GROWTH, OXYGEN-CONSUMPTION AND ACTIVITY OF JUVENILE TURBOT (SCOPHTHALMUS-MAXIMUS L) REARED UNDER DIFFERENT TEMPERATURES AND PHOTOPERIODS

Juvenile turbot (5-125 g) were reared under two experimental temperatu res: 10 degrees C and 16 degrees C, and three experimental photoperiod s: LDN (natural photoperiod), LD16:8 (16 h light: 8 h darkness), LD24: 0 (continuous light), to study effects of temperature and photoperiod on growth, activity and oxygen consumption. Growth was strongly affect ed by temperature and was higher at 16 degrees C than at 10 degrees C. Continuous light had a growth-promoting effect at 10 degrees C from m id-December to late March, while at 16 degrees C this effect was restr icted to December and January. A seasonal change in the condition inde x was found. The groups reared in continuous light had higher conditio n indices in winter. The experimental groups held at 16 degrees C had a higher O-2 consumption than those at 10 degrees C. The LD24:0 groups invariably had a higher overall O-2 consumption than did the LDN and LD16:8 groups, the differences being caused by reduced O-2 consumption in the latter groups during darkness. The LD24:0 groups displayed hig her activity than the LDN groups, in which activity was very low at ni ght.