Browsing by Author "Rypel, Andrew L."
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- Analysis of Grass Carp Dynamics to Optimize Hydrilla Control in an Appalachian ReservoirWeberg, Matthew Aaron (Virginia Tech, 2013-11-20)The primary objectives of this study were: 1) to evaluate the movement patterns, habitat use, and survival of triploid grass carp Ctenopharyngodon idella stocked to control hydrilla Hydrilla verticillata in a riverine reservoir (Claytor Lake, Virginia), 2) to examine grass carp population dynamics and hydrilla growth dynamics in Claytor Lake to guide long-term management efforts, and 3) to describe the aquatic plant community in the New River upstream of Claytor Lake to assess the potential for alterations due to potential grass carp herbivory. Only 3% of radio-tagged grass migrated out of Claytor Lake during the 2-year study. Grass carp movement patterns were significantly correlated with temperature-, weather-, and habitat-related variables. Grass carp selected specific cove, shoal and tributary habitats colonized by hydrilla. First-year survival of grass carp was 44% in 2011, and 25% in 2012. Grass carp growth rates were rapid in 2011, but declined in 2012 concurrent with significant reductions in hydrilla abundance. Based on grass carp population dynamics observed in Claytor Lake, our stocking model predicted that hydrilla could be controlled through 2030 by a grass carp standing stock of 5-6 metric tons. We documented 12 plant species in the New River upstream of Claytor Lake, 9 of which are preferred plants for grass carp suggesting that the plant community could be altered if migration rates increase. Grass carp can be effective for managing hydrilla in riverine reservoirs; however, continued monitoring of grass carp population dynamics, migration rates, and vegetation abundance could facilitate greater precision in management efforts.
- Declined fitness in larvae born from long-distance migrants of anadromous Coilia nasus in the lower reaches of the Yangtze River, ChinaHuang, Yan-Fei; Rypel, Andrew L.; Murphy, Brian R.; Xie, Song-Guang (Science Press, 2022-05-18)
- Diversity-production relationships of fish communities in freshwater stream ecosystemsMyers, Bonnie J. E.; Dolloff, C. Andrew; Webster, Jackson R.; Nislow, Keith H.; Rypel, Andrew L. (2021-09)Aim Ecological relationships between species richness and biomass production are increasingly thought to be pervasive across the globe. Yet, diversity-production relationships have not been explored extensively for freshwater fish communities even though fisheries production provides key services to humans. Our aim was to evaluate the diversity-production relationship of fish communities inhabiting freshwater streams across the Appalachian Mountain range and examine how diversity-production relationships varied across streams possessing different thermal signatures. Location Our study area included 25 freshwater stream ecosystems spanning from Vermont to North Carolina in the United States. Twenty sites were located in Maryland south to Tennessee and North Carolina, while five additional higher latitude sites were sampled in Massachusetts and Vermont. Methods We sampled the 25 study streams from June to September 2012 and collected fish population information to calculate biomass, species richness, the Shannon diversity index and annual production for each fish community. Linear mixed effects models were used to analyse the relationship between diversity indices and total community production. We also compared diversity and production relationships across other taxa. Results Across all streams, community fish production, biomass and P/B ratios ranged from 0.15-6.79 g m(-)(2) y(-)(1), 0.61-0.73 g m(-)(2) and 0.21-1.07 y(-1), respectively. Species richness had a significant positive effect (p = .012) on community fish production, while accounting for the thermal signature of the streams as a random effect and other habitat covariates. The Shannon diversity index did not have a significant effect (p = .101) on community production. Main conclusions The diversity-production relationship observed for stream fish communities was similar to other studies but demonstrated one of the highest slopes. Our results demonstrate that effects of biodiversity resonate to influence the production of fishes; thus, management of fisheries is more closely coupled to biodiversity than previously thought.
