Hydromechanical study of swim-and-glide behaviour on free-ranging flatfish

点击翻译按钮获取中文摘要

Intermittent swimming behaviour of marine fish with negative buoyancy, such as swim-glide behaviour, has been hypothesized to result in a saving of energy required for locomotion between two points. However, there have been no studies that tried to prove this hypothesis in the wild. This has been due in part to the difficulty of observing and monitoring free-ranging fish in the open sea. Previous conventional tagging experiments have indicated that Japanese flounder, Paralichthys olivaceus, sometimes migrated in the far distance, recaptured 1,000 km from the point of release, despite their lower swimming ability and morphological feature without swim bladder.In order to measure energetic cost of free-ranging flatfish during migration, it is important to know the activity and time budgets of flatfish on its migration route. Using a depth and acceleration data-logger on Japanese flounders, we obtained continuous record of swimming speed, depth, tailbeat activity and swimming angle of free-ranging flounders, simultaneously. We estimated and compared the migrating energy costs during continuous swim and swim-glide.We were successful in direct measurement of swim-glide behaviour from flatfish using tailbeat profiles recorded by the logger for the first time. Compared the migration cost between continuous swim and swim-glide, covering similar distance, migration by adopting swim-glide technique resulted in a 22.3% reduction in number of tailbeats. Thus, this energy-saving strategy allows flatfish with negative buoyancy to migrate the long-distance.