Predator-avoidance behaviours of sand-eel schools: why schools seldom split
Predator-avoidance behaviours of sand-eel schools: why schools seldom split
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沙鳗鱼群的躲避捕食行为：为什么鱼群很少分裂
DOI：
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发表时间：
1983
期刊：
影响因子：
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通讯作者：
C. J. Wyche
中科院分区：
文献类型：
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作者：
T. Pitcher;C. J. Wyche
在一个大型室外水箱中，250 条沙鳗 (Ammodytes sp.) 成群结队地游弋，当与游得更快的鲭鱼近距离接触时，它们表现出一致的行为。野外渔具附近的沙鳗也表现出类似的行为。巡航和避免是最常见的行为，其次是跟随、磨合、分裂和加入。闪光扩张、沙漏和空泡偶尔出现，而球则很少见。克鲁斯和米尔显然与掠夺无关。鱼群机动可以通过个体鱼的四种行为机制的组合来产生：（1）鱼群倾向，（2）惊吓反应，（3）最近邻距离，以及（4）允许入侵者的最小接近距离。最小接近距离带来了群聚和液泡等行为，可能代表了沙鳗及其捕食者相对游泳性能的优化，需要监测捕食者的行为。矛盾的是，最短接近距离可能仅仅通过沙鳗与入侵者进行群体教育来实现。闪电扩张后的鱼群快速改造、高度极性以及沙漏细“脖子”中保持的鱼群完整性，都证明了沙鳗进化出的高度鱼群化倾向。因此，学校很难分裂。当两个学校连接时，新的游泳方向是两个原始方向的合成向量。领先的鱼通过平稳地摆动到新的轨道上来加入，但初始加入下游的鱼逐渐更有可能继续其原来的路线，从而产生交叉。在鱼群的另一边，叉指状的外围鱼只有在大的不协调的转弯后才会采取新的路线。这创造了一个“混乱区”。这里首次报道的混乱区可能是“良好的教育”不可避免的结果。加入时产生的这种潜在危险区域可能解释了不愿意分裂的演变。
In a large outdoor tank 250 sand-eels (Ammodytes sp.) cruised as a single school performing consistent behaviours when close encounters with faster swimming mackerel occurred. Sand-eels near fishing gear in the wild showed similar behaviours. Cruise and Avoid were the most frequent behaviours, followed by Herd, Mill, Split and Join. Flash Expansion, Hourglass and Vacuole were occasional, whereas Ball was rare. Cruise and Mill were apparently unconnected with predation. School manoeuvres can be generated by combinations of four behavioural mechanisms of individual fish: (1) schooling tendency, (2) startle response, (3) nearest neighbour distance, and (4) minimum approach distance allowed intruders. The minimum approach distance, bringing about behaviours like Herd and Vacuole, may represent an optimization of the relative swimming performance of sand-eels and their predators with the need to monitor predator behaviour. Paradoxically, minimum approach distance may come about simply through sand-eels schooling with intruders. Rapid reformation of the school after Flash Expansion, high polarity, and the integrity of the school maintained in the thin ‘neck’ of Hourglass all testify to the high degree of schooling tendency evolved by sand-eels. Schools were difficult to split as a consequence. When two schools join, the new swimming direction is the resultant vector of the two original directions. Leading fish join by swinging smoothly onto the new track, but fish downstream of the initial join are progressively more likely to continue in their original course, producing interdigitation. At the far side of the school, interdigitated peripheral fish take up a new course only after large ill-coordinated turns; this creates a ‘Confusion Zone’. The Confusion Zone, reported here for the first time, may result inevitably from ‘good schooling’. Such a potential danger zone created on joining may explain the evolution of reluctance to split.