Fish body geometry reduces the upstream velocity profile in subcritical flowing waters

Abstract Fish body geometry is highly variable across species, affecting the fluid-body interactions fish rely on for habitat choice, feeding, predator avoidance and spawning. We hypothesize that may substantially influence velocity experienced by swimming. To test this hypothesis, we built nine full-scale physical prototypes of common freshwater species. The were placed in a large laboratory flume upstream time-averaged profiles measured with increasing distance from anterior-most location each body. measurements revealed can have significant profile, reducing flow field at one length fish. Furthermore, it was found species investigated study be normalized to single fit curve based freestream under subcritical conditions. These findings are significant, because they show conventional point overlook effect field, creating systematically biased representation flowing waters. This bias illustrated maps created without presence models three different Finally, provide an example how recalculated closer “the fish’s perspective”.