Brent Knights (Former Employee)
Science and Products
Filter Total Items: 48
Evaluating potential effects of bigheaded carps on fatty acid profiles of multiple trophic levels in large rivers of the Midwest, USA
Recent work indicates that the establishment of bigheaded carps (Hypophthalmichthys spp.) in the United States has led to a reduction in condition of native planktivores and may detrimentally affect other trophic levels by altering the base of aquatic food webs. We used fatty acids to evaluate potential effects of bigheaded carps on taxa from multiple trophic levels in the Upper Mississippi, Illin
Authors
Andrea K. Fritts, Brent C. Knights, Toben LaFrancois, Jonathan M. Vallazza, Lynn A. Bartsch, Michelle R. Bartsch, William B. Richardson, Sean Bailey, Rebecca Kreiling, Byron Karns
Stable isotope comparison between mantle and foot tissues of two freshwater unionids: Implications for food web studies
Unionid mussels are a key taxon for stable isotope studies of aquatic food webs, often serving as the primary integrator of the pelagic baseline. Past isotope studies with mussels have commonly used either foot tissue or mantle tissue, but no study has yet to quantify the relation of both carbon and nitrogen isotopes between these two tissue sources. This makes it difficult to justify cross-study
Authors
Toben LaFrancois, Andrea K. Fritts, Brent C. Knights, Byron Karns
Spatial and temporal variance in fatty acid and stable isotope signatures across trophic levels in large river systems
Fatty acid and stable isotope signatures allow researchers to better understand food webs, food sources, and trophic relationships. Research in marine and lentic systems has indicated that the variance of these biomarkers can exhibit substantial differences across spatial and temporal scales, but this type of analysis has not been completed for large river systems. Our objectives were to evaluate
Authors
Andrea K. Fritts, Brent C. Knights, Toben D. Lafrancois, Lynn A. Bartsch, Jonathan M. Vallazza, Michelle R. Bartsch, William B. Richardson, Byron N. Karns, Sean Bailey, Rebecca Kreiling
Using pharyngeal teeth and chewing pads to estimate juvenile Silver Carp total length in the La Grange Reach, Illinois River
The Silver Carp Hypophthalmichthys molitrix is an invasive species in the Mississippi River basin; an understanding of their vulnerability to predation as juveniles may inform control by native predators and predator enhancement (e.g., stocking). Digestion of Silver Carp prey recovered from diets makes it difficult to determine the size‐classes that are most vulnerable to predation by native fishe
Authors
Eli G. Lampo, Brent C. Knights, Jonathan M. Vallazza, Cory A. Anderson, Will T. Rechkemmer, Levi E. Solomon, Andrew F. Casper, Richard M. Pendleton, James T. Lamer
Evidence of Asian carp spawning upstream of a key choke point in the Mississippi River
Bighead Carp Hypophthalmichthys nobilis, Silver Carp H. molitrix, and Grass Carp Ctenopharyngodon idella(collectively termed “Asian carp”) were introduced into North America during the 1960s and 1970s and have become established in the lower Mississippi River basin. Previously published evidence for spawning of these species in the upper Mississippi River has been limited to an area just downstrea
Authors
James H. Larson, Brent C. Knights, S. Grace McCalla, Emy Monroe, Maren T. Tuttle-Lau, Duane Chapman, Amy E. George, Jonathan M. Vallazza, Jon Amberg
USGS Integration of New Science and Technology, Appendix A
This product summarizes the USGS plans for integration of new science and technology into Asian Carp control efforts for 2017. This includes the 1) implementation and evaluation of new tactics and behavioral information for monitoring, surveillance, control and containment; 2) understanding behavior and reproduction of Asian carp in established and emerging populations to inform deterrent deployme
Authors
Marybeth K. Brey, Brent C. Knights, Aaron R. Cupp, Jon Amberg, Duane Chapman, Robin D. Calfee, James J. Duncker
Spatial and temporal dynamics of suspended particle characteristics and composition in Navigation Pool 19 of the Upper Mississippi River
Suspended particles are an essential component of large rivers influencing channel geomorphology, biogeochemical cycling of nutrients, and food web resources. The Upper Mississippi River is a large floodplain river that exhibits pronounced spatiotemporal variation in environmental conditions and biota, providing an ideal environment for investigating dynamics of suspended particles in large river
Authors
Amanda S. Milde, William B. Richardson, Eric A. Strauss, James H. Larson, Jonathan M. Vallazza, Brent C. Knights
Do water level fluctuations influence production of walleye and yellow perch young-of-the-year in large northern lakes?
