In the present paper, we document a previously unknown phenomenon — the feeding of Myotis petax on fresh water pelagic crustaceans. A series of photographs are presented demonstrating the different phases of successful attacks of the bats on the amphipod Macrohectopus branickii. This crustacean, endemic to Lake Baikal, performs vertical migrations in the water column at night and sometimes forms mass accumulations near its surface. The observations presented expand the prey list of the ‘trawling Myotis’ and also supplement the picture of trophic relationships of the pelagic organisms of the ancient and deep Lake Baikal with terrestrial vertebrates.