A kinematic examination of wild sockeye salmon jumping up natural waterfalls

Wild Alaskan sockeye salmon Oncorhynchus nerka jumping natural waterfalls were observed and photographed to obtain insight into factors important to the fish in dealing with obstacles during their upstream spawning migrations. The fish showed preferences for specific sets of conditions related to heights of waterfalls and depths in pools below waterfalls. Successful jumps appeared to result from running starts, not standing fast starts. The proportion of observed jumps that were successful was low (10% at Brooks Falls, Katmai National Park, Alaska, U.S.A.). Successful jumping behaviour was modelled mathematically and predictions were compared to measured kinematic variables of successful and unsuccessful jumping obtained from analyses of digital video photographs. There were statistically significant differences between the two data sets, but the model identified takeoff velocities and angles, and distances between takeoffs and successful landings as important variables.