Many ecological processes depend on the regular rise and fall of water levels (WLs), and artificial manipulations to WL regimes can impair important ecosystem services. Previous research has suggested that differences in WL between late summer and early spring may alter the suitability of shoals used by Walleyes Sander vitreus for spawning. Other species, such as the Yellow Perch Perca flavescens,
Authors
James H. Larson, David F. Staples, Ryan P. Maki, Jon M. Vallazza, Brent C. Knights, Kevin E. Peterson
Genetic analysis shows that morphology alone cannot distinguish asian carp eggs from those of other cyprinid species
Fish eggs and embryos (hereafter collectively referred to as “eggs”) were collected in the upper Mississippi River main stem (~300 km upstream of previously reported spawning by invasive Asian carp) during summer 2013. Based on previously published morphological characteristics, the eggs were identified as belonging to Asian carp. A subsample of the eggs was subsequently analyzed by using molecular
Authors
James H. Larson, S. Grace McCalla, Duane Chapman, Christopher B. Rees, Brent C. Knights, Jonathan M. Vallazza, Amy E. George, William B. Richardson, Jon Amberg
Managing the Mississippi River floodplain: Achieving ecological benefits requires more than hydrological connection to the river: Chapter
Floodplains are vital to the structure and function of river-floodplain ecosystems. Among the many ecological services provided by floodplains are nutrient cycling and seasonal habitats for fish, including spawning, nursery, foraging and wintering habitats. Connections between the river channel and floodplain habitats are essential to realize these ecological services, but spatial and temporal asp
Authors
Harold Schramm, William B. Richardson, Brent C. Knights
Differences between main-channel and off-channel food webs in the upper Mississippi River revealed by fatty acid profiles of consumers
Large river systems are often thought to contain a mosaic of patches with different habitat characteristics driven by differences in flow and mixing environments. Off-channel habitats (e.g., backwater areas, secondary channels) can become semi-isolated from main-channel water inputs, leading to the development of distinct biogeochemical environments. Observations of adult bluegill (Lepomis macroch
Authors
James H. Larson, Michelle Bartsch, Steve Gutreuter, Brent C. Knights, Lynn Bartsch, William B. Richardson, Jonathan M. Vallazza, Michael T. Arts
Can mercury in fish be reduced by water level management? Evaluating the effects of water level fluctuation on mercury accumulation in yellow perch (Perca flavescens)
Mercury (Hg) contamination of fisheries is a major concern for resource managers of many temperate lakes. Anthropogenic Hg contamination is largely derived from atmospheric deposition within a lake’s watershed, but its incorporation into the food web is facilitated by bacterial activity in sediments. Temporal variation in Hg content of fish (young-of-year yellow perch) in the regulated lakes of th
Authors
James H. Larson, Ryan P. Maki, Brent C. Knights, Brian R. Gray
Science and Products
Filter Total Items: 48
Evaluating potential effects of bigheaded carps on fatty acid profiles of multiple trophic levels in large rivers of the Midwest, USA
Recent work indicates that the establishment of bigheaded carps (Hypophthalmichthys spp.) in the United States has led to a reduction in condition of native planktivores and may detrimentally affect other trophic levels by altering the base of aquatic food webs. We used fatty acids to evaluate potential effects of bigheaded carps on taxa from multiple trophic levels in the Upper Mississippi, Illin
Authors
Andrea K. Fritts, Brent C. Knights, Toben LaFrancois, Jonathan M. Vallazza, Lynn A. Bartsch, Michelle R. Bartsch, William B. Richardson, Sean Bailey, Rebecca Kreiling, Byron Karns
Stable isotope comparison between mantle and foot tissues of two freshwater unionids: Implications for food web studies
Unionid mussels are a key taxon for stable isotope studies of aquatic food webs, often serving as the primary integrator of the pelagic baseline. Past isotope studies with mussels have commonly used either foot tissue or mantle tissue, but no study has yet to quantify the relation of both carbon and nitrogen isotopes between these two tissue sources. This makes it difficult to justify cross-study
Authors
Toben LaFrancois, Andrea K. Fritts, Brent C. Knights, Byron Karns
Spatial and temporal variance in fatty acid and stable isotope signatures across trophic levels in large river systems
Fatty acid and stable isotope signatures allow researchers to better understand food webs, food sources, and trophic relationships. Research in marine and lentic systems has indicated that the variance of these biomarkers can exhibit substantial differences across spatial and temporal scales, but this type of analysis has not been completed for large river systems. Our objectives were to evaluate
Authors
Andrea K. Fritts, Brent C. Knights, Toben D. Lafrancois, Lynn A. Bartsch, Jonathan M. Vallazza, Michelle R. Bartsch, William B. Richardson, Byron N. Karns, Sean Bailey, Rebecca Kreiling
Using pharyngeal teeth and chewing pads to estimate juvenile Silver Carp total length in the La Grange Reach, Illinois River
