<b>Localized Flow-Coupled Return Behavior in Stream Fish: Underwater Video, Fish Trajectories, and Natural-Tracer Flow Data</b>

<p dir="ltr"><b>This dataset contains raw underwater video and derived trajectory and image-motion data documenting a field observation provisionally termed localized flow-coupled return behavior (LFCR) in small stream fish.</b></p><p dir="ltr"><b>Seven fish trajectories were visually confirmed from the underwater recording. Four trajectories met an operational return criterion, whereas three were classified as transit-type trajectories.

In all four return-type trajectories, the principal direction of fish displacement reversed between the outward and return phases. Image motion of naturally occurring particles surrounding the fish was independently analyzed as a proxy for local flow, and the direction of this local motion proxy also reversed between phases in all four return-type trajectories.</b></p><p dir="ltr"><b>The dataset includes the original underwater video, normalized fish trajectories, frame-level natural-tracer motion estimates, outward–return phase analyses, off-fish spatial controls, exploratory fish-centered optical-flow and vorticity analyses, derived figures, and documentation required to interpret the analysis.</b></p><p dir="ltr"><b>LFCR is used here as an </b><b>operational descriptor of an observed spatiotemporal pattern</b><b>, rather than as an established behavioral category.