VISUAL THRESHOLD FOR SCHOOLING IN NORTHERN ANCHOVY ENGRAULIS MORDAX
VISUAL THRESHOLD FOR SCHOOLING IN NORTHERN ANCHOVY ENGRAULIS MORDAX
复制标题
北方鳀鱼上学的视觉阈值
DOI：
--
复制
发表时间：
1985
期刊：
影响因子：
--
通讯作者：
R. Nicholl
中科院分区：
文献类型：
--
作者：
J. Hunter;R. Nicholl
在实验室测定了两组50尾成年北方凤尾鱼的视觉学习阈值。色散指数和到最近邻居的平均距离被用来衡量学校教育作为光强度的函数的变化。学校教育的门槛光照强度。6×10~(-11)W·cm~(-2)(2.6×10~(-4)mC)，估计在星夜30m和满月38m处，当叶绿素浓度为0.2mgCHa·m~(-3)时，阈值分别出现在8m和20m处。在夜间，上层10米内似乎有足够的光照，以便在凤尾鱼的大部分栖息地进行觅食。新产卵的垂直分布表明，最大产卵深度可能与最大产卵深度相近，可用最大产卵深度的视觉阈值来预测最大产卵深度。视觉在维持海洋中大多数鱼群方面发挥着主要作用。其他感觉器官，特别是侧线，在协调鱼群内鱼类的运动和间距方面很重要(Pcher等人)。1976年)，但单靠侧线感觉不太可能足以维持夜间海上学校的完整性。事实上，大量的实验室研究表明，如果光线足够减弱，鱼类就不再维持鱼群(Whitney 1969；Blaxter 1970)。因此，觅食的视觉阈值和光线的渗透深度可能决定了深海鱼类夜间在海洋中觅食的最大深度。我们的目标是确定成年北方凤尾鱼的视觉摄食阈值，并利用这一信息来预测夜间海洋中凤尾鱼的最大摄食深度。这一计算具有生态学意义，因为最大的觅食深度可能也是产卵和夜间摄食的最大深度。凤尾鱼只在夜间产卵，对其他鱼类的视觉识别可能对产卵和产卵同样重要。在我们认为的产卵行为中，几只雄性在不规则的路径上迅速追逐一只雌性，这一策略可能不可能使用视觉以外的感官。然而，这只是一个临时的实验室观察，需要进一步的文件证明。
The visual threshold for schooling was determined for two groups of 50 adult northern anchovy in the laboratory. The index of dispersion and the mean distance to the nearest neighbor were used to measure changes in schooling as a function of light intensity. The threshold light intensity for schooling. 6 x 10- 11 W cm - 2 (2.6 x 10 - 4 mc), was estimated to occur at a depth of 30 m on a starlit night and at 38 m during a full moon, when the chlorophyll concentration is 0.2 mg Chi a m-:J. At 2.0 mg Chi a m- 3 the threshold oc curs at a depth of 8 m on a starlit night and at 20 m under full moon light. Sufficient light appears to exist at night within the upper 10m for schooling to occur in most of the habitat of the anchovy. The vertical distribution of newly spawned anchovy eggs indicated that the maximum depth of spawning may be similar to the maximum depth of schooling and that the visual threshold for schooling could be used to forecast max imum spawning depth in the sea. Vision plays a primary role in the maintenance of most fish schools in the sea. Other sense organs, par ticularly the lateral line, are important in coor dinating movements and spacing of fish within the school (Pitcher et al. 1976), but it is unlikely that lateral line sense alone is sufficient for maintaining the integrity of schools at night in the sea. In fact, a large number of laboratory studies indicate that if light is sufficiently reduced, fish no longer maintain schools (Whitney 1969; Blaxter 1970). Thus the visual threshold for schooling and the depth of pene tration of light probably determine the maximum depth at which pelagic fishes are able to school at night in the sea. Our objective was to determine the visual thresh old for schooling in adult northern anchovy, Engraulis mordax, and to use this information to forecast the maximum schooling depth for anchovy at night in the sea. This calculation is of ecological in terest because the maximum depth for schooling is probably also the maximum depth for spawning and for nocturnal feeding. Anchovy spawn only at night and visual recognition of other fish is probably as essential for spawning as it is for schooling. During what we believe was spawning behavior, several males rapidly pursued a female over an irregular path, a tactic probably not possible using senses other than vision. This is a casual laboratory observa tion and requires further documentation, however.