The Silver Carp Hypophthalmichthys molitrix is an invasive species in the Mississippi River basin; an understanding of their vulnerability to predation as juveniles may inform control by native predators and predator enhancement (e.g., stocking). Digestion of Silver Carp prey recovered from diets makes it difficult to determine the size‐classes that are most vulnerable to predation by native fishe
Authors
Eli G. Lampo, Brent C. Knights, Jonathan M. Vallazza, Cory A. Anderson, Will T. Rechkemmer, Levi E. Solomon, Andrew F. Casper, Richard M. Pendleton, James T. Lamer
Evidence of Asian carp spawning upstream of a key choke point in the Mississippi River
Bighead Carp Hypophthalmichthys nobilis, Silver Carp H. molitrix, and Grass Carp Ctenopharyngodon idella(collectively termed “Asian carp”) were introduced into North America during the 1960s and 1970s and have become established in the lower Mississippi River basin. Previously published evidence for spawning of these species in the upper Mississippi River has been limited to an area just downstrea
Authors
James H. Larson, Brent C. Knights, S. Grace McCalla, Emy Monroe, Maren T. Tuttle-Lau, Duane Chapman, Amy E. George, Jonathan M. Vallazza, Jon Amberg
USGS Integration of New Science and Technology, Appendix A
This product summarizes the USGS plans for integration of new science and technology into Asian Carp control efforts for 2017. This includes the 1) implementation and evaluation of new tactics and behavioral information for monitoring, surveillance, control and containment; 2) understanding behavior and reproduction of Asian carp in established and emerging populations to inform deterrent deployme
Authors
Marybeth K. Brey, Brent C. Knights, Aaron R. Cupp, Jon Amberg, Duane Chapman, Robin D. Calfee, James J. Duncker
Spatial and temporal dynamics of suspended particle characteristics and composition in Navigation Pool 19 of the Upper Mississippi River
Suspended particles are an essential component of large rivers influencing channel geomorphology, biogeochemical cycling of nutrients, and food web resources. The Upper Mississippi River is a large floodplain river that exhibits pronounced spatiotemporal variation in environmental conditions and biota, providing an ideal environment for investigating dynamics of suspended particles in large river
Authors
Amanda S. Milde, William B. Richardson, Eric A. Strauss, James H. Larson, Jonathan M. Vallazza, Brent C. Knights
Do water level fluctuations influence production of walleye and yellow perch young-of-the-year in large northern lakes?
Many ecological processes depend on the regular rise and fall of water levels (WLs), and artificial manipulations to WL regimes can impair important ecosystem services. Previous research has suggested that differences in WL between late summer and early spring may alter the suitability of shoals used by Walleyes Sander vitreus for spawning. Other species, such as the Yellow Perch Perca flavescens,
Authors
James H. Larson, David F. Staples, Ryan P. Maki, Jon M. Vallazza, Brent C. Knights, Kevin E. Peterson
Genetic analysis shows that morphology alone cannot distinguish asian carp eggs from those of other cyprinid species
Fish eggs and embryos (hereafter collectively referred to as “eggs”) were collected in the upper Mississippi River main stem (~300 km upstream of previously reported spawning by invasive Asian carp) during summer 2013. Based on previously published morphological characteristics, the eggs were identified as belonging to Asian carp. A subsample of the eggs was subsequently analyzed by using molecular
Authors
James H. Larson, S. Grace McCalla, Duane Chapman, Christopher B. Rees, Brent C. Knights, Jonathan M. Vallazza, Amy E. George, William B. Richardson, Jon Amberg
Managing the Mississippi River floodplain: Achieving ecological benefits requires more than hydrological connection to the river: Chapter
Floodplains are vital to the structure and function of river-floodplain ecosystems. Among the many ecological services provided by floodplains are nutrient cycling and seasonal habitats for fish, including spawning, nursery, foraging and wintering habitats. Connections between the river channel and floodplain habitats are essential to realize these ecological services, but spatial and temporal asp
Authors
Harold Schramm, William B. Richardson, Brent C. Knights
Differences between main-channel and off-channel food webs in the upper Mississippi River revealed by fatty acid profiles of consumers
Large river systems are often thought to contain a mosaic of patches with different habitat characteristics driven by differences in flow and mixing environments. Off-channel habitats (e.g., backwater areas, secondary channels) can become semi-isolated from main-channel water inputs, leading to the development of distinct biogeochemical environments. Observations of adult bluegill (Lepomis macroch
Authors
James H. Larson, Michelle Bartsch, Steve Gutreuter, Brent C. Knights, Lynn Bartsch, William B. Richardson, Jonathan M. Vallazza, Michael T. Arts
Can mercury in fish be reduced by water level management? Evaluating the effects of water level fluctuation on mercury accumulation in yellow perch (Perca flavescens)
Mercury (Hg) contamination of fisheries is a major concern for resource managers of many temperate lakes. Anthropogenic Hg contamination is largely derived from atmospheric deposition within a lake’s watershed, but its incorporation into the food web is facilitated by bacterial activity in sediments. Temporal variation in Hg content of fish (young-of-year yellow perch) in the regulated lakes of th
Authors
James H. Larson, Ryan P. Maki, Brent C. Knights, Brian R. Gray