Seminar Date: TUESDAY July 25, 2017 (noon).

 

Speaker:

Chuck Madenjian

 

Title: Sex and contaminants in fish: “hot spots”, big testes, and high-activity males

 

Affiliation:

USGS Great Lakes Science Center

 

Local Host:

Mark Wuenschel

 

Abbreviated abstract

 

Whole-fish polychlorinated biphenyl (PCB) and total mercury (Hg) concentrations were determined in both females and males of a variety of fish species.  Hypothesis testing was used to identify the most plausible explanations for the patterns in observed differences in contaminant concentrations between the sexes.  These explanations appear to apply to most species of fish, as well as higher vertebrates.   

 

 

 

Full abstract

 

Whole-fish polychlorinated biphenyl (PCB) and total mercury (Hg) concentrations were determined in both females and males of a variety of fish species.  Males were consistently higher in PCB concentration than females, with the relative difference ranging from 15 to 45%.  Interestingly, the ratio of Hg concentration in males to Hg concentration in females was consistently lower than the ratio of PCB concentration in males to PCB concentration in females.  Hypothesis testing was used to identify the most plausible explanations for the patterns in observed differences in contaminant concentrations between the sexes.   We conclude that males were higher in PCB concentration compared with females primarily due to a higher rate of energy expenditure, stemming from higher activity and a higher resting metabolic rate (also referred to as standard metabolic rate, SMR).  A higher energy expenditure rate leads to a higher rate of food consumption, which in turn leads to a higher rate of PCB accumulation.  In some cases, the growth dilution effect also contributed to the observed difference in PCB concentration between the sexes.  Long-term elimination of PCBs by fish is negligible, whereas fish are capable of eliminating Hg from their bodies on a long-term basis.  Thus, the above-mentioned patterns in contaminant concentrations between the sexes of fish could be explained by males eliminating Hg from their bodies at a substantially faster rate than females.  We contend that our explanations for the observed patterns in contaminant concentrations between the sexes of fish apply to most species of fish, as well as higher vertebrates.