РАСХОЖДЕНИЕ ТРОФИЧЕСКИХ НИШ У СЕГОЛЕТКОВ ДВУХ СОВМЕСТНО ОБИТАЮЩИХ ВИДОВ РЫБ - ОБЫКНОВЕННОГО ГОЛЬЯНА PHOXINUS PHOXINUS (L.) И ОБЫКНОВЕННОГО ПЕСКАРЯ GOBIO GOBIO (L.)

Abstract

The article gives the results of determining feeding spectra of underyearlings of minnow ( Phoxinus phoxinus (L.)) and gudgeon ( Gobio gobio (L.)) living in the middle flow of the river Kes’ma (tributary of Rybinsk reservoir), as well as limits of feeding biotopes of their juveniles and proportion of structural zones determining their ecological niches at the first year of life. Analysis of similarity and distinction of food composition consumed by fry of both fish species utilizing common foraging resources in the process of sharing the same habitat was performed. It was shown that diet of gudgeon fry is more diverse, compared to minnow fry. Gudgeon was found to forage on invertebrates belonging to seven classes while minnow’s diet comprised representatives of four classes. Food objects common for both fish species were oligochaetes and larvae of amphibiotic insects. Chironomid larvae dominated in the food of both fish species. This can be observed in both the frequency of occurrence of these food items in the digestive tract (100%), as well as in the indices of its mass in the boluses. Species composition of chironomid larvae found in the food of gudgeon and minnow was significantly different. These differences are conditioned by both the biological features of single species such as their confinement to certain micro-habitats as well as the foraging behavior of fish fry. Because of current lack of hydrobiological research in the Kes’ma river, the prelist of invertebrates found in dietary intake of fish fry of the local habitat is considered to have a great practical value.