Rivers are important movement corridors for fishes that allow for population connectivity. Within the upper Mississippi River Basin, invasive Silver Carp (Hypophthalmichthys molitrix) use tributaries including the Des Moines, Iowa, and Cedar rivers; however, the extent Silver Carp move and intermix among these systems and pools of the upper Mississippi River (UMR) is largely unknown. We used acoustic telemetry and multistate models to (1) identify individual and spatial variability in movement strategies, (2) use survival and transition probability estimates to evaluate population dynamics and connectivity, and (3) evaluate the influence of temporal and environmental variables on survival and transition probabilities. Weekly transition probabilities generally increased with discharge and ranged between 0.01 from UMR Pool 20 to outside the study area at 575 m3/s to 0.75 from UMR Pool 18 to outside the study area at 7200 m3/s. Survival decreased as temperature increased from 0 to 30 degrees C and was higher in tributaries than mainstem pools correlated with lower discharge. Overall, Silver Carp displayed diverse movement strategies with high connectivity that can inform invasive species management strategies.

Invasive carp, including Silver Carp (Hypophthalmichthys molitrix) and Grass Carp (Ctenopharyngodon idella), are increasing their range within the Mississippi River Basin, threatening native fishes and ecosystem function. We conducted a 3-year field test of a multi-modal deterrent that uses sound, bubbles, and light to test its ability to impede upstream passage by invasive carp. The test was performed at a lock and dam on the Cumberland River, Kentucky, USA, using acoustic telemetry to track the movements of Silver Carp, Grass Carp, and several native fish species. When the deterrent was operating, the estimated probability of upstream lock passage was 53% lower (95% CI: 41%–63%) for Silver Carp but 74% higher (95% CI: 3%–190%) for Grass Carp compared to times when the deterrent was not operating. Paddlefish (Polyodon spathula) passage was reduced by 43% (95% CI: 71% reduction to 9% increase), although this was not statistically significant. We detected no significant effects on Freshwater Drum (Aplodinotus grunniens) or Smallmouth Buffalo (Ictiobus bubalus). However, sample sizes were small for these native species, limiting our ability to identify effects. Water temperature, tailwater elevation, and vessel lockages affected passage rates, although this varied among species.

Objective The management of invasive Silver Carp Hypophthalmichthys molitrix in the Tennessee River basin focuses on removal, and there is interest in extending removal efforts to the tailwater environments of high-head locks and dams along the Tennessee River, such as Kentucky Dam. We used acoustic telemetry data from Silver Carp to understand important ecological associations underlying their residence in the Kentucky Dam tailwater, measured by daily fish counts and mean residence time. Methods We used time-series-informed regression models, variance partitioning, and cross-correlation function analysis to associate six predictors, including lock and dam operations (total, spill gate, and turbine discharge and number of lockages), hydrology (tailwater elevation), and water temperature, with two measures of Silver Carp residency (daily counts and mean residence time). Results We found that spill-induced hydrology (total discharge + spill discharge + tailwater elevation) was negatively associated with daily counts but not with residence time, whereas temperature was positively associated with counts and negatively associated with residence times. Variance partitioning indicated that nearly all the variance in counts and residence times was jointly explained by temporal effects, lock and dam operations (discharge, tailwater elevation, and lockages), and temperature. The cross-correlations indicated that the counts were lagged by all predictors, sometimes up to 5 d, whereas residence times were lagged by both total and spill discharge and number of lockages. Conclusions We found that discharge and water temperature were principally associated with residency of Silver Carp in the Kentucky Dam tailwater. However, these associations were entirely temporally constrained, which can affect how strongly and how quickly Silver Carp respond to changing environmental conditions across different time scales. Managers can leverage these associations to plan removal periods where daily tailwater conditions/dam operations are favorable to invasive carp residence (e.g., >10 degrees C and <2,500 m(3)/s) and adjust fishing effort to optimize removal rates in response to changing conditions.