- Hindcasting Historical Breeding Conditions for an Endangered Salamander in Ephemeral Wetlands of the Southeastern USA: Implications of Climate ChangeChandler, Houston C.; Rypel, Andrew L.; Jiao, Yan; Haas, Carola A.; Gorman, Thomas A. (PLOS, 2016-02-24)The hydroperiod of ephemeral wetlands is often the most important characteristic determining amphibian breeding success, especially for species with long development times. In mesic and wet pine flatwoods of the southeastern United States, ephemeral wetlands were a common landscape feature. Reticulated flatwoods salamanders (Ambystoma bishopi), a federally endangered species, depend exclusively on ephemeral wetlands and require at least 11 weeks to successfully metamorphose into terrestrial adults. We empirically modeled hydroperiod of 17 A. bishopi breeding wetlands by combining downscaled historical climate-model data with a recent 9-year record (2006–2014) of observed water levels. Empirical models were subsequently used to reconstruct wetland hydrologic conditions from 1896–2014 using the downscaled historical climate datasets. Reconstructed hydroperiods for the 17 wetlands were highly variable through time but were frequently unfavorable for A. bishopi reproduction (e.g., only 61% of years, using a conservative estimate of development time [12 weeks], were conducive to larval development and metamorphosis). Using change-point analysis, we identified significant shifts in average hydroperiod over the last century in all 17 wetlands. Mean hydroperiods were shorter in recent years than at any other point since 1896, and thus less suitable for A. bishopi reproduction. We suggest that climate change will continue to impact the reproductive success of flatwoods salamanders and other ephemeral wetland breeders by reducing the number of years these wetlands have suitable hydroperiods. Consequently, we emphasize the importance of conservation and management for mitigating other forms of habitat degradation, especially maintenance of high quality breeding sites where reproduction can occur during appropriate environmental conditions.
- Rapid Life-History Diversification of an Introduced Fish Species across a Localized Thermal GradientZhu, Fengyue; Rypel, Andrew L.; Murphy, Brian R.; Li, Zhongjie; Zhang, Tanglin; Yuan, Jing; Guo, Zhiqiang; Tang, Jianfeng; Liu, Jiashou (PLOS, 2014-02-04)Climatic variations are known to engender life-history diversification of species and populations at large spatial scales. However, the extent to which microgeographic variations in climate (e.g., those occurring within a single large ecosystem) can also drive life-history divergence is generally poorly documented. We exploited a spatial gradient in water temperatures at three sites across a large montane lake in southwest China (Lake Erhai) to examine the extent to which life histories of a short-lived fish species (icefish, Neosalanx taihuensis) diversified in response to thermal regime following introduction 25 y prior. In general, warmwater icefish variants grew faster, had larger adult body size and higher condition and fecundity, but matured at smaller sizes. Conversely, coldwater variants had smaller adult body size and lower condition, but matured at larger sizes and had larger eggs. These life-history differences strongly suggest that key ecological trade-offs exist for icefish populations exposed to different thermal regimes, and these trade-offs have driven relatively rapid diversification in the life histories of icefish within Lake Erhai. Results are surprisingly concordant with current knowledge on life-history evolution at macroecological scales, and suggest that improved conservation management might be possible by focusing on patterns operating at microgeographical, including, within-ecosystem scales.
- Variations in Community Fish Production and Diversity Across the Appalachians: Implications for Climate ChangeMyers, Bonnie J. E. (Virginia Tech, 2014-03-04)Climate change is considered a major threat to freshwater ecosystems through altering biodiversity, structure, and function. Having a thorough understanding of how diverse ecosystems respond to temperature change is vital to ecosystem management and conservation. During summer 2012, I quantified fish biomass, somatic growth, secondary production, and habitat data for fish communities in 25 Appalachian streams from Vermont to North Carolina. Multiple statistical tests were conducted to determine the relationship between community fish production and air and water temperature, species thermal guild production and air and water temperature, and the relationship between community fish production and diversity. Community fish production estimates ranged from 0.15 to 6.79 g m-2 yr-1 and community P/B ratios ranged from 0.21 to 1.07. No significant differences existed between mean community production estimates at the cold-water, cool-water, warm-water, and extreme northern sites (P=0.19), but P/B ratios in the extreme northern streams were statistically higher than mean community P/B in cold- and cool-water streams in the southern Appalachians (P=0.002). Water temperatures had a positive effect on community fish production (P=0.01) while air temperatures did not (P=0.10). Both air and water temperatures were significant in predicting whether community production would be dominated by cold-water or cool-water fish (P=0.001, P<0.0001, respectively). Community fish production was significantly, positively related to species richness (R2=0.38, P=0.001) and was one of the highest correlates of community production (R2=0.52). As climate change alters freshwater ecosystems, fish communities may transform by means of shifting fish abundance, biomass, and production among species ultimately affecting ecosystem structure, function, and biodiversity.