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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.

Offspring survival, cohort performance, and ultimately population dynamics are strongly influenced by maternal characteristics (e.g., fecundity), whereas paternal contribution is often considered limited to genetic-driven fitness of males through sexual selection. However, male contribution to reproductive success can be particularly influential in species exhibiting paternal offspring care. Polychlorinated biphenyls (PCBs) are widespread, persistent contaminants that can disrupt maternal reproductive processes and negatively affect offspring. In contrast, how PCBs affect paternal reproductive success is largely unknown, but could ultimately affect population dynamics. We examined the effects of lifelong PCB exposure on the reproductive processes of male fathead minnows (Pimephales promelas), a species exhibiting sole paternal offspring care, by examining endocrine-associated gene expression, testes histology, secondary sexual characteristics, courtship ability, offspring care, and offspring survival. PCBs minimized male secondary sexual characteristics, but did not affect gonadal end points or inhibit ability to court females. Fathers exposed to high concentrations of dioxin-like PCBs had changes in gene expression, reduced offspring care behavior, and higher embryo mortality, possibly due to fathers spending less time within nests and less frequently tending to embryos. Through complex interactions among gene expression, physical characteristics, and behavior, PCBs inhibit paternal reproductive success and have the potential to suppress population size.

Population dynamics and ecological effects of invasive fishes are affected by offspring survival to sexual maturity (recruitment). Recruitment is oftentimes determined by conditions experienced during early life, and winter conditions become increasingly influential as species invade north in temperate regions. Bighead Carp (Hypophthalmichthys nobilis) and Silver Carp (H. molitrix) have invaded mid-latitudes of North America and threaten to invade farther north. We conducted pond experiments and bioenergetic simulations to: (1) assess the effects of mild winters on juvenile Bighead Carp and Silver Carp at mid-latitudes; (2) determine how conspecific density affects juveniles during mild winters; and, (3) determine effects of increased winter severity at increasing latitudes. Both species displayed high overwinter survival (85%) in pond experiments. Bighead Carp grew in length (mean 2 mm) and maintained initial body mass and percent dry mass (index of energy content). Silver Carp maintained initial length and mass and remained in high condition (dry mass). Conspecific densities tested did not affect growth, condition, or survival. Simulations suggest juvenile Bighead Carp could energetically survive the longest, coldest winter simulated (48° latitude); however, energy reserves at the start of winter became increasingly important for survival as latitude increased. Bighead Carp and Silver Carp recruitment success at mid-latitudes is likely driven by non-winter factors. If these species invade farther north, winter severity may play a stronger role in offspring survival, recruitment, and population dynamics. However, warmer and shorter winters at high latitudes caused by climate change will minimize this potential bottleneck and increase chances of successful recruitment.

Knowledge of the spatial distributions and dispersal characteristics of invasive species is necessary for managing the spread of highly mobile species, such as invasive bigheaded carps (Bighead Carp [Hypophthalmichthys nobilis] and Silver Carp [H. molitrix]). Management of invasive bigheaded carps in the Illinois River has focused on using human-made barriers and harvest to limit dispersal towards the Laurentian Great Lakes. Acoustic telemetry data were used to parameterize multistate models to examine the spatial dynamics of bigheaded carps in the Illinois River to (1) evaluate the effects of existing dams on movement, (2) identify how individuals distribute among pools, and (3) gauge the effects of reductions in movement towards the invasion front. Multistate models estimated that movement was generally less likely among upper river pools (Starved Rock, Marseilles, and Dresden Island) than the lower river (La Grange and Peoria) which matched the pattern of gated versus wicket style dams. Simulations using estimated movement probabilities indicated that Bighead Carp accumulate in La Grange Pool while Silver Carp accumulate in Alton Pool. Fewer Bighead Carp reached the upper river compared to Silver Carp during simulations. Reducing upstream movement probabilities (e.g., reduced propagule pressure) by ≥ 75% into any of the upper river pools could reduce upper river abundance with similar results regardless of location. Given bigheaded carp reproduction in the upper Illinois River is presently limited, reduced movement towards the invasion front coupled with removal of individuals reaching these areas could limit potential future dispersal towards the Great Lakes.

