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Hydropower plants have some adverse impacts on the environment and preservation of ecosystems. Various studies have been conducted to understand the effect of hydro plants on aquatic species populations, especially fishes. In preservation of ecosystems, downstream and upstream migration of fishes is very significant. Recent advances in the development of fish‐friendly turbines along with progress in water‐lubricated bearings (used in turbines) have been reported by several research projects (Hogan et al. 2014; Quaranta et al. 2017; Fjeldstad et al. 2018). Gravity water wheels and hydrodynamic screws which come under low head gravity turbines are fish‐friendly as opposed to conventional turbines. However, these turbines can be used in small hydro plants (very low head sites). For the large‐scale hydropower plant, two different approaches have emerged to allow fish migration, namely fishways facilities and usage of fish‐friendly turbines (Kougias et al. 2019).

Conventional turbines hinder the migration of fishes (upstream and downstream) so to allow the migration, hydraulic structures are used, termed as fishways (Quaranta et al. 2017). For making eco‐efficient fishways having optimal design, more studies are needed to understand their swimming ability and at what position inlet or outlet should be installed so that fishes can use them efficiently (Fjeldstad et al. 2018).

In the high head hydropower plants, fishways find some restrictions, so in order to overcome these restrictions, some advances are taking place in the turbine designs. For safe passage of fishes through hydraulic turbines, a technology termed as fish‐friendly turbine has emerged, owing to the developments in the area of advances in turbines. Recently, two different turbines with better designs have been introduced, the Alden turbine and the Minimum Gap Runner turbine. Usage of these turbines leads to more power generation, reduction in fish mortality rate and injury along with better downstream water quality (Hogan et al. 2014).