First Summer Survival and Channel-Unit Habitat Use by the Neosho Subspecies of Smallmouth Bass
Shannon K. Brewer, Brandon Brown, Thomas A. Worthington, Robert Mollenhauer, Anthony Rodger, Matt Skoog, and Jim Burroughs
Abstract.—Unique genetic lineages of Micropterus species are increasingly recognized; however, little effort has been devoted to identifying their ecological relationships despite recognition of their conservation value by management agencies. Our study objectives were to determine young-of-year, first-summer survival, and examine overall channel-unit habitat use by the Neosho subspecies of Smallmouth Bass Micropterus dolomieu velox from two Ozark streams (Spring and Buffalo creeks). We completed snorkel surveys approximately every 2 weeks from June–September 2013. As anticipated, young-of-year mortality was high during the first 2 weeks of the sampling period (85% in Buffalo Creek and 99% in Spring Creek). Mortality stabilized by the end of July in both streams and was similar over subsequent 2-week periods (95% CI: 0.13%–2.38% and 0.72%–3.48%, in Spring Creek and Buffalo Creek, respectively). In Spring Creek, backwater habitats were unavailable, and young-of-year fish used both pool and run habitats throughout the study duration. However, we observed different habitat-use patterns in Buffalo Creek: young-of-year fish used pools and backwaters throughout the season, use of run habitats increased by late July, and increased use of backwater habitats followed an increase in late summer discharge. In general, there was substantial habitat use variability both within and between streams. Considering both stream reaches combined, young-of-year fish densities in riffle habitat were statistically lower than other channel units. We show that young-of-year Neosho Smallmouth Bass mortality is high during the first few weeks following swim up, and that backwater habitats may be important to early life stages under certain environmental conditions.