Fraser river action plan resident fish condition and contaminants assessment

The condition of resident mountain whitefish and peamouth chub in the Fraser River basin was assessed based on health and tissue contaminant levels. All fish were examined in the field for external and internal abnormalities (HAI) and tissue samples were collected for histological examination. Analyses of mixed function oxygenase enzyme activity (EROD) in liver and tetrachlorinated dioxins in muscle and liver were used as indicators of contaminant exposure. A high incidence of HAI abnormalities occurred in these species throughout the basin and the HAI was not strongly correlated with age, EROD activity, or histological abnormalities. Tetrachlorinated dioxin (TCDD) residues in fish tissue and EROD activity in liver were elevated downstream of pulp mills and urban centres, but dioxin levels were low, near or below detection limits and guidelines.