Invasive Carp Research Articles

Experimental Evaluation of a Modular Electric Barrier for the Deterrence of Invasive Carp

Abstract We conducted a series of studies to assess the effectiveness of an electric barrier in deterring the movements of freshwater fish. Fish responses (detections·individual−1·hr−1 within the 3 m exclusion zone) were quantified for a mixed assemblage of native and nonnative fishes within 0.4 ha ponds. Additionally, we mapped the surface voltages generated by the electric barrier in a nearby stream. The electric barrier (operated at 10 kW) was effective at deterring native and invasive fishes, as > 99% of all fish detections within the exclusion zone occurred while the electric barrier was off. However, some fish detections occurred while the system was operated at full power, indicating the electric barrier was not 100% effective. A follow-up study found that fish responses differed between low (3.6 kW), medium (6.6 kW), and high (10 kW) field strengths, with smallmouth buffalo Ictiobus bubalus exhibiting a greater sensitivity to the low setting than bighead carp Hypophthalmichthys nobilis and silver carp H. molitrix. Maps of the surface voltages within a nearby stream indicated that the electric barrier was strong enough to deter silver carp (> 1 V/cm). However, the surface voltages quickly dissipated upstream and downstream of the electrodes. Overall, the electric barrier appears to be an effective tool that can be used to combat the spread of invasive fishes in freshwater environments. However, more evaluations are needed to test how the system performs in different conditions and to identify whether fish of varying sizes or life stages respond similarly.

Flooding and dam operations facilitate rapid upstream migrations of native and invasive fish species on a regulated large river

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.

Assessing the direct and indirect effects of bigheaded carp (Hypophthalmichthys spp.) on freshwater food webs: A meta‐analysis

Abstract The rapid growth of aquaculture over the last century has led to the widespread introduction of aquatic species to freshwater environments. Bighead carp (Cyprinidae: Hypophthalmichthys nobilis) and silver carp (Cyprinidae: Hypophthalmichthys molitrix), collectively referred to as bigheaded carp, are among the top finfishes produced in aquaculture. These filter feeders possess feeding structures that allow them to efficiently remove plankton and other particles from the water. Unfortunately, when introduced into the wild and outside their historical range, their feeding traits generally result in the exploitation and suppression of phytoplankton and zooplankton, reducing food resources for native invertebrates and vertebrates. We conducted a meta‐analysis of published experiments to examine how bigheaded carp directly and indirectly affect organisms in aquatic food webs to better understand their ecological role within ecosystems. Specifically, we addressed the following questions: (1) What is the overall magnitude and direction of bigheaded carp effects on different aquatic organisms? (2) Do bigheaded carp affect organisms in planktonic and benthic habitats? (3) Are effects similar between bighead carp and silver carp? (4) Are effects consistent among experimental arenas (i.e., mesocosm, ponds)? We detected direct and indirect effects of bigheaded carp across multiple trophic levels. Large zooplankton often exhibited the strongest negative effects, with taxa‐specific differences between carp species. The suppression of zooplankton cascaded down to primary producers, resulting in an increase in phytoplankton (i.e., indirect effect). However, we observed no compensatory increases in rotifers when large zooplankton were reduced. Growth rates of planktivorous native fishes were the slowest when stocked with bigheaded carp. Our results further indicated that egested waste from bigheaded carp appeared to subsidise (i.e., direct effect) some benthic invertebrates such as Chironomidae midges. Effects of carp on zooplankton were generally similar between mesocosms and ponds. Invasive bigheaded carp greatly restructure their surrounding food web, both positively and negatively, through a complex suite of direct and indirect effects. These changes manifested across multiple trophic levels and differing habitats. Our analysis provides a more complete understanding of how these invasive carps change their surroundings by exploiting food resources and transferring materials from planktonic to benthic habitats. Taken together, the suite of direct and indirect effects shows how an invasive species can create imbalances within aquatic ecosystems, often to the detriment of native taxa. Bigheaded carp are invasive in many countries across the globe because of their popularity in aquaculture. Our findings reaffirm the threat these planktivores pose to native freshwater organisms.

