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Last modified
7/14/2009 5:01:47 PM
Creation date
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UCREFRP
UCREFRP Catalog Number
8180
Author
Hamilton, S. J.
Title
Hypothesis of Historical Effects From Selenium on Endangered Fish in the Colorado River Basin.
USFW Year
1999.
USFW - Doc Type
\
Copyright Material
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<br />Hypothesis of Historical Effects from Selenium <br /> <br />sucker were collected in fall 1974 and 27 in spring 1975 from a gravel pit at <br />WWSvV.-\ on the Colorado River near Grand Junction, CO. Approximately 40 <br />razorback sucker were captured in a backwater area about 26 km upstream <br />from "VWSWA, referred to as Clifton Pond, which was flooded bv irrigation <br />flows in the spring of 1976. There was no e~idence of successful spawning of <br />razorback sucker or other native species such as the abundant flannelmouth <br />sucker in the gravel pit even though suspected spawning behavior was ob- <br />served in razorback sucker. Kidd (1977) reported that 28 razorback suckers <br />were captured at WWSWA in 1974,75 in 1975, and 16 in 1976, and 60 were <br />captured at Clifton Bridge backwater (i.e., Clifton Pond) in 1975, but none <br />were captured in 1974 or 1976. He also reported 14 Colorado pikeminnow <br />were captured at WW'SWA in 1974, 28 in 1975, and 2 in 1976. Valdez et at. <br />(1982) reported that nine Colorado pikeminnow and 37 adult razorback <br />sucker were collected in 1979 to 1981 from the gravel pit at WWSWA and <br />Clifton Pond. Osmundson and Kaeding (1989) also reported the use of <br />WvVSWA, Clifton Pond, and a third gravel pit by razorback sucker in 1986 to <br />1989. In 1995, the last razorback sucker found in the upper Colorado River was <br />captured at WWSWA. <br />All of the razorback sucker collected bv McAda and Valdez were considered <br />to be old fish; no juveniles or sub-adults were collected (C. McAda and R. <br />Valdez, personal communication, 1997). These razorback suckers may have <br />been the senescening adult population, as discussed earlier, from larvae re- <br />cmited in the 1900s prior to irrigated agriculture, much like the senescening <br />populations in lakes Mead and Mohave. <br />Although concentrations of selenium and other inorganic elements were <br />not measured at these sites by those investigators, the sites probably had <br />elevated selenium concentrations as demonstrated by recent measurements. <br />Samples collected in 1995 at two sites in the WWSWA channel area (the gravel <br />pit per se was lost during floods in 1983 and 1984, Bestgen, 1990) contained <br />selenium concentrations of 12 llg/L and 60 llg/L in May 1995 (unpublished <br />data). A sample collected from another site adjacent to and up-gradient from <br />the vvWSWA channel area, North Pond, contained 133 llg/L selenium in May <br />1995. The channel area and North Pond both receive groundwater through a <br />cobble aquifer (Phillips, 1986) that is recharged almost exclusively by irriga- <br />tion activities in the Grand Valley (Butler et at., 1989). A similar study in the <br />Reed Wash basin of the Grand Valley reported similar results, i.e., inflow of <br />groundwater with high selenium concentrations into surface waters. Virtually <br />all the groundwater flows directly into the Colorado River or is intercepted by <br />natural drainages, canals, or ditches. Selenium concentrations measured in <br />1991 to 1992 in water from a drainage ditch flowing into Clifton Pond were 86 <br />to 100 llg/L in the winter and 18 llg/L in the summer (Holley and Weston, <br />1995) . <br />Valdez et at. (1982) reported that Colorado pikeminnow congregated at the <br />mouths of irrigation drainage ditches that empty into backwater areas of the <br />Colorado River near GrandJunction, CO, including Reed Wash, [Little] Salt <br /> <br />Hum. Ecol. Risk Assess. Vol. 5, ~o. 6, 1999 <br /> <br />1169 <br />
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