Behaviour and ability of a cyprinid (Schizopygopsis younghusbandi) to cope with accelerating flows when migrating downstream

Abstract

The migration corridors in regulated rivers lead downstream fish migrants, particularly juveniles to pass through water infrastructure. Accelerating flow, experienced by fish, might trigger avoidance behaviour and then influence the downstream migration efficacy. It is essential to understand the causes of avoidance behaviour exhibited by downstream migratory fish in accelerating flow. In this study, the effect of three different accelerating flows on the downstream migration behaviour of Schizopygopsis younghusbandi (S.Y) was investigated using a constriction wedge in a circulating flume. The results showed that some fish (30%, 23%, and 39% under low, medium, and high flow conditions, respectively) repeatedly attempted to burst upstream with positive rheotaxis prior to successful passage downstream. Under the low‐, medium‐, and high‐accelerating levels, the average fish swimming speeds were 89.19, 91.28, and 111.94 cm/s, respectively; these values were close to the critical swimming speed (110.42 cm/s) of the target fish. The water velocities at the fish avoidance points were centrally distributed at approximately 73.03 cm/s. Regarding turbulence, the results exhibited that the S.Y generally responded to a discrete range of <50 cm2/s2 of turbulent kinetic energy and < 2 N/m2 of the horizontal component of the Reynolds shear stress (RSSxy). Also, the fish that exhibited avoidance behaviour were not centrally distributed in the lateral and longitudinal velocity locations, where there was an abrupt change in the gradient. This study highlighted the impact of accelerating flow on the downstream fish migration behaviour of a cyprinid. Furthermore, this study quantified the hydraulic factors that triggered this avoidance. Thus, it provided experimental support for optimizing the design of the hydraulic factors for downstream fishways.

Mutually promoting or constraining? Disentangling the superimposed effect of velocity and illuminance on fish motion in low‐velocity flows with a novel metric

“…The momentary locomotion also provides clues for the different early performances of downstream migration. To investigate the self‐defence manifestation of downstream fish migrants before the entrance of downstream passages, plenty of studies concentrate on determining the escape behaviour, which is related to the acceleration magnitude of attraction flow in front of the intake, and the critical responses of fish that allow them to switch swimming patterns and prevent entrainment (Li et al, 2020; Vowles & Kemp, 2021). For example, behavioural observation on juvenile Pacific salmonids ( Oncorhynchus gorbuscha ) revealed that flow acceleration, rather than other flume configurations, elicited the avoidance of test fish when the hydraulic conditions changed rapidly (Kemp et al, 2008).…”

A study of the hydraulic parameters and ecological significance of braided rivers under flow variations

“…Liu et al, 2020;Zhu, Chen, Yang, Ma, & Li, 2017). The S. younghusbandi juveniles (11.17 ± 1.39 cm) in the field experiment proved to be unable to stay in the 0.73-m/s flow region for long periods (M. Li et al, 2020). The sustained swimming speed of S. o'connori (13.4 ± 1.9 cm) in the laboratory has been found to be up to 0.6 m/s.…”

Swimming capability of target fish from eight hydropower stations in China relative to fishway design

“…Interestingly the flow velocity for juvenile Schizopygopsis younghusbandi avoiding downstream was near their U crit of 1.11 m/s (Li et al, 2020). Endurance was intended to identify flow velocities that fish could resist long enough to avoid becoming entrained into the turbines.…”