Quantitative recovery planning: understanding how human activities in watersheds can influence population dynamics and genetic structuring of diadromous fishes.

Bowlby, Heather Dawn (2016) Quantitative recovery planning: understanding how human activities in watersheds can influence population dynamics and genetic structuring of diadromous fishes. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Developing quantitative relationships that link human-induced environmental change with changes in population dynamics for species of conservation concern is hindered by: (1) a limited understanding of the cumulative effect (and relative importance) of population regulation, spatial dynamics, and demographic processes, (2) issues with detectability for species-environment interactions owing to data characteristics and (3) the cumulative or confounding nature of multiple threats. Taking a single-species approach based on endangered Atlantic salmon, I have partially addressed these challenges in my four research chapters. In chapter two, I characterized the conditions under which metapopulation structure would be expected to benefit a population assemblage and found that straying can reduce abundance and heighten extinction risk when productivity is low. For species of conservation concern, I would expect that remediation actions designed to influence demographic rates (e.g. mortality rates) would be more beneficial than actions influencing spatial dynamics. In chapter three, I accounted for the effects of observation and measurement error when quantifying relationships between hydrological variation and survival. Beyond the potential to change our interpretation of ecological relationships, I was able to infer the types of threats affecting juveniles in specific watersheds. In chapter four, I used patterns of effective dispersal to surmise the behavioural mechanism leading to watershed choice among straying adult salmon as well as the relative importance of multiple concurrent threats. My conclusions contradict some current perceptions on threats and suggest new directions for future research. In chapter five, I was able to develop a spatial tool that could inform management decisions or identify priority areas for restoration efforts. However, I was unable to fully characterize how environmental variation influences habitat utilization, distribution patterns, or population-level responses to human activities at multiple spatial extents. The relationships I describe are among the first to be developed for endangered Atlantic salmon in Nova Scotia at a population level. Several of the analyses represent novel applications to conservation questions and have the potential to be extended or more widely applied. Because freshwater fishes, including diadromous fishes, are collectively one of the most imperiled species groups in the world, such research represents a timely contribution to conservation biology.

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