THE EFFECTS OF DISSOLVED OXYGEN LEVELS ON RESTING OXYGEN CONSUMPTION AND SWIMMING PERFORMANCE IN JUVENILE DARKBARBEL CATFISH PELTEBAGRUS VACHELLI

To test the swimming performance,locomotive limiting factors and metabolic adaptive strategy of darkbarbel catfish Peltebagrus vachelli under different dissolved oxygen levels(DO),the effects of DO(125%,100%,75%,50% and 25% air saturation) on resting oxygen consumption rate(MO 2),critical swimming speed(U crit) and MO 2 at different swimming speeds up to U crit were investigated in juvenile darkbarbel catfish at 25 o C.Resting MO 2 decreased significantly with DO(P0.05),and the critical DO point([O 2 ] crit) for resting MO 2 was 14.52% air saturation(1.16 mg/L).The active MO 2 decreased significantly with the decrease of DO from 100% to 25% air saturation(P0.05);the U crit decreased significantly when DO fell below 75% air saturation(P0.05);neither U crit nor active MO 2 showed any elevation under hyperoxic conditions(125% air saturation);and the cost of transport(COT) was significantly lower under 25% air saturation than that of other groups at corresponding swimming speeds(P0.05).These results suggested that the swimming performance of darkbarbel catfish was limited by the cardio-respiratory system under hypoxia,while it was limited by the peripheral locomotory organs and musculature under normoxia.