Date of Award

8-2015

Level of Access

Campus-Only Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

Advisor

Gayle Zydlewski

Second Committee Member

Michael Kinnison

Third Committee Member

Joseph Zydlewski

Additional Committee Members

David Secor

Douglas Sigourney

Abstract

Shortnose sturgeon inhabiting the Gulf of Maine move extensively and appear to constitute a metapopulation, which contrasts with previous assertions that individuals remain in their natal river. The effects of among-river movements on local and regional population dynamics were uncertain. Local reproduction underpins the metapopulation concept, but has not been documented in all rivers where shortnose sturgeon have been reported in the Gulf of Maine. I developed a novel microchemical technique using dorsal scutes to infer life histories of shortnose sturgeon. Chronological and microchemical attributes of scutes were used to define putative freshwater to marine transitions. Based on these results, superficial sampling of dorsal scutes may allow microchemical reconstruction of past habitat including rivers of natal origin.

Because movements among local populations in a metapopulation are anticipated to influence local population dynamics, I characterized the demographic attributes of shortnose sturgeon in the two major rivers in the Gulf of Maine, the Kennebec River and Penobscot River. Individuals caught in the Penobscot River were larger and in better condition than those caught in the Kennebec River. The absence of relatively large individuals from the Kennebec River also suggests that individuals of greater size and condition may leave the Kennebec River for the Penobscot River. This may exemplify a conditional strategy representing a probable adaptive life history option providing a crucial demographic link between these two river systems.

Regional metapopulation dynamics of shortnose sturgeon were examined using a life history modeling framework. Using the model, mark-recapture abundance estimates of shortnose sturgeon inhabiting three rivers in the Gulf of Maine were successfully replicated. This model will be useful for identification of important knowledge gaps (e.g., model sensitivities) and for testing future scenarios of conservation interest (e.g., demographic disturbance).

I relate my findings to the recovery tasks of the National Marine Fisheries Service. For example, an evaluation of distinct population segment (DPS) stability (recovery task 1.1.3) should consider effects of connectivity with other DPS in the Gulf of Maine. My research illustrates that to implement recovery task 2 (protect shortnose sturgeon population and habitats) fully, consideration of overall regional dynamics is essential.

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