Adult zebrafish favor vision over flow sensing in increasingly complex hydrodynamic environments

Vertebrate life originated in water, where attenuated light and hydrodynamic currents challenge the sensorimotor abilities of animals differently than in terrestrial environments.^1,2,3 The mechanosensory lateral line system, which evolved alongside vision from deep genetic blueprints inherited from invertebrate ancestors,^4,5 allows fish to sense changes in water velocity and pressure.^6,7 Vision and the lateral line have been shown to work inextricably in tandem to detect predators, prey, and conspecifics.^8,9,10 Despite the growing interest in elucidating the sensory integration underlying ecological behaviors,^11,12 our understanding of how mechanosensation and vision interact in fish remains limited. Here, we challenge the lateral line system of adult zebrafish (Danio rerio) with hydrodynamic conditions ranging from more predictable (i.e., still water)^13,14 to less predictable (i.e., turbulent flow)^15,16 and quantify their behavioral responses to controlled visual perturbations using an augmented reality flow-tank assay. We find that fish exhibit compensatory optomotor responses to maintain position under turbulent, but not uniform, flow conditions during station-holding behavior. Furthermore, escape responses to looming visual stimuli are heightened when fish swim against water flow compared with still water, whether individually or in a group. Our results demonstrate an elevated role of vision in fish as hydrodynamic complexity increases. We propose that fish sensory strategies are not fixed but are dynamically tuned to the predictability of external water flow, thus favoring lateral line input under more predictable environments and visual cues under less predictable environments.