Am. Farag et al., Dietary effects of metals-contaminated invertebrates from the Coeur d'Alene River, Idaho, on cutthroat trout, T AM FISH S, 128(4), 1999, pp. 578-592
Benthic macroinvertebrates with elevated concentrations of metals were coll
ected from the Coeur d'Alene (CDA) River, Idaho, pasteurized, and fed to cu
tthroat trout Oncorhynchus clarki in the laboratory from start of feeding u
ntil 90 d posthatch. Invertebrates were collected from two sites known to c
ontain elevated concentrations of metals: near Pinehurst in the South Fork
of the CDA River and at Cataldo, approximately 5 km below the confluence of
the South Fork and the North Fork. Invertebrates collected from a relative
ly clean site in the North Fork were used as a reference diet. We performed
measurements of fish health that indicate reduced fitness of fish fed the
South Fork and Cataldo diets. Effects measured were reduced feeding activit
y, increased number of macrophage aggregates and hyperplasia of cells in th
e kidney, degeneration of mucosal epithelium in the pyloric caecae, and met
allothionein induction. These effects would likely reduce growth and surviv
al of fish in the wild. Vacuolization of glial cells were also observed in
fish fed the Cataldo diet. Metals in the water often exacerbated the histol
ogical effects observed. Although the invertebrates collected near Cataldo
had lower concentrations of arsenic (As), cadmium (Cd), copper (Cu), lead (
Pb), and zinc (Zn) than the invertebrates from the South Fork, fish fed the
Cataldo diet had equally high or higher concentrations of all metals excep
t As by day 44. The Cataldo diet also caused the most deleterious effects o
n survival and growth. These findings are especially important for early li
fe stage fish, whose diet consists wholly of benthic macroinvertebrates. Th
erefore, fish feeding on invertebrates in the CDA River below the Bunker Hi
ll smelting complex are at risk of reduced fitness.