Time of day of spawning in Japanese Spanish mackerel [Scomberomorus niphonius] in the Seto inland sea [Japan]
1990
Kishida, T. (Nansei National Fisheries Research Inst., Ono, Hiroshima (Japan))
The time of day of spawning in Japanese Spanish mackerel Scomberomorus niphonius was investigated. Three investigations were made in the Seto Inland Sea during 1987 and 1989. Relative intensity of spawning at each hour of the day was determined by the number of eggs in early molura and younger stages collected by two plankton nets. The highest peak of spawning appeared within four hours before and after sunset, and the second peak was observed at or shortly after sunrise. The highest peak occurred at 15:00, 18:00-20:00, and 22:00-23:00, respectively. The surface water temperature when the highest peak occurred ranged between 19 and 20 degrees C, though it fluctuated widely during afternoon and night. It is concluded, therefore, that the fluctuation in time of spawning may be caused by the diurnal fluctuation of surface water temperature
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