Objective Invasive carps continue to spread across the Mississippi River basin, posing significant ecological risk. Identifying technologies to slow their dispersal is critical. The use of sound has been proposed as a method to modify the behavior of Silver Carp Hypophthalmichthys molitrix, offering a nonstructural deterrent strategy.Methods Silver Carp implanted with acoustic transmitters were released into earthen ponds equipped with telemetry arrays. The fish were exposed to a 30-min playback of three underwater sounds (chirp saw, chirp square, and 100-hp boat motor). Movement trajectories were analyzed using a two-state hidden Markov model to estimate the effects of environmental and experimental variables on fish behavior.Results The results of the hidden Markov model supported two behavioral states. State 1 was characterized by longer step lengths (distance between positions) and greater directional persistence in turning angle (change in direction between two intervals), indicative of heighted activity. State 2 was defined by shorter step lengths and less directional persistence, suggesting reduced activity. Silver Carp that were exposed to the chirp square sound had an increased likelihood of entering state 1, whereas the 100-hp boat motor sound promoted transitions to state 2.Conclusions Underwater sounds distinctly influenced the movement of Silver Carp in earthen ponds. The chirp square sound elicited heightened activity levels, demonstrating potential for use in acoustic deterrent applications. However, the response of Silver Carp to these sounds may be influenced by the size of the study environment or the absence of natural drivers of fish behavior, such as food or reproduction. This study contributes to the development of nonstructural, species-specific deterrent systems by identifying sounds that influence the behavior of invasive carps. The application of sound-based methods may play a critical role in integrated pest management strategies for invasive carps, potentially limiting their spread while minimizing effects on native species. Invasive carps have rapidly expanded their range since their introduction into the United States in the early 1960s. Acoustic tools are currently in development to attempt to curtail this expansion. Understanding the influence of different sounds on the behavior of invasive carps may improve application and future species management. These findings suggest that invasive carps' behavior can be influenced by these underwater sounds.

The United States imports thousands of live vertebrate species annually as part of legal trade. Escapes and releases from captivity are major pathways of invasion, however, the risk posed by the thousands of imported vertebrate species has not been systematically assessed. We conducted a horizon scan that used a data-driven climate match to filter a list of nearly 15,000 taxa drawn from across the globe of imported fish, amphibians, reptiles, birds, and mammals for rapid assessment by taxonomic experts. Experts evaluated 840 species and identified 32 (22 reptiles and 10 fishes) as having the highest risk for establishment, spread, and negative impacts. Of those high-risk species, the majority have the capacity to disrupt ecosystem processes via their role as top predators or the unique ecological niches that they occupy, while several of the snake species pose a threat to human health. High-risk species were often scored with high confidence while in contrast, low scores were attributed to a combination of ecological redundancy, low propagule pressure, or low climate match while low confidence arose from a lack of information in the literature (i.e., data deficiency). Our study therefore highlights legally imported species likely to cause the greatest harm with the recognition that many other species could also become invasive in the United States. The ranked list of vertebrate threats can be used to prioritize watchlists and inform the development of targeted regulations for importation can be applied to regions to provide a rapid, preliminary screening for large pools of potential invaders.

Bigheaded carps (i.e., Silver Carp Hypophthalmichthys molitrix and Bighead Carp H. nobilis) are non-native species that continue to expand their ranges throughout North American river systems, including the Tennessee and Cumberland river systems in the southeastern United States. These species are known to have deleterious effects on native fishes. Management efforts have focused on reducing upstream passage at dams coupled with intensive removal of individuals occupying upstream reaches. Understanding mechanisms affecting the success of upstream fish passage through lock chambers is critical to determining immigration rates into upstream habitats, the likelihood of success for upstream removal efforts, and potential effects of upstream passage reduction using deterrents. We used acoustic telemetry to examine the timing of Silver Carp upstream and downstream dam passages, patterns of fish movement throughout the river systems, and the relationship between fish size and upstream passage through the lock chamber. During 2016-2019, 465 Silver Carp were surgically implanted with transmitters within the two river systems. We documented 37 upstream passages and 57 downstream passages of Barkley, Kentucky, and Pickwick dams. During the two years in which dam passages were observed, most upstream dam passages (89%) occurred during April-August when water temperature ranged from 12-31 degrees C. Most downstream passages (89%) occurred from late-February through July. The relatively small portion of Silver Carp tagged in Pickwick Lake (11% of total tagged), the uppermost reach of the study area, accounted for nearly two-thirds of all dam passages. Our findings may help managers model Silver Carp populations and inform decisions regarding fish deterrent placement and operation.

