Semester

Spring

Date of Graduation

2022

Document Type

Dissertation

Degree Type

PhD

College

Davis College of Agriculture, Natural Resources and Design

Department

Wildlife and Fisheries Resources

Committee Chair

Kyle Hartman

Committee Co-Chair

Amy Welsh

Committee Member

Amy Welsh

Committee Member

Quinton Phelps

Committee Member

John Sweka

Committee Member

David Thorne

Abstract

Central Appalachia has a unique history of human perturbation due largely to its historical economic reliance on extractive industry and timber harvest. Legacy impacts from these historic disturbances along with contemporary stressors in the form of continued industry, changing climates, altered land use, habitat fragmentation, and introduced species can present great threats to the region’s aquatic ecosystems. Brook Trout Salvelinus fontinalis are a species that has recreational and economic importance to the communities of central Appalachia but declines in size and abundance have been observed. Given the disturbances that threaten Brook Trout populations, understanding how their populations will respond to disturbance, its resilience is of great importance. Management actions aimed at imparting resilience to a population could help maintain their sustainability.

Understanding a population’s dynamics is a key aspect in understanding its resilience. A population can be defined by its recruitment, growth, and mortality. By understanding these vital rates, how a population will respond to a perturbation can be modeled. Through these modeling efforts, we can begin to understand what factors contribute to the resilience of a population. A wide variety of factors can affect resilience such as environmental, population, landscape, and genetic factors. This greater understanding can then help to guide management actions aimed at restoring population resilience.

The objectives of this research were aimed at gaining a greater understanding of the population dynamics and the resilience of central Appalachian headwater Brook Trout populations. My first objective was to evaluate the effects of stream flow on stock/recruitment relationships in Brook Trout. The second objective was to use yield per recruit modeling as a tool to evaluate population resilience. My third objective was to create a hypothesis based on long-term data that describes the mating system used in headwater Brook Trout. Finally, my fourth objective was to evaluate relationships between population genetic parameters and population resilience metrics.

My first chapter is a literature review containing previous research that has come out of the long-term Brook Trout monitoring project at West Virginia University Additionally, descriptions of the methods used and background about the streams sampled by the long-term project are described. Research regarding the different aspects and quantification of population resilience is also covered. Resilience has historically been difficult to define and quantify and as such, many different techniques have been presented to do so. These are themes that show up at multiples places in the dissertations and this chapter helps to lay out these critical background elements.

In the second chapter, I found that Brook Trout stock/recruitment dynamics fit best with the Ricker model. The results also indicated a negative relationship between mean fall discharge and recruit abundance the following year. Mean discharge in other seasons displayed important relationships, albeit weaker ones. Spring and winter discharge had weak positive relationships with recruit abundance while summer discharge exhibited a weak negative relationship. These results support previous research which has shown that density-independent factors work with density-dependent factors to shape stock/recruitment dynamics in lotic Brook Trout populations.

The results of my second chapter demonstrated the utility of optimum fishing pressure (Fopt) derived from yield per recruit models, which are familiar to management biologists, in describing the level of demographic compensation of a population. Additionally, the compensatory ability of a population was found to be negatively associated with drainage area and positively associated with the distance of the study stream to the confluence with a mainstem stream.

In the third chapter, I predict that a system exists in which diverse life history strategies exist primarily among male Brook Trout in headwater streams. Some male Brook Trout are likely moving into mainstem streams to access supplemental foraging habitats and improved growth rates while others remain in the headwaters to improve survival and act as satellite males during spawning. Using simulation modeling, I show a tradeoff between mortality and reproductive success that likely acts to maintain life history diversity in these systems.

Finally, the results of the fourth chapter suggest that population genetic parameters do influence the demographic resilience of a population. I found that inbreeding coefficient, rarefied allelic richness, and effective population size were all important factors in describing population resilience. The relationships I uncovered provide insight into the dynamics of gene flow and isolation in driving the resilience of a population.

This research helps to elucidate factors that affect resilience in headwater Brook Trout populations. In the face of the rapid global change that is currently facing ecosystems around the world, the results presented in these chapters can help to guide management to achieve sustainability of this recreationally and economically important fish. Additionally, the importance of long-term monitoring in understanding population dynamics is also displayed in this research. Resilience is a multifaceted topic and a full understanding of it is hard to achieve without having the proper data available. Through long-term monitoring and modern modeling techniques, a greater understanding can be gained.

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