Population Contributions of Large Females May be Eroded by Contaminant Body Burden and Maternal Transfer: A Case Study of Alligator Gar

Within a population, larger individuals tend to have higher fecundity and produce higher quality eggs. For this reason, larger, older females often disproportionately contribute to recruitment. However, increases in body size and age have also been shown to correlate with increased bioaccumulation of environmental contaminants, which negatively impact reproduction and larval survival. In this study, we tested for maternal age and size effects on fecundity, egg size and quality, contaminant body burden, and maternal transfer in Alligator Gar Atractosteus spatula to assess the potential for contaminant bioaccumulation to offset reproductive benefits of large females. We measured fecundity and egg quality (via lipid content) as well as tissue concentrations of mercury, polychlorinated biphenyls (PCBs), and organochlorine pesticides (OCPs) in female Alligator Gar from the Trinity River, Texas. Fecundity was positively correlated with body size, but egg lipid was not significantly correlated with body size or with fecundity. Total mercury (THg) in both liver and muscle was positively correlated with maternal body size, and egg THg was positively correlated with maternal body size and liver THg. All liver and egg samples contained detectable levels of PCBs and OCPs, which were positively correlated with body size. Concentrations of PCBs and OCPs were positively correlated between tissues for each female, with egg concentrations being generally higher than liver concentrations. Based on concentrations of Hg, PCBs, and OCPs known to cause biological impairment in adult and larval fishes, the concentrations observed in this study suggest that adult reproductive function and behavior—as well as egg hatching success, larval development, and survival—could be compromised. Our results provide data that are relevant for managing the lower Trinity River Alligator Gar population and also serve as a case study demonstrating that the reproductive benefits of larger, older females may be eroded by contaminant accumulation and maternal transfer.