Populations of the European Smelt Osmerus eperlanus (Osmeridae) in Small Lakes of the Vologda Oblast, Russia

Over a 160-year period of research into water bodies, the European smelt Osmerus eperlanus and above all dwarf form of European smelt (a small, short-cycle form of the species) have been recorded in 23 small lakes in the Vologda Oblast, Russia. Currently, this species is found in lakes Svyatozero and Ananyino (Vashkinsky District) and Lake Svyatoe (Kirillovsky District). The main reason for the survival of smelt in these lakes is temperature stratification with high content of dissolved oxygen. The maximum fish body length by Smith reached 18.2 cm in Lake Svyatozero, 16.3 cm in Lake Ananyino, and 17.9 cm in Lake Svyatoe; body weight, 42.1, 28.5, and 38.5 g, respectively; maximum age, 10+, 8+, and 6+. According to the complex of population characteristics (morphological features, size-age composition, growth rate), the studied European smelt populations in small lakes of the Vologda Oblast belong to its large form and differ significantly from dwarf (lake) form of European smelt Osmerus eperlanus eperlanus m. spirinchus inhabiting lakes Beloe and Vozhe. The smelt’s diet includes larvae and pupae of the genus Chaoborus, larvae of the family Chironomidae, Mysis relicta, zooplankton, ostracods (Ostracoda), and fish.