La Luz Splitfin

Zoogoneticus purhepechus is a small freshwater fish of the Goodeidae family, endemic to the Mexican states of Jalisco and Michoacán. Its historical distribution range covered a vast territory including the lower basin of the Lerma River, Lake Chapala, the Grande de Santiago River, as well as several lagoons (Atotonilco, San Marcos, Zacoalco, Zapotlán, Sayula) and the upper basin of the Ameca River. Today, the species has disappeared from most of these habitats, notably from the Grande de Santiago River and most of the lagoons. Its current distribution is fragmented into several isolated subpopulations with varying conservation statuses: listed as Endangered (EN) in Lake Chapala and the Duero River, Critically Endangered (CR) in the Ameca River and the Sayula Lagoon, and Data Deficient (DD) in the Zapotlán Lagoon where its presence has not been confirmed since 1990. Despite a minimal extent of occurrence of 12,000 km², the species is experiencing a severe decline due to pollution, droughts, and competition with exotic species.

Sexual dimorphism is marked by the structure of the anal fin and size. Females are usually larger and more robust than males, especially during gestation. Males are distinguished by their gonopodia (reproductive structures derived from the modification of anal rays) and sometimes by a brighter coloration or slightly more developed fins during courtship.

The current distribution is the result of a dramatic decline of its historical populations. In the Grande de Santiago River basin and Lake Chapala, the species survives only in sections of reed beds and adjacent lagoons (such as Los Negritos), threatened by extreme pollution (heavy metals, DDT, wastewater) and competition with introduced sunfish.

In the lower Lerma River, it is restricted to a few dams and tributaries like the Duero River, where agricultural pollution and invasive species (Poecilia, Xiphophorus, Oreochromis) exert constant pressure. The subpopulation in the upper Ameca River, likely limited to the Teuchitlán River and La Vega Dam, is critically endangered due to pollution related to sugarcane production and predation by exotic species. In the Sayula Lagoon, almost dried up by climate change, the species only persists in temporary ponds and ditches. Finally, in the Magdalena Lagoon, the species has almost disappeared from the lake and survives only in isolated springs like Almoloya and La Estancia de Ayones, despite the presence of tilapias and other competitors.