为考察不同营养状况对鲤科鱼类偏好游泳速度的影响,本研究以鲫鱼(Carassius auratus)为实验对象,(25±1.0)℃条件下设置3个不同营养状况实验组：对照组(禁食48 h)、饱食组(饱食)和饥饿组(饥饿14 d),将单尾实验鱼置于梯度流速选择仪(流速范围为11.86~65.45 cm/s,等距离划分为5个流速区域,从第一到第五流速区域流速连续增加)中拍摄1 h,采用Ethovision XT9软件分析视频资料并计算实验鱼在不同流速区域平均进入频次(F,次)、单次进入停留时间(T, s/次)和平均停留时间百分比(Pt,%)等流速选择行为指标。结果显示,对照组和饱食组的F值随水流速度上升而增加,对照组的T值不同流速区域间无差异(P>0.05),而饱食组第三和第四流速区域T值均显著大于其他流速区域(P<0.05),因此两实验组第三和第四流速区域的 Pt 均显著大于其他流速区域,其偏好游泳速度为20.12~41.30 cm/s。饥饿组流速偏好行为出现表型分化, I型实验鱼在第一流速区域Pt和T值显著大于其他流速区域(P<0.05),各流速区域的F值均显著小于其他实验组(P<0.05),故I型实验鱼的偏好游泳速度为11.86~15.18 cm/s。而II型实验鱼则与对照组相似,在第三和第四流速区域Pt均显著大于其他流速区域(P<0.05),故II型实验鱼的偏好游泳速度为20.12~41.30 cm/s。结果表明,饱食不影响鲫鱼的偏好游泳速度,可能是饱食不影响鲫鱼的游泳能力所致,但饱食组在各流速区域间的出入频次减少而停留时间有所增加。饥饿后鲫鱼偏好游泳速度出现表型分化, I型实验鱼的偏好游泳速度降低,而II型实验鱼则无明显变化, I型和II型实验鱼偏好游泳速度的差异可能是由于在饥饿条件下二者能量节约和游泳功能维持的策略不同。%Fish usually alter their swimming behavior to adapt to changes in food resources in their natural habitats. In this study, we investigated the effects of nutritional status on the preferred swimming behavior of the juvenile crucian carp (Carassius auratus). Three experimental treatment groups with different nutritional status were es-tablished: the control group (fasted for 48 h), the feeding group (fed to satiation), and the starvation group (starved for 14 days). The experimental fish were videoed individually with a hand-made device for determining the pre-ferred water velocity: a 1.5 m long conical raceway in which the water speed gradually increased from 11.86 cm/s to 65.45 cm/s at (25±1)℃. The water velocity of the 1st, 2nd, 3rd, 4th and 5th waster velocity intervals were 11.86–15.18 cm/s, 15.18–20.12 cm/s, 20.12–27.91 cm/s, 27.91–41.30 cm/s, 41.30–65.45 cm/s, respectively. The videos were analyzed with the Ethovision XT9 software, and several parameters were calculated in each water velocity interval: frequency(F), the average duration of stay(T), and the percentage of time stayed(Pt).F increased as the water velocity increased for both the control and feeding groups.Tshowed no significant variation across different water velocity intervals in the fasting group, whereas the feeding group displayed the longestT in both the third and fourth water velocity intervals.Pt was significantly higher in the third and fourth water velocity in-tervals than in the other intervals in both the control and feeding groups, and the preferred swimming speeds of both the control and feeding groups were 20.12–41.30 cm/s. Two distinctly different preferred swimming behav-iors were apparent in the starved group, which we arbitrarily designated the type I and type II preferred swimming behaviors. The type-I fish showed the largestPt andTvalues in the first water velocity interval, which were sig-nificantly higher than those in all other intervals. However, theFof these fish showed extremely low values across all water velocity intervals, and was much lower than those of the other groups. Therefore, the preferred swim-ming speed of the type I fish from the starvation group was 11.86–15.18 cm/s. However,Pt andF of the type II fish were similar to those of the control group, i.e.,Pt of the type II fish was significantly higher in the third and fourth water velocity intervals than in the other intervals, andF increased as the water velocity increased. In the type II fish,T was significantly higher in the fourth water velocity interval than in the first, second, or fifth, but was not higher than that in the third water velocity interval. Consequently, the preferred swimming speed of the type II fish from the starvation group was 20.12–41.30 cm/s. This study shows that satiation feeding does not af-fect the preferred swimming speed of the crucian carp. However, during digestion, the crucian carp showed fewer traverses across different water speed intervals, but a longer period of stay each time they arrived at a given inter-val. Starvation may enhance the interindividual variations in energy reserves and hence the maintenance of swim-ming capacity, resulting in two distinctly different types of preferred swimming behavior in the fasting crucian carp. The type I fish showed a profoundly reduced preferred swimming speed, whereas the preferred swimming speed of the type II fish did not differ from that of the normally fed fish.
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