From the study of chemical data, collected during the summer of 1963, six lakes in west central Manitoba were classified according to chemical type. With the addition of physical and morphometric data, a trophic classification was derived. The lakes studied are eutrophic-saline-glacial lakes, of the sulphate type. A study of numbers of certain meristic characters, vertebrae and rays of mesial fins, in the yellow perch, Perca flavescens (Mitchill), in relation to increasing salinity indicated that, at the concentrations encountered, this environmental factor could not be related to numerical changes in some of the meristic characters of this species.