Triploid landlocked Atlantic salmon (Salmo salar) were identified using microspectrophotometry to measure the DNA content of Feulgen-stained erythrocytes. Blood cell sizing by means of a Coulter Counter Channelyzer was a highly effective alternative for screening triploids, comparable with flow cytometry in speed and accuracy. The statistical analysis of various erythrocyte dimensions measured from blood smears was also a valid method for identifying triploids. No mosaic polyploids were found, and the existence of such fish is questioned.