Objective Targeted removals are used for management of some invasive fish populations. Tag-return studies are one approach that can be used to assess the efficacy of targeted removals. However, there are many decisions to make when designing a tag-return study. We used simulation modeling to outline general guidelines for consideration when designing efficient tag-return studies to measure annual removal rates of invasive fish, particularly invasive carps.Methods We simulated data sets using scenarios with varying numbers of fish tagged per year, removal rates, tag reporting rates, tag retention rates, and study durations. We generated the data sets under a set of "known" parameters with added stochasticity; we then fitted the simulated data sets to a Bayesian tag-return model and measured the precision and accuracy of the model-estimated removal rates.Results We found that the model was able to predict removal rates without bias for most of the scenarios. However, we did find patterns in the precision of the predictions that could help to inform tag-return studies. When the proportion of the population removed through harvest was constant, the proportion of the population removed per year and the probability that harvested tags were reported had the largest effect on precision. The number of tags released per year and the study duration also had moderate effects. For scenarios testing the ability of the model to predict removal rates in stochastic populations, the precision of the model was primarily influenced by the number of fish tagged, the underlying nature of the stochasticity, and whether fish were tagged during the year of the prediction.Conclusions Based on our simulations, we outline how study objectives, the underlying population variability, and the tolerance range for error can guide decisions regarding the number of fish to tag, how to monitor tag return rates, and how long to conduct a study. Tag-return studies can be used to monitor targeted removals of invasive fishes. Using simulations, we outline some considerations for managers when using this method to measure removal rates. Study design decisions depend on the objectives, underlying population conditions, and tolerance for error.

Understanding the movement patterns of an invasive species can be a powerful tool in designing effective management and control strategies. Here, we used a Bayesian multistate model to investigate the movement of two invasive carp species, silver carp (Hypophthalmichthys molitrix) and bighead carp (H. nobilis), using acoustic telemetry. The invaded portions of the Illinois and Des Plaines Rivers, USA, are a high priority management zone in the broader efforts to combat the spread of invasive carps from reaching the Laurentian Great Lakes. Our main objective was to characterize the rates of upstream and downstream movements by carps between river pools that are maintained by navigation lock and dam structures. However, we also aimed to evaluate the efficacy of the available telemetry infrastructure to monitor carp movements through this system. We found that, on a monthly basis, most individuals of both species remained within their current river pools: averaging 76.2% of silver carp and 75.5% of bighead carp. Conversely, a smaller proportion of silver carp, averaging 14.2%, and bighead carp, averaging 13.9%, moved to downstream river pools. Movements towards upstream pools were the least likely for both species, with silver carp at an average of 6.7% and bighead carp at 7.9%. The highest probabilities for upstream movements were for fish originating from the three most downstream river pools, where most of the population recruitment occurs. However, our evaluation of the telemetry array’s effectiveness indicated low probability to detect fish in this portion of the river. We provide insights to enhance the placement and use of these monitoring tools, aiming to deepen our comprehension of these species’ movement patterns in the system.

Fish movements in regulated rivers can be challenging to study because anthropogenic modifications, such as locks and dams, can influence animal behavior. Upper Mississippi River Lock and Dam 19 (LD 19), for example, is an invasive carp movement bottleneck due to an impassable dam. Upstream fish passage at LD19 is restricted to the lock chamber, making it an optimal location to test invasive fish deterrents that could limit further range expansion. Evaluating the effectiveness of experimental deterrents requires baseline knowledge of fish movements and suitable sample sizes of fish encountering the deterrents to ensure adequate statistical power. Some evidence indicates fish with prior upstream experience may return upstream or challenge potential deterrents at a higher rate than fish without such experience. To test how previous upstream experience could increase the rate at which fish moved upstream through a navigation lock chamber, we compared upstream passage through LD 19 using bigheaded carp captured below the dam (downstream-origin) and two groups of bigheaded carp captured upstream from the dam: those that swam downstream on their own volition (upstream-origin fish) and those that were captured upstream and translocated downstream of LD 19 (translocated upstream-origin). Translocated upstream-origin carp demonstrated the highest rate of upstream passage, with 59% of the fish detected downstream from LD 19 passing upstream during our study. In contrast, downstream-origin carp made no upstream passages over 2 years. Fish origin was shown to influence upstream passage success. This may be an important consideration for fish passage studies and deterrent evaluations.

