Investigating the environmental influences on elemental uptake and deposition in hard structures of sturgeon to identify natal origin and reconstruct life history
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Habitat-specific elemental signatures form when divalent cations such as strontium (Sr2+) are substituted for calcium (Ca2+) in the calcified hard structures of fishes (e.g., otoliths, fin rays, vertebrae) allowing for the retroactive interpretation of spatial and temporal changes in environmental life history. The ability to accurately reconstruct life histories of fish using microchemistry techniques relies on predictable responses to changes in the environment. As such, the overarching objectives of this thesis were to 1 – Examine how the environment influences the processes involved in the elemental pathway from initial uptake to crystallization in hard structures and 2 – Validate ways can we use this knowledge to make improved inferences on the ecology of sturgeon utilizing hard part microchemistry. To do this, I applied a multidisciplinary approach to describe the effect the environment (i.e., ambient water chemistry, temperature, pH) on the initial uptake, partitioning, and biomineralization of otoliths and fin rays in larval and juvenile Lake Sturgeon, Acipenser fulvescens, and White Sturgeon, A. transmontanus, followed by the application of microchemistry techniques to validate the use of elemental signatures in fin rays to determine natal origin (i.e, hatchery versus wild-spawned) and habitat use of juvenile and adult Lake Sturgeon. Data presented here indicate the initial uptake and deposition of Sr2+ into hard structures of larval Lake Sturgeon are inversely related to ambient calcium (Ca2+) concentrations and positively correlated to environmental temperature. Additionally, temperature, but not pH, had a significant effect on the biomineralization of sturgeon otoliths, independent of ontogeny, indicating the determination of otolith polymorph composition in sturgeons is controlled by both intrinsic and extrinsic factors. Microchemistry of fin rays collected from wild-caught juvenile and adult Lake Sturgeon of both known and unknown origin reflected the heterogeneity of water chemistry profiles in the environment. Development and validation of a novel analytical technique using multiple elements allowed for strong predictions of habitat use on a fine spatial scale. This thesis has made a significant contribution to our understanding of fish hard part structures and techniques developed will contribute to improved management strategies for the conservation of Lake Sturgeon and other migratory fishes.
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