Early Life History of Suckers (Catostomidae) in a Southern Appalachian River Syste

Suckers (Catostomidae) are a fish family that is of high conservation concern but has received relatively little attention from the scientific community. The knowledge gap in the early life history of suckers is related to the lack of efficient or standardized sampling methods and difficulty in identifying sampled fishes. The upper Hiwassee River system supports seven sympatric species of native suckers, including six species of redhorses (Moxostoma), which are vulnerable to effects of introduced species and habitat degradation. One of these species, the Sicklefin Redhorse Moxostoma sp., is imperiled with a restricted distribution and is of high conservation concern.;Efficiency of three techniques (drift netting, light trapping, and visual surveys) to sample larval fish assemblages was evaluated. The annual mean catch-per-unit-effort (CPUE) for drift nets was 1.64-1.70 suckers/100 m 3. The annual mean CPUE for light traps was 2.99-3.57 suckers/trap-night. Larval and juvenile suckers were visually observed at a mean density of 5.52 fish/m2 and at quadrat densities up to 100 fish/m2. The probability of catching suckers in light traps was negatively related to water velocity. Patch occupancy and abundance in visual surveys were also negatively related to water velocity, and no interspecific differences in habitat were detected.;By implementing a novel index of larval fish ontogeny and using genetic barcoding for species identification, phenology, ontogeny, and growth were estimated and compared among six sucker species. Emergence phenology paralleled previously described spawning phenology. Species with overlapping emergence periods exhibited significantly different mean ontogeny rates. Larval growth rates were similar among species, and high intraspecific size variability was observed. Differences in emergence timing, ontogeny, and size may mediate competition for food resources among sympatric larval suckers. Small innate differences in early life history among species likely facilitated the current sympatric diversity of suckers in the upper Hiwassee River system, or these differences may represent local adaptations that evolved as a result of specific competition pressures among species.;An understanding of the swimming ability of larval and juvenile fishes is important for identifying environmental influences during critical periods of early development. Swimming ability was studied via laboratory experiments, where water velocity was controlled and swimming behavior observed. A series of fixed velocity swimming tests was used to assess prolonged swimming speeds of larval and juvenile captive-reared Sicklefin Redhorse and four species of wild-caught suckers. The probability of prolonged swimming was negatively related to water velocity, positively related to fish total length, and differed slightly among species. The transition from pelagic to epibenthic swimming occurred at approximately the mid-point of the metalarva stage. Given the relative rarity of water velocity less than prolonged swimming speed for these fishes in riffles, short upstream migration may be possible, but is probably atypical.;Nonnative species introductions have been implicated as a major threat to the conservation of imperiled species. Blueback Herring Alosa aestivalis was introduced to the Hiwassee River system and became established in Hiwassee Lake by 1999. To evaluate possible predatory interactions of Blueback Herring with native sucker species, Blueback Herring were sampled from the Hiwassee River and Valley River using electrofishing. Stomach contents were examined visually and via genetic barcoding coupled with nextgeneration sequencing. Visual diet examinations detected 12 orders of aquatic invertebrates, as well as fish ova, fins, and larvae. Barcoding PCR allowed for identification of six sucker species in the Blueback Herring diet, but Sicklefin Redhorse was not detected.;The methods employed in this study addressed sampling considerations and demonstrated the effectiveness of genetics-based techniques for identifying cryptic samples. These findings may be applied to guide the conservation of suckers in the Hiwassee River and may be more broadly applied to other systems.