Evaluation of pool-and-weir fishway efficiency for the upstream spawning migration of Qinghai Lake's naked carp

Przewalski's Naked Carp (Gymnocypris przewalskii) is a typical migratory fish species of the Qinghai Lake region (China). This study focused on the Gangbei Channel fishway located in the Shaliu River, a tributary of Qinghai Lake. A fish passage study was conducted during the peak of the upstream migration of G. przewalskii, and entry proportion and passage efficiency in the Gangbei channel fishway was monitored in real-time using PIT-Telemetry. A detailed hydraulic characterization of the fishway was done using a 3-D numerical model validated by in-situ measurements, and combined with empirical swimming ability data for the species. The results showed that: (1) the proportion of released G. przewalskii entering and passing the fishway were 13% and 5%, respectively; (2) discharge, fish body length, salinity, and diel period were key factors affecting the attempt rate of the G. przewalskii; (3) The critical swimming speed and sprint swimming speed at 50% of G. przewalskii reaching fatigue were 1.02 m/s and 1.91 m/s, respectively; (4) Based on the swimming ability of G. przewalskii and the hydraulic characteristics of the fishway, the flow velocity at the weir sections of the fishway exceeded the sprint swimming ability of G. przewalskii, creating a velocity barrier. Data derived from this study will be used to provide a more comprehensive theoretical basis and data reference for the eco-hydraulic reconstruction of pool-and-weir fishways providing an efficient upstream passage for the conservation of G. przewalskii and other species.