 May and 15 June. Contributions to reproduction by fish <600 mm were clearly minimal. Population maturity of 241 females was described by the polynomial: Y = 444.88 + 5.88 X - 0.03)(2 (r2 = 0.988) where Y = fish length (mm) and X = percent mature. Females reached the 50% level of maturity at 661 mm and 100% were mature above 722 mm. Estimated ages at these lengths of maturity were 2: 10 and 2:9 years (50% mature) and 2: 11 and 2: 10 years (100% mature) in Kentucky and Tennessee portions of the reservoir, respectively.
