The extinction of the Catarina pupfish Megupsilon aporus and the implications for the conservation of freshwater fish in Mexico A RCADIO V ALDÉS G ONZÁLEZ,LOURDES M ARTÍNEZ E STÉVEZ M A .ELENA Á NGELES V ILLEDA and G ERARDO C EBALLOS Abstract Extinctions are occurring at an unprecedented ; Régnier et al., ). Since the start of the st century it rate as a consequence of human activities. Vertebrates con- has become clear that population depletion and extinction stitute the best-known group of animals, and thus the group of both freshwater and marine fishes is a severe and wide- for which there are more accurate estimates of extinctions. spread problem (e.g. Ricciardi & Rasmussen, ; Myers Among them, freshwater fishes are particularly threatened &Worm,; Olden et al., ; Burkhead, ). and many species are declining. Here we report the extinc- Extinction of freshwater fishes has been relatively well tion of an endemic freshwater fish of Mexico, the Catarina documented in North America (e.g. Miller et al., ; pupfish Megupsilon aporus, the sole species of the genus Burkhead, ). A compilation of the conservation status Megupsilon. We present a synopsis of the discovery and de- of freshwater fishes in Mexico has revealed that species scription of the species, the threats to, and degradation of, its have become extinct in the wild or have been extirpated habitat, and the efforts to maintain the species in captivity from the country, and . (% of all species in before it became extinct in . The loss of the Catarina Mexico) are facing extinction (IUCN, ; Ceballos et al., pupfish has evolutionary and ecological implications, and b; Table ). highlights the crisis of freshwater fish extinctions. It is a While compiling these data we found that the Catarina warning of the likely fate of more than freshwater fish pupfish Megupsilon aporus is the most recently extinct en- species threatened with extinction in Mexico. To save these demic freshwater fish in Mexico. This species, which be- species, the country urgently needs a national strategy to ar- longs to the Cyprinodontidae and is one of the smallest ticulate a bold conservation effort, with better policies on fishes in North America, was lost as a result of desiccation ecosystem management and water use. of the only freshwater spring it inhabited, in El Potosi, Galeana, Nuevo León (Miller et al., ; Bennett & Keywords Catarina pupfish, conservation, Cyprinodontidae, Conway, ). Unfortunately, this is not an isolated case. extinction, fish, Megupsilon aporus,Mexico Major threats to freshwater fishes in particular and fresh- water biodiversity in general have been grouped into five categories: overexploitation of water resources, water pollu- Introduction tion, flow modification, destruction or degradation of habi- tat, and invasive species (Silk & Ciruna, ; Dudgeon iodiversity loss is one of the most severe environmental et al., ). Inland waters in Mexico have experienced Bproblems, with thousands of species having gone ex- these threats, and currently % of main rivers are polluted, tinct since the start of the th century and hundreds of . , dams have modified their flow and . invasive thousands of populations being lost as a result of human ac- species inhabit inland waters (Carabias & Landa, ; tivities (Ceballos et al., a). The rate of extinction of ver- Domínguez-Domínguez et al., ; CONAGUA, ). tebrate species in this period has been up to times faster The effect of these threats on freshwater fishes depends than in the last million years (Ceballos et al., ). on the particular environmental conditions, the type and Extinctions of birds and mammals have been documented amount of pressure exerted by human activities, and the more thoroughly than extinctions of fishes and inverte- distribution range of species. For instance, species with re- brates, which have often been overlooked (e.g. Dirzo et al., stricted distributions, such as the Cuatro Cienegas platyfish Xiphophorus gordoni, which inhabits desert springs, and the Yucatan tetra Astyanax altior, endemic to cenotes in the ARCADIO VALDÉS GONZÁLEZ and MA.ELENA ÁNGELES VILLEDA Universidad Autónoma de Nuevo León, Nuevo León, Mexico Yucatan Peninsula, are more imperilled than those with a LOURDES MARTÍNEZ ESTÉVEZ (Corresponding author) Department of Ecology and wide distribution (Jelks et al., ; Contreras-MacBeath Evolutionary Biology, University of California, 115 McAllister Way, Santa Cruz, et al., ). Meanwhile, habitats in northern Mexico with California 95060, USA. E-mail [email protected] major water supply problems as a result of semi-arid and GERARDO CEBALLOS Universidad Nacional Autónoma de México, Mexico City, arid conditions are at higher risk of desiccation than Mexico aquatic