Suckermouth catfish wake flow in bionic robot design

Seafloor creatures that flexibly manipulate vortices through their unique body shape have gathered the interest of roboticists, but the quantitative analysis of wake flow and forces generated by the tail ends of benthic fishes — fishes that live at the bottom a body of water — remains unexplored. Suckermouth catfishes, in particular, leverage their asymmetrically divided tail and airfoil-like body shape to navigate and survive the extreme conditions of the benthic. Their hydrodynamic behavior provides a useful reference for the design of biomimetic robots.

To analyze the hydrodynamic behavior of the suckermouth catfish, Wang et al. utilized particle image velocimetry to visualize the flow fields around the fish’s tail during fast start. A vertical sheet laser illuminated near-neutrally buoyant glass beads seeded in a water tank, and two high-speed cameras recorded the caudal fins of the fishes, which were trained to perform specific behaviors in the tank after being frightened.

The authors noted that through controlling thrust and pitching moments, the suckermouth catfish’s caudal regions facilitate transitions between fast start and benthic postures, deepening the understanding of near-bottom motion.

“Our findings demonstrate how morphology-driven flow control enhances maneuverability and stability,” said author Jinhao Wang. “It provides inspiration for adaptive propulsion systems for robots operating on underwater substrates, such as seafloor explorers or environmental monitors.”

The authors plan to translate the biocontrol mechanics of the suckermouth catfish and other similar species into practical applications.

“Future projects will focus on modeling the tail design of vortex control in suckermouth catfish and exploring the provisioning strategies of other benthic species during adhesion and locomotion,” said Wang. “Through collaboration, we may extend this work to multifunctional bionic robots capable of substrate attachment and fast escape.”

Source: “Hydrodynamics of suckermouth catfish: The role of wake forces during the fast start,” by Jinhao Wang, Ge Shi, Long Zheng, and Luquan Ren, Physics of Fluids (2025). The article can be accessed at https://doi.org/10.1063/5.0270801 .