The “mosco” (Hemiptera: Corixidae and Notonectidae) of Lake Cuitzeo, Mexico: an unusual inland water fishery

Lake Cuitzeo is Mexico’s second-largest lake (~ 425 km²). The West Basin is shallow, seasonally astatic and alkaline, and it contains saltwater; it is in this extreme environment that there are fisheries maintained by local fishermen that are based on non-conventional products. These products include the “mosco” (hemipteran water boatmen and backswimmers: Corixidae and Notonectidae), which has become the most important “non-conventional resource” owing to high catch rates and its contribution to the local economy; its uses include its sale as pet food for songbirds and ornamental fishes. No other commercial fisheries of adult Hemiptera are known worldwide. This study records, for the first time, the species composition of the “mosco”, which was investigated through monthly sampling for twelve months at three sites in the West Basin. Seven species of aquatic Hemiptera were found: 5 species of the family Corixidae [Graptocorixa sp. (Hungerford), Corisella mercenaria (Say), Corisella edulis (Champion), Trichocorixa parvula (Champion) and Krizousacorixa azteca (Jaczewski)], and 2 species of the family Notonectidae [Buenoa scimitra (Bare) and Notonecta irrorata (Uhler)]. The seven species are new records for Lake Cuitzeo. Corixidae were more abundant than Notonectidae, at a ratio that varied from 2.3:1 to 34.2:1. Abundance peaks of up to 339 ind. m⁻² were recorded during the cold and dry season, from October/November until January, along with the highest salinity and lowest water temperatures. Graptocorixa sp. was the most abundant and widely distributed species in the West Basin, followed by Krizousacorixa azteca. The characteristics of the West Basin, such as its temporality and elevated salinity and pH, have favored the explosive development of this group, probably because these “extreme” conditions are unfavorable for competitors and predators.