Clinal Variation in Scale Characters of Atlantic Salmon (Salmo salar) Based on Discriminant Function Analysis

Abstract

Scales of adult Atlantic salmon (Salmo salar) were collected from 18 river systems in eastern North America from 55°33′N in Labrador to 44°33′N in Maine and to 44°23′N in Nova Scotia during 1968, 1973–75. Analysis of four scale characters, namely circuli in first annual river zone, circuli in second annual river zone, smolt age, and circuli in first annual marine zone, demonstrated that significant differences occurred in each of these characters between river systems and latitude. The numbers of circuli in each of the three growth zones increased from north to south, while the smolt ages decreased from north to south. A discriminant function applied to these four characters employing latitude as a "dummy" variable indicated that the discriminant function contributed significantly to the clinal trend and 73.7% of the total variation was explained by this discriminant function. Key words: adult Atlantic salmon; scale characters; salmon; latitudinal cline, scale characters; clinal discriminant function