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<br />~.
<br />
<br />HAZARD OF INORGANICS TO ENDANGERED FISH
<br />
<br />significant difference among the three species in their
<br />sensitivity to the seven inorganics based on a rank-order
<br />evaluation at the species level using geometric means for
<br />the three life stages combined for each species. No indi-
<br />vidual life stage of the three species was more sensitive to
<br />the seven inorganics tested than any other life stage,
<br />based on a rank-order evaluation.
<br />In general, the swimup life stage was more sensitive to
<br />boron, lithium, selenite, and zinc than the two older life
<br />stages of the three species. In contrast, the two juvenile
<br />life stages of the three species were more sensitive to
<br />vanadium than the swimup stage. An exception to this
<br />response was selenate toxicity to razorback suckers;
<br />older life stages were more sensitive than the swimup life
<br />stage. The two juvenile life stages of Colorado squawfish
<br />were less sensitive to selenite than the swimup stage, but
<br />there was no consistent response in razorback sucker or
<br />bony tail. Nevertheless, for each life stage tested for the
<br />three species, selenite was always mOre toxic than sel-
<br />enate. The toxicity of uranium to all life stages of the
<br />three species seemed to be unique in that the 96-hr LCso
<br />value and 95% confidence interval were the same. In
<br />tests with uranium the concentrations tested were 13,
<br />21.6, 36, 60, 100, 170, 280, and 470 mg/liter, yet all test
<br />results were identical.
<br />
<br />DISCUSSION
<br />
<br />Vanadium
<br />
<br />The toxicity of vanadium to the three endangered spe-
<br />cies in the present study was within the range of values
<br />reported by other investigators. The 96-hr LCso for va-
<br />nadium, as vanadium pentoxide, to adult American flag-
<br />fish (Jordanella floridae) was 11.2 mg/liter in very hard
<br />water (347 mg/liter as CaC03); the 28-day LCso was 1.13
<br />mg/liter (Hold way and Sprague, 1979). Knudtson (1979)
<br />tested four vanadium compounds in soft water (35 mg/
<br />liter as CaC03) and reported the 144-hr LCso ranged from
<br />2.45 to 8.08 mg/liter for goldfish (Carassius auratus) and
<br />from 0.37 to 1.05 mglliter for guppies (Lei:Jistes reticu-
<br />lata); sodium vanadate was more toxic than vanadium
<br />pentoxide. Beusen and Neven (1987) reported a twofold
<br />difference in sensitivity between zebrafish (Brachydanio
<br />rerio), which had a geometric mean of 4 mg/liter, and
<br />guppies (PoeciLia reticulata), which had a geometric
<br />mean of 8 mg/liter. Stendahl and Sprague (1982) tested
<br />rainbow trout (Oncorhynchus my kiss) for sensitivity to
<br />vanadium pent oxide and reported 96-hr LCso values
<br />ranged from 5.2 mglliter for 6.2-g fish to 10 mglliter for
<br />2.4-g fish tested at 100 mg/liter hardness. They also re-
<br />ported a 2.3-fold increase in toxicity in 7-day LCso values
<br />for large fish (11.7 g) compared with smaller fish (1.5 g).
<br />Ernst and Garside (1987) also found a threefold increase
<br />
<br />137
<br />
<br />in sensitivity of brook trout (SalveLinus fontinaLis) to va-
<br />nadium; they reported the 96-hr LCso for alevins was 24
<br />mg/liter, whereas for yearlings it was 7 mg/liter. Although
<br />these reports of increasing sensitivity with increasing size
<br />or age are uncommon for most inorganics, they are sim-
<br />ilar to findings in the present study.
<br />
<br />Zinc
<br />The toxicity of inorganics typically decreases with in-
<br />creased age of test organisms (Rand and Petrocelli, 1985),
<br />as was the case for zinc toxicity to the three life stages of
<br />the three species tested in the present study. The toxicity
<br />of zinc to the two older life stages of Colorado squawfish
<br />in the present study was similar to those of Beleau and
<br />Bartosz (1982). They reported 96-hr LCso values for 5-g
<br />Colorado squawfish of 4.2, 8.3, and 4.9 mg/liter tested in
<br />Palouse River water (32 mg/liter hardness) at 12, 17, and
<br />220C, respectively. Pickering and Vigor (1965) reported
<br />the 96-hr LCso for 1-day-old fathead minnow (Pimephales
<br />promeLas) was 0.87 mg/liter, whereas Mount (1966) re-
<br />ported that for older (1-2 g) fathead minnow the 96-hr
<br />LCso was 14-19 mg/liter. These values for a cyprinid are
<br />similar to those for the two cyprinids, Colorado squaw-
<br />fish and bony tail, tested in the present study. Although
<br />the three species in the present study responded similarly
<br />to zinc, a broad range of toxicity has been reported, due
<br />in part to the species tested, but also to water hardness
<br />and pH (Mount, 1966; Pickering and Henderson, 1966;
<br />Chapman, 1978).
<br />
<br />Selenium
<br />Previous work has demonstrated that the selenate form
<br />of selenium is less toxic than the selenite form (Hamilton
<br />and Buhl, 1990a; Buhl and Hamilton, 1991), as was found
<br />in this study. Hamilton and Buhl (l990a) reported that
<br />coho salmon (Oncorhynchus kisutch) were more sensi-
<br />tive to selenate (96-hr LCso 32.5 mg/liter) than were chi-
<br />nook salmon (Oncorhynchus tshawytscha) (96-hr LCso
<br />115 mg/liter). This difference in species sensitivity is sim-
<br />ilar to the difference observed in the sensitivity to sel-
<br />enate of older life stages of razorback sucker (25-36 mg/
<br />liter) compared with the corresponding life stage of Col-
<br />orado squawfish (286-331 mg/liter) and bony tail (217-246
<br />mg/liter), but to a greater extent. Acute toxicity of swim-
<br />up fish in the present study was similar to that reported
<br />by Niimi and LaHam (1976) for zebrafish (96-hr LCso 82
<br />mg/liter) and D. C. Chapman (personal communication,
<br />1993) for striped bass (Morone saxatiLis) (96-hr LCso 55
<br />mg/liter).
<br />Published data for selenium toxicity are mostly for the
<br />selenite form. The three endangered fish tested in the
<br />present study had similar sensitivity to selenite as chi-
<br />nook salmon (96-hr LCso 13.8 mg/liter), coho salmon (96-
<br />hr LCso 7.8 mg/liter; Hamilton and Buhl, 1990a), and
<br />rainbow trout (96-hr LCso 12.5 mg/liter, Geottl and Dav-
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