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<br />402
<br />
<br />COUGHLAN AND VELTE
<br />
<br />TABLE I.-Proximate analyses of uncontaminated .c
<br />golden shiners and selenium-contaminated red shiners 1II
<br />used to feed striped bass. A minimum of 50 shiners ~ 30
<br />constituted each replicate (composite sample). Cl
<br /> Proximate composition (%) ~ 20
<br /> I-
<br /> Repli- Mois- a.
<br /> :::E
<br />Fish cate Protein Fat Ash ture ~ 10
<br />Golden shiner I 16.4 2.7 4.02 76.2 Z
<br />0
<br /> 2 16.5 2.9 4.16 76.4 u
<br />Red shiner 1 16.3 4.1 4.30 74.9. z 0
<br /><(
<br /> 2 16.2 4.4 4.53 75.3 w 0
<br /> :::E
<br />
<br />cm3 blocks, fixed in Bouin's solution for 2 d, and
<br />soaked in repeated changes of 65% ethanol to re-
<br />move the fixative. Tissues were dehydrated in a
<br />graded series of ethanol solutions and then infi]-
<br />trated with and embedded in glycol methacrylate
<br />(Bennett et al. 1976). Sections (2 ILm thick) from
<br />treatment and control fish were stained with he-
<br />matoxylin and eosin and compared with each oth-
<br />er and with the findings of Groman (1982) for the
<br />presence of abnormalities. Histopathological in-
<br />terpretation was confirmed by Charlie E. Smith,
<br />U.S. Fish and Wildlife Service, Bozeman, Mon-
<br />tana.
<br />
<br />Results and Discussion
<br />Striped bass fed selenium-laden red shiners ex-
<br />hibited changes in behavior, negligib]e weight gain,
<br />elevated selenium concentrations in muscle, his-
<br />to]ogica] damage, and ultimately death, as de-
<br />tailed below; control fish survived, grew well, and
<br />behaved normally. Water quality and temperature
<br />were consistent throughout the experiment, and
<br />red and golden shiner prey had similar gross nu-
<br />tritiona] qualities (Table I). Therefore, the ob-
<br />served differences between control and treatment
<br />striped bass were attributed to differences in se-
<br />]enium content in their diets.
<br />The average whole-body selenium concentra-
<br />tion of red shiners (9.6 ILg Se/g wet weight) was
<br />greater than' 30 times the average concentration
<br />in golden shiners (0.3 ILg Se/g). Selenium depura-
<br />tion by red shiners held in the laboratory appeared
<br />to be negligib]e because samples taken from the
<br />same lot after 1, 5, and 7 d contained 12.4, 11.0,
<br />and 11.9 ILg Se/g wet weight, respectively. A pre-
<br />liminary survey of trace elements in the two shiner
<br />species found comparable concentrations of ar-
<br />senic, cadmium, copper, mercury, and zinc (Duke
<br />Power Company, unpublished data). However,
<br />synergistic or antagonistic interactions of these
<br />elements or any other undetermined toxicants with
<br />selenium cannot be discounted.
<br />
<br />
<br />. .
<br />'-', -.- ~\., ..;:.~"
<br />,,' ',,' ...., ~. TREATMENT
<br />"--\..r~-'.~.'--\ :--1';-,.111
<br />.., .......... 2 -~
<br />
<br />20
<br />
<br />80
<br />
<br />1.0
<br />DAY
<br />
<br />FIGURE 2.-Mean daily consumption by striped bass
<br />of selenium-contaminated red shiners (treatment, tanks
<br />I and 2) or uncontaminated golden shiners (control).
<br />The decline in consumption by control striped bass on
<br />day 64 was due to a temporary shortage of golden shin-
<br />ers.
<br />
<br />60
<br />
<br />Striped bass fed uncontaminated golden shiners
<br />consistently consumed more food (g shiner/fish),
<br />especially after day 10, than striped bass fed se-
<br />lenium-]aden red shiners (Figure 2). Control striped
<br />bass aggressively chased golden shiners during
<br />feeding and regularly broke the water surface. In
<br />contrast, striped bass fed red shiners were ]ethar-
<br />gic, made few attempts to feed when red shiners
<br />were first introduced, rarely broke the water sur-
<br />face, and occasionally were observed capturing a
<br />red shiner and then releasing it. Both tanks of
<br />treatment striped bass consumed roughly equal
<br />amounts during the experiment. The food avoid-
<br />ance demonstrated by treatment striped bass in
<br />our study also has been observed for rainbow trout
<br />Oncorhynchus mykiss (former]y Salmo gairdnen)
<br />fed selenium-supplemented diets (Hilton et al.
<br />1980), chinook salmon Oncorhynchus tsha-
<br />wytscha that consumed partial diets of selenium-
<br />contaminated mosquitofish Gambusia affinis
<br />(Hamilton et al. 1986), and bluegills fed selenium-
<br />contaminated mayfly nymphs (Fin]ey 1985).
<br />Control striped bass rarely ingested more than
<br />8 ILg Selfish per feeding session (Figure 3). No
<br />deleterious effects were observed at this level of
<br />intake (1.3 ILg Se/g, dry weight by calculation).
<br />However, both tanks of treatment striped bass in-
<br />gested far more selenium, especially until day 31,
<br />than control striped bass. Average selenium inges-
<br />tion was as high as 103 and 140 ILg/fish per feeding
<br />session in tanks 1 and 2, respectively. The calcu-
<br />]ated selenium concentration in the red shiner diet
<br />(38.6 p.g Se/g dry weight) exceeded concentrations
<br />that were hariuful to channel catfish Icta/urus
<br />punctatus and rainbow trout in laboratory feeding
<br />
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<br /> FIGUR
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