The Locomotive and Metabolic Strategies of Goldfish Under Different Dissolved Oxygen Level

To investigate the locomotive and metabolic adaptive strategy of euroxybiotic goldfish(Carassius auratus) under different dissolved oxygen level(DO),we measured the resting metabolic rate(RMR),active metabolic rate(AMR),critical swimming speed(Ucrit) and cost of transport(COT) at different swimming speed of juvenile experimental fish(6.75～13.70 g,n=49) maintained at water temperature of(25.0±1.0) ℃ under DO of 0.5,1,2,4 and 8 mg·L-1(close to 100% saturation).The results are discovered in that both Ucrit and AMR decreased profoundly with DO and there are significant differences among all treatment groups(p0.05),but both variables decrease more profoundly within lower DO range and the values of AMR decrease more profoundly than those of Ucrit.However,RMR remain unchang with DO decreased from 8 to 1 mg·L-1 and linearly decreased with DO when it is below 1 mg·L-1.The metabolic rate exponentially increases with swimming speed in all experimental groups.The COT does not vary with swimming speed in lower DO groups(0.5,1 and 2 mg·L-1 experimental groups) while it increases with swimming speed at higher DO groups(4 and 8 mg·L-1 experimental groups).After removing the energy component of RMR from COT,the COTnet increases with swimming speed in all experimental DO groups.As in the same swimming speed,COT of lower DO groups usually are lower than those of higher DO groups in lower swimming speed range.Moreover,such difference vanishes when swimming speed goes higher.The study shows that goldfish may adopt different locomotive and metabolic strategies under different ambient DO level.