Baseline measurements of indicators for sublethal effects of metals in lake whitefish (Coregonus clupeaformis)

Histological and metallothionein (MT) analyses of liver and kidney and measurements of serum electrolytes and hematocrit from lake whitefish (Coregonus clupeaformis), 3.5 years of age, were conducted over a 90-day period that included maximal gonadal maturation in females. Condition factors were higher in females at day 1 and when all data were combined over the 90-day sampling period. Significant differences between females and males of 1.8-fold in hepatic MT concentrations were observed at day 20 when ovaries appeared to be in the most advanced state of maturation, although this parameter was not quantified. Hematocrits were slightly but significantly lower at day 90. No sex differences were observed in the quantitative assessments of epithelium cell height, lumen diameter (LD), tubule diameter (TD), and ratio of LD:TD in the second segment of the proximal tubule (P2); and of hepatocyte area, hepatocyte nuclear diameters, and nucleus area:cytoplasmic area (N:C) ratio. Positive correlations were observed between N:C ratios and fish weight, fork length, and liver weight. No significant correlations between these histological morphometrics and MT concentrations were observed in liver or kidney. The results of this study provide baseline information for investigations designed to determine sublethal effects of metals in lake whitefish.