Biology and ecology of bigheaded carp in an invaded ecosystem

Globally, the homogenization of species has become a threat to biodiversity. As species are transported around the world, a portion of these species, released intentionally or accidentally, may become invasive and can produce negative impacts. Great effort has been invested into early identification and prevention of invasions as these are considered less expensive than managing an invasion. Unfortunately, species may exhibit varying characteristics across ecosystems, and so their behavior and potential survival in a new environment may be difficult to predict. Therefore, I examined trends in the biology and behavior of invasive fishes, including the plasticity surrounding these and how they may contribute to successful invasions, using bigheaded carps (Hypophthalmichthys spp., silver and bighead carp and their hybrids) in the Wabash River, Indiana (USA), as a case study. Trends in population characteristics appeared to vary with invasion stage. Female-skewed sex ratios, changing length-weight relationships, and earlier maturation are all characteristics that may ultimately contribute to the successful establishment of these fishes along invasion fronts. Movements could be extremely rapid but exhibited predictable patterns that may facilitate the management and control of these invasive fishes. Reproduction in these species was influenced by different environmental cues than those from their native ranges and was dependent on growing degree day rather than changes in river discharge. Hybrid bigheaded carp (silver x bighead carp) were not different from silver carp in any of the characteristics examined (i.e., movements, condition, diet) but are increasingly represented in adults and eggs in this system and may serve to increase heterozygosity. Stable isotope analysis indicated that there was little dietary overlap between bigheaded carps and native planktivores. Additionally, there was seasonal variation in resource use that may function to minimize this overlap. Overall, many of the variables examined in these studies may be influential in facilitating the successful establishment and spread of these invasive fishes

Sparta Training Area Asian Carp Removal Report

Aquatic invasive species have long been associated with negative ecological and socioeconomic impacts on freshwater ecosystems. In order to mitigate these potential negative effects of invasive species introductions, management and control techniques must be developed. Asian carp species (Silver Carp, Bighead Carp, Grass Carp, and Common Carp) are a problematic group of invasive species that can cause negative effects on native fish species and freshwater ecosystems through a series of trophic cascades. The current focus of Asian carp management and control techniques is directed at reducing population sizes in the upper Illinois River to reduce probability of invasion further upstream at the Illinois River-Great Lakes connection. However, smaller freshwater systems and their associated lakes and impoundments are also vulnerable to invasion and may require management techniques to reduce Asian carp populations. Flooding has resulted in strip mine lakes within the Army National Guard Sparta Training Area being invaded by Asian carps. Therefore, we sought to develop a harvest protocol to remove Asian carps from three Sparta Training Area lakes (S3, S5, and S6) based on a technique developed for Illinois River floodplain lakes that combines multiple net types, electrofishing, and surface sounds and disturbances to drive fish to a pre-determined harvest location. More specifically, lakes were divided into three zones and fish were funneled and herded through strategically-placed monofilament gill nets by surface sounds and disturbances and electrofishing from one end of the lake (zone 1) to the other end of the lake (zone 3) where congregated fish could be more efficiently harvested. To determine our effectiveness of removing Asian carps from these lakes, we used hydroacoustic surveys to estimate reductions in Asian carp density and biomass pre- and post-harvest. A total of 1,232 kg (n = 469) of Asian carps were removed from the three lakes, with much of the biomass being Silver Carp from S5 (n 3 = 250; 720 kg) and S6 (n = 155; 272 kg); S3 contained few Asian carps and removal was minimal (97 kg). Harvest times ranged from 4.25-6.50 hours with a crew of nine people with three boats resulting in 7-14 kg of Asian carp biomass removed per person-hour of work in S5 and S6. Pre- and post-harvest Asian carp density (number of fish / 1000 m3) and biomass (kg / 1000 m3) were reduced by 58-75% in S5 and S6. Effectiveness of the harvest protocol was predicated on our ability to drive fish from zone 1 to zone 3 in each lake. Catch per unit effort for our capture gears was often double to one-hundred fold higher in zone 3 compared to zone 1, indicating that efforts to herd fish into zone 3 were successful. The harvest protocol was effective at removing Asian carps in a relatively short time period. Refining our techniques by adding more zones, or increasing entanglement gears or number of electrofishing boats may improve harvest rates and biomass removed from each lake. The harvest protocol used in this project would likely be applicable to other Sparta Training Area lakes infested with Asian carps that have similar lake morphologies and characteristics; it is unknown how effective this technique will be in larger lakes such as L1, L2 or S11. However, physical barriers would likely be needed at Sparta Training Area lakes to prevent future Asian carp (young-of-year or juvenile) invasions during flooding, particularly lakes in close proximity and elevation to Plum Creek. This study improved our knowledge and techniques for removing Asian carp populations from Sparta Training Area lakes and is anticipated to be applicable to similar small, recreational fishing lakes in other areas. Use of the removal technique described herein would help mitigate the negative ecological effects and nuisances of invasive Asian carps in small lakes. However, future research investigating the techniques used in this study and their effectiveness at removing invasive species should be conducted on lakes with different morphometric characteristics

