Abstract
We determined whole-fish Hg concentrations of 26 female and 34 male adult lake whitefish (Coregonus clupeaformis) from northern Lake Huron captured during November 2010. Subsampling from these 60 fish, Hg concentration was also determined in both somatic tissue and ovaries (n = 5), while methylmercury (MeHg) concentration was determined in whole fish (n = 18). Bioenergetics modeling was used to assess the growth dilution effect on the difference in Hg concentrations between the sexes. Mean whole-fish Hg concentration in females (59.9 ng/g) was not significantly different from mean whole-fish Hg concentration in males (54.4 ng/g). MeHg accounted for 91% of the mercury found in the lake whitefish. Bioenergetics modeling results indicated that the growth dilution effect did not contribute to the difference in Hg concentrations between the sexes. We estimated that females increased in Hg concentration by 17.9%, on average, immediately after spawning due to release of eggs. Using polychlorinated biphenyl (PCB) data for the same 60 lake whitefish from a previous study, we detected a significant interaction between sex and contaminant type (Hg or PCBs), which was attributable to males being significantly higher in PCB concentration than females. Males may be eliminating Hg at a faster rate than females.
Highlights
Lake whitefish (Coregonus clupeaformis) populations in the upper Great Lakes (i.e., Lakes Superior, Huron, and Michigan) have supported highly valued commercial fisheries [1,2]
For each of the 60 lake whitefish, weight was determined to the nearest 10 g, total length (TL) was measured to the nearest mm, and sex and maturity were determined by visual inspection of the gonads
Our results were in accord with results from studies by Madenjian et al [27] on lake trout and by Madenjian et al [23] on burbot
Summary
Lake whitefish (Coregonus clupeaformis) populations in the upper Great Lakes (i.e., Lakes Superior, Huron, and Michigan) have supported highly valued commercial fisheries [1,2]. Lake whitefish were prized as a food fish by both aboriginal people and early European settlers of the upper Great Lakes region. Some of these settlers described lake whitefish as the “best fish in the world” while proclaiming that “one could eat if for days and never grow tired of it” [3]. The first commercial fisheries in the upper Great Lakes were focused on lake whitefish due to its excellent quality as a food fish and because spawning aggregations would concentrate in shallow water close to shore where they could be harvested with gill nets and seines by early settlers [2]. Lake whitefish have exhibited a remarkable ability to adapt their diet in response to changes in the food web brought about by biological invasions [4,5]
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