Stefansson, Emily SuzanneDietary methylmercury (MeHg) uptake in relation to fish lifestage, species, and level of exposure are poorly understood in lower trophic levels, particularly in estuarine species. Furthermore, little is known about the transfer of accumulated MeHg from female to offspring. Dietary MeHg accumulation, as well as growth and survival, were compared in two species of estuarine forage fish: <italic>Cyprinodon variegatus</italic> and <italic>Menidia beryllina</italic>. Results indicated that <italic>M. beryllina</italic> was more sensitive to dietary MeHg exposure than <italic>C. variegatus</italic>. Growth rate and the level of dietary exposure strongly influenced MeHg tissue concentrations in both species. In a second experiment, the source of maternally transferred MeHg was examined using a stable mercury isotope approach. A significant portion of Hg in eggs was from the burden stored in female tissues, suggesting that historical mercury exposure can be important in the context of maternal transfer.ThesisToxicologyEnvironmental scienceAnimal sciencesBioaccumulationEstuarine fishMaternal transferMethylmercuryStable mercury isotopeTrophic transfer