Abstract: In this study, we applied ecological methods to measure the critical swimming speed and the oxygen consumption rate of three age groups of Salvelinus leucomaenis (one-year old, two-year old and three-year old) at different water temperatures (4, 8, 12, 16, 20, 24℃) and the flow velocity. The results showed that both the water temperature and the body weight had significant effects on the critical swimming speed (P0.05), however, the interaction between the two factors did not (P0.05). At the same water temperature, the critical swimming speed of Salvelinus leucomaenis increased along with the aging/increase in weight. At 4℃, the critical swimming speed was the lowest, which were (21.61.06) cm/s, (22.930.61) cm/s and (30.271.29) cm/s for the three groups respectively. The critical swimming speed increased along with the rise of the water temperature in all groups, and reached the maximum at 16℃, which were (39.60.80) cm/s, (46.800.80) cm/s and (53.731.22) cm/s for the three groups respectively. Then the speed slightly decreased as the water temperature rose to 20℃. However, there was no statistical difference in the speed at 16℃and at 20℃ (P0.05). When the water temperature further rose to 24℃, the critical swimming speed dropped significantly. The water temperature, the flow velocity and the interaction between these two factors displayed significant effects on the oxygen consumption rate (P0.05). Under the same suitable conditions, the oxygen consumption rate of Salvelinus leucomaenis significantly decreased as the weight increased. Overall, the oxygen consumption rates of the three groups were all increased with the rise of the water temperature and the flow rate, but the swimming oxygen consumption appeared to decrease when the water temperature and the flow rate reached a certain value. This study demonstrated that heavier individuals had higher swimming ability against the water flow given the same water temperature. The suitable water temperature for the three groups of Salvelinus leucomaenis should not exceed 20℃, and the maximum flow rate should be no higher than 32 cm/s, 40 cm/s and 48 cm/s for the three groups respectively.