CHANGES OF THE PREFERRED TEMPERATURE IN S TRIPED BEAKPERCH, OPLEGNATHUS-FASCIATUS, DURING THE JUVENILE GROWTH

Temperature preference of 2-14 month old striped beakperch, Oplegnathu s fasciatus, (B.L. 3.3 -14.9 cm) hatched on the same day was tested us ing a vertical temperature gradient tank. Fish were acclimated to 25 d egrees C for more than 18 days before the experiments. Temperature was a dominant factor affecting fish distribution in a vertical temperatu re gradient, since the distribution was shifted in accordance with the location of preferred temperature. No clear change in the preferred t emperature was shown with exposure to the temperature gradient for mor e than 24 hours. The preferred temperatures were related to the growth of the fish. Two to eight month old fish preferred a progressively co oler temperature from 28.6 to 24.7 degrees C as they grew. Fish older than 8 months preferred a narrower temperature range of 25 and 26 degr ees C.