Biological characteristics of anadromous masu salmon (Oncorhynchus masou) in the Kitakami river system and nearby rivers of northeastern Honshu, Japan
1990
Kiso, K. (Tohoku National Fisheries Research Inst., Shiogama, Miyagi (Japan)) | Kasahara, K.
Biological characteristics of anadromous masu salmon collected in the Kitakami River system and nearby rivers were investigated based on body size, gonad weight, egg size and scale patterns. The study was supplemented with additional information from fishermen and anglers. Upstream migration occurs during the period from February to July and occasionally in September, peaking between March and June. This fairly long upstream migration season is the same as in other rivers on Honshu. The fork length of masu salmon caught in the rivers was 53.9 +- 3.8 cm and age was estimated at two years old (including more than one year of freshwater life) based on scale readings. Spawning starts in September and continue until November. 62 out of 63 individuals were female and the estimated fecundity per female was 3895 +- 915. The fork lengths during the downstream migration (mainly March to April) and first annulus formation (October) were estimated at 13.9 +- 2.0 cm and 11.8 +- 1.6 cm, respectively, based on scale patterns and the relation between scale radius and fork length
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