Threatened Fishes of the World: Dionda diaboli Hubbs & Brown, 1956 (Cyprinidae)

Abstract

Common name: Devils River minnow. Conservation status: Listed as threatened by the U.S. Fish and Wildlife Service 1999. Identification: Darkly outlined scales above the lateral stripe give a cross-hatched appearance. Also with a black spot on the caudal fin base that is often wedgeshaped, a black lateral stripe through the eye and onto the snout, and double dashes along the lateral line. Adults typically 30–40 mm SL. Drawing by Robert G. Howells. Distribution: Type locality is Baker’s Crossing on the Devils River, Val Verde County, Texas (Hubbs & Brown 1956). It is known to occur in Texas in the Devils River, San Felipe Creek and Sycamore Creek, Val Verde County. Extirpated from Las Moras Creek, Kinney County (Garrett et al. 1992). There are also historic records of occurrence in two small streams in Coahuila, Mexico, the Rio San Carlos and Rio Sabinas. Because no collections have been made there since the early 1970s, their current status in Mexico is unknown but, at best they are thought to be rare (Miller 1978). Abundance: The Devils River minnow has a spotty distribution within its range. At various times it has been relatively abundant (Hubbs & Brown 1956, Harrell 1978), yet at other times exceedingly rare (Garrett et al. 1992). Habitat and ecology: Little is known of the life history of the species and habitat specificity is not known. Often found in association with spring outflows and adjacent to aquatic macrophytes and may inhabit a microhabitat associated with the interface between spring runs and the river (Hubbs & Garrett 1990). Reproduction: Likely to spawn in the spring with non-adhesive and demersal eggs, similar to traits reported for D. serena (Hubbs 1951). Threats: Populations appear to have become reduced in number and size in recent history (Garrett et al. 1992). Reasons for this decline are not known, although remaining populations are potentially threatened by loss of habitat through reduced spring flows, reduction in water quality and predation and competition with exotic species. However, since little is known of the life history requirements or the ecological interactions of the Devils River minnow, it is difficult to properly assess threats or fully implement recovery actions. Conservation action: A Conservation Agreement was developed in 1998 among the Texas Parks and Wildlife Department, the City of Del Rio and the U.S. Fish and Wildlife Service and is designed to foster research to ‘eliminate or significantly reduce the probability that potential threats to the minnow will actually harm this species and to recover populations of the minnow to viable levels’. A critical subset of the range of D. diaboli is now owned by the Texas Parks and Wildlife Department and the Nature Conservancy of Texas. Conservation recommendation: The conservation actions and recommendations listed in the Conservation Agreement should be fully implemented in order to ensure survival of the species. Further research on the ecological requirements of this species is especially warranted.