A little fish known as “tequila splitfin” or “zoogoneticus tequila” once swam in a river in western Mexico, but it vanished before the end of the 20th century. But now there is hope.

Due to the introduction of invasive, exotic fish species and water pollution, the tequila fish (Zoogoneticus tequila), a little species of goodies fish that grows no longer than 70mm, became extinct in the wild in 2003. Its success is now intertwined with the community’s identity and being touted internationally, reports AP News.

It all started in Teuchitlán, a community near the Tequila volcano, more than two decades ago. A group of around a half-dozen students, including Omar Domnguez, were concerned about the tiny fish that could fit in the palm of your hand and had only ever been observed in the Teuchitlán river. It had vanished from local waters, owing to pollution, human activity, and the introduction of non-native species, according to experts.

Domínguez, now a 47-year-old researcher at the University of Michoacán, says that then only the elderly remembered the fish called “gallito” or “little rooster” because of its orange tail.

Conservationists from Chester Zoo and Mexico’s Michoacana University collaborated in 1998 to reintroduce around 1500 fish to a succession of springs in the Teuchitlán River in the state of Jalisco. Domnguez stated they brought numerous pairs of tequila splitfin fish from collectors’ aquariums.

The fish started reproducing in tanks, and Domnguez and his colleagues decided to try restoring them to the Teuchitlán river after a few years. “They told us it was impossible, (that) when we returned them they were going to die.”

As a result, they began looking for alternatives. They constructed an artificial pond for a semi-captivity stage and placed 40 pairs there in 2012.

After two years, there were approximately 10,000 fish. The initiative has been recognized as an example of successful global reintroductions by the International Union for Conservation of Nature (IUCN), with current scientific investigations indicating the fish are prospering and spawning in the river.

“When I started the environmental education program I thought they were going to turn a deaf ear to us … and at first that happened,” Domínguez said.

However, patience and years of puppet shows, games, and lectures on the ecological and health importance of “zoogoneticus tequila”—the fish help control mosquitos that cause dengue fever—paid off for the conservationists.

The small fish was given the moniker “Zoogy” by some of the locals. They drew caricatures and founded the “River Guardians,” an all-kids group. They clean the river, collect trash, and remove alien plants.

Because there is no past data to compare, Domnguez said it is difficult to evaluate whether water quality has increased, but the ecology as a whole has improved. There are fewer non-native species in the river, and cattle are no longer allowed to drink in some locations.

The team also carried out two years of field surveys in and around the Teuchitlán River, including diversity and population studies of zooplankton, phytoplankton, invertebrates, fish and parasites, to identify the best release sites. In parallel, they also undertook education work within local communities to improve awareness of aquatic habitats and show the value of healthy water sources.

Inside their floating cages, the fish quickly multiplied. They were marked so that they could be tracked and released. It was late 2017, and the population had more than doubled in six months, increasing 55%. Last month, the fish had expanded to another part of the river.

Experts say they have created a blueprint for future reintroductions of other extremely endangered fish species, and the golden skiffia (Skiffia francesae), restoration is now well underway.

“This is the first time an extinct species of fish has ever been successfully reintroduced in Mexico and so it’s a real landmark for conservation.” as told by Domínguez.

The reintroduction into the nature of species that were extinct in the wild is complex and time-consuming. Przewalski’s horse and the Arabian oryx are among successful examples. The Chester Zoo said on Dec. 29 that the tequila splitfin had joined that small group.

The tequila splitfin is listed as endangered on the IUCN’s red list of threatened species. Pollution, over-extraction of water resources, and other causes are putting stress on Mexico’s freshwater ecosystems. According to 2020 research sponsored by the IUCN and the ABQ BioPark in the United States, more than one-third of the country’s 536 freshwater fish species are threatened with extinction.

Nonetheless, Domnguez and his team in Mexico are already working on another extinct fish, the “skiffia francesae.” In the Teuchitlán River, the Golden Skiffia might one day join “Zoogy.”

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