Feeding Features of the Nine-Spined Stickleback Pungitius pungitius (Gasterosteidae) In Water Bodies of the North-West of Russia

Abstract

The diet of the nine-spined stickleback Pungitius pungitius has been studied in two water bodies in the north-west of Russia: in the subarctic lake Krivoe (Karelia) and the estuary of the Neva River (Leningrad Oblast). Diptera larvae (Chironomidae, Ceratopogonidae, Simuliidae, and Limoniidae) and planktonic crustaceans formed the basis of the food bolus of fish; however, their abundance and weight ratios differed in the studied water bodies. The seasonal changes of the dominant groups of food objects of the stickleback of Lake Krivoe have been revealed. Additionally to invertebrates and fish eggs, which form the basis of the stickleback diet in winter season, aquatic mosses as well as filamentous and diatom algae present in the fish diet in summer. The comparison of the nitrogen isotope composition of the muscles of stickleback, perch, and invertebrates shows that the stickleback of Lake Krivoe occupies the third trophic level, approaching predatory fish in δ15N values (5.2–8.6‰). A specific feature of the diet patterns of P. pungitius is the transition from a diverse diet of the summer–autumn period to a monotrophic animal diet (chironomid larvae and fish eggs) of the under-ice winter–spring period.