Culture Studies of the Devils River Minnow

Abstract

Requirements for indoor culture of the threatened Devils River minnow Dionda diaboli were developed and refined. Spawning over gravel previously occurred in experimental systems with a riffle area under a compressed seasonal cycle (temperature and photoperiod). Subsequently, spawning occurred without the riffle area and seasonal cycle. Given only gravel (15- 25 mm) and rock (40–80 mm) as spawning substrate, more eggs were found in the gravel (Mann-Whitney tests, P < 0.001). Additionally, pairwise breeding was achieved in both wild-stock and first-generation fish; average survival from egg to fry was improved from about 25% to 45%; a growth curve was developed, in which fish averaging 7 mm total length (TL) grew to an average of 35 mm TL in 192 d; growth rate was noted to decline as culture density increased (nonlinear regression, P < 0.001). Sexually dimorphic characteristics (yellow fins, blue body coloration, and nuptial tuberculation) and aspects of spawning behavior (substrate necessity, territoriality, and mating) are discussed.