Effects of Habitat Utilization on the Life Histories of Two Imperiled, Sympatric Dionda (Cyprinidae) in the Rio Grande Basin, Texas

The genus Dionda consists of at least 12 species, of which most inhabit springdominated streams within the western Gulf slope drainages of North America and demonstrate some differences in habitat selection within these systems. The purpose of this study was to assess the influence of stenothermal spring or eurythermal stream habitat selection on the life history strategies of the stream-associated Dionda argentosa, a population of Dionda diaboli restricted to the spring influenced portions of Pinto Creek (Kinney County, Texas), and a population of D. diaboli utilizing stream habitats in the Devils River (Val Verde County, Texas). While differences in spawning seasons between the two species were noted, all three populations displayed life histories characteristic of opportunistic strategists including early maturation, long spawning seasons, production of multiple batches of oocytes, and short lifespans (<3 y). Differences in reproductive season between the spring-and stream-associated Dionda were consistent with the hypothesis stenothermal waters of springs lack terminating cues to induce gonadal quiescence in fishes.