The mystery of Mexico's 'lake of death': More than 70 tons of dead fish have been hauled from the waters near Cajititlán this week - but what's killing them?

It is the latest ecological disaster to hit the country recently, including leaks of crude oil and toxic waste

“The water used to be blue and crystal clear. You could see the sand and the fish beneath the surface,” said Dolores Herrera, a middle-aged fisherman’s wife from Cajititlán, a lakeside village in western Mexico. “The entire town used to bathe in the lake. Now I wouldn’t dare dip my feet in it.”

More than 70 tons of dead popoche chub fish have been hauled out of Lake Cajititlán since Sunday, when the now grey-green surface was covered in floating bodies for about as far as the eye could see. The sudden death of hundreds of thousands of freshwater fish remains an unsolved mystery, but this is only the latest in a string of ecological disasters to hit Mexico in recent weeks.

It came just days after illegal drilling in the eastern state of Veracruz led to 4,000 gallons of crude oil leaking into a nearby river, turning the water red and killing hundreds of turtles, rabbits, mice, birds and fish. Earlier in August, Mexico suffered another environmental catastrophe when more than 10 million gallons of toxic waste from a copper mine spilled into two rivers in the northern state of Sonora, leaving 24,000 people without clean water.

Located in the municipality of Tlajomulco de Zúñiga in Jalisco state, Cajititlán lies 16 miles south of Guadalajara, Mexico’s second biggest city. Home to 5,300 inhabitants, it is the largest of six villages that hug the shore of Lake Cajititlán. The foul stench of putrid fish greets visitors to the lake, where local fishermen, restaurants and boatmen who make a living by taking tourists across the water have all suffered as a result of the incident.

Although the popoche chub are not edible – and the mojarra fish that fishermen catch appear not to have been poisoned – population numbers have declined drastically in recent years. “There are far fewer fish than there used to be. Eight years ago a single fisherman could catch between 200 kilos and half a ton of fish in a day. Now you’ll only catch three or four kilos,” said Octavio Cortés, president of the Cajititlán Fishermen’s Association. “Now nobody wants to buy what little fish we can catch because of the bad publicity, even though the mojarra haven’t been contaminated.”

Hundreds and thousands of fish have died in the lake over the past six days from unknown causes Hundreds and thousands of fish have died in the lake over the past six days from unknown causes (Getty)
Lakeside seafood restaurants that once sold freshly caught fish from the lake now import their produce from elsewhere. “We have very few clients, and fewer still with this bad publicity,” said a female restaurant owner, who asked not to be identified. “Many of us have begun to lose confidence in the authorities,” she added. “It’s easier for them to build another housing complex and dump their sewage in the water than it is for them to clean up the lake, because there’s more money in it for them.”

Felipe López Sahagún, director general of the Tlajomulco Civil Protection and Fire Department, said 150 environmental workers, firemen, fishermen and townspeople have been working to clear the lake of the dead fish. Several days after the outbreak began dozens of workers could still be seen shovelling bucketloads of the silver, finger-length fish from modest wooden vessels into an endless stream of wheelbarrows. The rotting cargo was then scooped by tractor into waiting trucks and finally buried in a concrete pit.

“This is the worst case we’ve seen,” López Sahagún said, noting that three smaller hauls of dead fish had previously surfaced in May, June and August.

Samples have been sent to environmental experts to determine the cause of death, but almost everyone in Cajititlán has a different explanation for the phenomenon.

Local residents have complained of factories dumping industrial waste into the lake, while the ongoing rainy season may have exacerbated the damage by washing fertiliser from surrounding cornfields into the water.

Citing a 2013 study by the Jalisco environmental agency, the Tlajomulco Mayor, Ismael del Toro, suggested the deaths were merely the result of “natural cycles caused by changing temperatures and reduced oxygen levels”. Yet the state environmental secretary, Magdalena Ruiz Mejía, rejected this explanation and argued that inefficient municipal waste-water treatment facilities were to blame.

Water pollution is a serious problem because Mexico suffers from “very lax environmental regulation,” said Dr Raul Pacheco-Vega, a water policy expert and assistant professor at Mexico’s Centre for Economic Research and Teaching University. “I did a study of environmental fines and discovered that the most a company would typically pay is the equivalent of $500 (approximately £300). That’s nothing, it’s absurd.”

Moreover, regulatory bodies lack the capacity to enforce the law because “you have thousands of miles of rivers to monitor and a lot of these industrial plants are in very remote areas,” Dr Pacheco-Vega added. “The government really needs to increase enforcement capabilities and create a very well co-ordinated regulatory framework.

“We don’t have a robust enough framework to allow citizens to sue industrial plants that have contaminated water bodies,” he concluded.

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