水流对草鱼幼鱼趋光行为的影响

为了探讨水流对鱼类趋光性的影响, 利用自制的循环水槽装置, 以草鱼(Ctenpharyngodon idellus)幼鱼为研究对象, 研究其在光照度为300 lx, 不同流速工况(0、0.1和0.2 m/s)下的趋光性行为, 同时设黑暗静水工况为对照组。结果表明: (1) 0.2 m/s的流速可完全激发草鱼幼鱼的趋流性, 使其游泳方向多数与顶流方向呈± 20°。(2)根据草鱼幼鱼在不同流速工况下随光照度衰减在水槽内的分布情况, 计算得其在3种流速工况下的光强期望值分别为: 52.45, 34.62和37.86 lx。(3)当照度为300 lx时, 静水工况下的实验鱼在水槽中呈现“两头高, 中间低”的分布情况, 并未表现出对某一光强范围的偏好行为; 在小于感应值的低流速下, 草鱼幼鱼的分布情况总体趋势与静水工况类似, 但在远离光源处的分布较多, 多呈“逆流后退”行为; 当流速值超过感应流速时, 在趋流性的作用下, 鱼类在尾部的聚集情况明显下降, 同时在水槽中的分布更加均匀, 其原有光环境的作用减弱。研究初步证明了略大于感应值的小流速所引发的草鱼趋流性即可对其光环境响应行为产生影响。

THE EFFECT OF WATER FLOW ON THE PHOTOTAXIS OFJUVENILE GRASS CARP

To investigate the impact of water flow on fish phototaxis, this study tested the light preference behavior of juvenile grass carp (Ctenpharyngodon idellus), adopting a self-made recirculating channel, under 300 lx light source with three velocity treatments (0, 0.1 m/s and 0.2 m/s respectively) and control group (dark, still water). The results indicated that the flow velocity of 0.2 m/s was able to adequately stimulate the rheotaxis of grass carp juveniles, constraining the dominant swimming direction within ± 20° from the opposite direction of flow. According to the distribution of juvenile grass carps in the test channel with light intensity attenuation, the illumination expectations of test fish at the three given velocity levels were 52.45 lx, 34.62 lx, and 37.86 lx respectively. During the 300 lx trial, fish in still water displayed high distribution on the lateral sides and low distribution in the middle of the channel without a preference for any specific range of light intensities. At the low-velocity level less than the induced value, the overall distribution of juvenile grass carp was similar to that in still water, but farther away from the light source, and more individuals performed " reverse flow backwards” behavior. When the flow velocity surpassed the induced value, the accumulation of fish on the rear side reduced due to the effect of the rheotaxis, and the distribution was more uniform, and the light environment influence is reduced. This study demonstrated that grass carp rheotaxis caused by a small flow velocity, which is slightly larger than the induction value, could affect its light environment response behavior.