A major fish die-off killed roughly 100 metric tons of tilapia Guerrero’s El Gallo reservoir this week, local fishermen have reported.

Fishing groups across the region blame the massive die-off on a lack of oxygenation in the water due to poor management at the Mexicana de Hidroelectricidad Mexhidro (Mexhidro) hydroelectric plant, located in the municipality of Cutzamala de Pinzón.

“For four days now, the tilapia has been dying in the entire dam; it is sad that neither the state nor the federal government pay attention. Who knows what they want us to do?” a local group of fishermen from the Guerrero town of La Dicha told the newspaper La Jornada.

Mexico’s National Water Commission (Conagua) constructed the El Gallo dam on the Cutzamala River in the northwestern part of the state of Guerrero to expand the irrigation system to the valleys of Cutzamala and Ciudad Altamirano.

In 2007, Mexhidro completed a hydroelectric plant to produce clean energy for the states of Morelos, Michoacán, Guerrero and México state.

Fishing groups say that the floodgates at the dam are not opened often enough, leading to a lack of water oxygenation, which then causes mass fish die-offs. The eight cooperatives operating in the region have reported similar experiences along the reservoir’s 30-kilometer length.

🎥| Alertan por pérdida de unas 100 toneladas de tilapia en la presa El Gallo.
👇https://t.co/agH2S1jgGE pic.twitter.com/eHIOWaHd2z

— El Sur periódico de Guerrero (@elsurdeguerrero) December 31, 2024

The cooperatives have been reporting the issue since 2013 and are now calling on President Claudia Sheinbaum to intervene. Fishermen previously caught between 20 and 30 metric tons of fish a year in the region, supporting the supply of Mexico City’s famous La Viga fish market. However, this figure has fallen significantly in recent years.

Each metric ton of fish lost is valued at 50,000 to 60,000 pesos (US $2,420-2,905), according to reports from the news site Sur Acapulco.

Local fishing groups have threatened to protest if the government does not intervene.

Cutzamala: A key Mexican waterway

The Cutzamala River originates in the central state of Michoacán and ends in Guerrero. Dams on the upper part of the river provide water to Mexico City, via an aqueduct over the mountains known as the Cutzamala System.

The system is one of the world’s largest networks of dams, canals and pipes, supplying around 27% of the capital’s water. However, in recent years, water levels in the system have decreased due to drought and other factors, falling to a historic low of below 30% in May 2024, according to Conagua.

As Mexico City officials race to develop alternative water networks, Mayor Clara Brugada last week announced a plan to halve the capital’s reliance on the Cutzamala reservoir system for the next two years. The goal of cutting withdrawals is to allow the water levels of Cutzamala System reservoirs to recover from extended drought conditions, and any excess water could boost downstream reservoirs like El Gallo in Guerrero.

With reports from La Jornada, Sur Acapulco, The New York Times and Infobae