流水和静水条件下鲢幼鱼对不同强度光源的趋性行为研究

结合鱼类的集群行为,探究了在流水和静水处理下鲢(Hypophthalmichthys molitrix)幼鱼的光强偏好。实验流速工况设置包括静水和流水(流速为0.1m/s),光强水平设置为0、10、20、40、70、110lx,并依次进行了实验对象的个体(1尾)实验和群体(5尾)实验。结果显示:(1)个体流水处理在不同光照度水平下的吸引率和排斥率均无显著性差异(P0.05),但个体静水处理20lx和110lx组的光吸引率显著大于40lx和70lx组(P0.05),其他均无显著差异(P0.05);(2)不同流速和实验鱼数量下的光吸引率,由高到低依次为群体流水处理、群体静水处理、个体流水处理、个体静水处理。光排斥率由高到低依次为个体静水处理、个体流水处理、群体静水处理、群体流水处理。研究表明,一定水流速度能够刺激鲢幼鱼趋流,从而提高光的吸引作用,且群体的趋光性要强于个体;(3)流水处理下,鲢幼鱼的最近邻距离(DNN,群体紧凑程度指标)随光强的增大,先减小后增大,集群程度先升高后降低,其中,70lx水平对应的DNN显著高于0lx(F=1.489,P0.05),而静水处理下各光强水平对应的实验鱼DNN无显著性差异(P0.05),集群行为无明显变化。

Phototaxis of Individual and Group Hypophthalmichthys molitrix in Flowing and Still Water

Water control structures have changed the ecology of natural rivers, interrupting connectivity and decreasing fish populations and diversity. Fish behavior is highly dependent on vision and eyesight relating with light intensity. In this study, the effects of light intensity and flow velocity on phototaxis and schooling behavior of Hypophthalmichthys molitrix (silver carp) were investigated. Experiments included the behavior of a single fish and groups of five fish at flow velocities of 0 m/s (still water) and 0.1 m/s (flowing water) and at light intensity levels of 0, 10, 20, 40, 70 and 110 lx. And video recording system was used to help observe and collect the experimental data, the occurring frequencies in each area were collected to calculate the attraction and repulsion rates There were three primary findings: (1) For individual fish in still water, the rates of optical attraction for 20 lx and110 lx groups were significantly higher those in 40 lx and 70 lx groups, and the optical repulsion rate did not vary with light intensity. For individual fish in flowing water, the rates of optical attraction and repulsion did not vary with light intensity.(2) At different flow velocities and group size, the optical attraction rate was in the order, group in flowing water > group in still water > individual in flowing water > individual in still water and the optical repulsion rate was in the reverse order. This shows that flow enhances phototaxis in silver carp fingerlings and phototaxis is more pronounced in a group (schooling) than with an individual fish. (3) In flowing water, the distance to nearest neighbor (DNN) increased and then decreased with illumination intensity and DNN at 70 lx was significantly higher than at 0 lx (F=1.489, P<0.05). In still water there were no significant differences (P>0.05) among illumination treatments and no changes were observed in fish schooling behavior.