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l40 HAMILTON ET AL. Waddell and May (1995) reported that selenium concentra- tions in muscle plugs from all the adult razorback suckers caught at Stewart Lake Drain (1 fish; 23.9 Ilg/g) and Ashley Creek (9 fish; 11.9-54.1Ilg/g) and 3 of 12 caught at Razor- back Bar (11.5-32.0 Ilg/g) were greater than 8Ilg/g. Sel- enium concentrations in muscle tissue equal to or greater than 8 Ilg/g have been implicated in reproductive failure in fish (Lemly and Smith, 1987). Stephens and Waddell (1998) reported selenium concentrations in muscle plugs from ad- ditional wild razorback suckers collected from the Green River. Selenium concentrations in 7 of 12 muscle plugs from razorback sucker caught in the Escalante Bar-Razorback Bar area were 8llg/g or higher (8-46Ilg/g), whereas an additional 8 razorback suckers caught in the Old Charlie Wash area of the Green River all had concentrations of 5 Ilg/g or less (3.1-5.0 Ilg/g). Their combined data demon- strate that 10 of 26 adults from the Escalante Bar-Razor- back Bar area, 10 of 10 adults from the Stewart Lake Drainj Ashley Creek area, and none of 9 from the Old Charlie Wash area had selenium concentrations above 8 Ilg/g in muscle plug. The elevated selenium concentrations in fish from the Stewart Lake Drain/Ashley Creek area may have been a result of adults temporarily using the Stewart Lake Drain/Ashley Creek area at some point prior to spawning. Consequently, some ofthe larvae evaluated in the present study may have come from adults with elevated amounts of selenium in their tissues. Others have reported that adult razorback sucker have been captured in Stewart Lake (E. Peterson, USFWS, per- sonal communication, 1997) or in Stewart Lake Drain and Ashley Creek (Tyus, 1987; Tyus and Karp, 1990; Waddell and Wiens, 1992). Modde (1993) reviewed adult razorback sucker capture data between 1975 and 1991 and concluded that the Stewart Lake Drain/Ashley Creek area was regular- ly used by razorback suckers in both high and low flow water years. He also concluded that because of the documented high selenium concentrations at the Stewart Lake Drain/Ashley Creek area in water, sediments, and biota reported by Stephens et al. (1988, 1992), and Peltz and WaddeIl (1991), "it is likely that a significant portion of the remaining razorback sucker population in the middle Green River have been exposed to selenium contamination." The selenium concentrations in some of the wild adults reported by Waddell and May (1995) and Stephens and Waddell (1998) were substantially higher than those in adult razorback suckers held for a year at three sites with varying amounts of selenium in water and food near Grand Junc- tion, Colorado, as part of a reproduction study (S. Hamil- ton, USGS, unpublished data). In that study, adults at the reference site, Horsethief Canyon State Wildlife Area, had selenium concentrations in muscle plugs ranging from 4.4 to 5.2 Ilg/g, (means of 2-9 fish at each sampling). At a second site, Adobe Creek, where selenium concentrations in water ranged from 2 to 10 Ilg/liter and in zooplankton from 14 to 52 Ilg/g, selenium in muscle plugs increased from 3.9 ~lgl g at stocking to 12 Ilg/g a year later. At a third site, North Pond at Walter Walker State Wildlife Area, where selenium con- centrations in water ranged from 4 to 141lgjliter (2 months prior to stocking the site had 115-133Ilg/liter) and in zoo- plankton from 21 to 40llg/g (2 months prior to stocking, invertebrates at the site had up to 66 Ilg/g), selenium in muscle plugs increased from 4.1Ilg/g at stocking to 17 Ilg!g a year later. Forty percent (18 of 45) of the adults sampled by Waddell and May (1995) and Stephens and Waddell (1998) had selenium concentrations equal to or higher than the fish held at the Adobe Creek and North Pond sites, even though those fish were held at these two elevated selenium environments for a year and they had no opportunity to move to low selenium environments. The higher selenium in a substantial portion of the fish reported by Waddell and May (1995) and Stephens and Waddell (1998) may indicate that some adults choose, or are forced by lack of uncon- taminated habitat, to use habitat with high selenium in water, food organisms, or both. It also suggests that wild razorback sucker can accumulate substantial amounts of selenium in their tissues even though they are free to move throughout the Green River in search of suitable habitat. Modde (1993) reviewed the capture records for razorback suckers and concluded that the Stewart Lake Drain/Ashley Creek area was regularly used by adults, especially in low flow years when contaminant effects from selenium would not be ameliorated by dilution with river water as in high flow years. Hamilton and Waddell (1994) reported that selenium concentrations in eggs of wild adult razorback suckers col- lected from Razorback Bar in 1992 ranged from 3.7 to 1O.6Ilg/g. These concentrations were within the range of those reported in eggs of razorback sucker near Razorback Bar in 1988 (4.9Ilg/g, Peltz and Waddell, 1991) and in 1992 (28 Ilg/g, Waddell and Wiens, 1992). Hamilton and Waddell (1994) concluded that selenium concentrations in eggs were sufficiently elevated to suspect reproductive problems that may be contributing to the decline of razorback sucker in the upper Colorado River basin. [n the reproduction study with adult razorback suckers held at three sites in Grand Junction, Colorado, the mean selenium concentration in eggs from fish at the reference site was 6.5 Ilg/g, whereas at the two sites with elevated selenium, eggs contained 46 Ilg/g at Adobe Creek and 38 Ilg/g at North Pond (S. Hamilton, USGS, unpublished data). Adverse effects in larvae hatched from those eggs such as reduced growth and survival and a variety of deformities were observed. Because the muscle plugs in these captive held adults contained lower selenium concentrations than in 40% of the adults sampled by Wad- dell and others, it seems reasonable to assume that eggs and the resulting larvae from wild adults would probably con- tain elevated selenium concentrations, which would result in reduced survival of larvae in the environment.