Changes in body length and proportion of mature fish at first spawning age in relation to strength of year class in the Ishikari Bay herring (Clupea pallasii Valenciennes)
2010
Takayanagi, S., Hokkaido. Central Fisheries Experiment Station, Yoichi (Japan) | Yamaguchi, M. | Ishida, R.
Annual changes in body size and the proportion of mature fish at first spawning age (1 year old) were examined for the Ishikari Bay herring (Clupea pallasii) on the basis of samples collected during January and March from 1998 to 2007 in offshore waters, near the main spawning ground along the Sea of Japan coast in Hokkaido. The proportion of mature females varied from 27% (in the 2001 year class) to 100% (in the 1996, 1999 and 2002 year classes). Average fork length ranged from 217 mm (in the 2001 year class) to 245 mm (in the 2002 year class). On the other hand, the abundance of 1-year-old fish was extremely high in the 2001 year class and relatively low in the 1996-2000 and 2002-2003 year classes, and at a medium level in the 2004 and 2005 year classes. Spearman's rank correlation revealed significant correlations among the proportion of mature females, average fork length and stock number. These results suggest that body size and the proportion of mature fish are closely associated with strength of year class.
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