Feeding efficiency of planktivorous perch Perca fluviatilis and roach Rutilus rutilus in varying turbidity: an individual-based approach.

The feeding rate of perch Perca fluviatilis showed high individual variation at low and moderate turbidities, when one individual had consumed more Daphnia pulex than any other fish, whereas no such variation in feeding efficiency was observed with roach Rutilus rutilus. There was a significant decrease in total consumption of D. pulex by P. fluviatilis with increasing turbidity, but no correlation was observed in the case of R. rutilus. The results suggest that the difference in the ontogeny of P. fluviatilis and R. rutilus may be detectable as behaviour-related species-specific trait differences in the early planktivorous feeding stage of the two common species.