Bayesian multistate models for measuring invasive carp movement and evaluating telemetry array performance.

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.

Large-scale serial replacement of invasive tench (Tinca tinca) by invasive carp (Cyprinus carpio) in the presence of redfin perch (Perca fluviatilis) in the Murray-Darling River system, Australia

Ecosystems worldwide are increasingly being invaded by multiple species, and the rate of biological invasion is accelerating, leading to more interactions among invasive species. One such interaction that has received little attention is the phenomenon of ‘serial replacement’ or ‘over-invasion’, where an established invasive species is supplanted by a second invasive species. Understanding this interaction is important as controlling the second species could inadvertently lead to an increase in the abundance of the first species. We used a hierarchical state-space model to analyse changes in annual abundances (commercial catch-per-unit-effort) of three invasive fish species, tench (Tinca tinca), common carp (Cyprinus carpio) and redfin perch (Perca fluviatilis), in the Murray-Darling River system (MDRS), Australia between 1954–2002. Tench were present at low abundances until the mid-1970 s, before declining to the point of no commercial catch post-1989. This rapid decline coincided with a significant increase in carp abundance, suggesting that carp may have driven the tench decline through habitat modification (particularly the destruction of aquatic plants), consistent with findings from European studies that show the disappearance of tench from ponds with intensive carp farming. Redfin perch populations, were inferred to be much less impacted by the invading carp population. While carp were present in the MDRS for the duration of the study, the rapid increase in carp abundance in the early 1970 s coincided with the introduction of a specific genetic lineage—the “Boolarra strain”. Our analysis provides compelling evidence of serial replacement of long-established tench by invading common carp triggered by the introduction of a novel carp strain.

Angler knowledge of live bait regulations and invasive species: insights for invasive species prevention

The prevention of aquatic invasive species is one of the most cost-effective management strategies for reducing negative ecological, economic, and social impacts to freshwater ecosystems. The release of leftover baitfish via the live bait trade has been identified as a high-risk pathway for introducing invasive species beyond physical barriers (e.g., mountains, dams). To assess differences in behavior surrounding live bait use and angler knowledge of invasive species, we conducted in-person angler surveys at waterbody access sites (i.e. boat ramps with available shore fishing and a shore fishing location with no boat ramp) along the Missouri River, above and below Gavins Point Dam (Yankton, South Dakota, USA). We were primarily interested in whether angler behavior and knowledge differed among fishing locations over the course of a year because of potential variation in risk. Gavins Point Dam is impervious to fish passage and prevents the spread of invasive silver carp Hypophthalmichthys molitrix and bighead carp H. nobilis (collectively known as bigheaded carp), but bigheaded carp could be transported above this dam by the use of live baitfish. Regardless of where respondents fished (above the dam/carp absent, below the dam/carp present, or both), 70% ± 11.12 of anglers used live baitfish and 57% ± 3.14 participated in ‘higher risk’ baitfish practices including release. Knowledge of bigheaded carp was limited, as only 2% ± 1.31 of respondents identified both bigheaded carp as invasive in an image collage, 51.82% ± 4.48 could not identify where invasive carp are present/absent, and 40% ± 3.34 of anglers had not received any information regarding bigheaded carp. These findings highlight limitations in angler knowledge, compliance, and identification of native and invasive species. Future implementable actions could include invasive species and baitfish release outreach via electronic media sources or additional signage that address these knowledge gaps.

