Contribution of organic matter sources to cyprinid fishes in the Chany Lake–Kargat River estuary, western Siberia

Abstract

Although omnivorous cyprinid fish often dominate fish communities in shallow eutrophic lakes, their role in the food web is poorly known. In the present study, carbon sources of six cyprinid species were examined in a littoral freshwater habitat in a saline lake complex (Lake Chany, western Siberia, Russia) using stable isotope analyses (SIA). In this habitat, microalgae (phytoplankton and epiphytes), macrophytes and riparian vegetation comprised the major producer groups with distinctive δ¹³C values. Zooplankton and most benthic invertebrates functioned primarily as microalgae-based consumers, whereas the amphipod Gammarus lacustris depended largely on macrophytes or macrophyte-derived detritus. Cyprinids, Carassius carassius L., Car. auratus gibelio Bloch. and Abramis brama L., mainly utilised microalgae-derived carbon (δ¹³C-based isotope mixing model: 66–97%) via zooplanktonic trophic mediations. In contrast, Cyprinus carpio L., Leuciscus idus L. and Rutilus rutilus L. depended more on macrophytic and/or riparian production (52–80%) than on microalgal production. Observations and SIA of foregut contents indicated highly opportunistic feeding habits of R. rutilus and L. idus and preference for macrophytes. These results suggested that cyprinid fishes link pelagic, benthic and riparian food webs in this shallow, eutrophic lake ecosystem.