Spawning Behavior and Nest Association by Dionda Diaboli in the Devils River, Texas (Notes) (Report‪)‬

The Devils River minnow (Dionda diaboli) is federally listed as threatened (United States Fish And Wildlife Service, 1999). This cyprinid occurs in spring-fed waters of the Rio Grande drainage of western Texas, specifically the Devils River, San Felipe and Sycamore creeks (Val Verde County), and Pinto Creek (Kinney County). Captive breeding has been described, including preference for a gravel substrate for spawning (Gibson et al., 2004), aggressive behavior of males over gravel (Gibson and Fries, 2005), and formation of territorial dominance hierarchies over gravel prior to broadcasting in pairs or trios (Phillips et al., 2009). However, D. diaboli never has been observed spawning in the wild and we do not know if laboratory observations are representative of its natural reproductive behaviors. Furthermore, observations of populations made via snorkel survey in the Devils River revealed little preferred nesting substrate (clean gravel, 2-5 cm in maximum-dimension) in the main channel where most D. diaboli were observed. Clean gravel was mainly in spring outflows where fewer D. diaboli were present. Therefore, if D. diaboli requires clean gravel substrate for reproduction in the wild, it must move into spring areas or, depending on season and environmental conditions, must find suitable substrate elsewhere to spawn. Nest association, spawning in nests of other nest-building fishes, is a strategy that other cyprinids may use when suitable substrate is unavailable. This strategy may be parasitic (e.g., dusky shiner Notropis cummingsae and redbreast sunfish Lepomis auritus; Fletcher, 1993), beneficial to the associate (e.g., striped shiner Luxilus chrysocephalus and hornyhead chub Nocomis biguttatus; Johnston, 1994a), or mutualistic, benefiting both the host and nest associate (e.g., green sunfish Lepomis cyanellus and redfin shiner Lythrurus umbratilis; Johnston, 1994b). There are several nest-building fishes in the Devils River (e.g., centrarchids, cichlids, and cyprinids), and it is possible that D. diaboli may use these nests for spawning in the absence of other clean gravel areas. Objectives of our study were to observe D. diaboli spawning in the wild, describe these behaviors, and compare them to laboratory observations.