Abstract
Patterns in the relative differences in contaminant concentrations between the sexes of mature fish may reveal important behavioral and physiological differences between the sexes. We determined whole-fish total mercury (Hg) concentrations in 23 female summer flounder (Paralichthys dentatus) and 27 male summer flounder from New Jersey coastal waters. To estimate the change in Hg concentration due to release of eggs at spawning, Hg concentration in the somatic tissue and ovaries of 5 of the 23 female summer flounder were also determined. To ascertain whether most of the Hg in the summer flounder was methylmercury (MeHg), whole-fish MeHg concentrations were determined in all 50 summer flounder. Whole-fish Hg concentrations averaged 113 ng/g for females and 111 ng/g for males. Thus, females were 2% higher in Hg concentration than males, on average, but the difference was not statistically significant. Based on Hg determinations in the somatic tissue and ovaries, we predicted that Hg concentration of females would increase by 3.7%, on average, immediately after spawning due to release of eggs. On average, 92% of the Hg in the summer flounder was MeHg. To determine whether the effect of sex on Hg concentration was significantly different from the effect of sex on polychlorinated biphenyl (PCB) concentration, we paired our Hg determinations with PCB determinations from a previous study, and applied regression analysis. Sex significantly interacted with contaminant type (Hg or PCBs), as males were 43% higher in PCB concentration than females, whereas females were 2% higher in Hg concentration than males. Males eliminating Hg from their bodies at a faster rate than females was a likely explanation for this discrepancy between the two contaminant types. Overall, the Hg and PCB concentrations in the summer flounder were relatively low, and therefore our findings also had implications for continued operation of the summer flounder fishery.
Highlights
Three species of freshwater teleost fishes (lake trout (Salvelinus namaycush), burbot (Lota lota), and lake whitefish (Coregonus clupeaformis)) share the characteristic of the ratio of whole-fish polychlorinated biphenyl (PCB) concentration in males to wholefish PCB concentration in females substantially exceeding the ratio of whole-fish total mercury (Hg) concentration in males to whole-fish Hg concentration in females [1]
For these three fish species, mature males were between 20% and 35% higher in whole-fish PCB concentration than aged mature females, and this difference appeared to be primarily due to a greater rate of energy expenditure in mature males stemming from higher activity and a higher resting metabolic rate [5,6,7]
Mean whole-fish Hg concentration of summer flounder caught in New Jersey coastal waters was 113 ng/g for mature females and 111 ng/g for mature males, but this difference was not statistically significant
Summary
Three species of freshwater teleost fishes (lake trout (Salvelinus namaycush), burbot (Lota lota), and lake whitefish (Coregonus clupeaformis)) share the characteristic of the ratio of whole-fish polychlorinated biphenyl (PCB) concentration in males to wholefish PCB concentration in females substantially exceeding the ratio of whole-fish total mercury (Hg) concentration in males to whole-fish Hg concentration in females [1] This apparent pattern has been attributed to males eliminating Hg from their bodies at a faster rate than females, whereas long-term elimination of PCBs by fish is negligible for both sexes [1,2,3,4]. In contrast to the relative differences in PCB concentrations between the sexes, male lake trout were only 8% higher in Hg concentration than female lake trout, and females were higher than males in Hg concentration for both burbot and lake whitefish
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