Date of this Version
Diet variations of black crappie (Pomoxis nigromaculatus) and white crappie (Pomoxis annularis) were investigated at Hayes Center State Lake, a turbid 20-hectare state lake in southwest Nebraska. Zooplankton and insects accounted for most of the diet of all black crappie and of white crappie less than 200 mm long. The daily ration of planktophagic crappie declined to 1.3% as both species approached a length of 200 mm. Black crappie longer than 200 mm did not convert to fish and the daily ration declined to 0.8%. The dietary shift of white crappie to fish significantly increased the average volume of food as the daily ration increased to 1.6 and 2.9% at 200-249 and ≥250 mm, respectively. Crappie growth and survivorship were affected by the nature of the food. White crappie were 2.4 times more numerous and grew faster with improved survival at Age IV compared to the less dense black crappie population. Mortality rates of black crappie related positively to their size and water temperature during the growing season. Many black crappie longer than 200 mm died during July and August at 26-28 C; 71, 89, and 100% mortality of respective 200-209, 210-219, and 220-229 mm black crappie was estimated during summer. Black crappie (≥200 mm) were less adapted to capturing fish in turbid water, resulting in an energy trap during summer. The ability of ≥ 200-mm white crappie to prey on fish increased the daily ration above maintenance level during summer.