SPECIFIC FEATURES OF FEEDING EUROPEAN VENDACE COREGONUS ALBULA (L.) IN RYBINSK RESERVOIR

The article describes Coregonus albula (L.) inhabiting the open pelagial of the Main reach and the river reaches of the Rybinsk Reservoir together with other fish species that form the feeding colonies of planktophagous fish. The feeding spectra of vendace for the summer-autumn period are determined. Mass species of cladocerans are present in the diet of fish feeding in the productive biotopes of the main reach of the reservoir, in the zones of stable high concentrations of feed invertebrates in the summer, during the maximum development of zooplankton. In this period of the year there dominate Bosmina zooplankton (the relative significance ratio in nutrition (IR) varies from 67.2 to 98.5%), Daphnia species (IR 98.1%) and Bythotrephes species (22.1%). The diet of vendace is more diverse in the estuaries of large tributaries of the river reaches. There they feed on the larvae and adults of amphibiotic insects Chironomidae, Simuliidae and Syrphidae, whose larvae live on the bottom, while adult insects keep a ground-air lifestyle. An invasive amphipod species Gmelinoides fasciatus presents in the diet of vendace in the near-dam zone of the reservoir in autumn. The appearance of benthic organisms in the nutrition of vendace in the autumn period coupled with a significant decrease of plankton invertebrates in the diet may be explained, on one hand, by a seasonal decrease in the biomass of zooplankton in the reservoir’s pelagial and search for new forage places, and, on the other hand, a food competition from the another plankotophage, the Ponto-Сaspian kilka. Despite the fact that vendace is morphologically adapted to feeding on small invertebrates in the water column, it demonstrates a certain degree of plasticity in the selection of food organisms in the Rybinsk reservoir, and its feeding spectrum changes depending on the season and productivity of the reservoir

Quantitative and Qualitative Composition of Diet of the Ural Owl, Strix Uralensi (Strigidae, Strigiformes), in the Central Part of European Russia (The Example of the Republic of Mordovia)

The results of the study of the Ural Owl feeding spectrum are presented. In Russia the Ural owl eats over twenty species of mammals, thirty bird species and a number of animals of other classes. The research tasks included the identification of the species of the victims of a large owl in Mordovia, their quantitative data and the characteristics of osteological material from pellets. It was found out that mammals, in particular rodents, are the basis for the Ural owl food. The Ural Owl’s diet consists mainly of gray voles (47.7 %). On the second place there is a red vole (31.4 %). The share of mice is only 7.3 %. Th e predator hunts for the forest mouse most oft en. In pellets the mass fraction of bone remains varies in the range from 3.4 to 44.8 %. Th e average proportion of bone remains is, as a rule, up to 25 %, with the content of only one or two small rodents in pellets; the remains of three to six individuals - up to 45 % of the weight of dry pellet. Among all the bones of mammals, the lower jaws, femoral and tibia bones give the greatest information about the number and composition of victims of the Ural owl. In pellets the brachial and nameless bones of the victims are presented in smaller numbers.

Feeding ecology of the non-indigenous fish Hypomesus nipponensis in Lake Ulungur, China: insight into the relationship between its introduction and the collapse of the native Eurasian perch population

Studies of feeding ecology are essential in gaining an understanding of how established non-indigenous fish species interact with the invaded communities. In the present study, we investigated the composition and seasonal variation in the diet of the introduced Japanese smelt Hypomesus nipponensis, a small planktivorous fish, in Lake Ulungur, China. The objective was to examine the ecological role of this established non-indigenous smelt through the analysis of its diet, which might give more insight into the relationship between its introduction and the collapse of the native Eurasian perch population. Results showed that the Japanese smelt had a broader feeding spectrum than had been previously reported. Of 10 taxonomic or ecological categories of food, cladocerans (54.70%) and rotifers (15.39%) were the most important food items in terms of the index of relative importance (IRI), whereas surface food and chironomid larvae were the most important by weight. Although cladocerans were consistently the most important food, rotifers and copepods, together with surface food and chironomid larvae, substituted when cladocerans were scarcer. Because both rotifers and chironomid larvae are important food of larval and young perch, introduction of Japanese smelt into the lake might be responsible for the collapse of the perch population because of the suppression of rotifers and chironomid larvae in spring through seasonal predation.

Feeding habits and morphometry of Iheringichthys labrosus (Lütken, 1874) in the Uruguay River (Uruguay)

Body size and diet of organisms are fundamental attributes which determine their ecology and natural history. Iheringichthys labrosus is one of the most common fish species of the Uruguay River. However, its natural history is poorly known and there is little information about its diet and interactions with other species. This paper describes the feeding habits of this species, relating feeding patterns to the size classes and morphometry of individuals and to the temporal variations. Fishes were captured in May and November of 2006 in three zones of the lower Uruguay River. A total of 101 stomach contents was analyzed (standard length: 60-224 mm). The species exhibited a broad feeding spectrum with most items belonging to the benthic community. We found significant diet differences between size classes and studied months. However, we have not found a close relationship between changes in morphometric variables and diet shifts between size classes.

The diet of Scinax angrensis (Lutz) tadpoles in an area of the Atlantic Forest (Mangaratiba, Rio de Janeiro) (Amphibia, Anura, Hylidae)

Scinax angrensis (Lutz, 1973) is an endemic species, which occurs in low altitude hillside forests, distributed from the municipalities of Mangaratiba to Parati in the south of the state of Rio de Janeiro, Brazil. The aim of this study was to compare the morphology of S. angrensis tadpoles in two different stages of development, and verify their feeding spectrum. The mouth morphology of the two stages studied (27 and 37) appeared similar, with a difference in the size of the oral opening as well as an increase in the dimensions of the body. The examined species presented a trophic spectrum comprised of algae, protozoan, rotifers, microcrustaceans, nematodes, vegetation and invertebrate remains, fungus hyphae, and sand grains. Significant differences were found between dimensions of the two stages, but not between diets, although a differentiated preference with regards to planktonic items has been verified. The results suggest that the partitioning of feeding resources is not only related to morphology and occupation of different microhabitats but also to the feeding behaviour of tadpoles. The relevance of important food items to the natural diet of S. angrensis tadpoles, especially the diatoms and filamentous algae, reveal the importance of the periphytic community to the conservation of this species in the Atlantic Forest.