Without warning, hundreds of thousands of dead fish have been floating to the surface of Lake Cajititlan in the Mexican state of Jalisco over the past week. Local authorities claim the deaths are part of a “natural cycle,” but state authorities disagree, saying that the phenomena is due to “poor management” of the lake. This isn’t the first time this has happened either – 10 tons of fish were found dead in the same lake last October. Is this really an annual event, or yet another occurrence caused by the harmful activities of humans?

Lake Cajititlan, popoche chub, Mexico, freshwater fish, freshwater pollution, Maria Magdalena Ruiz Mejia, Jalisco, water pollution

So far this year, around 50 tons of dead popoche chub, a type of freshwater fish, have been removed from Lake Cajititlan. Jalisco’s secretary for the environment Maria Magdalena Ruiz Mejia does not believe the causes are natural: “We have no evidence to support that it is natural and cyclical, to the contrary, we have a series of variables which lead us to believe this phenomenon is not only recurrent and becoming more frequent and severe, but also that it is caused by the poor management of the body of water.”

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State authorities are confident that improper management of sludge produced by local wastewater treatment plants is to blame. The only problem is that they have so far been denied access to the plants, and therefore been unable to gather any concrete evidence.

The argument in favor of natural causes is that between the months of August, September and October, a lack of oxygen in the water, caused by the drag of organic matter during the rainy season causes many of the freshwater fish in the lake to die. While this seems logical, the fact that the number has increased so dramatically since last year (10 tons to 50, and counting) points to other variables. Until there is more evidence, all state authorities have been able to do is issue an environmental alert for the lake.


Images by La Jornada Jalisco and Monica PC