Campaigners say building more power stations on Loch Ness could be a disaster for wild fish populations.
The Ness District Salmon Fishery Board wants an immediate moratorium on further pumped storage hydro schemes after plans were lodged for a third.
Between them, they say the schemes will be capable of raising and lowering the water levels by more than two feet.
Industry body Scottish Renewables says pumped storage is a vital component in decarbonising the electricity grid.
Pumped hydro works by using excess off-peak power to push water uphill into a holding reservoir high up the mountain.
When the electricity is needed, the water rushes through turbines while travelling back down to the lower reservoir.
It was originally used to supplement supplies at times when demand was high but is growing increasingly important as a means of storing renewable energy for when the wind is not blowing or the sun not shining.
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