Morphometric and meristic variability among North American Atlantic salmon (Salmo salar)

To investigate the morphometric and meristic variation of Atlantic salmon (Salmo salar) in North America, juveniles from 16 anadromous and 5 nonanadromous populations were collected from an area extending from Labrador to New York state. The findings from the analysis of these characters were supplemented by an examination of malate dehydrogenase variation on a subset of specimens from selected populations. Newfoundland – Labrador and Gaspé – Maritime populations were found to belong to distinct regional stocks. This conclusion was supported by the accuracy of the morphometric discriminant function and a discontinuity in Mdh-3,4(100) allele frequencies. The lack of a clinal relationship between morphometric characters, latitude, longitude, and number of degree-days above 7 °C also suggested a pattern of distinct regional stocks. Considerable overlap among populations was found for meristic characteristics, and these were considered unsuitable for stock identification purposes. While no somatic differences were found between anadromous and nonanadromous populations, there were significant differences in Mdh-3,4(100) frequencies. The congruence of morphometric and malate dehydrogenase characteristics in delineating regional stocks emphasizes the importance of a multiple character approach in solving stock identification problems.