POPULATION-DYNAMICS AND FOOD OF BLEAK (ALBURNUS-ALBURNUS L) IN THE LITTORAL-ZONE OF LAKE BALATON, HUNGARY

Intra- and interspecific effects together with changing environmental conditions regulate the dynamics of the fragile bleak populations in L ake Balaton. Size- and age-structures, length-weight relationships and mortality were studied on 1493 individuals and growth history were de termined using scales from 703 specimens. The population growth rate w as slow and the basic population parameters showed area variations alo ng the longitudinal axis of the lake. Gut contents were analyzed in 22 4 individuals. The bleak stocks are trophically strongly related to th e littoral zooplankton and benthos; and they play a significant energy -mediating role in the food-webs between the periphytic communities an d fish assemblages in the littoral zone of Lake Balaton.