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 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 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 three-dimensional movement analysis, we found that the reduction in feeding rates was related to modulation of the eel's movements, whereby the expected increase of 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 due to 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.
Effects of prey density and flow speed on plankton feeding by garden eels: A flume study
Currently Viewing Accepted Manuscript - Newer Version Available
Kota Ishikawa, Heng Wu, Satoshi Mitarai, Amatzia Genin; Effects of prey density and flow speed on plankton feeding by garden eels: A flume study. J Exp Biol 2022; jeb.243655. doi: https://doi.org/10.1242/jeb.243655
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