北海道春ニシンの親子の量的関係および地域的漁況の変動について

抄録

1) Taking the total catch C of a certain year as the index of the amount of parent spawners in that year and as the index of the year-class size spawned by these parent spawners we take the accumulated catch V of this year-class throughout its life in fishery, the dots of the calculated log V/C for the corresponding values of C shows a tendency of gathering in the following periods: (A). 1907-1921, (B). 1922-1931, (C). 1932-1948, and (D). 1949-1954.
2) Within each period a linear relationship between log V/C and C was obtained except in period (B). The level of the relationship of log V/C and C shows a gradual decreasement from period (A) onward and the heterogeneity of regression coefficient is highly significant, yet the fitting of reproduction curve that was proposed by Ricker is not fit so well except in period (D).
3) No significant difference between the variance about the arithmatic mean and that about the reproduction curve can be recognized, except in period (D), but the gradational decreasement of mean values in periodical order is apparent. Each period possesses a different level of relationship between the parent spawners and the resultant year-class spawned by them, even though it is obvious the variation of the year-clss size within the period is large.
4) Within each period there is a tendency for the extremely poor year-class to be associated with an abundant catch or a poor catch and that dominant year-class to be associated with a medium or a rather poor catch.
5) The gradational decreasement of the level of the relationship between the parent spawners and the resultant year-class spawned by them is coincidental with the gradational reduction of local catches towards the northern area only.