Laserfiche WebLink
CHAPTER 3 <br />AFFECTED ENVIRONMENT AND ENVIRONMENTAL CONSEQUENCES <br />the complex habitat required by the endangered fish. The flow regimes include the channel maintenance <br />needed to clean the cobble and gravel areas used for spawning and to provide the low-velocity habitat for <br />larval and young-of-the-year fish. <br />Razorback Sucker <br />Intensive ongoing collections between 1990 and 1994, part of a continuing research program by the <br />SJRBRIP, have not resulted in the capture of any additional wild razorback suckers from riverine habitats <br />in the San Juan River. Hatchery-raised razorback suckers (939 individuals) were introduced into the San <br />Juan River between March 1994 and October 1996 (Ryden 2000b). Fifty-seven of the razorback suckers <br />were implanted with radio transmitters and followed to determine habitat use and movement. The <br />remainder of the stocked razorback suckers was implanted with PIT tags for identification before release. <br />The fish originally stocked in 1994 are still being collected during the annual monitoring of the river <br />(Ryden 2000b). <br />Results of this study provided insight into habitat use and behavior of razorback suckers in the San Juan <br />River. Results of radio tracking indicated that fish used less complex, higher velocity habitats during <br />warmer months, but used habitats with higher complexity (where they mostly occupied areas of low <br />velocity) during the cold water months. Sections of the river that were apparently preferred by razorback <br />suckers included two locations associated with backwater habitats (RM 38.6 and RM 77.3), and one <br />location that may be associated with spawning (RM 100.2) (Ryden 2000b). During May 1997 two larval <br />razorback suckers were collected downstream from RM 90. This represented the first documentation of <br />successful spawning by razorback suckers in the San Juan River. A five-year plan for augmentation of <br />razorback suckers in the San Juan River was initiated during 1997 (Ryden 2000b). <br />3.7.4 Environmental Consequences and Mitigation <br />The following sections discuss potential impacts to special status species of Refined Alternative 4, <br />Refined Alternative 6, and the No Action Alternative. In addition, mitigation measures are proposed to <br />reduce or eliminate potential impacts to special status species. <br />3.7.4.1 Refined Alternative 4 <br />Refined Alternative 4 Special Status Species Impact 1 - Less than Significant: Flow alterations in <br />the Animas River could alter riparian vegetation composition and abundance, and affect bald eagle <br />perch or roost sites. <br />The bald eagles in the project area are primarily a wintering population, although nesting has occurred <br />both to the north and south of the project area. Reclamation has conducted six years of aerial surveys to <br />determine bald eagle use in the project area. Primary use sites include cottonwood trees along the <br />Animas and La Plata Rivers and occasionally those adjacent to some irrigation canals. Results of <br />Reclamation surveys indicate that currently, unrelated to the project, cottonwood trees are being felled <br />and development is encroaching on areas of eagle use, reducing available habitat. Additional <br />Reclamation studies of wetland/riparian impacts associated with altered flows in the Animas River <br />indicate negligible impacts on cottonwood trees and bald eagle perch/roosting habitat. <br />This potential impact is considered to be below the level of significance. However, the following <br />mitigation measure would reduce the potential for the impact to occur. <br />Weeminuche Construction Authority <br />P.O. Box AA - Towaoc, CO 81334 <br />3.7 SPECIAL STATUS SPECIES 3-116 No kM A.5 C cacatr? Cotz? 9 <br />C1t?4t('?rT t? - p?a4? N -