Proof-of-Concept Studies Demonstrate That Food and Pheromone Stimuli Can Be Used to Attract Invasive Carp So Their Presence Can Be Readily Measured Using Environmental DNA

he utility of environmental DNA (eDNA) as a detection tool for fisheries management is limited by dilution and degradation, especially in areas of low fish abundance. This proof-of-concept study addressed these challenges by testing whether food or pheromones might be used to attract invasive carp so they can be measured more readily using eDNA. In two experiments, PIT-tagged carp were stocked into ponds (N = 3 for silver carp; N = 1 for common carp) while one of two stimuli (planktonic food [spirulina] for silver carp and a sex pheromone [prostaglandin F2α] for male common carp) was added to determine if we could attract fish to one side while measuring both fish presence (detections) and eDNA concentrations. The addition of spirulina increased detections of silver carp by 2–3 fold, while eDNA concentrations increased by 4-fold on the test side when compared to the side without the stimulus. The addition of the sex pheromone increased detections of common carp by ~25-fold, where a 6-fold increase in eDNA concentrations was measured (p \u3c 0.05). A strong positive correlation was noted between fish presence and eDNA concentration for both species. These experiments demonstrate that food and pheromone stimuli could be used to attract invasive carp so they could be measured more easily and accurately

Early generation hybrids may drive range expansion of two invasive fishes DataSet

Introgressive hybridization between two invasive species has the potential to contribute to their invasion success and provide genetic resiliency to rapidly adapt to new environments. Additionally, differences in the behaviour of hybrids may lead to deleterious ecosystem effects that compound any negative impacts of the invading parental species. Invasive silver carp (Hypophthalmichthys molitrix) and bighead carp (H. nobilis) exhibit introgressive hybridization which could influence their invasion ecology. In order to investigate the role hybrids may have in the invasion ecology of bigheaded carps, [CAA1] we examined the distribution, movements, and environmental cues for movement of two invasive fishes (bighead carp, silver carp) and their hybrids in the Illinois River (USA). Early generation hybrids (e.g., F1,F2, and first generation backcross individuals) composed a greater proportion of the population at the invasion front where abundances of bigheaded carp were low. A greater proportion of early hybrids passed through dams upstream towards the invasion front than did other hybrids and parental species. The movements and environmental cues for movement of late-generation backcrosses (more genetically similar to parental genotype) were not different from the parental species with which they shared the most alleles. Although the direction of the relationship between movement and environment was sometimes different for the parental species and associated advanced generation hybrids, these results indicate that management for parental species will also influence most hybrids. Although early generation hybrids are rare, our results indicate they may disperse towards low-density population zones (i.e., invasion fronts) or are produced at greater frequency in low density areas. These rare hybrids have the potential to produce a variety of unique genetic combinations which could result in more rapid adaptation of a non-native population to their invaded range potentially facilitating the establishment of invasive species

MetaIPM: Placing Integral Projection Models Into a Metapopulation Framework

1. Metapopulation models include spatial population dynamics such as dispersion and migration between subpopulations. Integral projection models (IPMs) can include demographic rates as a function of size. Traditionally, metapopulation models do not included detailed populaiton models such as IPMs. In some situations, both local population dynamics (e.g. size-based survival) and spatial dynamics are important. 2. We present a Python package, MetaIPM, which places IPMs into a metapopulation framework, and allow users to readily construct and apply these models that combine local population dynamics within a metapopulation framework. 3. MetaIPM includes an IPM for each subpopulation that is connected to other subpopulations via a metapopulation movement model. These movements can include dispersion, migration or other patterns. The IPM can include for size-specific demographic rates (e.g. survival, recruitment) as well as management actions, such as length-based harvest (e.g. gear specific capture sizes, varying slot limits across political boundaries). The model also allows for changes in metapopulation connectivity between locations, such as a fish passage ladders to enhance movement or deterrents to reduce movement. Thus, resource managers can use MetaIPM to compare different management actions such as the harvest gear type (which can be length-specific) and harvest locations. 4. We demonstrate how MetaIPM may be applied to inform managers seeking to limit the spread of an invasive species in a system with important metapopulation dynamics. Specifically, we compared removal lengths (all length fish versus longer fish only) for an invasive fish population in a fragmented, inland river system. MetaIPM allowed users to compare the importance of harvesting source populations away from the invasion front, as well as species at the invasion front. The model would also allow for future comparisons of different deterrent placement locations in the system. 5. Moving beyond our example system, we describe how MetaIPM can be applied to other species, systems and management approaches. The MetaIPM packages includes Jupyter Notebooks documenting the package as well as a second set of JupyterNotebooks showing the application of the package to our example system

Incorporating metapopulation Dynamics to Inform Invasive Species Management: Evaluating Bighead and Silver Carp Control Strategies in the Illinois River

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 deterrents 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 allocating 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 multipronged 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

Receiver Mount Design, Transmitter Depth, and Wind Speed Affect Detection Probability of Acoustic Telemetry Transmitters in a Missouri River Tributary

