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Selenium in Razorback Sucker Accumulation of high selenium concentrations in fish gonads is believed to be the cause of reduced reproduction and subse- quent species disappearances in Belews Lake, North Carolina (Cumbie and Van Horn 1978), Hyco Reservoir, North Carolina (Woock and Summers 1984), and Martin Lake, Texas (Garrett and Inman 1984; Sorensen 1988). Reports of studies of ele- vated selenium concentrations in gonads of fish in laboratory and field studies are presented in Table 2. Selenium concentrations in fish eggs are apparently due to transfer from the parent to the egg. Schultz and Hermanutz (1990) reported 24-h-old eggs from fathead minnows reared in artificial streams with 10 µg/L selenium for 1 year (i.e., com- bined waterborne and dietary exposure through food chain) contained 16 µg/g selenium (reported as 3.91 µg/g wet weight). In contrast, eggs from reference adults, which con- tained 1.2 µg/g selenium (reported as 0.31 µg/g wet weight) before exposure, took up only 0.56 µg/g selenium after expo- sure for 24 h to 10 µg/L selenium in water, thus indicating selenium in eggs comes from parental exposure and not expo- sure of eggs in water with elevated selenium concentrations. Similarly, Gillespie and Baumann (1986) reported that in 18 artificial crosses of bluegill with high or low selenium concen- trations in gonads, edema and mortality occurred in larvae from high-selenium females (even when crossed with reference males), but not in high-selenium males (when crossed with reference females). Camlina Power and Light (1984) reported similar results in artificial crosses of adult bluegill from sele- nium-impacted Hyco Reservoir and adults from a reference site. Larvae from Hyco females fertilized with either male type had abnormal development and 100% mortality prior to swimup, whereas larvae from reference females fertilized with either male type had normal development. 'T'hus, selenium in fish larvae seems to be primarily due to parental transfer in ova and not milt, with very mirror amounts absorbed during water exposure prior to hatching. Woock et al. (1987) also showed exposure of adults to selenium in the diet or to selenium in both water and diet resulted in significant mortality and deformities in larvae; unfortunately, no residue data for adults, eggs, milt, or larvae were reported. Developing ovaries of fish are adversely affected by sele- niumexposure. Sorensen (1988) reported that ovaries of redear sunfish (Lepomis microlophus) from selenium-contaminated Martin Lake, Texas, contained l7 µg/g selenium (reported as 4.33 µg/g wet weight). I?arly development stages of ovaries of these fish contained numerous atretic or disintegrated oocytes, connective tissue hypertrophy, and large areas of necrotic tis- sue, whereas later oocyte development was asynchronus. Al- though Sorensen (1988) did not measure selenium concentra- tions in male gonads of redear sunfish from Martin Lake, she did report that the testes were small and immature, and had significantly lower testosterone and ll-ketotestosterone than males from a reference lake. No selenium-induced alterations in the morphological appearance of the mature testes were apparent at the microscopic level (Sorensen 1988). Sorensen et a[. (1984) found similar abnormalities in ovaries of green sun- fish (Lepomis cyanellus) collected from selenium-contaminated Belews Lake, North Carolina, but no abnormalities were found in testes. The concentrations of selenium in eggs of razorback suckers in the present study, although above background concentra- tions, are less than those in selenium-exposed fish from labora- tory and field studies where adverse biological effects occurred 199 (Table 2). In these studies, larvae of females with elevated selenium concentrations had high mortality before the swimup life stage (Gillespie and Baumann 1986; Hermanutz et al. 1992). in field studies, species disappeared due to adverse effects on reproduction (Cumbie and Van Horn 1978; Garrett and Inman 1984). [n our study, it cannot be stated unequivocally that the above- normalconcentrations of selenium in eggs of razofiack suckers are adversely affecting reproductive success. Because of the very few reproductive studies with fish that have been con- ducted, the concentration of selenium that can be present in the egg without causing adverse effects in young has not been defined and may vary with species. Based on the limited infor- mation available, the selenium concentration that adversely affects eggs is somewhere between background concentrations that cause no adverse effects (2.0-3.1 µg/g) and the concentra- tions in ovaries currently reported to cause adverse effects in larvae [ 18 µg/g in bluegill (Hermanutz et al. 1992); 24 µg/g in fathead minnow (Schultz and Hermanutz 1990)]. Because the selenium concentrations found in razorback sucker eggs from the Green River (3.7-10.6 µglg) are within this range, the effects of selenium on larvae are a concem, and may be ad- versely affecting razorback sucker reproduction. The three failed spawns of razorback suckers at the CRI'P laboratory may be linked to elevated selenium concentrations in the eggs, be- cause previously hatching attempts were successful. Most probably none of the eggs in the razorback sucker collected in 1991 from the Razorback Bar in the Green River that had 28 µg/g selenium would have resulted in any larvae surviving. Peitz and Waddell (1991) reported two other endan- gered fish collected from the Green River had above-back- gmund selenium concentrations in their gonads. A humpback chub (Gila cypher) collected in 1986 had 7.3 µg/g selenium, and a Colorado squawfish (Ptychocheilus Lucius) collected in 1982 had 6.5 µg/g selenium. These elevated selenium concen- trations are also of concern foc possible adverse reproductive effects in these species. Spawning Behavior Although adults may contain elevated concentrations of sele- nium, spawning behavior may not be affected. Hermanutz et al. (1992) reported that, although growth and survival were reduced in adult bluegill after exposure to 10 µg/L selenium for 258 days in artificial streams, spawning activity was not altered compared to control fish. Similarly, Pyron and Beitinger (1989) reported spawning behavior was not affected by exposure of fathead minnows to 20 or 30 mg/L selenium in water for 24 h and then allowing them to spawn in water without selenium. Ogle and Knight (1989) reported no effects on spawning activ- ities, such as number of spawns per adult pair or number of eggs per spawn, in fathead minnows fed selenium in the diet for 100+ days. Carolina Power and Light (1984) reported similar results with adult bluegill from selenium-impacted Hyco Reser- voir and adults from a reference site exposed to either 20% or 50°k ash pond effluent for up to 2 months; prespawning activity (nest building) seemed normal, although no young were pro- duced by Hyco adults. Based on the above discussion, altered spawning behavior of razorback suckers in the Green River would not be expected, and has not been reported (Tyus 1987; Tyus and Karp 1990).