Hydrocarbons and Complaints About Fish Quality in the Mackenzie River, Northwest Territories, Canada

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Abstract
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

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