Fish health in the Peace, Athabasca and Slave river systems

The response of large river systems to human development isoften hard to predict. The spatial scale of these systems makes themdifficult to study and their ecology (particularly in the case of largenorthern rivers) is often poorly understood. To provide an ecologicalassessment of three large river basins in northern Canada, the NorthernRiver Basins Study (NRBS) undertook a multi-disciplinary approach toassess environmental and socio-economic impacts of development. Resultspresented here focus on key findings relating to studies of fish healthwithin the basins. It was known at the outset of the NRBS that dioxins,furans and other organic contaminants would be present in the system.However, NRBS research indicated low levels of environmentalcontamination, particularly compared to other systems in Canada andelsewhere in the world. In addition, contaminant loads in fish generallyconform to Canadian guidelines for both aquatic and human health;although, levels of dioxins, furans, PCBs and mercury in biota didexceed guidelines at certain times and in certain locations. The weightof evidence indicates that many of the fish in these basins exhibitsigns of physiological stress. Of particular concern was the findingthat sex hormone levels in burbot and longnose sucker collected fromnear-field pulp-mill locations were significantly depressed, and thatnumbers of immature fish in these same locations were unexpectedly highand more likely to show external abnormalities. In addition, there is aperception that fish in the lower reaches of the Peace-Athabasca basinsand in the deltas are of lower quality. Studies of fish health have beenintegrated with other technical studies in a cumulative effectassessment and will provide a basis for future research and managementdecisions within these basins.