抄録
For the purpose of elucidating the stock system of fish group chiefly composed of 4 year-old fish found around the area of the Ayan in the summers of 1971-1973, fork lengths and scale patterns of 4 year-old fish taken from the different areas in the northern part of the Okhotsk Sea were examined. It was confirmed that the mean fork length of 4 year-old fish around the area of the Ayan was consistently about 1 cm smaller than that of the eastern area of the Okhotsk. Scale patterns also differ considerably among areas and they are divided roughly into the two types of Tauisk and Ayan. The results of analyzing the ratio of distance among the annuli and the fork length estimated at the 1st annulus formation indicate that these two 4 year-old groups with the different scale patterns had lived under different circumstances after the first year of life. However, these fish groups are not always isolated from each othe through the stages in development. Comparison of scale ratio Ri/fork length relationships shows that fish group in the area of the Ayan in 1973 is mixture, which arose during the third year of life, of fish with the different scale pattern of Tauisk and Ayan types.
Otherwise, it was found that the fish with the specific values of scale ratio r2/r3 could be used as an indicator of presence of fish appeared around the area of the Ayan in each year.
