Foraging of Juvenile Crappies: The Difference Is Black and White

Turbidity can fluctuate rapidly during the early life of fishes, impacting foraging behaviors, and thus growth and survival. Black and white crappies have been hypothesized to respond strongly and distinctly to increased turbidity, with black crappies thought to respond more negatively than white crappies. To compare effects of three representative turbidity levels (0, 25, and 50NTU) on juvenile crappie foraging, controlled experiments were used to quantify 1) overall consumption and size selectivity of one prey (Daphnia) and 2) prey type selection, consumption, and energetic value of diets for three distinct prey types (Daphnia, Chaoborus, and Chironomus). Black crappies exhibited universally greater diet biomass than white crappies. Black crappies had higher prey consumption and were more size selective of Daphnia, whereas white crappies were less size selective and maintained similar consumption with increasing turbidity. Both species showed similar selection patterns among prey types in all treatments, preferring Chaoborus and avoiding Chironomus. Black crappies avoided Daphnia, whereas white crappies consumed them neutrally. Observed differences in growth and survival likely result from increased foraging activity in turbidity. Increased energy expenditure for similar foraging return may lead to reduced growth and increased exposure to predators, supporting previous observations.