Fish increasingly endangered by hydroelectric dams

Hydro-Québec's Eastmain 1A hydroelectric power station in Eastmain, Quebec. (Jacques Boissinot/The Canadian Press)

A new study shows energy produced by hydroelectric dams may not be as green as originally thought, as it can affect aquatic species at risk of losing their natural habitat.

“Hydroelectric dams produce low-carbon energy, which makes them green energy from a climate perspective, but from an ecological standpoint, particularly in terms of biodiversity, the impacts are very real,” said Habiboulaye Gano, a master’s student in environmental science at Université du Québec à Trois-Rivières.

“There should still be some nuance to this (green) label,” he argued.

He said managing water flows according to electricity demand for dams to produce energy does not necessarily correspond to the needs of Quebec river ecosystems.

From June to September, water is generally stored in reservoirs for use during colder months, when household electricity demands increase.

“This results in low flows downstream at a time when fish need water to reproduce, feed and survive,” said Gano.

The situation in winter also affects ecosystems, as the water that is released causes artificial flooding, “unlike the natural regime where rivers are usually low and frozen,” he said.

Several well-known river species are threatened by this water management, such as, according to Gano, brook trout, which likes cold water and reproduces in winter.

Black and red minnows are also affected by rapid changes in flow.

“In several rivers, there are declining populations of sensitive species, where we are seeing a decrease in fish densities and a loss of diversity in certain species,” he summarized.

Gano added that some waterways are more sensitive to variations, notably the Saint-Maurice River downstream from the Gouin Dam and the Gatineau River downstream from the Cabonga Dam.

Insufficient solutions?

Management practices have been put in place to limit environmental impacts, like fish ladders that allow certain fish to cross dams.

However, their results are variable, according to Gano.

Ecological flow reserves, which dictate the minimum amount of water that must be maintained in rivers to ensure the survival of aquatic ecosystems, are even more vital.

According to Gano, these minimum flows are not always respected.

“The solutions are there, but they are insufficient,” he said.

This report by The Canadian Press was first published in French July 30, 2025.