Author: David Arthur Dippold

Publisher:

Published: 2020

Total Pages: 398

ISBN-13:

The dynamics of fish populations are determined by demographic processes such as growth, survival, mortality, and movement that are influenced directly and indirectly by a suite of biotic and abiotic factors. Human-induced environmental change (e.g., climate change, nutrient pollution) is altering these processes, influencing the ability of ecosystems to support their resident populations, as well as the valuable ecosystem services they provide. The impacts of human-induced environmental change are often negative, can occur at a variety of spatial and temporal scales, and can vary with ontogeny. Therefore, understanding the historical and anticipated effects of environmental change on the dynamics of fish populations is critical to maintaining them, including the valued services and fisheries that they support. My research has sought to better understand the factors that influence population-level responses of exploited fish populations to changing environmental conditions, and to anticipate what these responses may look like amidst future change. To help achieve this research goal, my collaborators and I developed and applied numerous quantitative approaches to economically and ecologically important Lake Erie fish populations. Specifically, we forecasted the recruitment dynamics of several fish populations (walleye Sander vitreus, yellow perch Perca flavescens, and white perch Morone americana) under future climate change scenarios (Chapter 2), investigated historical changes in walleye recruitment dynamics in response to environmental factors (Chapter 3), anticipated how environmental change might alter early-life growth and survival of walleye via changes in larval stage duration (Chapter 4), and identified the role of demographic and environmental factors on the spatial patterning of walleye recreational harvest rates in Lake Erie (Chapter 5). These studies demonstrate that the dynamics of Lake Erie’s fish populations have changed in the past, and that environmental change is likely to continue to alter the dynamics of Lake Erie’s fish populations in the future. In Chapter 2, our modeling showed that walleye and yellow perch recruitment were forecasted to decline under future climate change, owing to shorter and warmer winters. For yellow perch, these declines were projected to be exacerbated by the implementation of agricultural conservation practices that reduce nutrient inputs into the west basin of Lake Erie. By contrast, recruitment of invasive white perch was projected to remain stable or increase relative to the past. In Chapter 3, my colleagues and I developed a modeling framework to build more informative environment-recruitment models. By applying this framework to the Lake Erie walleye population, we determined that the timing and importance of environmental factors previously associated with walleye recruitment (e.g., winter severity, spring warming rate, river discharge) have likely changed in the recent past. In Chapter 4, we linked output from a physical model to a bioenergetics model to show that walleye larval stage duration has likely changed in the recent past, with significant differences in direction and magnitude among Lake Erie’s three basins. Using historical environmental variability, we anticipated how future climate change might affect early-life growth and survival. Finally, in Chapter 5, my colleagues and I demonstrated that the relationships between temperature and walleye population size and recreational harvest rates vary spatially, and we anticipated how future ecosystem change could necessitate changes to the management of walleye in Lake Erie, owing to this spatial dependency. Collectively, the results of my research have helped to understand how Lake Erie’s fish populations respond to environmental change, to the benefit of fisheries management.