Brent Knights (Former Employee)
Science and Products
Filter Total Items: 47
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 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
Mercury and water level fluctuations in lakes of northern Minnesota
Large lake ecosystems support a variety of ecosystem services in surrounding communities, including recreational and commercial fishing. However, many northern temperate fisheries are contaminated by mercury. Annual variation in mercury accumulation in fish has previously been linked to water level (WL) fluctuations, opening the possibility of regulating water levels in a manner that minimizes or
Authors
James H. Larson, Ryan P. Maki, Victoria G. Christensen, Mark B. Sandheinrich, Jaime F. LeDuc, Claire Kissane, 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
Fatty acid composition at the base of aquatic food webs is influenced by habitat type and watershed land use
Spatial variation in food resources strongly influences many aspects of aquatic consumer ecology. Although large-scale controls over spatial variation in many aspects of food resources are well known, others have received little study. Here we investigated variation in the fatty acid (FA) composition of seston and primary consumers within (i.e., among habitats) and among tributary systems of Lake
Authors
James H. Larson, William B. Richardson, Brent C. Knights, Lynn Bartsch, Michelle Bartsch, J. C. Nelson, Jason A. Veldboom, Jonathan M. Vallazza
Science and Products
Filter Total Items: 47
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 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
Mercury and water level fluctuations in lakes of northern Minnesota
Large lake ecosystems support a variety of ecosystem services in surrounding communities, including recreational and commercial fishing. However, many northern temperate fisheries are contaminated by mercury. Annual variation in mercury accumulation in fish has previously been linked to water level (WL) fluctuations, opening the possibility of regulating water levels in a manner that minimizes or
Authors
James H. Larson, Ryan P. Maki, Victoria G. Christensen, Mark B. Sandheinrich, Jaime F. LeDuc, Claire Kissane, 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
Fatty acid composition at the base of aquatic food webs is influenced by habitat type and watershed land use
Spatial variation in food resources strongly influences many aspects of aquatic consumer ecology. Although large-scale controls over spatial variation in many aspects of food resources are well known, others have received little study. Here we investigated variation in the fatty acid (FA) composition of seston and primary consumers within (i.e., among habitats) and among tributary systems of Lake
Authors
James H. Larson, William B. Richardson, Brent C. Knights, Lynn Bartsch, Michelle Bartsch, J. C. Nelson, Jason A. Veldboom, Jonathan M. Vallazza