Conservation Applications of Watershed-Level Brook Trout Riverscape Genetics

Contemporary Brook Trout Salvelinus fontinalis populations are often fragmented due to anthropogenic influences. Although research and conservation actions have traditionally focused at the stream-reach level, inter-stream movements may connect seemingly isolated populations to form larger metapopulations. The overall goal of my research was to use watershed-level riverscape genetics to inform Brook Trout conservation. Specifically, my objectives were to 1) present a synthesis of existing Brook Trout literature and identify future research directions, 2) evaluate Brook Trout genetic population structuring and identify gene flow barriers at the watershed level, 3) validate and modify a pre-existing Brook Trout habitat patch spatial layer that can be used to predict extant Brook Trout metapopulations, and 4) develop decision support tools to identify Brook Trout conservation opportunity areas (COAs) at watershed levels. Using empirical data, I found evidence of genetic connectivity among streams spanning 5 – 15 km of mainstem habitat. Watersheds with high levels of development were associated with increased differentiation, suggesting that development acts a barrier to gene flow at the watershed level. The pre-existing patch layer adequately predicted many genetic metapopulations, however patches with dams or high levels of development often exhibited higher levels of genetic structuring. Modifying the patches reduced evidence of genetic structuring, which suggested a better representation of existing genetic patterns. Using the set of COA tools, I identified patches and watersheds across Connecticut to target for specific conservation actions. Simulating barrier removals, I found rapid (1 - 10 years) increases in genetic diversity, however barrier severity and monitoring location strongly influenced the observed effects. Through this research, I have demonstrated that Brook Trout, despite being isolated by “unsuitable” mainstem habitat, exist in metapopulations at the watershed level. Such dynamics are important for long term population viability, and thus conservation actions should take watershed-level processes into consideration. Using the modified patch layer and the set of COA tools I developed as part of this research, resource managers can visualize and identify areas across broad landscapes to target for Brook Trout conservation. Doing so will promote the long-term resilience and adaptive potential of Brook Trout metapopulations