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<br />Hamilton
<br />
<br />INTRODUCTION
<br />
<br />Historically, selenium was linked with the death of cavalry horses at Fort
<br />Randall, on the Missouri River in the Dakota Territories, in the 1850s as a
<br />young United States moved west (Trelease and Beath, 1949). Early concerns
<br />about selenium were due to its toxic effects on livestock, and its contamination
<br />in range plants and agricultural crops used to feed them. Several U.S. Depart-
<br />ment of Agriculture (DOA) personnel in the 1930s and 1940s promoted
<br />irrigation as a way to reduce the selenium content of soils, so as to lower
<br />selenium concentrations in agricultural crops, but without concern for in-
<br />creased concentrations in drainage water or receiving waters (Williams and
<br />Byers, 1935; Trelease and Beath, 1949; Anderson et al., 1961).
<br />Anthropogenic selenium contamination of the aquatic environment first
<br />became prominent in the late 1970s at Belews Lake, NC (Cumbie and Van
<br />Horn, 1978; Lemly, 1985), and at Martin Lake, TX (Garrett and Inman, 1984;
<br />Sorensen, 1988), which gave the impression that it was a contaminant problem
<br />associated with coal-fired power plants. The next awakening to selenium
<br />contamination came from California with the discovery of mortality and ab-
<br />normalities in waterfowl (Ohlendorf, Hoffman, Saiki, and Aldrich, 1986; Saiki,
<br />1986), and anecdotal information of fish disappearances (Harris, 1986; Vencil,
<br />1986) at Kesterson Reservoir in the San Joaquin Valley. This event linked
<br />selenium contamination of aquatic environments with agricultural irrigation
<br />practices.
<br />Thus, the connection between selenium and aquatic ecotoxic problems is
<br />thought to be a recent phenomenon. I present information here in support
<br />of the hypothesis that selenium began to adversely affect aquatic ecosystems in
<br />the 1890 to 1910 period and is part of the cause for the endangerment offish
<br />in the Colorado River basin. Consequently, evidence of anthropogenic sele-
<br />nium contamination of aquatic ecosystem is not a recent ecotoxic problem
<br />beginning with Belews Lake, NC, in the 1970s, but rather can be traced back
<br />to the 1890 to 1910 period near the beginning of irrigation activities in the
<br />West (Table 1).
<br />
<br />ENDANGERED FISH
<br />
<br />As a result of its long isolation, the Colorado River basin supports the most
<br />distinctive ichthyofauna in North America (Figure 1). Several fish species have
<br />declined in the Colorado River basin, which originally contained 32 native
<br />species of which 75% were endemic (Minckley, 1991). The humpback chub
<br />(Gila cypha) and Colorado pikeminnow (Ptychocheilus Lucius) were the first two
<br />fish listed as endangered by the U.S. Department of the Interior (001, 1967).
<br />Later, bonytail (Gila elegans) was listed as endangered in 1980 (USFWS, 1980)
<br />and razorback sucker (Xyrauclum texanus) in 1991 (USFWS, 1991a). Other fish
<br />in the Colorado River basin are now listed as Species of Concern, including
<br />flannelmouth sucker (Catostomus latipinnis) and roundtail chub (Gila Tabusta)
<br />(USFWS, 1991b).
<br />
<br />1154
<br />
<br />Hum. Eco\. Risk Assess. Vol. 5, No.6, 1999
<br />
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