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Fingerling chinook salmon (Oncorhynchus tshawytscha) were chronically exposed in the laboratory to nonlethal biologically treated bleached kraft mill effluent (TBKME) at concentrations and temperatures typical of the Fraser River. Laboratory exposure was for 144 d in freshwater followed by 66 d in seawater without TBKME. Exposed fish bioconcentrated chlorophenols, chloroguiacols, and extractable organochlorine substances in proportion to the aqueous concentrations of the substances. Polychlorinated dibenzo-p-dioxins (PCDD's) and polychlorinated dibenzofurans (PCDF's) were also bioaccumulated, but the low body burdens compared with wild fingerling chinook indicated that the laboratory environment did not account for biomagnification via the food chain. Growth, mortality, hematocrit, protein and fat content, liver somatic index, sorbitol dehydrogenase, and tolerance to hypoxia were not affected by TBKME exposure. Increased nuclear diameters of interrenal cells among TBKME-exposed fish indicated that these fish were experiencing chronic stress. Hepatic and renal granulomas of Bacterial Kidney Disease origin were observed in some TBKME-exposed fish, but there was only a tenuous link between TBKME exposure and disease resistance. Hepatic ethoxyresorufin-O-deethylase (EROD) activity was correlated with dioxin toxic equivalency (TEQ). From this analysis, we estimated a threshold for EROD induction between 0.3 and 1.0 ng TEQ∙kg−1.

Rainbow trout fry, chironomid larvae, and duckweed plants were exposed to a series of Carbon-14 ( 1 4 C)-labeled compounds in different water types in order to establish whether the water type influences the accumulation of compounds in the test organisms. Fish, insects, and plants consistently accumulated compounds less efficiently from river water than from dechlorinated city water. Suitable regression equations were found empirically to describe the accumulation of compounds in organisms, and the best equations for predicting the accumulation of methoxychlor were presented. The effect of the water type could not be attributed to the specific chemical components in each water type. Sorption to suspended solids was thought to contribute to the differing efficiencies of uptake but not to fully explain the phenomenon. When methoxychlor was sorbed to celite particles prior to its presentation to organisms, nonfilter feeders accumulated methoxychlor much less efficiently than when this pesticide was presented as an emulsifiable formulation.

On June 4, 1974, the Athabasca River was treated with methoxychlor for control of blackfly larvae. Pesticide was introduced into the water in a manner calculated to generate a 15-min pulse of treated water containing 300 μg methoxychlor/ℓ. A preliminary experiment with rainbow trout (Salmo gairdneri) indicated that liver or kidney residues of methoxychlor would be suitable for monitoring likely times and places to expect toxic effects on fish in the river. Fish (Salmo gairdneri, Catostomus commersoni, C. catostomus, and Hybopsis gracilis) were caged in order to observe residues and mortality. Caged fish were not killed by methoxychlor but they contained lower liver residues than wild fish of the same species captured near cages. Contaminated wild fish were found upstream of the treatment site after treatment. Residues were below detection limits by June 16. Residue measurements suggested that the most likely times to expect fish poisoning were the 2 wk following treatment and that the most likely places were those river areas extending a few kilometres in both directions from the point of application. Evidence of fish movements and low pesticide residues in caged individuals reduced confidence in residue methods as monitoring tools.

The Mackenzie River in northwestern Canada is the largest North American source of freshwater to the Arctic Ocean There are continuous discharges of petroleum into the river from an oil field at Norman Wells both from refinery and natural seepage sources. Recently oil production was expanded using several artificial islands constructed in the river Coincident with the expansion native DENE fishermen in downstream communities complained that the quality of fish deteriorated. Specifically, the liver of burbot (Lota lota) was reported to have become small and dark in colour, and our investigation of that complaint is the subject of this report. Examination of the burbot revealed that the liver condition was associated with a low content of fat The question posed was whether this quality problem could be related to petroleum inputs from Norman Wells. Residue analyses of the fish showed low, but consistent, contamination with low-boiling aromatic hydrocarbons, with fish taken in winter more highly contaminated than fish taken in summer. The low levels in summer fish were found in fish from many freshwater locations with no obvious connection to a petroleum source This may reflect a broad atmospheric dispersal of these materials. Burbot from the lower Mackenzie River did not have elevated liver mixed-function oxidase enzyme activities relative to a reference population from Lake Winnipeg Experimental treatments with oil induced these enzyme activities, and so fish seem unlikely to have been affected by the enzyme inducing components of petroleum. Experimental starvation of burbot in the laboratory resulted in a loss of liver fats and in development of apparently the same liver condition The condition of the fish seems more likely to be of natural origin through factors related to nutrition or parasitism, although pollution cannot be ruled out definitively. Unexpectedly high concentrations of toxaphene (up to 5000 ng/g wet weight) and other organochlorines were found in burbot livers