Foraging of juvenile crappies in turbidity: the difference is black and white

Environmental conditions like turbidity can fluctuate rapidly during the early life of fishes and can impact foraging behaviors, and thus growth and survival. Black (Pomoxis nigromaculatus) and white (P. annularis) crappies have been hypothesized to respond strongly and distinctly to changes in turbidity, with black crappies often thought to respond more negatively than white crappies. To compare effects of three representative turbidity levels (0, 25, and 50 NTU) on juvenile crappie foraging, controlled experiments were used to quantify 1) overall consumption and size selectivity of a single prey type (Daphnia) and 2) prey type selection, total consumption, and energetic value of diets when three distinct prey types (Daphnia, Chaoborus, and Chironomus) were offered. Unexpectedly, black crappies exhibited universally greater diet biomass than white crappies. Black crappies displayed relatively higher prey consumption and were more size selective of a single prey type, whereas white crappies were less size selective and maintained similar overall consumption with increasing turbidity levels. Both species showed similar selection patterns among three prey types at all turbidity levels, preferring Chaoborus and avoiding Chironomus. However, black crappies also avoided Daphnia, whereas white crappies consumed them without preference. Overall, turbidity did not appear to impair the foraging of juvenile crappies