Changes in Maturity, Plasma Sex Steroid Levels, Hepatic Mixed-Function Oxygenase Activity, and the Presence of External Lesions in Lake Whitefish (Coregonus clupeaformis) Exposed to Bleached Kraft Mill Effluent

Lake whitefish (Coregonus clupeaformis) exposed to primary treated bleached kraft mill effluent (BKME) had reduced gonadal development and increased liver size relative to two reference populations. These results parallel our previous work on the white sucker (Catostomus commersoni) exposed to BKME at the same Lake Superior site. More detailed studies conducted in 1990, after the installation of an aeration stabilization basin at the pulp mill, found that lake whitefish exhibited reduced gonad sizes, delayed age to maturation, decreased levels of the plasma sex steroids testosterone and 17β-estradiol, and elevated hepatic mixed-function oxygenase (MFO) activity. Liver size was smaller following operation of the secondary treatment system. More than 20% of the lake whitefish collected at the BKME site in 1990 exhibited lateral, slash-like lesions which penetrated the body cavity. Histological examination revealed no evidence of an infectious etiology, and the wounds could not be accounted for by known causes. Similar lesions were found in 1991 near a second BKME discharge.