Re-introduction of the Morelos minnow in the “Barranca de Chapultepec” protected area, Cuernavaca, Morelos, Mexico

Summary

The Morelos minnow (Notropis boucardi), a threatened fish endemic to a small stream system near Cuernavaca, Mexico that has lost 49% of its historical range in 50 years to water pollution, water management and invasive species, was targeted for reintroduction to the Barranca de Chapultepec protected area by Morelos state authorities and the Universidad Autónoma del Estado de Morelos, guided by IUCN reintroduction guidelines and a genetic study defining the founding population. Because remaining wild populations are small, only a limited number of fish could be collected, and only after the reproductive season; a sustained communication campaign, including journal articles, billboards and media coverage, built public and government recognition of the minnow as the state's only endemic vertebrate. Implementation began with eradicating invasive rainbow trout and common carp from the stream via electrofishing and netting, after which 72 minnows were collected from a heavily polluted but still-inhabited donor stream 3.2 km away and released directly into Barranca de Chapultepec. Post-release monitoring initially found no evidence of establishment, but later surveys detected roughly 300 fish near the release site, including spring-born fingerlings, suggesting a population may be taking hold, though an unanticipated threat emerged from a locally protected population of invasive Muscovy ducks preying on the minnows. Difficulties included this unexpected predation, complicated by local opposition to controlling the ducks, and a narrow annual collection window tied to the species' reproductive cycle. The project rates itself successful based on these preliminary signs, while acknowledging that establishing a truly viable population will require multiple further release events over a longer period.