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 A recently published genetic study conducted by researchers from the University of Colorado - Boulder(Metcalf et al. 2012) compared mitochondrial DNA of extant cutthroat trout populations from Colorado with cutthroat trout museum specimens collected in the late 1800s, thereby providing an understanding of the native ranges of cutthroat trout in Colorado prior to major fish stocking efforts. Several significant conclusions resulted from this study, namely that the greenback is native only to the South Platte River drainage and that a different subspecies was native to the Arkansas River drainage. This subspecies, the yellowfin cutthroat trout(O. C. macdonaldi), is considered to be extinct(Metcalf et al. 2012; Wiltzius 1985). Another significant conclusion of the Metcalf et al. study (2012)is the identification of two distinct lineages of cutthroat trout on the West Slope of Colorado, one of which is the Colorado River cutthroat trout and the other is a newly identified lineage, which we temporarily refer to as the green lineage cutthroat, based on the map provided in the Metcalf et al. 2007 report in which these fish were shown in a green color. The common and scientific name will be described for the green lineage cutthroat in the near future. This study identified an additional cutthroat lineage; this lineage was located in the San Juan River drainage and is also considered to be extinct. Populations of the Colorado River cutthroats that are present on the east side of the Continental Dive are presumably due to stocking from West Slope sources in the past. Populations of the green lineage cutthroat trout are also present on the east side of the Continental Divide although uncertainty remains of the origin of these fish. A concurrent meristic study of cutthroat trout in Colorado (Bestgen et al. 2013) complemented the 2012 genetic study. The meristic study was conducted by researchers at the Larval Fish Laboratory at Colorado State University, and included cutthroat trout specimens collected from all major drainages in Colorado, Wyoming, Utah, and New Mexico. Both meristic and genetic analyses were conducted on these specimens in a"double-blind" fashion in which neither group of researchers was aware of the origin of the specimens. The meristic study was completed in the spring of 2013 and a final report was presented to the Greenback Cutthroat Recovery Team in 2014. The observed meristic differences supported the genetic study while also providing an even greater refinement of cutthroat trout groups than previously identified through the genetic study. Designated Critical Habitat Critical habitat has not been designated for the greenback cutthroat trout. Threats The main reasons cited for the subspecies' decline are hybridization, competition with non- native salmonids, and overharvest. New threats have arisen or have become more prevalent and include increased human population growth within the range of the subspecies, along with potential for new water depletions; new introductions of non-native species; fragmentation and genetic isolation of small populations; the effects of fire and firefighting with chemical retardants; and the effects of global climate change. Additional threats exist with impacts limited July 2017 25