Ameca splendens Miller & Fitzsimons, 1971

Conservation: Ameca splendens is evaluated by the international union for the conservation of nature in the iucn red list of threatened species as (CR) critically endangered (2018). The distribution range of this species has been rapidly declining in recent decades, and the remaining population is extremely vulnerable (Köck, 2019, Lyons et al., 2019). Of the two populations reported in the 1990s and 2000s (those of Lake Sayula and the Almoloya springs) that of Lake Sayula is believed to be extinct after the springs and pool where A. splendens was found dried up. The population at the Almoloya springs is rapidly declining (Lyons et al., 2019:131), most likely by the introduction of Pseudoxiphophorus bimaculatus, a carnivorous Poeciilid known to outcompete and threaten the survival of other goodeid species (Ramírez Carrillo & Macías-García, 2015). P. bimaculatus is very aggressive and a formidable fry predator, as well as producing more fry than A. splendens does. In the close San Marcos area streams, P. bimaculatus is abundant and goodeids, common before, are now very rare or even absent.

The population in Rio Ameca/Rio Teuchitlán has shrunk to just the upper reaches of the Teuchitlán River and the springs inside the El Rincón recreational area. It is estimated that the population in this area probably numbers in the high hundreds or low thousands (Lyons et al., 2019:130). Twenty years ago, I could easily estimate thousands of them while visiting the area. López-López & Paulo-Maya (2001) found that of 20 native historically known species from the upper Ameca River, only six remained at the time of their study.

While apparently not as abundant yet, Poecilipsis bimaculatus has also been introduced to Teuchitlán River (Ramírez-García et al., 2020:9). There is currently no known way to eradicate most exotic species, like P. bimaculatus.

After arduous work by a group of biologists from the Universidad Michoacana de San Nicolás de Hidalgo [Morelia], leaded by Omar Domínguez-Domínguez, they have managed to create consciousness of the problem in local inhabitants and officials at Teuchitlán. The good news is that Ameca splendens is common in aquariums all over the world, but even this has a limited value if the habitat cannot be restored to allow wild populations to be restored and thrive. As for aquarium keeping, it is of course fine to keep A. splendens for enjoyment only, but in case you want to make a much needed contribution to the conservation of this species, there are two aspects to consider:

First, keep as large a population as you can, having a dozen fish helps very little, the genetic drifting and loss of genetic diversity that occurs when such a small number is kept, particularly when kept in an artificial environment where natural selection pressures are not in place, can quickly degrade the genetic quality of the stock. Bailey et al., 2007 found that wild population of A. splendens is much more genetically diverse than aquarium stocks which have been maintained in captivity for up to 10 years. The good news is that maintaining a commonsensical high enough density of A. splendens is possible and may actually be beneficial for them.

Second, dispose of those fry with obvious deformities, since if you allow them to reproduce, they may fix defects in the captive population that could demean the usefulness of your population for long term keeping. This problem has been observed with Skiffia francesae, another extinct in the wild fish from Teuchitlán, some of which captive populations deriving from 1971 wild stocks exhibit chronic deformities. Also to consider in order to maintaining a population as close to nature as possible is not to select for particular traits, regardless of their attractiveness, for example there is an attractive black morph of A. splendens developed by Michael Kempkes (Köck, 2021), but those forms should be kept aside of natural forms.