Dams commonly restrict fish movements in large rivers but can also help curtail the spread of invasive species, such as invasive bigheaded carps (Hypophthalmichthys spp). To determine how dams in the upper Mississippi River (UMR) affect large-scale invasive and native fish migrations, we tracked American paddlefish (Polyodon spathula) and bigheaded carp across > 600 river km (rkm) and 16 navigation locks and dams (LD) of the UMR during 2 years with contrasting water levels. In 2022, a low-water year, both native paddlefish and invasive bigheaded carp had low passage rates (4% and 0.6% respectively) through LD15, a movement bottleneck being studied for invasive carp control. In contrast, flooding in 2023 led to open-river conditions across multiple dams simultaneously, allowing 53% of paddlefish and 46% of bigheaded carp detected in Pool 16 to move upstream through LD15. Bigheaded carp passed upstream through LD15 rapidly (μ = 32 rkm per day) a maximum of 381 rkm, whereas paddlefish moved an average of 9 upstream rkm per day (maximum of 337 rkm). Our results can inform managers examining trade-offs between actions that enhance native fish passage or deter movements of invasive species. This understanding is critical because current climate change models project increases in flooding events like that observed during 2023.

Technology advancements in fisheries science can provide useful tools to support natural resource management and conservation. However, new technologies may also present challenges for decision makers due to the lack of a standardized process to assess technologies for consideration within management plans. Future technology development in fishery and water resources could benefit from a framework that assigns an appropriate technology development stage and defines the readiness for implementation. Technology Readiness Levels (TRL) are one established research and development scale used throughout engineering and related disciplines that could be applied to natural resource management tools. The TRL assess the maturity of a technology from nascent idea through a fully developed technology. Steps within this scale could provide a general framework for researchers to follow when planning and conducting studies, while similarly providing a standard scale for resource managers to assess readiness for technology transfer and implementation. The goal of this paper is to describe TRL in the context of natural resource management tools and offer this existing framework as one option to facilitate communication between researchers and managers.

First posted August 11, 2023 For additional information, contact: Director, Upper Midwest Environmental Sciences CenterU.S. Geological Survey2630 Fanta Reed RoadLa Crosse, Wisconsin 54603Contact Pubs Warehouse Invasive carp (Hypophthalmichthys nobilis [Richardson, 1845; Bighead Carp], H. molitrix [Valenciennes in Cuvier and Valenciennes, 1844; Silver Carp], Ctenopharyngodon idella [Valenciennes in Cuvier and Valenciennes, 1844; Grass Carp], and Mylopharyngodon piceus [Richardson, 1846; Black Carp]) expansion threatens the Laurentian Great Lakes and other major waterways. Numerous tools and techniques are being tested or developed to curtail the upstream expansion of invasive carps while minimizing the effect to native species. Underwater sound is one technology that has shown promise as a deterrent in the laboratory and ponds and is being considered for use at bottleneck locks and dams to reduce the risk of invasive carps moving to uninvaded areas. To test this technology at a management-relevant scale, an underwater acoustic deterrent system (UADS) was designed and installed at Lock 19 on the Mississippi River in 2021. The experimental UADS operates on a continuous schedule of 80 hours on and 80 hours off to allow for comparisons of fish behavior during varying environmental, operational, and navigation traffic conditions. Two telemetry systems, operating at 69 and 307 kilohertz, were deployed to evaluate how the UADS may affect movement and behavior of invasive carps and native fish species. During 2021–22, Silver Carp were twice as likely to pass over the UADS and into the lock when it was off compared to on; however, Bigmouth Buffalo, a native fish, were 1.2 times more likely to make upstream passage when the UADS was off compared to on.

