高体鳑鲏幼鱼集群行为研究

Schooling Behavior of Juvenile Rose Bitterling (Rhodeus ocellatus)

为了探究高体鳑鲏(Rhodeus ocellatus)幼鱼的集群行为,选取248尾幼鱼,分别了组成单独1尾个体和2、4、8和16尾高体鳑鲏幼鱼的群体(N=8),在(25±1)℃水温条件下进行15 min的视频拍摄,随后进行运动轨迹的提取和分析,得到游泳速度以及空间分布特征的相关数据。结果显示:(1)高体鳑鲏的自发游泳速度在0~10 cm/s,1、2、4、8和16个体组的速度中位数分别为4.3 cm/s、4.1 cm/s、3.6 cm/s、3.2 cm/s和4.6 cm/s,其中8个体组的速度中位数显著低于1和16个体组(P<0.05)。各组游泳速度的同步性较高,且随群体大小的上升呈显著下降的趋势(P<0.05);(2)焦点鱼和群体中其它个体的最近邻距离(NND)出现在0~10 cm,2和4个体组的NND分别为3.1 cm和2.7 cm,显著大于8和16个体组的1.9 cm和2.4 cm(P<0.05);(3)2和4个体组排列的极性为91.5%和91.2%,显著高于8和16个体组的82.6%和77.2%(P<0.05)。研究结果表明,高体鳑鲏幼鱼具有显著的集群性特征,可能为其适应复杂的生境、提高觅食效率和降低捕食压力的结果;群体大小对高体鳑鲏集群行为特征有显著影响,随群体大小的上升,其群体凝聚力上升,但协调性下降。

Schooling or shoaling is a commonly observed phenomenon in natural fish populations. Schooling behavior derives benefits that include defense against predators,improved swimming efficiency and more successful foraging. Rose bitterlings（ Rhodeus ocellatus）,belong to Cypriniformes,Cyprinidae and Acheilognathinae and primarily inhabit lakes,ponds and the shallow water of rivers. The species is ideal for fish behavior research because of evident schooling. In this study,we investigated the schooling behavior of juvenile rose bitterlings in groups of different size（ 1,2,4,8 and 16 individuals per group）,aiming to understand the effects of group size on behavior.Juvenile rose bitterlings with an average body weight of（ 0. 56 ± 0. 03） g and body length of（ 3. 02 ± 0. 04） cm were collected from local ponds in Chongqing and acclimated for two weeks in the laboratory at（ 25 ± 1） ℃ and DO saturation ≥90%. After acclimation,the behavior of healthy juvenile rose bitterlings in differently sized groups were tested in containers（ 60 cm × 35 cm × 15 cm） at（ 25 ± 1） ℃,with eight repetitions per group. Video was captured for 15 min during each test and the swimming speed and spatial distribution characteristics of individuals were calculated and analyzed using trajectory tracking software（ id Tracker）. The effects of group size on median swimming speed,synchronization of swimming speed,nearest neighbor distance（ NND） and orientation polarity were assessed. Results show that：（ 1） the spontaneous swimming speed of the rose bitterlings varied between 0 and10 cm/s and the median swimming speeds were 4. 3,4. 1,3. 6,3. 2 and 4. 6 cm/s for groups of 1,2,4,8 and 16 individuals,respectively. The median swimming speed was significantly lower in groups with 8 individuals compared to groups with 1 or 16 individuals. Swimming was highly synchronized but the degree decreased with increasing group size（ P〈 0. 05）;（ 2） the range of NND was 0-10 cm and the NND of groups of 2,4,8 and 16 individuals were 3. 1,2. 7,1. 9 and 2. 4 cm,respectively. The NND of groups of 2 and 4 individuals were significantly higher than groups of 8 and 16 individuals（ P〈 0. 05）;（ 3） the polarities in the groups of 2 and 4 individuals（ 91. 5% and 91. 2%） were significantly higher than those with 8 and 16 individuals（ 82. 6% and 77. 2%,P〈 0. 05）. Our findings indicate：（ 1） juvenile rose bitterlings exhibit significant schooling behavior,attributed to long term natural selection that enhances foraging efficiency and decreases risk of predation;（ 2） group size has profound effects on schooling behavior,characterized by an increase in group cohesion and a decrease in group coordination as group size increases.