Marine Biophysics Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, Japan, 904-0495.
The Interuniversity Institute for Marine Sciences in Eilat and Department of Ecology, Evolution and Behavior, The Hebrew University of Jerusalem, Eilat 88103, Israel.
J Exp Biol. 2022 Apr 15;225(8). doi: 10.1242/jeb.243655. Epub 2022 Apr 22.
Feeding by zooplanktivorous fish depends on their foraging movements and the flux of prey to which they are exposed. While prey flux is a linear function of zooplankton density and flow speed, those two factors are expected to contribute differently to fish movements. Our objective was to determine the effects of these factors for garden eels, stationary fish that feed while anchored to the sandy bottom by keeping the posterior parts of their bodies inside a burrow. Using a custom-made flume with a sandy bottom, we quantified the effects of prey density and flow speed on feeding rates by spotted garden eels (Heteroconger hassi). Feeding rates increased linearly with prey density. However, feeding rates did not show a linear relationship with flow speed and decreased at 0.25 m s-1. Using label-free tracking of body points and 3D movement analysis, we found that the reduction in feeding rates was related to modulation of the eel's movements, whereby the expected increase in energy expenditure was avoided by reducing exposure and drag. No effects of flow speed on strike speed, reactive distance or vectorial dynamic body acceleration (VeDBA) were found. A foraging model based on the body length extended from the burrow showed correspondence with observations. These findings suggest that as a result of their unique foraging mode, garden eels can occupy self-made burrows in exposed shelter-free sandy bottoms where they can effectively feed on drifting zooplankton.
以浮游动物为食的鱼类的摄食取决于它们的觅食运动和暴露于其中的猎物通量。虽然猎物通量是浮游动物密度和流速的线性函数，但这两个因素对鱼类运动的影响应该不同。我们的目标是确定这些因素对花园鳗鱼的影响，花园鳗鱼是一种静止的鱼类，它们通过将身体的后部分锚定在沙质底部的洞穴中来进食。使用带有沙质底部的定制水槽，我们量化了猎物密度和流速对斑点花园鳗鱼（Heteroconger hassi）摄食率的影响。摄食率随猎物密度呈线性增加。然而，摄食率与流速之间没有线性关系，并且在 0.25 m/s 的流速下降低。通过对身体关键点进行无标记跟踪和 3D 运动分析，我们发现摄食率的降低与鳗鱼运动的调节有关，即通过减少暴露和阻力来避免预期的能量消耗增加。没有发现流速对攻击速度、反应距离或向量动态体加速度（VeDBA）的影响。基于从洞穴延伸出的身体长度的觅食模型与观察结果相符。这些发现表明，由于其独特的觅食方式，花园鳗鱼可以占据暴露在无遮蔽沙质底部的自制洞穴，在那里它们可以有效地摄食漂流的浮游动物。
