| Swimming behaviors and energy metabolism of juvenile Barbodes schwanenfeldi of twosizes group L was 0.126(±0.008) kg and group S 0.063(±0.005) kg in four water currentvelocities, 0.00 m·s-1, 0.10 m·s-1, 0.30 m·s-1 and 0.50 m·s-1, were studied, with the aim toinvestigate the influence of water current on juvenile B. schwanenfeldi from the angle of fishethology and bioenergetics.(1) Under 28(±0.5)℃, rheotaxis frequency, beat tail frequency and oxygen consumption rateof juvenile B. schwanenfeldi was affected by water current velocity. The theotaxis frequency, beattail frequency and oxygen consumption rate increased along with the ascend of the water currentvelocity. They would be at peak at water current velocity of 0.30 m·s-1, but the degressive valuewould appear at water current velocity of 0.50 m·s-1. The beat tail frequency have significantlylinear correlativity with rheotaxis frequency and oxygen consumption rate (p＜0.01). Oxygenconsumption rate of group S was significantly higher than that of group L at water currentvelocity of 0.00 m·s-1 (contraposed) and 0.30 m·s-1 (p＜0.05); Oxygen consumption rate of groupS and L have no significant difference (p＜0.05) at water current velocity of 0.30 m·s-1 and 0.50m·s-1.(2) Under this experiment, TN excretion rate and Ur.-N excretion rate of juvenile B.schwanenfeldi was different in different water current velocity, but NH3-N excretion rate has nochange. TN excretion rate and Ur.-N excretion rate increased along with the ascend of watercurrent velocity peaking at water current velocity of 0.50 m·s-1. The beat tail frequency havesignificantly linear correlativity with TN excretion rate and Ur.-N excretion rate (p＜0.01). TNexcretion rate and NH3-N excretion rate of group S were all significantly higher than group L(p＜0.05) at the same water current velocity. Ur.-N excretion rate of group S was significantlyhigher than that of group L (p＜0.05) at water current velocity of 0.00 m·s-1 (contraposed), 0.10m·s-l and 0.50 m·s-1. Ur.-N excretion rate of group S and L have no significant difference (p＜0.05)at water current velocity of 0.30 m·s-1.(3) The rate of oxygen and nitrogen of juvenile B. schwanenfeldi were fluctuated between33.4 and 57.8, up at water current velocity of 0.30 m·s-1and down at water current velocity of0.00 m·s-1 (contraposed). Rate of oxygen and nitrogen of group L.was significanthy higher thanthat of group S (p＜0.05) at water current velocity of 0.50 m·s-1, and the difference was nosignificant (p＞0.05) at other water current velocity. At water current velocity of 0.30 m·s-1 and 0.50 m·s-1, the primary energy substrate was carbohydrate, the proportions of carbohydrate inmetabolic substrate of group L was 57.0% and 86.0% at these two water current velocities,respectively, and those of group S was 80.4% and 76.8% respectively. At water current velocityof 0.00 m·s-1(contraposed) and 0.10 m·s-1,The primary energy substrate is fat, the proportions oflipid in metabolic substrate of group L was 84.2% and 63.0% at these two water current velocitiesrespectively, and those of group S was 96.9% and68.0% respectively.(4) In the 24 hours continuous observation, changes of rheotaxis frequency, beat tailfrequency and oxygen consumption rate of juvenile B. schwanenfeldi of group L and S is even atwater current velocity of 0.00 m·s-1(contraposed); they were all present up-trend at the first 3hours, they all gradually descended and inclined to stabilization.
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