Limiting the prevalence of invasive species is a global conservation priority. Invasive species can have varying ecosystem effects and responses to control throughout an invaded range, and removal near invasion fronts may inadvertently alter these characteristics. Bigheaded carp (bighead carp (Hypophthalmichthys nobilis Richardson) and silver carp (H. molitrix Valenciennes)) are invasive fishes from Asia invading North American freshwater ecosystems. We used mobile hydroacoustic surveys to examine bigheaded carp population characteristics from 2012 to 2015 across an invasion gradient in the Illinois River (USA), one of the most likely pathways to the Laurentian Great Lakes. These bigheaded carp species comprised 23–46% of fish community abundance and 45–78% of fish biomass across reaches, with lower contribution near the invasion front where intensive management by harvest occurs. Bigheaded carp prevalence in the community did not differ by habitat and comprised >50% of community abundance and biomass throughout the river for most size classes. We identified negative relationships between density and relative weight (an index of body condition) of bigheaded carp, suggesting evidence of potential density-dependent intraspecific competition. Efforts to reduce invasive species abundances near invasion fronts may reduce prevalence. However, this could inadvertently release individuals from density-dependent competition and could enhance reproductive potential, growth or movements. By employing a suite of control efforts, including continuous removal efforts (including novel approaches) and by limiting movements (e.g., utilizing roads, fences, dams), it may be possible to offset undesired consequences of increased condition.

Water guns have shown the potential to repel nuisance aquatic organisms. This study examines the effects of exposure to a 1966.4 cm3 seismic water gun array (two guns) on the abundance and behavior of Bighead Carp Hypophthalmichthys nobilis, Silver Carp H. molitrix (collectively referred to as bigheaded carp) and native fishes (e.g., Smallmouth Buffalo Ictiobus bubalus). Water guns were deployed in a channel that connects the Illinois River to backwater quarry pits that contained a large transient population of bigheaded carp. To evaluate the effect of water guns, mobile side-looking split-beam hydroacoustic surveys were conducted before, during and between replicated water gun firing periods. Water guns did not affect abundance of bigheaded carp, but abundance of native fish detected during the firing treatment was 43 and 34% lower than the control and water guns off treatments, respectively. The proximity of bigheaded carp to the water gun array was similar between the water guns on and water guns off treatments. In contrast, the closest detected native fish were detected farther from the water guns during the water guns on treatment (mean ± SE, 32.38 ± 3.32 m) than during the water guns off treatment (15.04 ± 1.59 m). The water gun array had a greater impact on native fish species than on bigheaded carp. Caution should be taken to the extrapolation of these results to other fish species and to fish exposed to water guns in different environments (e.g., reduced shoreline interaction) or exposure to a larger array of water guns, or for use of water guns for purposes other than a barrier.

Dams are a conservation threat because they function as barriers to native fish movement; however, they may prevent the spread of invasive species. Invasive bigheaded carps (Hypophthalmichthys spp.) threaten the Great Lakes ecosystem and are advancing towards Lake Michigan via the Illinois River. Navigation dams on the Illinois River may deter bigheaded carps' upstream movement. We investigated the permeability of the Starved Rock Lock and Dam (SRLD), the most downstream gated Illinois River dam, to bigheaded carps' migration by examining the timing of individuals approaching and passing through SRLD in relation to gate openness, tailwater elevation, and water temperature. Using acoustic telemetry of (N = ~104 per year) tagged fish, 13 upstream passages of bigheaded carps occurred through SRLD between 2013 and 2016. Eleven passages occurred through the dam gates and 2 through the lock chamber, indicating deterrents (e.g., CO2) placed in SRLD lock chamber may only limit passage of a small proportion of all fish passing through the lock-and-dam structure. Passages were documented only in 2013 and 2015. Most of the dam gate passages occurred during high water when gates were completely out of the water. Timing of bigheaded carps approaching SRLD was positively correlated with rising water temperature and high tailwater elevation, and all fish approached during late March through mid-September. Movement through dams is rare; modifying gate operations to reduce gate openness during late spring and summer could further reduce the permeability of gated dams such as SRLD to bigheaded carps, slowing their upstream advance.

Detection of three fish hormones, cortisol, insulin-like growth factor 1 (IGF-1), and vitellogenin is reported using both electrochemical impedance spectroscopy (EIS) and quartz crystal microbalance (QCM). For cortisol, IGF-1, and vitellogenin, the EIS (QCM) detection limits are 7.9 (0.50) μM, 3.0 (2.4) nM, and 43 (13) pM, respectively, in PBS buffer. Thus the two detection methods, EIS and QCM, have similar sensitivity, but QCM is ~ 4 × more sensitive, which is consistent with the published literature. The molecular weights of cortisol, IGF-1, and vitellogenin are 362.5 Da, 7.3 kDa, and 440.5 kDa, respectively. For both EIS and QCM, the sensitivity and detection limit improve dramatically with increasing molecular weight, reflecting the larger change in polymer-protein film thickness at the Au electrode upon recognition and binding of larger analytes. This is the first time that such a trend has been reported for EIS biosensing, since the published literature does not show any clear trend with molecular weight. Potential applications to understanding of fish physiology are discussed, including hormone detection in fish blood plasma, and ambient water.

