Vertical Distribution and Habitat Partitioning Between Different Size Classes of Vendace, Coregonus albula, in Thermally Stratified Lakes

Abstract

Diel vertical distribution of juvenile and adult vendace, Coregonus albula, was studied acoustically and by gill netting during summer in thermally stratified lakes in southern Sweden. Daytime distribution of adult vendace was restricted to hypolimnion (minimum 5 °C). During nocturnal vertical migrations, adults moved into the metalimnion, but temperatures greater than 18 °C were avoided. In contrast, juvenile vendace were often found in the warmer and more shallow water of the metalimnion during the day. At night, the juveniles experienced a temperature change of 10° as they migrated into the epilimnion. All age classes had a nocturnal/crepescular diel rhythm. The diel vertical distribution of vendace is interpreted as a response to temperature stratification and to diel changes in light intensities. The different responses of the age classes are influenced by ontogenetic changes in temperature and light preferences as well as by size-related intraspecific interactions.