First posted August 11, 2023 For additional information, contact: Director, Upper Midwest Environmental Sciences CenterU.S. Geological Survey2630 Fanta Reed RoadLa Crosse, Wisconsin 54603Contact Pubs Warehouse Invasive carp (Hypophthalmichthys nobilis [Bighead Carp], Mylopharyngodon piceus [Black Carp], Ctenopharyngodon idella [Grass Carp], and H. molitrix [Silver Carp]) continue to spread in the United States and deterrents at river navigation locks are one emerging control strategy for slowing the spread. High-head navigation dams on large rivers serve as impediments to the upstream spread of these populations. One possible control technique is using a multimodal deterrent that utilizes a combination of lights, sound, and air bubbles to guide fish away from a location. Laboratory tests and small-scale field deployments of similar multi-stimuli deterrents have demonstrated potential for deterring invasive carp. These earlier studies led to the deployment and initiation of a field study of a multimodal deterrent in 2019 at the downstream lock approach at Barkley Lock and Dam on the Cumberland River near Grand Rivers, Kentucky. We are using two types of telemetry systems to evaluate how the multimodal deterrent affects movement and behavior of Silver Carp, Grass Carp, and four native species: Aplodinotus grunniens (Freshwater Drum), Polyodon spathula (Paddlefish), Ictiobus bubalus (Smallmouth Buffalo), and Acipenser fulvescens (Lake Sturgeon). We are evaluating fish movements in response to the multimodal deterrent by using a study design that cycles between 1 week with the multimodal deterrent on and 1 week with it off. This weekly cycling provides baseline comparisons across variable environmental conditions. When the multimodal deterrent is on, the number of Silver Carp completing upstream passage through Barkley Lock is reduced by about one-half. This study that began in 2019 can provide insights into the effectiveness of a multimodal deterrent for limiting upstream movement of invasive carp or effects on native fishes through strategic navigation locks on large rivers.

1. Invasive species management can benefit from predictive models that incorporate spatially explicit demographics and dispersal to guide resource allocation decisions.2. We used invasive bigheaded carps (Hypophthalmichthys spp.) in the Illinois River, USA as a case study to create a spatially explicit model to evaluate the allocation of future management efforts. Specifically, we compared additional harvest (e.g. near the invasion front vs. source populations) and enhanced movement deter- rents to meet the management goal of reducing abundance at the invasion front.3. We found additional harvest in lower river pools (i.e. targeting source populations) more effectively limited population sizes upriver at the invasion front compared to al- locating the same harvest levels near the invasion front. Likewise, decreasing passage (i.e. lock and dam structures) at the farthest, feasible downriver location limited invasion front population size more than placing movement deterrents farther upriver.4. Synthesis and applications. Our work highlights the benefits of adopting a multi- pronged approach for invasive species management, combining suppression of source populations with disrupting movement between source and sink populations thereby producing compounding benefits for control. Our results also demonstrate the importance of considering metapopulation dynamics for invasive species control programs when achieving long- term management goals.

Despite significant efforts devoted to understanding the underlying complexity and emergence of collective movement in animal groups, the role of different external settings on this type of movement remains largely unexplored. Here, by combining time series analysis and complex network tools, we present an extensive investigation of the effects of shady environments on the behavior of a fish species (Silver Carp Hypophthalmichthys molitrix ) within earthen ponds. We find that shade encourages fish residence during daylight hours, but the degree of preference for shade varies substantially among trials and ponds. Silver Carp are much slower and exhibit lower persistence in their speeds when under shade than out of it during daytime and nighttime, with fish displaying the highest persistence degree and speeds at night. Furthermore, our research shows that shade affects fish schooling behavior by reducing their polarization, number of interactions among individuals, and the stability among local neighbors; however, fish keep a higher local degree of order when under shade compared to nighttime positions.

