FOOD RELATIONS BETWEEN WHITEFISH SPECIES IN THE LOWER COURSE OF THE USA RIVER IN THE AUTUMN PERIOD

Abstract

Feeding characteristics of the Siberian whitefish (pizhyan) and the White Sea least cisco in the Usa River, which is one of the main right-bank tributaries to the Pechora River, are considered. It has been found that while the food spectrum was quite wide (23 groups of food items), the bulk of the diet was made up of invertebrates in various developmental stages, as well as the blue-green colonial algae and indigestible particles. Analysisof the weight shares of the components showed that the biggest contributor to the whitefish diet was aquatic larvae of insects of the Chironomidae family (60.0 %); and in the diet of the least cisco this index was the highest for adult Simuliidae (43.0 %). No significant age-related differences in feeding were found in either of the two species. Their food spectra differ significantly both in terms of the main ontogenetic stages of invertebratesand the main groups of food items, wherefore the trophic tension is low. Low values of the food similarity index and trophic niche overlap indicate a weak competition for foodbetween these fish species in the autumn period. The whitefish acts as a typical benthos feeder with a broad food spectrum, while the least cisco is euryphagous, easily switching between various groups of food item when necessary.

Keywords

• usa river
• general feeding patterns of the siberian whitefish (coregonus lavaretus pidschian) and the white sea least cisco (coregonus sardinella marisalbi)
• age-related changes in feeding
• frequency of occurrence
• relative significance index
• food relati