Browsing by Author "Anderson, Gregory B."
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- Assessing impacts of the Roanoke River Flood Reduction Project on the endangered Roanoke logperch (Percina rex): Summary of Construction-Phase MonitoringRoberts, James H.; Anderson, Gregory B.; Angermeier, Paul L. (2013-08-12)The United States Army Corps of Engineers (USACE) has partnered with the City of Roanoke to carry out the Roanoke River Flood Reduction Project (RRFRP), a suite of floodplain modifications to the Roanoke River. The incidental take permit issued to USACE requires that USACE monitor populations of the federally endangered Roanoke logperch (Percina rex) prior to (Phase A), during (Phase B), and after (Phase C) construction, to estimate effects of incidental take during the course of the project. This report summarizes logperch relative abundance, suitable habitat, and water quality conditions across Phase B and compares these data to Phase A. We also conducted additional research in 2011 to assess the representativeness of permanent monitoring sites, estimate the sampling efficiency of the electrofishing methodology, and evaluate the statistical power and appropriateness of alternative impact-detection methods. Despite substantial fluctuation of the relative abundance of adult logperch over the course of monitoring, we found no statistical evidence for an impact of RRFRP construction. Thus USACE has maintained compliance with its incidental take permit during Phase B. Young-of-year logperch density, habitat availability, and water quality conditions also varied considerably over time and space during Phase B, but not in ways that could be attributable to the RRFRP. We found that permanent sites were representative of reach-wide conditions, suggesting that our findings can reasonably be extrapolated to the entire study area. The sampling efficiency of our standard electrofishing method was estimated to be low (~ 11%), yet our assessment method produced indices of abundance that were strongly correlated with true population estimates. Herein we demonstrate a new, generalized linear modeling approach to impact assessment that should provide greater insight and statistical rigor than the traditional t-test approach.
- A Long-Term Study of Ecological Impacts of River Channelization on the Population of an Endangered Fish: Lessons Learned for Assessment and RestorationRoberts, James H.; Anderson, Gregory B.; Angermeier, Paul L. (MDPI, 2016-06-03)Projects to assess environmental impact or restoration success in rivers focus on project-specific questions but can also provide valuable insights for future projects. Both restoration actions and impact assessments can become “adaptive” by using the knowledge gained from long-term monitoring and analysis to revise the actions, monitoring, conceptual model, or interpretation of findings so that subsequent actions or assessments are better informed. Assessments of impact or restoration success are especially challenging when the indicators of interest are imperiled species and/or the impacts being addressed are complex. From 1997 to 2015, we worked closely with two federal agencies to monitor habitat availability for and population density of Roanoke logperch (Percina rex), an endangered fish, in a 24-km-long segment of the upper Roanoke River, VA. We primarily used a Before-After-Control-Impact analytical framework to assess potential impacts of a river channelization project on the P. rex population. In this paper, we summarize how our extensive monitoring facilitated the evolution of our (a) conceptual understanding of the ecosystem and fish population dynamics; (b) choices of ecological indicators and analytical tools; and (c) conclusions regarding the magnitude, mechanisms, and significance of observed impacts. Our experience with this case study taught us important lessons about how to adaptively develop and conduct a monitoring program, which we believe are broadly applicable to assessments of environmental impact and restoration success in other rivers. In particular, we learned that (a) pre-treatment planning can enhance monitoring effectiveness, help avoid unforeseen pitfalls, and lead to more robust conclusions; (b) developing adaptable conceptual and analytical models early was crucial to organizing our knowledge, guiding our study design, and analyzing our data; (c) catchment-wide processes that we did not monitor, or initially consider, had profound implications for interpreting our findings; and (d) using multiple analytical frameworks, with varying assumptions, led to clearer interpretation of findings than the use of a single framework alone. Broader integration of these guiding principles into monitoring studies, though potentially challenging, could lead to more scientifically defensible assessments of project effects.