A concise review of geographic variation in adult body size in anadromous masu salmon, Oncorhynchus masou

摘要

Adult body size (size at maturity) is one of the key life history traits and is well known to sometimes correlate with latitude in anadromous salmonids. However, it is poorly understood whether geographic size patterns except for latitudinal trends occur or why such patterns have been shaped. The present paper briefly reviewed body size variation between anadromous returns of masu salmon Oncorhynchus masou in the Okhotsk group (10 populations along the Sea of Okhotsk coast), the Pacific group (2 populations along the Pacific Ocean coast) and the Sea of Japan group (24 populations along the Sea of Japan coast). The Okhotsk group was smaller than the Sea of Japan group. Although the statistical analysis detected no differences among the remaining combinations, the Okhotsk group was possibly smaller than the other groups because the size of the Pacific group seemed to be within range of the Sea of Japan group but tended to be larger than that of the Okhotsk group. Future research should first test whether size at maturity genetically differs between the Okhotsk group and the other two groups to explore further evolutionary factors shaping geographic size variation.