Estimating the population size and habitat quality of the Endangered fish Tlaloc hildebrandi in Mexico

The Chiapas killifish Tlaloc hildebrandi is an Endangered and endemic fish that inhabits wetlands, mountain streams, and rivers in Chiapas, Mexico. This species is considered vulnerable due to accelerated human population growth in its distribution range and the species' low genetic diversity. To evaluate the conservation status of the species, we assessed habitat quality and estimated the population size of the remnant populations in the Amarillo River subbasin using the capture-mark-recapture technique. Our results showed substantial levels of habitat perturbation in the Amarillo River subbasin, including water pollution with a high presence of coliforms, the presence of exotic species, and modified habitat quality, which has resulted in a decrease in population sizes and the extirpation of certain populations. Our estimates of the population sizes of T. hildebrandi based on the Jolly-Seber model showed dramatically low population sizes, ranging from 93 to 208 fish across sites. Gross population sizes varied temporally, and the location of these populations in isolated sites may increase demographic stochasticity. To preserve some of these populations, urgent conservation and management activities must be implemented. We suggest the establishment of conservation areas for the species in the Fogotico River (which has the best water quality and habitat conditions) and habitat restoration in the protected areas of La Kisst and Maria Eugenia Mountain Wetlands, where populations of T. hildebrandi could be reintroduced. Finally, we propose the implementation of ex situ conservation programs to maintain genetic diversity and prevent local extinctions of the most vulnerable populations.