Threatened fishes of the world: “Xenotoca” eiseni Rutter, 1986 (Goodeidae)

Abstract

Common names: Redtail splitfin, redtail goodeid, mexicalpique cola roja (Miller et al. 2005). Conservation status: Listed as endangered by Jelks et al. (2008) and Dominguez-Dominguez et al. (2005), but not by IUCN (IUCN 2009) or SEMARNAT (NOM 2001). Identification: Possesses a single posteriorly positioned dorsal fin, orange to red-orange pigmentation on the caudal peduncle extending to the caudal fin, most prominent in males; fins without dark pigment; dorsal surface dusky; females lighter ventrally without irregular spotting on body; maximum size 75 mm SL (Miller et al. 2005). Illustration by CSK-L (male, 43 mm SL). Phylogenetic and phylogeographic analyses conducted by Webb et al. (2004), Doadrio and Dominguez (2004), and Kenway (2008). Distribution: Tributaries of the Rios Grande de Santiago, Ameca, Ayuquila, Compostela, and Coahuayana and endorheic Lago de Magdalena basins, Mexico. Abundance: Dominguez-Dominguez et al. (2008), De la VegaSalazar (2006), Dominguez-Dominguez et al. (2005) and our own sampling (2006 & 2008) indicated that many populations are extirpated, or have become small and localized. It was common in the Santiago and Magdalena basins, and present, but not abundant in the Rios Ameca and Compostela. Decreases in abundance occurred at Rio Compostela from 2006–2008 despite similar environmental conditions. In 2008, Poecilia butleri was more abundant than previously; possibly indicating competition between these two species. Ecology: Occurs in spring-fed pools, streams, and lakes to depths of 1 m, aquatic vegetation is occasionally present. Produces young in March and April (Miller et al. 2005). Threats: Habitat degradation, specifically water pollution and extraction of water for irrigation, and introduction of non-natives. Conservation action: “Xenotoca” eiseni receives no governmental protection. Conservation recommendation: Additional surveys are needed to investigate environmental conditions and population sizes of extant populations. Institution of a monitoring program and Environ Biol Fish (2010) 87:219–220 DOI 10.1007/s10641-010-9584-2