European whitefish Coregonus lavaretus of the Nizhnetulomskoye Reservoir (Tuloma River basin, Murmansk region) and its habitat conditions

Abstract

The modern biological characteristics of the most common polymorphic species of European whitefish Coregonus lavaretus (L.) in Northern Europe were studied in the conditions of its habitat in the oldest riverbed reservoir in the Murmansk region. A number of features of the functioning of the ecosystem of the Nizhnetulomskoye Reservoir (hereinafter NTR) have been identified, including eutrophication of the reservoir, accompanied by the development of cyanoprokaryotes in phytoplankton communities, including potentially toxic species. The introduction of the Onega smelt Osmerus eperlanus (L.) into the Tuloma River system half a century ago led to the transformation of the structure of the NTR fish community from whitefish-salmon to whitefish-smelt. Whitefish (hereinafter, this species name is only used in regard to the European whitefish) in the NTR are represented by a polymorphic population and, according to length-weight characteristics, belong to the group of medium-sized whitefish of the Murmansk region watercourses with early maturation. Based on the type of feeding, it can be classified as a benthophage with a wide range of consumption of food organisms. The stomach contents of whitefish in the summer-autumn period correlate well with the seasonality of the development of aquatic invertebrates. Artificial feeds used by the farms of rainbow trout Oncorhynchus mykiss (Walbaum) in the reservoir are currently of great importance in the feeding of the NTR whitefish. Understanding the mechanisms of structural and functional differentiation of whitefish populations is both of fundamental importance in revealing the mechanisms and direction of microevolution and adaptation of fish in changing environmental conditions and of fundamental practical importance in the implementation of protection and rational fishing, their artificial reproduction.