Predator-Prey Interactions: an Example of Sander Sander lucioperca and Tyulka Clupeonella cultriventris of the Rybinsk Reservoir in Conditions of Climate Warming

Abstract

The food composition of sander Sander lucioperca in the Rybinsk Reservoir was studied during the period of regional climate warming and along with significant fluctuations in the harvests of the southern invasive fish species, tyulka Clupeonella cultriventris. In the period of the relatively low abundance of tyulka (2007–2014) compared to the year following its mass outbreak (2016), the proportion of this species in zander diet was two-fold less (28.3 versus 60.7% of the number of prey consumed). In 2007−2016 tyulka took the first place in the food of sander: its share in the diet in riverbed and floodplain sections of the reservoir was 39.5 and 33.9%, respectively. In 2010 the period of intensive feeding of sander lasted until December inclusive. Compared to the period of the climatic norm, in the younger age groups of sander (3 + −6 +) the dates and places of feeding have changed: they fed on biotopes of open and protected littoral, feeding on juvenile roach Rutilus rutilus. Tyulka, an inhabitant of riverbed zones, remains the main prey for individuals older than 6+.