Common name: Gray Redhorse. Conservation status: Considered threatened (Propst 1999; CONABIO 2002; Jelks et al. 2008). Identification: Dorsal and lateral region olive to yellowish, ventral region whitish to pale yellow (Thomas et al. 2007). Dorsal and caudal fins dusky in inter-radial spaces (Sublette et al. 1990). D 11–12, A 6–7, P 15–16, lateral line scales 44–46 (Sublette et al. 1990). Distribution: Moxostoma congestum occupies upland streams from the Brazos drainage in Texas to the Rio Soto la Marina drainage in Mexico (Jenkins 1980; Conner and Suttkus 1986). Abundance: Relative abundance typically less than 1% (Platania 1990; Cantu and Winemiller 1997; Watson 2006; Bean et al. 2007). Habitat and ecology: Occupies clear streams (Rose and Echelle 1981) and is associated with deep (>0.8 m), low current velocity (<0.1 m·s) habitats such as large runs and pools (Bean et al. 2007). Benthic invertivore (Cowley and Sublette 1987; Bean and Bonner 2008) with diet primarily of aquatic insects (47%), mollusks (42%), and amphipods (5%). Most common aquatic insects were Diptera and Ephemeroptera larvae (Bean and Bonner 2008). Reproduction: Individuals spawn over two periods; first in late February or early March and again in late April or early May; single or multiple clutches per period unresolved (Bean and Bonner 2008). Developing oocytes absent in females <392 mm (Bean and Bonner 2008). Spawns in groups of two to seven individuals over gravel and cobble substrate in tails of pools (Martin 1986; Miller et al. 2005). Threats: Populations have declined in streams with reduced water quality and discharge (Hoagstrom 2001). Depletion of surface water is a major cause of decline (Sublette et al. 1990) and threatens habitats where M. congestum occurs (Bowles and Arsuffi 1993). Conservation recommendations: Protection through management of water quality and quantity where populations persist.