Fishes have an enormous diversity of body shapes and fin morphologies. From a hydrodynamic standpoint, the functional significance of this diversity is poorly understood, largely because the three-dimensional flow around swimming fish is almost completely unknown. Fully three-dimensional volumetric flow measurements are not currently feasible, but measurements in multiple transverse planes along the body can illuminate many of the important flow features. In this study, I analyze flow in the transverse plane at a range of positions around bluegill sunfish Lepomis macrochirus, from the trai領 edges of the dorsal and anal fins to the near wake. Simultaneous particle image velocimetry (PIV) and kinematic measurements were performed during swimming at 1.2·body·lengths·s1 to describe the streamwise vortex structure, to quantify the contributions of each fin to the vortex wake, and to assess the importance of three-dimensional flow effects in swimming. 德國LaVision PIV/PLIF粒子成像測速場儀 Imager intense PIV相機 用于粒子成像測速(PIV)的熒光示蹤粒子