Responses of White Crappie and Black Crappie to Threadfin Shad Introductions in a Lake Containing Gizzard Shad

Osage State Fishing Lake, Kansas, was stocked with threadfin shad (Dorosoma petenense) at a density of 12.5/hectare in May 1980 and 25/hectare in May 1981 to determine their impact on small lake crappie populations in Kansas. No winterkilled threadfin shad were found in 1980 but, in December 1981, winterkilled threadfin shad ranged from 39 to 120 mm TL. During 1980, the mean growth increment for Age‐1 white crappie (Pomoxis annularis) was 150 mm, a 67‐mm increase over the mean increment for the 1974‐1978 year classes. The mean change in growth increment for Age‐2 and ‐3 white crappie in 1980 was +44 mm and +7 mm, respectively. Black crappie (Pomoxis nigromaculatus) mean growth increased 3 mm for Age 1, but increased 30 mm for Age‐2 and 19 mm for Age‐3 fish. Doubling the stocking density of threadfin shad did not sustain the increased growth of crappie in 1981 and may have increased competition for zooplankton with young crappie. Mean spring condition factor (Wr) of white crappie greater than 200 mm long increased from 66 before threadfin shad introduction to 94 and 91 during the spring of 1981 and 1982, respectively. The 1981 mean spring condition was lower than that observed in October 1980 (102). Mean condition factors for black crappie greater than 200 mm long increased from 88 to 93 after stocking threadfin shad. Like white crappie, there was a decrease from October 1980 to May 1981 of 96 to 93.