systems in south-east Mexico (Contreras-Balderas Received September . Revision requested November . Accepted April . First published online December . & Lozano-Vilano, ; Carabias & Landa, ; Ceballos Oryx, 2020, 54(2), 154–160 © 2018 Fauna & Flora International doi:10.1017/S003060531800056X Downloaded from https://www.cambridge.org/core. IP address: 170.106.35.229, on 25 Sep 2021 at 23:58:58, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S003060531800056X Extinction of the Catarina pupfish 155 TABLE 1 Freshwater fish species that are extinct in the wild or extirpated in Mexico (Ceballos et al., b). Species Distribution Status Cyprinodon alvarezi Mexico, endemic Extinct in the wild Cyprinodon longidorsalis Mexico, endemic Extinct in the wild Cyprinodon veronicae Mexico, endemic Extinct in the wild Skiffia francesae Mexico, endemic Extinct in the wild Xyrauchen texanus North America Extirpated Gila elegans North America Extirpated Hybognathus amarus North America Extirpated Notropis simus North America Extirpated Ptychocheilus lucius North America Extirpated Rhinichthys osculus North America Extirpated et al., a,b). Watershed management in Mexico therefore requires addressing local conservation issues with a regional PLATE 1 The Catarina pupfish Megupsilon aporus was a freshwater fish endemic to Mexico; it is now extinct: (a) male, perspective, to ensure the maintenance of these habitats and (b) female. Photograph by Daniel Garza Tobón. their fish populations in the long term (Stiassny & Bianco, ; Ceballos et al., b). The Catarina pupfish (Plate ) was discovered in .It the dorsal fin in females, and particular behavioural traits was described in as the only species of the genus (see below; Uyeno & Miller, ; Miller & Walters, ). Megupsilon, and only years after its scientific discovery The small Catarina pupfish exhibited sexual dimorph- it became extinct in the wild. We present a historical synop- ism. Males were smaller ( mm in length) than females sis of the species and the causes of its decline, and discuss the ( mm; Miller & Walters, ). Adult males were steel implications of the extinction process for the conservation blue on the back and sides of the body, with a golden of freshwater fish diversity in Mexico. sheen in the caudal peduncle, the caudal fin was orange, and a there was a vertical black bar above and below the pupil on the eyes. Adult females had a golden olivaceous col- ouration over the body (Miller & Walters, ). The discovery and description of a new species Available information on the biology and ecology of the Habitat Catarina pupfish is scarce but examination of peer-reviewed and grey literature provided us with sufficient details to docu- The Catarina pupfish was endemic to a freshwater spring at ment the sequence of events and factors that led to the El Potosi, on the west side of Sierra Madre Oriental, and with- species’ decline (Miller & Walters, ; Contreras-Balderas in the Sandia basin, Galeana, Nuevo León, Mexico (°′N & Lozano-Vilano, a,b; Contreras-Balderas et al., ; °′W; Fig. ). This location, at , m, was also home to Echelle et al., ; Jelks, et al., ;Bennett&Conway, the Potosi pupfish Cyprinodon alvarezi and the fresh- ;Burkhead,; Liu & Echelle, ). water crayfish Cambarellus alvarezi (Rodríguez-Almaraz & The first recorded individual of the Catarina pupfish was Campos, ), both also endemic to this small spring. The collected from the wild by R.R. Miller and H.L. Huddle in spring was a remnant of a larger water body in an endorheic , but the species was not described until (Miller & basin known as La Hediondilla (Miller & Walters, ). It is Walters, ). Megupsilon aporus is an endemic Mexican believed that during the Pleistocene the larger lake was con- species (Miller, ). The generic name and species were nected with the Rio Conchos basin and Rio Bravo tributaries assigned based on two particular characters: Megupsilon in in the north. reference to the huge Y chromosome in males, and aporus in Habitat descriptions by Miller & Walters () men- reference to the lack of pores in the cephalic sensory system tioned the presence of a main pond (c. ha) with an inner (Miller & Walters, ). Although the species is related to stream and some secondary ponds. Clear water was present Cyprinodon, the characters that classified it as a separate spe- year-round, with depths of .– m (Miller & Walters, cies, along with those previously mentioned, were a different ). These conditions remained until the early s number of chromosomes between males () and females (Plate ; Rodriguez-Almaraz & Campos, ). The vegeta- (), the presence of side scales between the dorsal and tion in the area included pennywort Hydrocotyle sp., anal fins, the lack of a black terminal