Watershed-Scale Conservation of Native Fishes in the Brazos River Basin, Texas
Kevin B. Mayes, Gene R. Wilde, Monica E. McGarrity, Brad D. Wolaver, and Todd G. Caldwell
Abstract.—The Brazos River crosses eight ecoregions on its journey from New Mexico through the heart of Texas to the Gulf of Mexico. This diverse stream ecosystem supports at least 85 fish species, many of which—including two endangered, migratory, pelagic broadcast-spawning cyprinids, Smalleye Shiner Notropis buccula and Sharpnose Shiner N. oxyrhynchus—have life histories that track the natural flow regime. These two shiners were listed as endangered in part because of severe range reductions that left each with one viable population in the upper Brazos River. Given their short life span, a single adverse event, such as a persistent drought of two consecutive years, could lead to extinction. This concern was nearly realized in 2011 when a record drought and heatwave resulted in complete reproductive failure of these species, which led to rescue efforts for imperiled shiners confined to drying pools. Seventeen major reservoirs control streamflow and create distinct, disconnected fragments in the Brazos River basin. Long-term ecological studies have provided a strong science foundation for guiding water and environmental flow management and watershed conservation. Implementation of both upland and riparian best management practices in the upper Brazos River watershed, including management of invasive saltcedar Tamarix spp., seeks to improve habitat for fish and wildlife. Hydrological monitoring and modeling is being conducted to evaluate the potential for saltcedar control to improve base flows. Identification of stream reaches most threatened by drying and where aquifer pumping may reduce groundwater inflows to streams is the focus of ongoing research on groundwater–surface water relationships. Fish passage barriers hinder successful recruitment, migration, and recolonization of prairie fishes. Removal and mitigation of barriers, as appropriate, will be critical to restoring ecological functions and connectivity required for migratory fishes. Research on propagation and repatriation of prairie fishes is needed to inform conservation and recovery efforts. A watershed-scale, multidisciplinary approach coordinated across borders and among entities is critical to ensure conservation efforts result in the persistence of native fishes in the Great Plains, including the Brazos River.