Threadfin shad (Dorosoma petenense) impingement at the Tennessee Valley Authority's Cumberland Steam-Electric Plant followed a seasonal pattern related to the abundance and length distribution of young-of-year fish. Electrofishing samples taken near the plant showed a similar pattern. The number ofimpinged fish (larger than 50 mm) decreased rapidly with increasing length due to reduction in abundance by natural mortality. Impingement mortality was found to be length dependent. Most individuals. less than 50 mm in length passed through the screens, while increasingly larger individuals were more likely to become impinged. Impinged fish less than 100 mm total length tended to be more plump than fish collected in rotenone samples, while impinged fish larger than 100 mm tended to be in poorer condition.