Correction: Effects of invasive bigheaded carp and environmental factors on larval fish growth

Correction: Effects of invasive bigheaded carp and environmental factors on larval fish growth

Applying local and global sensitivity analysis to inform bigheaded carp management

Abstract Natural resource managers commonly use population-level models to aid in understanding the status of target populations or the potential implications of management actions. Sensitivity analyses, specifically, local sensitivity analysis (LSA) and global sensitivity analysis (GSA), exist as tools to improve understanding of these models, the importance of specific parameters to model outcomes, and the assumptions inherent to population models. However, applied ecology and closely related fields such as fisheries and wildlife management rarely use LSA or GSA. Here, we apply LSA and GSA to the Spatially Explicit Invasive Carp Population model, a population-level model used to simulate and compare management actions on the invasive silver carp Hypophthalmichthys molitrix population in the Illinois River. The spatial structure within the model arises from the navigation “pools” that exist between navigation lock-and-dam in the river and are also the focus of fisheries management in the river. We completed LSA and GSA for two reasons: (1) to compare the importance of model input parameters on simulated model populations and (2) to demonstrate the use of LSA and GSA for population-level models. In our system, the most important sensitivity values generally were detected in Alton Pool. This pool is the farthest downstream and includes a direct connection with the Mississippi River. These results indicate that the population dynamics in Alton Pool are an important driver of the population dynamics throughout the Illinois River. Management outcomes in this system will, therefore, be strongly dependent on the dynamics of Alton Pool.

Isotopic niches reveal the impact of topmouth gudgeon and gibel carp on native crucian carp

Invasive species pose a major threat to natural ecosystems and directly outcompete many native species, placing them at imminent threat of extinction. The topmouth gudgeon (Pseudorasbora parva) is on the EU’s blacklist of invasive freshwater species and threatens biodiversity, especially in wetland and floodplain ecosystems, aquacultures and village ponds. The crucian carp (Carassius carassius) is native to Europe and its populations have declined in large part of its native range, with invasive gibel carp (C. gibelio) suspected as a major cause of its decline. Invasions by topmouth gudgeon have been implicated in the decline of crucian carp populations but this still needs to be verified. The aim of this study was to evaluate by the experimental approach the competitive interaction between the two species, topmouth gudgeon and crucian carp, focusing on isotopic niche sizes and their overlap in syntopy. A four-month mesocosm experiment was performed to determine the isotopic niche of crucian carp and topmouth gudgeon living alone and in syntopy. Additionally, stable isotope data were collected at the sites where the two species co-occur to compare niche sizes and overlaps. Experimental data showed that the isotopic space of topmouth gudgeon responded more flexibly (reducing niche size at syntopy) than that of the crucian carp and confirmed a high isotopic niche overlap between the species. Field studies have shown that topmouth gudgeon has invaded the isotopic niche of the crucian carp, especially when another invasive species, the gibel carp, lived in the community (25% at 40% ellipse area and 50% at 95% ellipse area). When only the topmouth gudgeon and crucian carp were present in the field, the overlap was lower (3% and 48%, respectively) and directional overlap modelling showed that the crucian carp was more likely to invade the isotopic niche of topmouth gudgeon than vice versa. The data indicated that competition between crucian carp and topmouth gudgeon is likely, especially in syntopy with other invasive species. This study shows that the feeding plasticity of topmouth gudgeon likely facilitates its establishment outside its native range and, due to high isotopic niche overlap, threatens native fish with similar feeding ecology with competitive displacement.

Contribution of invasive carp (Cyprinus carpio) to fish biomass in rivers of the Murray–Darling Basin, Australia

