摘要：The distribution of age 0 percids (perch, Perca fluviatilis and pikeperch, Sander lucioperca) was investigated in a shallow, wellmixed reservoir during a 24-h period in late May, using acoustic and netting methods.Diel vertical migrations (DVMs) were acoustically recorded between the layers close to the bottom and the whole water column.The netting data showed a high abundance of larvae and juveniles at night (nearly 1 ind m-3, or 6 ind m-2), whereas negligible numbers of age 0 percids were present in the water column during the day (3% of night abundance).Age 0 percids remained during the day in the layer very close to bottom.Smaller pikeperch larvae dominated the pelagic age 0 fish assemblage during daylight, while larger perch prevailed at night.A strong difference between day and night abundances along with a clear pattern discerned by acoustic methods revealed the DVM of age 0 percids.Analyses of the fish digestive tract contents indicate that DVM was not governed by feeding behaviour, but rather a defensive strategy against predation.This is in agreement with the size distribution of age 0 percids, since they were smaller in water column during the day as opposed to the night.
