EFFECTS OF BIOTREATED BLEACHED KRAFT MILL EFFLUENT ON FINGERLING CHINOOK SALMON (ONCORHYNCHUS-TSHAWYTSCHA)

Fingerling chinook salmon (Oncorhynchus tshawytscha) were chronically exposed in the laboratory to nonlethal biologically treated bleached k raft mill effluent (TBKME) at concentrations and temperatures typical of the Fraser River. Laboratory exposure was for 144 d in freshwater f ollowed by 66 d in seawater without TBKME. Exposed fish bioconcentrate d chlorophenols, chloroguiacols, and extractable organochlorine substa nces in proportion to the aqueous concentrations of the substances. Po lychlorinated dibenzo-p-dioxins (PCDD's) and polychlorinated dibenzofu rans (PCDF's) were also bioaccumulated, but the low body burdens compa red with wild fingerling chinook indicated that the laboratory environ ment did not account for biomagnification via the food chain. Growth, mortality, hematocrit, protein and fat content, liver somatic index, s orbitol dehydrogenase, and tolerance to hypoxia were not affected by T BKME exposure. Increased nuclear diameters of interrenal cells among T BKME-exposed fish indicated that these fish were experiencing chronic stress. Hepatic and renal granulomas of Bacterial Kidney Disease origi n were observed in some TBKME-exposed fish, but there was only a tenuo us link between TBKME exposure and disease resistance. Hepatic ethoxyr esorufin-O-deethylase (EROD) activity was correlated with dioxin toxic equivalency (TEQ). From this analysis, we estimated a threshold for E ROD induction between 0.3 and 1.0 ng TEQ.kg-1.