On the physiological-biochemical state of kilka Clupeonella cultriventris (Clupeidae, Clupeiformes) in Rybinsk Reservoir (Russia)

Abstract

The results of studies into lipid total content and fractional composition in the tissue and wholebody levels in kilka (Clupeonella cultriventris) are given. The fish studied belonged to various size-age groups and were sampled in Rybinsk Reservoir during active feeding periods in 2002 and 2005. A trend was revealed of deterioration of the physiological-biochemical state in adult specimens of this invasive species. This was especially true of the modal (in terms of their proportion in population) two-year-old fish. This was evidenced by a decrease in contents of total and reserve (triacylglycerol) lipids in fish muscles during the whole study period. It is shown that, in young kilka caught in all reservoir stretches in autumn, the values of these parameters depend on the time and rate of the reservoir water level decrease during the active feeding period. Probable reasons for changes in the physiological-biochemical state in adult and young specimens in the kilka population are discussed. The discussion is in view of the recent state of the Rybinsk Reservoir ecosystem which undergoes successional modification of the pelagic zooplankton community both at the level of large taxa and of some dominant species.