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北海道東部沿岸域の野付湾, 風蓮湖, 厚岸湖(2標本), 湧洞沼に産卵する太平洋ニシンの標本を用い, 体節的形質を用いた形態的方法およびアイソザイムを用いた遺伝的方法で系群を判別した。その結果, 形態的にも遺伝的にも湧洞沼で産卵する標本群のみが他と異なった。これは湧洞沼での産卵時期が4月下旬から5月上旬と, 他よりも約半月遅いことが要因となっているものと考えられた。湧洞沼以外の標本群間での形質の差違は, 厚岸湖の2標本間の差違と同程度であったため, 同一系群であることが示唆された。
In order to clarify population structure of local herring in eastern Hokkaido, and to design an effective release program of seed fish artificially cultivated in aquariums, five samples of Pacific herring, Clupea pallasii, were caught from four spawning grounds. Six meristic characters were counted and statistically analyzed. Furthermore, allele frequencies of two enzymatic loci, GPI and PGM, were examined by using a starch gel electrophoresis. The sample from Yudo Lake had significantly fewer numbers in the upper and the lower gill rakers than in the others. A cluster analysis using the six meristic measurements on five samples showed that there are two local populations in the eastern Hokkaido, i. e. Yudo population and others, the former was a morphologically specific population different from the latter. In addition, Nei's genetic distances using allozyme data of the two loci also suggested that the Yudo sample is the farthest distances from all other samples. It is suggested that the singular characteristics of the Yudo population were connected with a later spawning time in this ground than in others.