The establishment of nonnative Silver Carp Hypophthalmichthys molitrix and Bighead Carp H. nobilis (collectively referred to as “bigheaded carp”) in the central United States may have negative ecological consequences and economic impacts. Our objectives were to quantify patterns and habitat associations of adult bigheaded carp reproduction, larval production, and habitat use; such information is important for control strategies and identifying recruitment sources. During May–August 2011, we sampled adults and larvae at 10 sites distributed adjacent to and within the main channel of the Mississippi River at Pool 26 (study area = 28 river kilometers). Female reproductive status, adult location, and larval density were compared to environmental conditions, including temperature, site velocity, and turbidity. Large females spawned earlier than their smaller counterparts. No clear spawning aggregations of adults were observed, suggesting plasticity in staging habitat. Larvae were distributed across all sites during flooding. Larval density was positively related to velocity and turbidity, suggesting that nondepositional areas may facilitate recruitment. Bigheaded carp larvae comprised 10% of the ichthyofauna. Although pooled reaches are a source of recruitment for bigheaded carp in the Mississippi River system, the low densities of bigheaded carp larvae relative to native larvae cannot explain the dominance of adults in this system. Our findings provide insights into the plastic nature of bigheaded carp reproduction and habitats associated with larval development. Control efforts that target large adult females should be conducted earlier during the spring spawn. To maintain fishing pressure, such control efforts would likely need to continue through the summer, when smaller individuals spawn, discharge decreases, and CPUE increases. However, we found no specific mass staging area or habitat type where adult females could be targeted. Received July 19, 2016; accepted December 14, 2016 Published online March 21, 2017

To evaluate how bigheaded carps use a restored backwater habitat, their passages into and out of and residency within a backwater was monitored using acoustic telemetry. This dataset describes the results of this study and was used to compare activity of bigheaded carps between species, at a diel scale, among seasons, and how activity related of environmental conditions. Calculation of passages and residency are available in the thesis of Douglas Schultz (Southern Illinois University, 2006).

River modifications have altered critical habitats for fishes at a variety of spatial scales and caused global declines of many fluvial species. At small spatial scales (

Detecting nuisance species at low abundance or in newly established areas is critical to developing pest management strategies. Due to their sensitivity to disturbance and erratic jumping behavior, Silver Carp Hypophthalmichthys molitrix can be difficult to collect with traditional sampling methods. We compared catch per unit effort (CPUE) of all species from a Long Term Resource Monitoring (LTRM) electrofishing protocol to an experimental electrofishing technique designed to minimize Silver Carp evasion through tactical boat maneuvering and selective application of power. Differences in CPUE between electrofishing methods were detected for 2 of 41 species collected across 2 years of sampling at 20 sites along the Illinois River. The mean catch rate of Silver Carp using the experimental technique was 2.2 times the mean catch rate of the LTRM electrofishing technique; the increased capture efficiency at low relative abundance emphasizes the utility of this method for early detection. The experiment...

Although environmental DNA (eDNA) is increasingly being used to survey for the presence of rare and/or invasive fishes in aquatic systems, the utility of this technique has been limited by a poor understanding of whether and how eDNA concentrations relate to fish density, especially in rivers. We conducted a field study to systematically test whether the eDNA released by a model invasive fish, Silver Carp (Hypophthalmichthys molitrix), was related to the density of this species in a large river. We quantified fish density throughout the 460 km long Illinois River using hydroacoustic surveys at 23 sites while concurrently collecting 192 surface water samples for eDNA analysis. We found that Silver Carp numerical density and biomass density were positively and non-linearly related to eDNA concentration and detection rate. Both eDNA concentration (copy number) and detection rate increased rapidly as Silver Carp density increased but plateaued at moderate densities. These relationships could prove useful for estimating Silver Carp relative abundance in newly invaded locations where population numbers are low to moderate. Future studies should explore the causes of this nonlinear relationship as it would ultimately benefit aquatic species monitoring and management programs.

