Seasonal and diel patterns of may fly (Ephemeroptera) drift in korge stream, latvia

A complex set of biotic and abiotic factors affects a drift. Mayfly drift has been extensively studied worldwide, but the manner in which the environmental factors interact is not completely clear. The aim of the present study was to characterize mayfly seasonal and diel drift patterns in relation to abiotic factors in a mediumsized lowland stream in Latvia. Drift samples were collected at three-hour intervals in a riffle section in May, August and September 2007. Distinct seasonal and diel patterns of the mayfly drift were observed in the Korge stream. These were not directly infuenced by primary hydraulic factors e.g. current velocity and discharge, but depended on the active growth period of the mayfly species.