Shifts in Prey Selection and Growth of Juvenile Pikeperch ( Sander lucioperca) over Half a Century in a Changing Lake Võrtsjärv

Abstract

Analysis of historical and recent data is essential to understand how eutrophication and/or climate change might trigger shifts in the feeding mode of fish and trophic dynamics of shallow lakes. To assess long-term changes in the diet and growth of juvenile pikeperch (Sander lucioperca), the prey selection and growth of pikeperch fry from Lake Võrtsjärv was investigated in 2007-2010 and compared with data from 1920 to 1970. Over the observed period, larger cladocer-ans have become less frequent in the diet as eutrophication has altered the zooplankton community. Furthermore, cli-mate change has triggered a mismatch between the predator and its prey: the smelt population has collapsed but other fish fries are too large for YOY (young-of-the-year) pikeperch. However, the mean length of fish has decreased mainly due to the postponed diet shift.