Date of Award

2011

Level of Access Assigned by Author

Campus-Only Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Wildlife Ecology and Wildlife Conservation

Advisor

Joseph Zydlewski

Second Committee Member

Linda Kling

Third Committee Member

Ellen Marsden

Abstract

Maine lakes once held whitefish populations, but surveys indicate a statewide decline. Introduced rainbow smelt populations have been linked to declines in coregonid recruitment. Declines in coregonid recruitment are hypothesized to be driven by competition and predation of larvae by smelt. The ability of smelt or other factors to influence whitefish population health will depend on habitat use. Vertical activities of whitefish were studied using acoustic telemetry. Vertical habitat selection varied seasonally and was influenced by temperature. Whitefish displayed a strong diurnal pattern of activity that varied across seasons. Diel vertical migrations occurred with whitefish rising in the water column during nighttime and occupying deeper waters during the day. The strong linkage between temperature and habitat use may limit the current range of whitefish and be directly impacted by climatic change. As larval fish, the initiation of external feeding is critical to survival and failure can limit recruitment. To understand early life history in whitefish, we experimentally reared whitefish with conspecifics and larval smelt to determine growth responses to intra- and interspecific competition. The growth response of whitefish in the intraspecific trials was correlated with the estimated number of prey items per individual. During interspecific trials, whitefish growth mirrored the response to their own density observed in intraspecific trials, suggesting that whitefish growth is more influenced by per capita intraspecific competition and less by per capita interspecific competition with smelt. To investigate the impact of predation, I sought to identify the size of whitefish preyed upon by adult smelt and how predation efficiency changes with increasing sizes of whitefish. In the laboratory, larval whitefish were exposed to adult smelt and predation efficiencies were observed. The predatory window for whitefish appears to be from ~12 mm to 43 mm. The impact smelt predation has on whitefish is dependent on whitefish growth rates, environmental conditions, and overlap of habitat use. The distribution of whitefish populations in Maine is poorly understood because non-targeted survey data often misrepresents whitefish presence. To identify lakes that have or did have whitefish, I developed predictive models using a subset of lakes. The most efficient model used historic fish assemblage data to predict whitefish presence. This model had high discriminating power and required readily available data.

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