Increases in temperature due to climate change will have large implications for aquatic ecosystems. Warmwater fish species, such as smailmouth bass, Micropterus dolomieu, may have access to additional favourable thermal habitat under increased surface-water temperatures, thereby shifting the northern limit of the distribution of the species further north in Canada and potentially negatively impacting native fish communities. A database comprised of over 50,000 lakes was assembled consisting of data on geography, lake morphology, water chemistry, climate, and fish community composition. Based on a comparison of several statistical approaches (multiple regression, regression tree, artificial neural networks, and Bayesian multiple regression) and several climate-change scenarios, water temperatures were predicted to increase by as much as 18°C by 2100, with the greatest increase in water temperature in northern Canada. By 2100, smallmouth bass thermal habitat is predicted to shift to the north with the majority of Canadian lakes expected to contain suitable thermal habitat. A comparison of logistic regression, classification tree, linear discriminant analysis, and artificial neural networks indicated that smallmouth bass distribution is predicted by winter and summer air temperatures. Climate-change modeling, in conjunction with artificial neural networks, predicted that smallmouth bass will have suitable thermal habitat throughout the majority of aquatic systems in the continental United States and Canada by 2100. The presence of smallmouth bass will negatively impact native fish communities, particularly native lake trout populations. Lake trout populations residing in smaller lakes are more vulnerable to the effects of smallmouth bass establishment due to the decreased presence of alternate prey resources. Examination of the pelagic and littoral forage fish communities identified nearly 9,700 lake trout populations threatened by 2100AD under climate-change scenarios, due to the potential invasion of smallmouth bass. The current range expansion of smallmouth bass has been facilitated by stocking by governmental agencies, unauthorized and accidental introduction by anglers, and dispersal through drainage networks. This stresses the importance of intensifying public education and regulation to limit the potential dispersal of invasive species, such as smallmouth bass.

Species distribution models are useful tools that can be used to evaluate tradeoffs of management and conservation strategies under scenarios of environmental change. Modeling efforts for fish species have largely focused on cold-water, commercial, and recreationally-valued species, even though warm-water, non-game species have important roles in ecosystem services and processes. I developed species distribution models for fourteen warm-water fish species native to the Central United States and evaluated environmental drivers and predictive performance. I used an ensemble model approach produced by combining forecasts of five single-model techniques. Response plots and variable importance calculations were used to evaluate the influence of individual variables. The predictive performance of the ensemble models was assessed using area under the curve (AUC) of the receiver-operating characteristic plot. Ensemble model AUC values generally performed better than single-model types, suggesting ensemble models are more reliable and applicable for management purposes than single-models. Most models were influenced by a mix of climate, land use and geophysical variables; however, climate variables were the dominant environmental drivers across models. Next, I projected distribution responses of 14 warm-water fish species to climate and land use scenarios using the ensemble models combined with scenario analyses. I incorporated different time periods, greenhouse gas emissions scenarios, and general circulation models into the scenario analysis. I then tested the effect of climate change scenario and the incorporation of land use on range change. Although it has been hypothesized that warm-water fishes will generally benefit from future climate changes through range expansion, I found wide variability in range change across the species modeled. There was a significant effect of greenhouse gas scenario and year on overall range change for half of the species modeled. The incorporation of future land use projections into scenarios generally led to increased range expansion. I combined all scenarios into consensus projections to visualize range change projections across all scenarios. Some species expanded their range to the north and into higher elevations while other species were projected to lose significant portions of their range. For example, orangethroat darter ( Etheostoma spectabile ) is projected to gain between 30 to 90 percent new range and lose between 0 to 6 percent of its current range while bigmouth shiner (Hybopsis dorsalis ) is projected to gain between 0 to 20 percent new range and lose 75 to 100 percent of its current range. Variability in climate change responses across warm-water species may be a result of ecological traits, such as range size and fecundity. The variability in warm-water species' responses suggests management of these species can be informed through the use of species distribution modeling and scenario analysis.

These documents summarize some of the recent studies of the relationships among climate, the aquatic environment, and the dynamics of fish populations. The studies are mostly from the North Pacific ocean, but there are reports of investigations from the North Atlatic Ocean and from fresh water. Various papers include numerous examples of the relationships between fish abundance trends and the environment.

Climate change can have both direct and indirect impacts on food webs and fish populations. Growing evidence suggests that these impacts are affecting the relative abundance and presence of freshwater fishes. It may be possible to detect climate-induced changes in game fish populations by analyzing data from Fishbrain, a smartphone application that anglers in the United States have used to report catches from 2015-2020. We used generalized linear mixedeffects modeling to determine the temporal trend in catch proportions by subbasin, and then mapped the location of these trends to identify spatial patterns. Results suggest that warm-water species are becoming more common in catches, usually at the expense of cool-water species. These patterns were strongest in the Great Lakes region, the Northeast, and parts of the West Coast. Single-species analyses detected increases in Largemouth Bass (Micropterus salmoides), declines in Channel Catfish (Ictalurus punctatus), Northern Pike (Esox lucius), and Rainbow Trout (Oncorhynchus mykiss), patchy results for smallmouth bass (Micropterus dolomieu), and no response in bluegill (Lepomis macrochirus). Spatial results of the single-species analyses were interesting and will be discussed. Despite the short time frame of this study (6 years), our analyses of catch data produced results that were consistent with expected changes in the relative abundance of game fishes in response to climate change. Future work should focus on refining the use of app data as a tool for monitoring game fish responses to climate change, especially as the length of the time series increases.

Effects of global warming on the physical, chemical, ecological structure and function and biodiversity of freshwater ecosystems are not well understood and there are many opinions on how to adapt aquatic environments to global warming in order to minimize the negative effects of climate change. Climatic Change and Global Warming of Inland Waters presents a synthesis of the latest research on a whole range of inland water habitats – lakes, running water, wetlands – and offers novel and timely suggestions for future research, monitoring and adaptation strategies. A global approach, offered in this book, encompasses systems from the arctic to the Antarctic, including warm-water systems in the tropics and subtropics and presents a unique and useful source for all those looking for contemporary case studies and presentation of the latest research findings and discussion of mitigation and adaptation throughout the world. Edited by three of the leading limnologists in the field this book represents the latest developments with a focus not only on the impact of climate change on freshwater ecosystems but also offers a framework and suggestions for future management strategies and how these can be implemented in the future. Limnologists, Climate change biologists, fresh water ecologists, palaeoclimatologists and students taking relevant courses within the earth and environmental sciences will find this book invaluable. The book will also be of interest to planners, catchment managers and engineers looking for solutions to broader environmental problems but who need to consider freshwater ecology.