Diel feeding periodicity in larvae of the vendace (Coregonus albula L.) and influence of food availability and environmental factors on food intake

Abstract

Abstract— Samples were taken every 2 h for 10 days to determine diel foraging periodicity of vendace larvae in the littoral zone of Lake Lentua, northern Finland and to assess environmental factors affecting food intake. Feeding was associated with daylight conditions, so feeding ceased in the dark. Soft‐bodied, rapidly digested rotatorians indicated the periodicity more clearly than hard‐shelled prey such as cladocerans and copepodites. Wind events and waves in the littoral zone were the major factors affecting food abundance and feeding by the larvae. Waves induced by strong inshore winds reduced zooplankton density, increasing the occurence of larvae with empty guts to 80%. Reduced food availability was reflected in the guts of larvae within 6 h. The density of suitably‐sized zooplankton, together with wind effects and photoperiodism, explained most of the variation in gut content in the larvae.