Background One of the most important considerations for acoustic telemetry study designs is det:ection probability between the transmitter and the receiver. Variation in environmental (i.e., wind and flow) and abiotic (i.e., bathymetry) conditions among aquatic systems can lead to differences in detection probability temporally or between systems. In this study we evaluate the effect of distance, receiver mount design, transmitter depth, and wind speed on detection probabilities of two models of acoustic transmitters in a mid-sized river. InnovaSea V16-6H (hereafter V16) and V13-1L (hereafter V13) tags were deployed in the James River, SD at 0.36 m (deep) and 2.29 m (V16 tag) or 1.98 m (V13 tag; shallow) above the benthic surface downstream of InnovaSea VR2W stationary receivers at distances of 100, 200, or 300 m. We used two receiver mount designs that included a fixed position within a PVC pipe on the downstream side of a bridge piling or a metal frame deployed in the middle of the river channel. Tags were deployed for 72 h at each location, and hourly detections were summarized. We evaluated downstream distance, receiver mount design, tag depth, and wind effects on tag detection using Bayesian logistic regression. Results: Detection probability decreased as distance increased for all combinations of tag types and mount designs and varied from nearly 100% at 100 m to less than 10% at 300 m. The V16 transmitter had greater detection probability by the receiver mounted in the pipe than in the midriver frame. For both mounts, the deep V16 transmitter had greater detection probability than the V16 shallow transmitter. Detection probability of the V13 transmitter was similar between receiver mounts or transmitter depths. Wind speed had a negative impact on detection probabilities of both transmitter types and depths, except the deep V16 transmitter. Conclusions: Deploying acoustic receivers in PVC pipes rather than midriver frames provided greater downstream detection probabilities for V16 transmitters under conditions evaluated in this study. In addition, V16 transmitters had greater detection probabilities when positioned deep within the water column rather than near the surface. We also demonstrated that wind speed can have a negative impact on detection probabilities

Analysis of Per Capita Contributions from a Spatial Model Provides Strategies for Controlling Spread of Invasive Carp

Metapopulation models may be applied to inform natural resource management to guide actions targeted at location-specific subpopulations. Model insights frequently help to understand which subpopulations to target and highlight the importance of connections among subpopulations. For example, managers often treat aquatic invasive species populations as discrete populations due to hydrological (e.g., lakes, pools formed by dams) or jurisdictional boundaries (e.g., river segments by country or jurisdictional units such as states or provinces). However, aquatic invasive species often have high rates of dispersion and migration among heterogenous locations, which complicates traditional metapopulation models and may not conform to management boundaries. Controlling invasive species requires consideration of spatial dynamics because local management activities (e.g., harvest, movement deterrents) may have important impacts on connected subpopulations. We expand upon previous work to create a spatial linear matrix model for an aquatic invasive species, Bighead Carp, in the Illinois River, USA, to examine the per capita contributions of specific subpopulations and impacts of different management scenarios on these subpopulations. Managers currently seek to prevent Bighead Carp from invading the Great Lakes via a connection between the Illinois Waterway and Lake Michigan by allocating management actions across a series of river pools. We applied the model to highlight how spatial variation in movement rates and recruitment can affect decisions about where management activities might occur. We found that where the model suggested management actions should occur depend crucially on the specific management goal (i.e., limiting the growth rate of the metapopulation vs. limiting the growth rate of the invasion front) and the per capita recruitment rate in downstream pools. Our findings illustrate the importance of linking metapopulation dynamics to management goals for invasive species control

Assessing variation in maize grain nitrogen concentration and its implications for estimating nitrogen balance in the US North Central region

Accurate estimation of nitrogen (N) balance (a measure of potential N losses) in producer fields requires information on grain N concentration (GNC) to estimate grain-N removal, which is rarely measured by producers. The objectives of this study were to (i) examine the degree to which variation in GNC can affect estimation of grain-N removal, (ii) identify major factors influencing GNC, and (iii) develop a predictive model to estimate GNC, analyzing the uncertainty in predicted grain-N removal at field and regional levels. We compiled GNC data from published literature and unpublished databases using explicit criteria to only include experiments that portray the environments and dominant management practices where maize is grown in the US North Central region, which accounts for one-third of global maize production. We assessed GNC variation using regression tree analysis and evaluated the ability of the resulting model to estimate grain-N removal relative to the current approach using a fixed GNC. Across all site-year-treatment cases, GNC averaged 1.15%, ranging from 0.76 to 1.66%. At any given grain yield, GNC varied substantially and resulted in large variation in estimated grain-N removal and N balance. However, compared with GNC, yield differences explained much more variability in grain-N removal. Our regression tree model accounted for 35% of the variation in GNC, and returned physiologically meaningful associations with mean air temperature and water balance in July (i.e., silking) and August (i.e., grain filling), and with N fertilizer rate. The predictive model has a slight advantage over the typical approach based on a fixed GNC for estimating grain-N removal for individual site-years (root mean square error: 17 versus 21 kg N ha−1, respectively). Estimates of grain-N removal with both approaches were more reliable when aggregated at climate-soil domain level relative to estimates for individual site-years