Progress in the reintroduction program of the tequila splitfin in the springs of Teuchitlán, Jalisco, Mexico

Summary

The tequila splitfin (Zoogoneticus tequila), Critically Endangered and confirmed extinct in its native Teuchitlán River in Jalisco, Mexico, became the focus of a reintroduction led by the Universidad Michoacana de San Nicolás de Hidalgo and Chester Zoo, following IUCN reintroduction guidelines and funded by international aquarium and livebearer conservation groups. The founder population came from a 15-year captive lab colony; 80 individuals were first released into large artificial ponds in 2012, growing to an estimated 10,000 fish over four years and providing both a study population and a source for reintroduction. Two years of surveys found the river's upper reaches and springs offered the best habitat, identified an invasive livebearer as a key competitor needing removal, and found parasite loads posed low risk. After clearing exotic fish and treating fish and habitat for parasites, researchers released 629 splitfin into five mesh net cages and 80 into an exotic-free spring; within three months about 84% of caged fish died, but survivors produced 84 offspring and 32 pregnant females, while 45% of spring-released fish survived and also reproduced. A parallel environmental education program and 22-volunteer community water-monitoring group raised local awareness, with 75% of surveyed residents reporting greater appreciation of the aquatic habitat after two years. Ongoing pressure from non-native fish connected to a nearby dam remains a major obstacle to fully securing the upper river. The project rates itself only partially successful so far, noting the species is demonstrably capable of surviving and reproducing in the wild but that conclusive results require several more years of monitoring.