2020-10-27_PERMIT FILE - C1981035 (20)

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Biological Assessment Federal Coal Lease Modification(COC-62920)and Federal Mine Permit(CO-0106A)Revision and Renewal 5.1 Descriptions of Species and Critical Habitat Analyzed in Detail 5.1.1 Rio Grande Silvery Minnow The Rio Grande silvery minnow was once one of the most widespread and abundant fish in the Rio Grande River basin of New Mexico, Texas, and into Mexico. The decline of the species has been attributed to modification of stream flows, stream channelization, channel desiccation by impoundments, water management practices, competition with and predation by non-native fishes, and reduced water quality (USFWS 1994, 1999b). Life History The Rio Grande silvery minnow is a freshwater schooling fish species. It has a small, heavy body that is round to ovate in cross section and rarely exceeds 4 inches in length. It is light greenish- yellow dorsally and light cream to white on its ventral side, with dorsal and pectoral fins rounded at the tips. The Rio Grande silvery minnow is a pelagic spawner, producing thousands of semi-buoyant, non-adhesive eggs that drift downstream while developing (USFWS 2007). Developing eggs and larvae drift passively with river currents for about 3 to 5 days (Platania and Altenbach 1998). Drift distances may cover more than 620 miles with elevated river flows during the spring spawning period. Spawning is associated with high-flow events—such as spring runoff or summer rainstorms—and typically occurs over a relatively brief period (1 month)in May or June, although spawning can occur later in the season. Spawning takes place in the water column when water temperatures range between 68°F and 75°F (USFWS 2007). The Rio Grande silvery minnow feeds on algae, larval insect skins, and plant material scraped from bottom sediment(Sublette et al. 1990). Habitat Rio Grande silvery minnows prefer large streams with slow to moderate currents over a mud, sand, or gravel bottom. Habitat includes pools and backwaters of low-gradient creeks and small to large rivers (Page and Burr 2011). This riverine minnow occurs in perennial sections of the Rio Grande and associated irrigation canals (Sublette et al. 1990). Most often it occurs over silt substrates (much less often sand) and typically inhabits pools, backwaters, or eddies formed by debris piles; larger individuals use a broad spectrum of habitats, including main- and side- channel runs, but this species rarely uses areas with high water velocities (USFWS 2007). The species most commonly occurs in depths of less than 8 inches in the summer and 12 to 16 inches (median)in the winter; few individuals use areas with depths greater than 20 inches (USFWS 2007). Winter habitat tends to be near instream debris piles (USFWS 2007). July 2017 21