Following the introduction of the ‘Boolarra’ strain to Australia in the mid 1960’s, Common carp (Cyprinus carpio) rapidly spread in waterways across the Murray–Darling Basin (MDB) in southern-eastern Australia. A previous study of the population expansion based upon data up to the early 2000s suggested the carp population may have reached, and was fluctuating around, the ecosystem carrying capacity. It has been widely stated in the scientific literature and media that carp comprise up to 90% of fish biomass in MDB rivers; however, this figure is largely based on sparse data collected in the 1990s and the accuracy of this estimate is uncertain. Here, we analyse three decades (1994–2023) of electrofishing data to estimate the median proportion of total fish biomass contributed by carp across > 1,400 sites in lowland rivers (< 700 m elevation) of the New South Wales (NSW) portion of the MDB. The proportion of sites with fish biomass dominated (> 90%) by carp has declined from ≈ 33% of sites in the mid-1990s to ≈ 20% of sites. The proportion of biomass comprised by carp varied depending on the scale of analysis. Across the NSW MDB, carp accounted for a median of 57% (95% CI: 42.5–70.4) of fish biomass at the site level. At the river catchment scale estimates ranged from ≈ 45–66%. In contrast, the median proportion of carp within key rivers ranged from ≈ 46–80%, suggesting that carp can dominate total fish biomass in some rivers for short time-periods. The proportion of biomass contributed by carp at the NSW MDB scale was remarkably stable across decades, suggesting that the carrying capacity of carp may have been reached. Our revised estimates of the contribution of carp to overall fish biomass can facilitate informed debate around the dominance of carp in MDB rivers and provide important information for carp management in the future.

Density‐dependent trophic consequences of invasive mrigal carp on native mud carp in Chinese fresh waters

Abstract Understanding the strength, direction and consequences of the trophic impacts of invasive fish on functionally analogous native fishes is important in invasion impact assessment and for informing management programmes. As functionally analogous native and invasive fishes can share prey resources, there is high potential for competitive interactions, which could affect trophic niche sizes and positions. The highly invasive mrigal carp Cirrhinus mrigala and native mud carp Cirrhinus molitorella now co‐exist in many freshwaters in southern China, raising concern on the consequences for mud carp. The trophic interactions of the two species and their consequences (for growth rates and trophic niche sizes as the isotopic niche, calculated using δ13C and δ15N) were tested in a pond enclosure experiment based on additive and substitutive treatments using fish in allopatric and sympatric contexts, with results compared with invaded wild communities. In the experiment, specific growth rates decreased significantly as fish abundance in treatments increased. These density‐dependent effects were observed in both species and were independent of whether the treatment was allopatric or sympatric. In allopatric treatments, isotopic niches of mud carp increased in size with fish number. Conversely, in sympatric treatments, mud carp isotopic niche size decreased with increased mrigal carp number. For mrigal carp, isotopic niche sizes decreased as fish number increased in both allopatric and sympatric treatments. In sympatric experiment treatments, the isotopic niches of mud carp and mrigal carp were always divergent. This was, however, in contrast to four invaded wild communities, where the isotopic niches of the two fishes always had some overlap. Experimental and field data suggest that although native mud carp could be impacted by mrigal carp, these impacts might only manifest when the species are at very high abundances and inter‐specific competitive interactions could be intense. These results also suggest the two species have mechanisms that reduce their inter‐specific interactions to minimise their competitive interactions, thus any ecological impacts from mrigal carp might manifest more from indirect than direct processes.

Effects of invasive bigheaded carp and environmental factors on larval fish growth

Effects of invasive bigheaded carp and environmental factors on larval fish growth

Semi-automated system for capturing and removing invasive carp during seasonal migrations

Semi-automated system for capturing and removing invasive carp during seasonal migrations

Natural shorelines support greater diversity and abundances of fishes than armoured shores along Chicago's waterways

Abstract Shoreline armouring is one of the most ubiquitous alterations to aquatic systems globally. Armouring and hardening to prevent erosion and maintain land uses reduce or eliminate habitat complexity that softer and more natural, vegetated shorelines offer. The effects that shoreline armouring has had on biodiversity of coastal and estuarine communities are well studied, while studies in freshwater systems remain sparse. Data collected during a large‐scale long‐term fish survey with high spatial resolution from the Invasive Carp Regional Coordinating Committee's Monitoring and Response Work Group were re‐analysed to assess the effects that bulkhead versus natural shorelines have on fish diversity and abundance. Lengths of bulkhead, natural and riprap shoreline were calculated within 300 m of each sampling location, which occur every 100 m throughout the Chicago Area Waterway System. Water depths of each sampling location were also classified into deep (&gt;6 m), mid‐range (4–6 m) or shallow (&lt;4 m) to account for potential variations in gear efficiencies. Fish species richness and abundance increased with increasing proportions of natural shoreline, which can be contrasted with stronger (i.e., steeper slope) decreases as proportions of bulkhead shorelines increased. The results show strong evidence for the negative effects of shoreline armouring of freshwater ecosystems and are consistent with those shown in coastal ecosystems studies. As cities continue to encroach on freshwater systems, greater emphasis on maintaining natural riparian shorelines and ecoengineering hardscapes will increasingly be important for freshwater conservation.

