The Chapultepec Park in Mexico City is one of the largest metropolitan parks in the western hemisphere with about 685 hectares of extension. For the Aztecs that inhabited the valley of Mexico, it was a retreat for their rulers. Nowadays the park is a favorite place for local people with an estimated 15 million visitors each year. Those people value the park as a cultural, historic area, as well as a green space. The park serves several other functions inside Mexico City as well, such as a lung for the city, rain attractor, and refuge for migratory birds and local fauna, among others.
Inside the park there are three lakes, two of them well-known. The most visited is the artificial (created at the late 19th century) Lake Chapultepec, found in the first of the three sections in which the park is divided. This lake is one of the most popular attractions of the park. In the second section lays a larger lake known as Lago Mayor (larger lake), which includes a monumental fountain and it is surrounded by restaurants and cafés, and, nowadays, plays an additional important role in the conservation of the local aquatic fauna.
After many years of being inhabited by an assortment of exotic species such as carp, tilapia and others, the Lago Mayor was redesigned in 2006 due to a water-seeping crack in part of the concrete lining of the lake. After the lake was drained and repaired, it was decided, after consultation with the Institute of Biology of the University in Mexico City (Universidad Nacional Autónoma de México), to no longer introduce exotic species but to populate the lake with the remaining endemic aquatic species of the valley. Among them is the Mexcalpique (Chapultepec splitfin) Girardinichthys viviparus, a highly endangered Goodeid endemic of the valley, now present in the three lakes inside the park. G. viviparus is listed by the International Union for the Conservation of Nature (IUCN) in their “IUCN Red List of Threatened Species” with a category “Critically Endangered”, which includes species that face an extremely high risk of extinction in the wild in the immediate future. The species is also listed in the Mexican Official Norms (NOM-059-SEMARNAT-2010) with category “In danger of extinction”.
A couple of days ago some news called my attention. In a press release by the National Polytechnic Institute (Instituto Politécnico Nacional) in Mexico City, a PhD thesis by biologist Hugo Fernando Olivares Rubio was awarded the best of 2013. The thesis deals with the effects on the reproduction of the present population of Girardinichthys viviparus of toxic elements present in the lake. The problem was detected in the treated water used to keep the level of the lake steady, which contains pollutants that affects the hormone balance, affecting the reproduction mainly of males of the species. The suggestion offered from the research was to decrease the official level of allowed contaminants in the treated water used in the lakes, given that the pollutants could also affect humans in addition to the fish.
Girardinichthys viviparus is a fish that has a hard time to survive. It is endemic to the endorheic basin of the Valley of Mexico — which is the largest metropolitan area on earth with a human population of over 20 million people (INEGI 2010 Census)— and has seen, over the past years, a decrease of habitat and an increase of pollution of its remaining bodies of water.
To make matters worse, it is a difficult fish to keep in captivity. James Langhammer from the United States reported his struggle to maintain a population of this species in captivity, which turned out to be very prone to fish tuberculosis. As a result of his efforts, he was able to obtain a tuberculosis-free captive population after rapid and repeated breeding of subsequent generations of this species, in which he intended to leave behind the tuberculosis by giving no time for it to infect the new line. Jim also found that in order to properly maintain this fish it had to be fed constantly. The species has an uncoiled intestine no longer than the length of the body, and he found it is susceptible to emaciation if left without food, even for a couple of days. Not a fish for the casual aquarist it seems!
Yet, this fish represents the effects of human expansion on a native species’ habitat and the results and problems faced in trying to keep it from extinction. Let’s hope the efforts of interested people are able to safe this species of what appears to be its doom.
- Olivares Rubio, Hugo Fernando. 2013. "Disrupción endocrina en Girardinichthys viviparus expuesto a mezclas complejas de metales y xenoestrógenos". PhD thesis, Instituto Politécnico Nacional (unpublished) (ffm00591)
© Copyright 2014 Juan Miguel Artigas Azas, all rights reserved
Artigas Azas, Juan Miguel. (febrero 20, 2014). "The hard life of Girardinichthys viviparus". Freshwater Fishes of Mexico. Consultado en octubre 18, 2021, desde: https://mexfish.info/section.php?id=2&lang=es.