Acoustic deterrents are currently being considered for deployment at strategic bottlenecks, such as lock and dams of major rivers, to deter upstream movement of invasive carp. Previous studies have demonstrated that bighead and silver carp (Hypophthalmichthys nobilis and H. molitrix, respectively) display negative phonotaxis to playbacks of broadband sound recordings produced from a 100 hp outboard boat motor. However, there is concern that acoustic deterrents may impact the movement of non-target native fishes in the Upper Mississippi River. We evaluated the potential impacts of a broadband underwater acoustic deterrent on native ostariophysans [bigmouth buffalo (Ictiobus cyprinellus), channel catfish (Ictalurus punctatus) and fathead minnow (Pimephales promelas)], invasive ostariophysans [bighead carp, common carp (Cyprinus carpio), grass carp (Ctenopharyngodon idella) and silver carp], and native non-ostariophysans [(American eel (Anguilla rostrata), gizzard shad (Dorosoma cepedianum), hybrid striped bass (M. saxatilis x M. chrysops), lake sturgeon (Acipenser fulvescens) and paddlefish (Polyodon spathula)]. Fish were exposed to playback of the broadband sound (60-10000 Hz), and their behavior was evaluated. Bighead carp showed a strong negative phonotaxis response to the stimulus [12.3 +/- 7.5 (SD) mean consecutive reactions], silver carp and grass carp showed moderate responses (4.5 +/- 5.2 and 3.8 +/- 3.5 reactions), and common carp displayed low responses (1.3 +/- 1.9 reactions). Of the native fish, bigmouth buffalo (2.1 +/- 2.9 reactions) and hybrid striped bass (0.3 +/- 0.5 reactions) were the only species to demonstrate observable response to the acoustic stimulus. Based on this small-scale behavioral screening, acoustic deterrents should have minimal impact on native species; however, larger pond and field trials are necessary to confirm this finding.

Vessel sound is now globally recognized as a significant and pervasive pollutant to aquatic life. However, compared to marine environments, there is a paucity of data on sound emitted by vessel activity in freshwater habitats. The Upper Mississippi River (UMR) is home to a diverse array of aquatic life as well as being a key route for barge transportation with 29 locks and dams. In this study, passive acoustic monitoring was conducted at Lock and Dam 19 near Keokuk, Iowa, on the UMR between 20 June - August 28, 2019 to coincide with peak navigation use. There was a significant increase in median sound pressure level (SPL; 50-12,000 Hz) recorded during vessel passages (123 dB re. 1 mu Pa for recreational vessels and 137 dB re. 1 mu Pa for commercial vessels) compared to median background levels (111 dB re. 1 mu Pa). Results provide information on the ambient soundscape at a navigation lock, providing a baseline essential for future studies gauging the effect of anthropogenic sound on aquatic life. Lock 19 has also been identified as a potential site for acoustic deterrent deployment to prevent invasive fish movements. The results of this study can help determine the sound level or frequency deterrents would need to emit, to avoid those currently produced during vessel passage.

Invasive Bighead Carp Hypophthalmichthys nobilis and Silver Carp H. molitrix have infested and caused largescale ecological and economic damage to the Illinois, Mississippi, and Ohio rivers. We compiled demographic data from 42,995 fish from 23 pools in the Illinois, Mississippi, and Ohio rivers, which universities and management agencies previously collected as part of management, monitoring, and research activities. We used this data set to test whether demographic rates (length–weight relations including body condition, mortality, growth curves, and female maturity curves) varied among subpopulations across a gradient of invasion status. We found that length–weight relations and growth curves varied among subpopulations, whereas maturity curves did not. Our findings demonstrated spatial variability in demographic rates for Bighead and Silver carp across a broad geographic area in relation to invasion status and river conditions. Herein, we provide general subpopulation management options and present different hypotheses to explain the observed spatial variability in demographic rates.

Invasive carps are ecologically and economically problematic fish species in many large river basins in the United States and pose a threat to aquatic ecosystems throughout much of North America. Four species of invasive carps: black carp (Mylopharyngodon piceus), grass carp (Ctenopharyngodon idella), silver carp (Hypophthalmichthys molitrix) and bighead carp (Hypophthalmichthys nobilis), are particularly concerning for native ecosystems because they occupy and disrupt a variety of food and habitat niches. In response, natural resource agencies are developing integrated pest management (IPM) plans to mitigate invasive carps. Control tools are one key component within a successful IPM program and have been a focal point for development by governmental agencies and academic researchers. For example, behavioural deterrents and barriers that block migratory pathways could limit carps range expansion into new areas, while efficient removal methods could suppress established carp populations. However, control tools are sometimes limited in practice due to uncertainty with deployment, efficacy and availability. This review provides an overview of several emerging modelling approaches and control technologies that could inform and support future invasive carp IPM programs.