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Brent Knights

My work focuses on the ecology, behavior and impacts of invasive carp in the Mississippi River basin to inform control efforts.  We employ a variety of techniques for these studies including acoustic and satellite telemetry, otolith and fin ray chemistry, diet and condition metrics, and population dynamics.  Current work is investigating dam passage of Asian carp at strategic high-head dams to inform the deployment of deterrents in locks and lock approaches of these dams.  We are also investigating the timing and factors that influence, off-channel area use by Asian carp to help direct removal by contracted and commercial fishers.

Science and Products

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FishTracks Telemetry Database and web application map interface with available search filters and map legend

Database and web application for invasive carp telemetry data (FishTracks)

Four types of invasive carp fish species, are currently found in the United States: black, grass, silver, and bighead carps. These species are fast growing, prolific feeders that out-compete native fish species and drastically alter the natural ecosystems they invade. To prevent the spread of invasive carp into the Great Lakes, the multi-agency Asian Carp Regional Coordinating Committee (ACRCC)...
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Upper Midwest Environmental Sciences Center
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Database and web application for invasive carp telemetry data (FishTracks)

Four types of invasive carp fish species, are currently found in the United States: black, grass, silver, and bighead carps. These species are fast growing, prolific feeders that out-compete native fish species and drastically alter the natural ecosystems they invade. To prevent the spread of invasive carp into the Great Lakes, the multi-agency Asian Carp Regional Coordinating Committee (ACRCC)...
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Otolith microchemistry and microstructure of age-0 silver carp for determining early-life environments and spawning periodicity in the Upper Mississippi River in 2016

In 2016, for the first time, an abundance of age-0 silver carp (Hypophthalmichthys molitrix) were captured at several sites upstream of Lock and Dam 19 on the Upper Mississippi River near Keokuk, Iowa. These data were collected in an attempt to determine the early life environments and frequency and timing of the reproductive events that led to a large year class of age-0 silver carp. This info
By
Upper Midwest Environmental Sciences Center

Data for dam passage analysis of bigheaded carps in Pools 15-19 of the upper Mississippi River during 2014-2017

Acoustic telemetry data (Vemco, Inc) were collected on invasive silver carp (Hypophthalmichthys molitrix), bighead carp (H. nobilis) and their hybrids in the upper Mississippi River (navigation pools 15-19) to determine movement patterns and preferred habitats during September 2013 through November 2017. We consolidated these data into intervals of fish within-pool residency and intervals of fish
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Upper Midwest Environmental Sciences Center

Otolith microchemistry of adult bigheaded carp for determining early-life environments in the Upper Mississippi River 2016-2018

Data set includes water Sr:Ca, Ba:Ca, and δ18O for the Mississippi River and tributaries, and otolith Sr:Ca, Ba:Ca, and δ18O data from bigheaded carp (Silver Carp and BIghead Carp) collected in navigation pools 16-19 of the Upper Mississippi River in 2016 to 2018. Bigheaded carp (Bighead Carp and Silver Carp) are invasive species in the US and have spread throughout most of the lower Mississippi R
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Upper Midwest Environmental Sciences Center
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Timing and hydrological conditions associated with bigheaded carp movement past navigation dams on the upper Mississippi river

As the range of non-native bigheaded carps (Hypophthalmichthys spp.) continues to expand throughout river systems of the United States, managers are tasked with preventing or slowing the spread of these invasive species. Main stem navigation dams on the upper Mississippi River, long considered a deterrent to fish migration, may slow or prevent the spread of invasive fish species. As discharge incr
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Ecosystems, Upper Midwest Environmental Sciences Center

USGS Illinois River monitoring and evaluation

Asian carp monitoring and contract removal will continue throughout the Upper Illinois Waterway system as needed for adaptive management to mitigate, control, and contain Asian carp. Compiling data from monitoring and removal efforts into a centralized database (Illinois River Catch Database application) facilitates data standardization, quality, accessibility, sharing, and analysis to aid in Asia
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Ecosystems, Upper Midwest Environmental Sciences Center

Mercury and water level management in lakes of northern Minnesota

Water level (WL) fluctuations substantially alter the fauna, flora, and microbial community of nearshore aquatic ecosystems. Water level management therefore has the potential to strongly influence a wide variety of ecosystem processes. Many northern temperate lake food webs experience substantial methylmercury contamination, which is partially mediated by the action of sulfate-reducing bacteria o
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Ecosystems, Upper Midwest Environmental Sciences Center

Lock operations influence upstream passages of invasive and native fishes at a Mississippi River high-head dam

Asian carps continue to expand their range in North America, necessitating efforts to limit the spread and establishment of reproducing populations. Mississippi River Lock and Dam 19 is a high-head dam that represents a population ‘pinch-point’ as passage through the lock chamber is the only means by which fishes can complete upstream movement. As such, this location could be a pivotal control poi
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Ecosystems, Upper Midwest Environmental Sciences Center

Estimating the degree to which distance and temperature differences drive changes in fish community composition over time in the upper Mississippi River

Similarity in community composition declines as distance between locations increases, a phenomenon that has been observed in a wide variety of freshwater, marine and terrestrial ecosystems. One driver of the distance-similarity relationship is the presence of environmental gradients that alter the suitability of sites for particular species. Although some environmental gradients, such as geology
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Ecosystems, Upper Midwest Environmental Sciences Center

Influence of a high-head dam as a dispersal barrier to fish community structure of the Upper Mississippi River

In river systems, high‐head dams may increase the distance‐decay of fish community similarity by creating nearly impermeable dispersal barriers to certain species from upstream reaches. Substantial evidence suggests that migratory species are impacted by dams, and most previous studies in stream/river networks have focused on small streams and headwaters. Here, we assess whether a high‐head dam (L
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Ecosystems, Upper Midwest Environmental Sciences Center

Development of a quantitative PCR method for screening ichthyoplankton samples for bigheaded carps

Monitoring ichthyoplankton is useful for identifying reproductive fronts and spawning locations of bigheaded carps (Hypophthalmichthys spp.). Unfortunately, sorting and identifying ichthyoplankton to monitor for bigheaded carp reproduction is time consuming and expensive. Traditional methods require frequent egg-larvae sampling, sorting of all samples to obtain presumptively identified bigheaded c
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Ecosystems, Upper Midwest Environmental Sciences Center

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
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Ecosystems, Upper Midwest Environmental Sciences Center

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
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Ecosystems, Upper Midwest Environmental Sciences Center

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
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Ecosystems, Upper Midwest Environmental Sciences Center

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
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Ecosystems, Upper Midwest Environmental Sciences Center

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
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Ecosystems, Columbia Environmental Research Center, Upper Midwest Environmental Sciences Center

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