Ecological inferences on invasive carp survival using hydrodynamics and egg drift models

Bighead carp (Hypophthalmichthys nobilis), silver carp (H. molitrix), black carp (Mylopharyngodon piceus), and grass carp (Ctenopharyngodon idella), are invasive species in North America. However, they hold significant economic importance as food sources in China. The drifting stage of carp eggs has received great attention because egg survival rate is strongly affected by river hydrodynamics. In this study, we explored egg-drift dynamics using computational fluid dynamics (CFD) models to infer potential egg settling zones based on mechanistic criteria from simulated turbulence in the Lower Missouri River. Using an 8-km reach, we simulated flow characteristics with four different discharges, representing 45–3% daily flow exceedance. The CFD results elucidate the highly heterogeneous spatial distribution of flow velocity, flow depth, turbulence kinetic energy (TKE), and the dissipation rate of TKE. The river hydrodynamics were used to determine potential egg settling zones using criteria based on shear velocity, vertical turbulence intensity, and Rouse number. Importantly, we examined the difference between hydrodynamic-inferred settling zones and settling zones predicted using an egg-drift transport model. The results indicate that hydrodynamic inference is useful in determining the ‘potential’ of egg settling, however, egg drifting paths should be taken into account to improve prediction. Our simulation results also indicate that the river turbulence does not surpass the laboratory-identified threshold to pose a threat to carp eggs.

Multi-scale effects of behavioral movement deterrents on invasive carp metapopulations

Behavioral deterrents of among-pool movement represent a promising tool for controlling invasive fish populations. To date, much of the research in this area has been focused on the direct effectiveness of different methods of deterrence. However, the effect of these structures on populations in spatially complex habitats is unknown. We combine a metacommunity model with movement data of two invasive species (bighead carp and silver carp) in a large river to assess local and river-wide scale population outcomes of deterrent locations. We calculated (1) which potential deterrent locations are most effective at reducing the growth at the invasion front (2) the river-scale population effects at each location, and (3) what, if any, are the risks imposed by altering the current spatial dynamics. We found that the effects on the population dynamics at the invasion front varied with the location of deterrents, ranging from near zero to effects equal to the reduction in an individual’s movement across the deterrent. The river-scale population growth rate was slightly increased by all potential deterrent placements because the deterrents tended to concentrate more of the river-scale population into pools with the highest recruitment rates. The short-term, transient dynamics followed a strictly decreasing pattern after deterrent placement suggesting no additional short-term risk. These results suggest that deterrents can be an effective and low-risk intervention for the control of invasive carp, although the population level effect will depend on the interaction of the traits and behavior of the species with the physical character and spatial structure of the habitat.

