2010-11-22_REVISION - M2009023 (7)

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some other spawning site. Of the 12 individual razorbacks handled in 1987, eight were running ripe males while the other four specimens were females that appeared gravid. In 1988, a total of 10 razorback suckers were handled at the same general location, 5 of which were in reproductive condition (Platania et al. 1991). Six of the ten individual specimens in the 1988 samples were recaptures from 1987. Also, in 1988, a single adult tuberculate male razorback sucker was captured at approximately RM 80 on the San Juan River near Bluff, Utah. Particularly noteworthy is that this is the first confirmed record of this species from the main stem San Juan River. The presence of this reproductively mature specimen suggests that the razorback may be attempting to spawn in some unknown location within the riverine portion of the San Juan drainage. No razorback suckers were captured in 1989. In fact, no known wild razorback suckers have been collected on the San Juan River since 1988 (Dale Ryden, USFWS, pers. comm., 2002). The existing scientific literature and historic accounts by local residents strongly suggests that razorback suckers were once a viable, reproducing member of the native fish community in the San Juan River drainage.- Currently, the razorback sucker is rare throughout its historic range and extremely rare in the main stem San Juan River. There is no evidence from anywhere in the Colorado River system that indicates substantial recruitment to any population of razorback sucker (Bestgen 1990, Platania 1990, Platania et al. 1991, Tyus 1987, McCarthy and Minckley 1987, Osmundson and Kaeding 1989). Because razorback sucker are so rare in the San Juan River, an experimental stocking program was initiated. In March 1994, fifteen radio-tagged razorback suckers were stocked in the San Juan River at Bluff, Utah (RM 79.6); near Four Corners Bridge (RM 117.5); and above the Mixer in New Mexico (136.6). In October 1994 an additional 16 radio-tagged adults were stocked as well. as 656 PIT-tagged fish in the same locations as well as an additional site just below the Hogback Diversion in New Mexico (RM 158.5). Monitoring found that these razorback suckers used slow or slackwater habitats such as eddies, pools, backwaters, and shoals in March and April and fast water 92.2 percent of the time in June and August (Ryden and Pfeifer 1995b). During 1995, both radio-tagged fish and PIT-tagged fish were contacted or captured. Razorback suckers were found in small numbers from the Hogback Diversion (RM 158.6) to 38.1 river miles above Lake Powell (Dale Ryden, USFWS, pers. comm. 2002). An additional 16 razorback suckers were stocked in September 1995 and in October 1996, 237 fish were stocked. Results of the monitoring efforts indicated that the San Juan River provides suitable habitat to support subadult and adult razorback sucker on a year-round basis (Ryden and Pfeifer 1996). This led the Program to initiate a 5-year augmentation program for the razorback sucker in 1997 (Ryden 1997). Between September 1997, and November 2001, 5,896 subadult razorback suckers were stocked below Hogback Diversion Dam. Furthermore, an additional 25 subadults were stocked in 2002 (USFWS, unpublished data). As of 2001, about 2 percent of the fish stocked from 1994 to 2001 were recaptured and 40 adult or subadult razorback suckers were recaptured in 2002 (USFWS, unpublished data). Four ripe male razorback sucker collected via electrofishing at RM 100.2 in spring 1997 appeared to be part of a spawning aggregation. Three other razorback sucker were positively identified within the aggregation of fish but could not be successfully netted. Several of the collected fish had moved up or down the river to the general location of the aggregation, 15