Patterns of Mercury Uptake with Respect to Life History, Diet, Environment, and Health of the Estuarine Predator Longnose Gar, Lepisosteus osseus
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Smylie, Meredith
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Abstract
Methylmercury (MeHg) is one of the most threatening contaminants affecting fisheries worldwide. Patterns of bioavailability and bioaccumulation of this metal remain poorly understood, especially within estuaries. We examined biotic and abiotic factors which influence mercury (Hg) bioaccumulation within a largely unstudied estuarine predator, longnose gar (Lepisosteus osseus), while describing its life history and dietary patterns. Chapter I introduces the state of knowledge of Hg bioaccumulation within estuaries and longnose gar biology. Chapter II outlines age, growth, and reproduction of this long-lived and highly fecund fish within two coastal rivers. Longnose gar display determinate fecundity and are batch spawners with group-synchronous oocyte development spanning most of the year. Chapter III describes the dietary components and ontogenetic shift of this species from small benthic fishes to large pelagic fishes. Chapter IV concludes that longnose gar are not representative of other fishes in MeHg bioaccumulation, though they are excellent indicators of MeHg exposure for estuarine fishes. This is the second study to explore reproductive offloading of Hg in a spawning fish and found predictable Hg levels within oocytes. Chapter V summarizes that these studies provide valuable insight into the ecological role of longnose gar and their patterns of Hg uptake.