Introducing Copi as a Positive Path Toward Combatting Invasive Carps in North America

A group of loosely related, large‐bodied fishes collectively called carps have had a complex relationship with North Americans. Despite lessons learned about invasive Common Carp Cyprinus carpio in the early 1900s, Bighead Carp Hypophthalmichthys nobilis, Black Carp Mylopharyngodon piceus, Grass Carp Ctenopharyngodon idella, and Silver Carp H. molitrix were introduced to the United States more than 50 years ago and are expanding throughout the Mississippi River basin. Increased economic value in the North American seafood market could aid management. Complete eradication through harvest is unlikely, but controlling densities and containing dispersal may be possible. Improving perceptions of nutrition, palatability, and safety of wild‐caught carps should increase consumer demand. A branding and marketing effort launched in June 2022 renamed the foodstuff produced from the four species as the trademarked brand Copi. The “Choose Copi: Eat Well. Do Good.” campaign allows consumers to know that these fishes are an environmentally sound and responsible alternative to other seafood choices. The Copi brand has gained interest nationwide, with food processors and distributors engaged, although the contribution of Copi to harvest removal from rivers and resulting population dynamics is yet to be quantified. Developing a regional fishing industry for Copi, while also aiding fisheries and aquaculture for native species, remains an economic and logistical challenge within the vast river network.

Limiting downstream dispersal of invasive carp egg surrogates using a laboratory-scale oblique bubble screen

We conceptualize and test a non-intrusive barrier, comprised of an oblique bubble screen (OBS) oriented at an angle to the mean flow, to prevent the downstream dispersal of invasive carp egg surrogates. Three surrogates of different densities and diameters were tested. Secondary flows created by the OBS were tuned to redirect surrogate eggs to facilitate their capture. Surface particle image velocimetry and acoustic Doppler velocimetry were used to characterize secondary flows. We assessed the influence of airflow rate, OBS angle, mean flow velocity, and surrogate density on particle redirection. In general, redirection efficiency improves by increasing the OBS angle with respect to the cross-section. At a mean flow velocity of 0.75 metres per second (m/s), the OBS system redirected up to 60% (%) of positively buoyant particles (specific gravity SG = 0.9, and diameter d = 7.09 millimetres [mm]) and 40% of semi-buoyant particles (SG = 1.001, d = 3.1 mm). Negatively buoyant particles (SG = 1.04, and d = 5.90 mm) were redirected by the physical structure of the diffuser rather than by OBS-induced flow. The study shows that an OBS system can be used to effectively redirect carp-egg surrogates over a wide range of particle sizes and densities, allowing for selective targeting of undesired particles in streams.

Lessons learned from eDNA adoption in the management of bigheaded carps in Chicago IL USA Area Waterways

AbstractThe Chicago Area Waterway System (CAWS) connects the Great Lakes watershed with the Mississippi watershed via canals that withdraw water from Lake Michigan. From 2009 through 2011, collaborators and I provided research, development, and application of eDNA to invasive species management in the CAWS in cooperation with the US Army Corps of Engineers (USACE). The research team's approach was a high‐stakes test of a novel combination of proven technologies (field sampling techniques and laboratory genetics). In the first application of eDNA to a large scale, urgent management goal, we quickly discovered eDNA of two species of bigheaded carps in parts of the waterway where traditional tools had not captured fish. The central research question was whether the sensitivity (probability of detecting a fish when it was present) of eDNA was higher than that of traditional fish sampling tools (e.g., nets, electrofishing). The effort was part of what became a very large, complex, on‐going initiative to reduce access by invasive species to Lake Michigan. This immediately garnered much attention, initiating a dialog about the reliability of eDNA, public discussion about the benefits and costs of the CAWS, and skepticism from industries that use the CAWS. Government agencies formed the Asian Carp Rapid Response Workgroup, which eventually became the Invasive Carp Regional Coordinating Committee (ICRCC). The ICRCC continues its coordinating role on the use of eDNA and other management responses in the CAWS. With the benefit of hindsight, I draw several lessons from the experience that may help in other settings where eDNA is now being deployed with increasing confidence and acceptance; evaluate the on‐going CAWS surveillance and management effort; and recommend strengthening the current approach by broadening and deepening participation in a collaborative governance approach. Stronger public‐private partnerships would accelerate research, development, commercialization, and application of eDNA analysis to the benefit of society.

Upstream experience and experimental translocation of invasive bigheaded carps results in increased upstream passage success at a navigation lock in a large river

AbstractFish 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.