Using Habitat, Climate, and Biotic Interactions to Predict Co-Occurring Smallmouth Bass and Largemouth Bass in the Ozark National Scenic Riverways

A shift in species distribution caused by disturbance and climate change may affect how agencies manage fish populations. The Ozark National Scenic Riverways (ONSR) in Missouri has both smallmouth bass Micropterus dolomieu (SMB) and largemouth bass M. salmoides (LMB), with SMB dominating. Anecdotal evidence suggested that LMB populations may be increasing and affecting SMB populations. Our objective was to determine factors influencing these species abundance within ONSR. Seven sites were sampled six times from 2006 to 2014 to determine whether habitat, climate or biotic interactions could predict the relative abundance of Age-0 and >Age-0 SMB and LMB. Redundancy analysis was used with parsimonious variables within the habitat, climate, and competition models to determine the proportion of variance in relative abundance each model could explain. Sites with greater wetted channel width and distance to nearest cool-water spring had greater >Age-0 LMB and SMB relative abundance, respectively, while Age-0 LMB and SMB relative abundance increased with warmer winter and summer water temperatures, respectively, and that competition may influence these species the downstream reaches where they co-occur. Our results suggest water temperatures that increase juvenile abundances may influence SMB and LMB dynamics into the future, and LMB may out-compete SMB where they co-occur.