Summary The range of Shovelnose Sturgeon (SVS) Scaphirhynchus platorynchus in the great rivers of central North America has contracted, but most remaining populations are considered stable, likely due to a combination of successful harvest regulations and longitudinal continuity of many river reaches, despite damming in upper reaches. The evolutionary relationships of SVS relative to sister taxa is still a matter of debate. Genetic diversity varies across the range, with substantial haplotype overlap among SVS and its congeners. Shovelnose Sturgeon mature early at 5–7 years, and spawn every 2–3 years. Some individuals may spawn in fall. Whether this species migrates is debatable, but individuals move long distances with larvae dispersing greater than 250 km, and adults moving >1900 km. Shovelnose Sturgeon appear to complete all aspects of their life cycle in the main channel of rivers, with sand and associated dunes playing an important role in station holding even at high flows. The greatest threats to this species include river temperatures exceeding 26°C that may impair growth and survival of young life stages, dams that impair movement during spring flooding, loss of critical mid-channel island habitats which may be important nursery areas, and increases in harvest pressure for the caviar trade. Given the broad distribution of this species across the jurisdiction of multiple states in the US, a species-wide conservation plan should be in place to ensure that SVS populations remain stable or increase.

The threat posed by bigheaded carps (Hypophthalmichthys spp.) to novel ecosystems has focused efforts on preventing further range expansion; upstream progression in the Illinois River is a major concern due to its connection with the uninvaded Great Lakes. In addition to an electric barrier system, commercial harvest of silver carp (H. molitrix) and bighead carp (H. nobilis) in the upper river is intended to reduce propagule pressure and prevent range expansion. To quantify demographics and evaluate harvest efficacy, the upper river was sampled between 2012 and 2015 using mobile hydroacoustic methods. Reach-specific densities, size structures and species compositions varied interannually but the advancing population was characterized longitudinally as small-bodied, silver carp-dominated at the highest densities downstream, shifting to large-bodied, bighead carp-dominated at the low-density population front. The use of hydroacoustic sampling for harvest evaluation was validated in backwater lakes; there was a significant positive correlation between density estimates and the corresponding harvest catch-per-unit-effort of bigheaded carps. Localized densities of bigheaded carps were reduced by up to 64.4 % immediately post-harvest but generally rebounded within weeks. However, annual sampling of the entire upper river indicated that density of bigheaded carps decreased by over 40 % (between 2012 and 2013) and subsequently remained stable (between 2013 and 2014). The annual harvest of bigheaded carps increased during this period (from 45,192 to 102,453 individuals), in years of contrasting discharge conditions. At this spatiotemporal scale, harvest appears to have contributed to initial reduction, and subsequent maintenance of, bigheaded carps density levels, but discharge likely plays an important role (e.g., through immigration) in determining the extent of its impact. Mobile hydroacoustic sampling enabled robust quantification of the population over varying spatial scales and density gradients, highlighting the potential of this approach as an assessment tool for invasive fishes in riverine environments.

We investigated the environmental life history of widely distributed threatened and endangered sturgeons in large rivers of the central United States that experience different regulatory regimes and management priorities. Using microchemistry techniques, our goal was to assess how to improve species conservation by dampening the incongruity that often occurs between management and species’ ecological requirements, particularly at large spatial scales. Pallid sturgeon (Scaphirhynchus albus), shovelnose sturgeon (Scaphirhynchus platorynchus), and their hybrids were analyzed for88Sr and44Ca and related to a geographically relevant range of Sr:Ca values for the Missouri and Mississippi rivers to quantify large-scale environmental history. We found natal origin of 81% of all wild sturgeon collected was the lower Missouri River. Pallid and hybrid sturgeon used the middle and upper Mississippi rivers more frequently as they aged, whereas shovelnose sturgeon occupied the lower Missouri River more often throughout life. Our results highlight a mismatch between conservation boundaries and sturgeon river use. Managers should consider expanding current protections for pallid sturgeon to include the unprotected sections of the Mississippi River and that research and conservation actions consider the importance of Mississippi River habitats to Scaphirhynchus sturgeon throughout their life history. Our findings have implications for conserving wide-ranging riverine species at large spatial scales using the framework described here.

In the central United States, recovery efforts for populations of the federally endangered Pallid Sturgeon Scaphirhynchus albus have been ongoing since its listing in 1990. Its congener, the Shovelnose Sturgeon S. platorynchus, has also recently been listed as threatened where it overlaps with Pallid Sturgeon. The status of both species in the Mississippi River is unknown and so are habitat enhancement priorities that would benefit their recovery. Using field data collected from 2002 through 2005, we (1) estimated the adult population size of both species using mark–recapture methods and (2) quantified habitat use of these sturgeons with multiple gears to elucidate habitat enhancement priorities in the middle Mississippi River—an important fluvial corridor that connects the upper Mississippi River and Missouri River basins with the lower Mississippi River basin. Population size was estimated to be 1,516 (95% CI = 710–3,463) Pallid Sturgeon (five individuals per river kilometer [rkm]) and 82,336 (9...

