Correlation analysis between upstream swimming speed and tail-beat behavior ofHypophthalmichthys molitrix

One of the key problems of the hydraulic design of fish pass structure is the fish first orient to the flow. Obtaining fish behavior parameter in the process of upstreaming is beneficial to the research of target fish physiological characteristics, swimming capability and its response to hydraulic environmental factors. In this paper, taking theHypopthalmichthys molitrix as the research object, the correlation among flow velocityU, tail-beat frequencyf, relative tail-beat amplitudeA, absolute swimming speedV and swimming accelerationa was analysed in the state of holding station and moving forward during upstream by behavioral analysis software. Result showed tail-beat frequency and flow velocity were in a positive relationship during holding station; relative tail-beat frequencyA was (0.0876 ± 0.0098) BL, while there was no clear relation between tail-beat frequencyf and relative tail-beat amplitudeA; during moving forward, tail-beat frequencyf was greater than that during holding station, while in contrast, little difference lay in relative tail-beat amplitudeA; tail-beat frequencyf and absolute swimming velocityV were in definite positive relation, while there was no obvious relationship between tail-beat frequency and relative tail-beat amplitudeA; in the process ofH. molitrix moving forward, swimming acceleration a changed as time went by, and most of swimming acceleration varied from 0.02g to 0.06g 55.84%. In the paper, experiments are conducted in the flume and we had a single flow field, but the flow field is relatively complex in natural environment. The relationship between fish behavior and hydraulic factor requires further research.