Variation in number of vertebrae and gill rakers of sockeye salmon, Oncorhynchus nerka, in North America

Abstract

The latitudinal, regional, and annual variation in number of vertebrae and number of gill rakers present in sockeye salmon, Oncorhynchus nerka, stocks in North America was examined. Stocks in more northern areas had higher numbers of vertebrae and gill rakers than did those in more southern ones. Significant annual variability in the frequencies of these meristic characters within stocks was observed. When stocks were grouped into three regions (southern, central, and northern), heterogeneity in vertebral and gill raker frequencies was greater among regions than among stocks within the regions. Similarly, heterogeneity was greater among stocks than among sampling years within stocks. Differences in vertebral and gill raker frequencies are only useful for stock identification of sockeye salmon on a broad regional basis.