Thousands of dead fish washed up on the shores of Lake Cajititlan this week, provoking fears of serious contamination in the water basin often referred to as Chapala’s younger sibling.
But the demise of some 800 tons of fish – mostly mojarra – is nothing to be alarmed about and happens two or three times a year, according to Semadet (the state’s environment and land development agency).
The mass fatalities are caused by a combination of factors, Semadet says. Primarily, the combination of the end to the rainy season and a drop in temperature provokes an increase in algae and a reduction in the lake’s oxygen levels.
The fish species affected are known as Astyanax aeneu but referred to locally as popochas or pittas. They are especially sensitive to changes in oxygen levels, say Semadet officials.