Interactive Effects of Flow Regime, Climate Change, and Angler Harvest on Smallmouth Bass at the Southern Range Extent

The Ozark-Ouachita Interior Highlands of Arkansas, Oklahoma, and Missouri are the southern extent of native Smallmouth Bass Micropterus dolomieu range. Smallmouth Bass are an important species economically and ecologically, but it is unknown how climate change may affect them in this region and in particular how Smallmouth Bass may be affected differently across streams from various flow regimes. Here I present three projects investigating how climate change, flow regime, and angler harvest may interact to affect Smallmouth Bass over the coming century. I first modeled present and future water temperatures and calculated growth rate potential for Smallmouth Bass from streams within both groundwater and runoff flow regimes. Currently, water temperatures in runoff streams warm past optimal conditions for Smallmouth Bass during summer months and this is expected to be exacerbated by climate change. By the end of the century, my results predict that Smallmouth Bass growth could increase in winter, fall, and early spring in streams from both flow regimes, but will strongly decline during summer months in runoff streams. I next conducted an empirical study to examine differences in Smallmouth Bass body condition at present during summer months in both runoff and groundwater streams. I found in two out of three years of collections that Smallmouth Bass body condition declined during summer months in both groundwater and runoff streams with no significant difference between stream types. The final portion of my research examines population level effects of climate change on Smallmouth Bass from a runoff stream. I used empirical data to parameterize a simulation model where I simulated various climate scenarios such as increased flooding and drought probabilities. I found that increases in drought are likely to cause strong declines in adult Smallmouth Bass populations. Changes in harvest regulations could help protect Smallmouth Bass populations somewhat, but would likely not prevent population declines in the coming century. The effects of climate change on Smallmouth Bass at the southern range extent will likely be complex, but groundwater streams may mitigate some of the negative effects of climate change on Smallmouth Bass