Habitat and Substrate Use in Reproduction of Captive Devils River Minnows

Abstract

The Devils River minnow Dionda diaboli is a threatened species once endemic to a portion of the Rio Grande drainage in western Texas and northern Mexico but now found only in the Devils River and San Felipe and Pinto creeks. Because little is known about the biology of this species, it is difficult to establish protocols for maintaining captive populations. We monitored the production of Devils River minnows in two laboratory culture systems containing four substrate types (rocks, gravel, sand, and Spawntex) within each of two habitat types (riffle and pool) that had two subhabitat types each (upper and lower riffle, covered and uncovered pool). A total of 38 adult fish (mean weight = 1.38 g; mean total length = 54 mm) were introduced into the two culture systems (19 fish each, approximately equal sex ratio) on 5 September 2001. From 18 September to 6 December, 2,269 young were removed. A significantly greater number (1,922; three-factor nested analysis of variance [ANOVA], Fisher's least-significant-difference tests, P ≤ 0.05) were in gravel substrate (2–5 cm diameter). However, no differences were found in the counts of young with respect to habitat or subhabitat type. The indoor culture of Devils River minnows is possible using gravel as a spawning substrate and, since parental stock can be manipulated, the technique can be used for establishing refugium populations and for augmenting wild populations.