DEVILS RIVER MINNOW } Dionda diaboli
DESCRIPTION: A small fish, the Devils River minnow reaches lengths of only about two inches. It has a narrow head and body with a pronounced lateral stripe extending through the eye to the snout, above which are located dark markings that produce a cross-hatched appearance when the fish is viewed from the top. It also has a distinguishing wedge-shaped spot near the tail.
HABITAT: The minnow is found in channels of fast-flowing, spring-fed waters over gravel substrates often associated with emergent aquatic vegetation. It usually occurs where a spring flow enters a stream.
RANGE: Before 1980, the Devils River minnow was known to occur in Texas’ Las Moras, Sycamore, and San Felipe creeks, as well as in the Devils River from near its confluence with the Rio Grande to Beaver Lake near Juno. It was also found in Mexico in the Río San Carlos and the R ío Salado drainages. Today the minnow inhabits only the middle Devils River, Pinto Creek, and San Felipe Creek tributaries to the Rio Grande. It may also persist in the Río Salado.
MIGRATION: Devils river minnows are not known to migrate.
BREEDING: Little is known about the Devils River minnow’s reproduction, but it is thought to be similar to that of the closely related fish Dionda episcopa, which spawns from January through August and deposits non-adhesive eggs near stream bottoms, sometimes beneath several millimeters of gravel.
LIFE CYCLE: The life history of the fish is not known. Its life span has not been studied, but it is estimated to be one to two years.
FEEDING: Based on their long, coiled intestinal tract, species of the genus Dionda are thought to feed primarily on algae.
THREATS: The Devils River minnow is most adversely affected by habitat loss from dam construction, spring de-watering, and other stream modifications. It is also threatened by the introduction of nonnative fishes, degradation of water quality, reduced stream flow, and drought.
POPULATION TREND: The minnow population has decreased immensely and suffered a significant range reduction since the species was first collected in the early 1950s. In 1989, sampling from 24 sites within the fish’s historical range turned up only seven minnows at five sites, and by 1998 the fish could be found in only three locations in Texas.