Escape trajectories are deflected when fish larvae intercept their own C-start wake

Area of Science:

• * Biophysics
• * Ichthyology
• * Fluid Dynamics

Background:

• * Fish larvae utilize rapid escape maneuvers called C-starts to evade predators.
• * The hydrodynamics of C-starts, particularly wake interactions, are crucial for escape performance.
• * Previous research suggests larvae may interact with their own generated wake during turns.

Purpose of the Study:

• * To investigate the effects of self-wake interception on the escape performance of larval zebrafish (Danio rerio).
• * To analyze the fluid dynamics and body dynamics coupling during C-start maneuvers.
• * To quantify the impact of wake interception on turning angle and escape trajectory.

Main Methods:

• * Employed a computational fluid dynamics (CFD) approach to simulate free swimming.
• * Coupled hydrodynamic and body dynamics to model fish-water interactions.
• * Performed counterfactual simulations to isolate the effects of wake interception.

Main Results:

• * Simulations confirmed that larval zebrafish can intercept their own wake during turns of 100-180°.
• * Wake interception significantly increased lateral force and reduced the turning angle by over 5°.
• * No significant changes in tangential acceleration or total power output were observed due to wake interception.

Conclusions:

• * Self-wake interception by larval zebrafish modifies escape trajectories, potentially hindering predator evasion.
• * Larger fish may have greater capacity to avoid wake interception through under- or overshooting.
• * Fish may need to incorporate wake dynamics into their escape route planning for optimal survival.