Entrainment. Entrainment (inadvertent capture of fish into an irrigation ditch) can permanently remove individual fish from a population and strand them when irrigation headgates are closed, resulting in mortality of entrained Arctic grayling. In the Centennial Valley, entrainment was likely a historical threat for Arctic grayling at some locations (Xxxxxxx 1989, p. 10; Xxxxxx 2001, pp. 2-4, 3- 18, 3-25), particularly outside of the Refuge (Xxxxx 2010, pers. comm.). Currently, one irrigation ditch is present on the Red Rock Lakes National Wildlife Refuge. To minimize entrainment of fry, this ditch is not operated when Arctic xxxxxxxx xxx are expected to be migrating and vulnerable to entrainment in Red Rock Creek (West 2014a, pers. comm.). However, entrainment of older and larger Arctic grayling at other times of the year is unknown. Other irrigation ditches are present upstream and downstream of the Refuge boundary; however, there is currently no information about entrainment of Arctic grayling in ditches on non-Federal land in the Centennial Valley.
Entrainment. (1) Chelan PUD shall conduct no more than 140 days of entrainment sampling over four sampling years, using the same methodology used during the 2000 and 2001 field seasons, or another methodology of comparable cost recommended by the LCFF, and approved by WDFW, USFWS, and WDOE. Upon request of WDFW, Chelan PUD shall develop a sampling plan in consultation with USFWS, WDOE, and the LCFF, subject to approval by WDFW. The plan shall specify the sampling years and the allocation of sampling days among such years. The first sampling year shall not be prior to the seventh anniversary of the effective date of the New License, and the last sampling year shall be no later than the 35th anniversary of the effective date of the New License. The purpose of the sampling is to determine if significant numbers of adult spawnable age/size adfluvial westslope cutthroat trout are entering the power tunnel entrance.
