EFFECTS OF COPPER ON IMMUNE-SYSTEM PARAMETERS OF RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)

Agricultural, urban, industrial, and mining sources release metals; in to waterways. The effects of sublethal concentrations of metals on int egrated physiological processes in fish, such as immunocompetency, are not well understood. The objective of this study was to determine the physiological effects of a range of sublethal copper concentrations ( 6.4, 16.0, and 26.9 mu g Cu/L) on Shasta-strain rainbow trout (Oncorhy nchus mykiss) exposed in sofi water. Trout were sampled after 3, 7, 14 , and 21 d of exposure to copper. The percentage of monocytes was cons istently elevated at 26.9 mu g Cull,, and the percentage of lymphocyte s was decreased. A consistent increase in the percentage of neutrophil s occurred at 26.9 and 6.4 mu g Cult. Respiratory burst activity was d ecreased for all concentrations at all sampling days, but a significan t reduction occurred only at 14 and 21 d of exposure to copper. B-like cell proliferation was decreased by exposure to the higher copper con centrations. Proliferation results, however, had high variability. T-l ike cell proliferation and phagocytosis were not altered. Hepatic copp er concentration was consistently elevated in trout exposed to 26.9 mu g Cu/L; no correlation was found between hepatic copper concentration and the Immune system responses investigated. Consistent alterations in immunological parameters suggest that these parameters could serve as indicators of chronic metal toxicity in natural systems.