Lake Cuitzeo, Michoacán, México: Effects of Environmental Deterioration

ABSTRACT Cuitzeo is the second‐largest lake in Mexico (452 km 2 ). With an age of 6.0–8.0 million years, it is considered one of the oldest lakes on Earth. Field, laboratory and documentary research were developed to integrate an environmental diagnosis. The lake is very shallow, with a mean depth of 1.6 m. According to electric conductivity values, it is divided into three lacustrine zones: the eastern zone, with very low electric conductivity values (429.0 μS/cm); the western side, with up to 8950.0 μS/cm; and the central part, with intermediate values. Water quality analyses indicate that Cuitzeo is a hypereutrophic aquatic ecosystem, highly turbid and with increasingly saprobic conditions. Despite the basin area (3675 km 2 ) receiving an average annual rainfall and surface runoff of almost 4000 Mm 3 , intensive water overexploitation and high evaporation rates resulting from deforestation and land‐use change cause Lake Cuitzeo to receive less than 10% of the water input from the basin. Consequently, during arid seasons, up to 70% of the lake surface desiccates, and dust storms are present on the western side. The fishery is near collapse due to intensive fishing and frequent desiccation episodes. From 5546 tons/year of fish catch registered in 1993, fish productivity has fallen to less than 250 tons/year in 2006. Forty‐five years ago, up to 18 fish species were registered, of which 15 were native. Nowadays, only six species are present, of which three are native species.