Communities of the cottoid fish (Cottoidei) in the areas of hydrothermal vents and cold seeps of the abyssal zone of Baikal Lake

The hydrothermal vent in Frolikha Bay and the methane cold seep “Saint Petersburg” in Baikal Lake are characterized by the highly productive communities of the aquatic invertebrates and cottoid fish (Cottoidei). The benthic and pelagic ichthyofauna of the vent comprises twelve key species belonging to eight genera, while that of the seep comprise eight species (six genera belonging to three families). The only one obligate hydrothermal species, N. thermalis, has been found; it dominated by abundance (91.6% of total abundance) in Frolikha Bay. N. werestschagini dominated in the cold seep community (39.5%). The spatial distribution of the fish around the hydrothermal vents and the cold seeps was patchy. The largest schoolings has been observed in two biotopes, in the areas of the silty bottom sediments and at the areas covered by the bacterial mats, as well as in the near-bottom water layer.