Review on Nature-Like Step-Pool Fishways

Dams constructed along rivers serve as barriers to the migration of fish. Consequently, the demise of many fish species populations across the globe has been noticed. Many conventional fishways are developed to restore the longitudinal connectivity in the river. However, for non-target species such as cyprinid, carp, and all non-salmonid species, their efficiency is very poor. Recently, nature-like fishways have gained popularity as they are ecologically viable by attracting diverse fish species and are economical due to less construction and management costs. Among all NLFs, step-pool bed morphology in the mountainous stream shows varying flow hydrodynamics and high energy dissipation. This feature of step-pools makes them very suitable for use in ecological environments such as creating close-to nature like step-pool fishways. Hence, a comprehensive study of flow hydrodynamics and turbulence associated with nature like step-pool-type fishways is essential. However, understanding fish behavior in the flow field is a prerequisite for developing and incorporating them into the design guidelines for a fishway. This paper reviews the geometry, flow field, and performance of a nature-like step-pool fishway and the future work to be done. Also, a review of how fish behavior and fish response to the flow field inside the fishway is essential to designing a fishway is presented. Finally, the significance of experiments with high-frequency instruments to capture accurate flow velocity, limitations, and future scopes of work is discussed.