13 December 2018

The tequila splitfin, a small species of goodied fish which grows to just 70mm in length, disappeared from the wild completely in 2003 due to pollution and the introduction of invasive, exotic fish species in waters where it had previously thrived.

The combined expertise of our conservationists and a determined team at the Michoacana University of Mexico has led to more than 1500 fish being returned to springs in the Teuchitlán River in the state of Jalisco in south west Mexico.

With the fish thriving and already breeding in the river, the project has been cited as an International Union for the Conservation of Nature case study for successful global reintroductions.

Professor Omar Dominguez, from the Michoacana University of Mexico, said:

“This is the first time an extinct species of fish has ever been successfully reintroduced in Mexico. The tequila splitfin is a very important species, used by scientists to study the evolution, biogeography and live bearing reproduction techniques of fishes. We couldn’t allow it to disappear.

“This project sets an important precedent for the future conservation of the many fish species in the country that are threatened in the wild, but which rarely take our attention.”

In 1998, at the outset of the project, we provided the university’s Aquatic Biology Unit with five breeding pairs of tequila splitfin, from which their scientists were able to found a new colony in the laboratory. Experts there maintained and expanded their numbers over the next 15 years.

In preparation for the reintroduction, 40 males and 40 females from the colony were released into large, artificial ponds, where they were exposed to a semi-natural environment.There the fish encountered fluctuating resources such as prey items, potential competitors, parasites, and predators such as birds, turtles and snakes. Another four years on, this population was estimated to have increased to 10,000 individuals and became the source for the reintroduction to the wild.

Two years of field surveys in and around the Teuchitlán River enabled the team to identify the best release sites, while education work with local communities helped them improve awareness of aquatic habitats and show the value of healthy water sources. A long-term monitoring programme, involving local people trained to assess water and habitat quality, was also established. With the river and its surrounding environment restored, both the fish and the community can once again enjoy the beautiful area and all the benefits of a healthy river.

Dr Gerardo Garcia, our Curator of Lower Vertebrates and Invertebrates, added:

“It is a real privilege to have helped save this charismatic little fish and it just goes to show that with the skill and expertise of conservationists, and with local communities fully invested in a reintroduction project, species can make a comeback from environments where they were once lost.

“This is also a great example of how good zoos can play a pivotal role in species conservation. We have been involved technically and financially and, without our aquarists keeping the species alive for many years at the zoo, this fish would have been lost forever.

“Following years of hard work by our partners, the wild population is, thankfully, now going in the right direction. It just goes to show that animals can re-adapt to the wild when reintroduced at the right time and in the right environments. Chester Zoo’s mission is to prevent extinction and that’s exactly what we’ve done.”