The State of Thermophylic Ichthyofauna in the Water Bodies of Arkhangelsk Oblast: Report 1. Formation and Distribution

Materials determining the possible pathways of Arctic zone colonization by representatives of thermophilic ichthyofauna are presented. The previously proposed hypothesis that the fish of the thermophilic complex that lived in the White Sea basin during the Subboreal period (sterlet, blue bream, common rudd, white-eye bream, and asp) and were considered extinct during the subsequent cooling in the Subatlantic period, adapted to changed conditions, stayed in particular areas of their range, and became part of the modern ichthyofauna in limited numbers have been elaborated and confirmed. The possible pathways of spontaneous introduction of the Caspian thermophilic species, white-eye bream, and asp to the Northern Dvina basin are considered. Populations of rudd and blue bream, rare thermophilic species for the region, have been detected and studied in the lakes of the Kenozersky National Park. Rudd, a relict species of the Holocene thermal maximum, was previously recorded only in several floodplain lakes of the middle reaches of the Northern Dvina River. The Kenozero population of rudd is the first case of finding epresentatives of this species in the Onega River basin. Blue bream can be also considered a relict found in the territory of the region only in one lake system of the Kenozersky National Park and several small lakes of the Siysky State Nature Reserve.