Traits of Biology of European Wels Catfish Silurus glanis from the Volga–Ahtuba Water System, the Lower Volga

Abstract

Seasonal distribution, biology of reproduction, body length/weight composition, age of sexual maturation, and features of feeding in wels catfish Silurus glanis from the Volga River channel areas within the Volga–Ahtuba water systems (the lower Volga) have been studied. Within the study region, wels habitats are confined to the system of river-channel pits and to the deep-water sites of the main river channel; the fish roam within the surroundings of the pits. Wels spawns in the waterbodies of the subordinate system of the river: eriks (shallow channels) and branches between the Volga and Ahtuba rivers. In the study region, wels is represented by a long-lived late-maturing group. The fish of different body lengths/weights differ in the feeding modes: the specimens with body weights of <5 kg consume various small-sized prey, including nonfish food; larger individuals feed on large fish prey. Comparative analysis of the structures of wels populations from the Volga River delta and channel areas revealed considerable differences indicating the presence of two spatial groups of the population or subpopulation ranks: deltaic migrant and river channel settled. Development of an optimal strategy for exploitation of this valuable fish necessitates a differentiated approach and detailed analysis of biological traits of this species within the Volga basin. Such analysis should include population-genetic methods.