New material of fish fossils from the west part of Most Basin is described here. Disarticulated and articulated fish remains were discovered in several layers in the Holešice and Libkovice members. Fossil fish occurrence, their taxonomic structure and taphonomy were evaluated in the context of the sediments. The data indicate that conditions in the lake, which formed when the coal swamp was flooded, were variable. Most of the time, the water was well oxygenated; occasionally the oxygen saturation was reduced to hypoxia and even anoxia. Conditions subsequently changed, and the lake became well oxygenated. Especially in the Libkovice Member, the fish-containing layers appear to be characterized by relatively quick sedimentation.