<p>Floodplain habitats undergo seasonal changes via the flood pulse, which restructures predator–prey interactions, mediating how schooling fish may perceive predation risk. We investigated whether changes to the visual background, designed to increase the level of perceived risk, elicited shifts in the collective tendencies of floodplain-associated schooling fish within a managed floodplain habitat of the Lower Mississippi River Basin. Using high-resolution imaging sonar, we quantified and compared school area, alignment, and inter-individual distances between a high-contrast background and the natural substrate at sites differing in distance from the initial inundation point of Mississippi River inundation. Schools encountering the experimental manipulation at the far site consistently formed larger schools than those at the near site, or when compared to the natural background, suggesting that perceived predation risk was higher. Nearest neighbor distances and alignment were not altered by the change in perceived predation risk. Site-specific seasonal inundation levels emerged as a consistent driver of variation in collective tendencies, underscoring the high degree of structural and behavioral plasticity in floodplain fish. Together, these findings suggest that the seasonal flood pulse mediates perceived predation risk, and that changes in collective tendencies of floodplain-associated schooling fish reflect the level of perceived risk.</p>