Abstract: Temperature changes usually induce the adaptive regulations of physiological function and swimming behavior of fish. The aim of present study was to investigate the effects of temperature acclimation on preferred swimming behavior in crucian carp (Carassius auratus). To achieve our goal, experimental fish were firstly videoed individually in a selfmade preferred water velocity determining device, i.e., a 1.5m long conical raceway with water speed gradually increasing from 11.86 to 65.45 cm·s^-1 (which was evenly divided into five velocity intervals) at (25±1) ℃ and (15±1) ℃. The videos were then analyzed by the software Ethovision XT19, and those parameters, including frequency (F), the average duration of each fish stayed (T) and the percent time stayed (P_t) at each water velocity interval were calculated. Our results showed that P_t of crucian carp reached 47% at the fourth water velocity interval when acclimated at 25 ℃, and it was significantly higher than those at the other water velocity intervals due to the combinative effects of increased water velocity on F and T. However, when acclimated at 15 ℃, the F showed no significant change from the first to the third water velocity intervals, but the F of the fourth and fifth water velocity intervals dropped significantly. Meanwhile, the maximal value of the T appeared at the first water velocity interval. Hence, the P_t of the first water velocity interval was 37%, which was higher than those of other intervals (P<0.05). The F of 25 ℃ group was significantly lower than that of 15 ℃ group from the first to third water velocity interval, and the T of 25 ℃ group was larger than that of 15 ℃ group at the fourth water velocity interval (P<0.05). Thus, the P_t of 25 ℃ group was lower than that of 15 ℃ group at first and second water velocity intervals, whereas the P_t value of 25 ℃ group was higher than that of 15 ℃ group at the fourth and fifth water velocity intervals (P<0.05). The present study suggests that the preferred swimming speeds of the experimental fish were 27.91-41.30 and 11.86-15.18 cm·s^-1 at 25 and 15 ℃, respectively. The preferred swimming speed of the crucian carp decreased with water temperature, which may be related to the downregulation of the physiological functions of fish acclimated at the cold environment.

Key words: quality of population urbanization, coupled coordination, quality of land urbanization