Inhibitory control of maturation in 0-year-old Rheopresbe kazika in high-density rearing conditions was examined using 3 replicate trials. In each trial, 4 groups of 52 fish at 90 days after hatching were reared in four 150 liter tanks. Juveniles at 180 days after hatching were reared in the following 4 different conditions：1) duration of lighting and water temperature were not treated (control), 2) duration of lighting was not treated but water temperature kept at 22℃ (heating treatment), 3) duration of lighting was extended but water temperature not treated (long-day treatment), 4) both extended duration of lighting and water temperature kept at 22℃ (long-day and heating treatment). These experiments were continued until 300 days after hatching. Gonad indices in the control condition were higher than the other rearing conditions, and those in the long-day and heating treatment condition were lower than the other rearing conditions. Therefore, it seems that the rearing method of maintaining the duration of lighting at long-day and water temperature kept at 22℃ is an available method for inhibitory controlling 0-year-old of R. kazika in an immature condition in high-density rearing.
Inhibitory control of maturation
Cottus kazika
Rheopresbe kazika
Heating condition
Long-day condition