Invasive bigheaded carps, genus Hypophthalmichthys, are spreading throughout the Mississippi River basin. To explore the efficacy of a consumer-based market (i.e., invasivorism) to manage them, we developed a conceptual model and evaluated three harvest approaches&mdash, direct contracted removal, volume-based incentives (&ldquo, fisher-side&rdquo, control), and set-quota harvest (&ldquo, market-side&rdquo, control). We quantified the efficacy of these approaches and potential population impact in the Illinois River. Contracted removal was effective for suppressing small populations at the edge of the range but cannot support a market. &ldquo, Fisher-side&rdquo, removals totaled 225,372 kg in one year. However, participation was low, perhaps due to reporting requirements for fishers. The &ldquo, set-quota approach removed &gt, 1.3 million kg of bigheaded carp in less than 6 months. Larger, older fish were disproportionately harvested, which may hinder the ability to suppress population growth. Total density declined in one river reach, and harvest may reduce upstream movement toward the invasion fronts. With sufficient market demand, harvest may control bigheaded carp. However, lack of processing infrastructure and supply chain bottlenecks could constrain harvest, particularly at low commodity prices. Given the geographical scale of this invasion and complicated harvest logistics, concerns about economic dependence on invasivorism that encourage stock enhancement are likely unmerited.

Many fishes are planktivorous during early life and switch to piscivory or consume larger food items as ontogeny progresses. In contrast, paddlefish start as particulate feeders and later become filter feeders. Few studies have identified food items essential for paddlefish growth, survival and recruitment surrounding this ontogenetic diet shift. The objectives of this study were to investigate (i) prey types consumed by paddlefish, (ii) variability in prey selection surrounding an ontogenetic diet shift and (iii) whether habitat affected paddlefish prey selection or foraging success. We analysed gut contents of 189 wild age-0 paddlefish from the middle Mississippi River (MMR) and also conducted a laboratory experiment to address these objectives. We found that paddlefish primarily foraged on benthic macroinvertebrates in the MMR, which differed from previous studies in lentic systems, suggesting young paddlefish prey selection may be labile depending on habitat (i.e., lotic versus lentic). Dominant prey of wild-caught and experimental age-0 paddlefish were caddisfly larvae (Trichoptera), followed by hemipterans and amphipods. We found little evidence that habitat attributes affected foraging success, but the most common prey items consumed were associated with wing dike habitat and the upstream and downstream tips of alluvial islands. Our experimental study revealed that if provided a mixture of organisms, age-0 paddlefish will primarily consume macroinvertebrates while age-1 paddlefish will mainly filter zooplankton. Overall results suggest young paddlefish prey selection can be highly variable, but also heavily reliant on a narrow group of prey resources.

We evaluate the feasibility of quantifying surface soil properties over large areas and at a fine spatial resolution using high-resolution airborne imaging spectroscopy. Airborne Visible Infrared Imaging Spectrometer (AVIRIS) data collected by the National Aeronautics and Space Administration immediately after the large 2011 Mississippi River flood at the Birds Point New Madrid (BPNM, $\approx 700\ \mathrm{km}^{2} $ ) floodway in Missouri, USA, was used in a data mining lasso framework for mapping of soil textural properties such as percentages of sand, silt, clay, soil-organic matter, and many other soil chemicals constituents. The modeling results show that the approach is feasible and provide insights in the accuracy and uncertainty of the approach for both soil textural properties and chemical constituents. These models were further used for a pixel-by-pixel prediction of each the soil constituent, resulting in high-resolution (7.6 m) quantitative spatial maps in the entire floodway. These maps reveal coherent spatial correlations with historical meander patterns of Mississippi River and fine-scale features such as erosional gullies, represented by difference in constituent concentration, e.g., low soil organic matter, with the underlying topography immediately disturbed by the large flooding event. Further, we have argued and established that the independent validation results are better represented as a probability density function as compared with a single calibration–validation set. It is also found that modeled soil constituents are sensitive to NDVI and the calibration sample sizes, and the results improve with stricter (lower) NDVI thresholds and larger calibration sets.

Understanding the ecological function of developed large rivers remains elusive because these systems have long been altered for multiple uses. In particular, floodplains of large rivers, such as the Mississippi River, have been contained behind extensive levees. A historic flood occurred in the lower Mississippi River system during spring of 2011, prompting the US Army Corps of Engineers to activate the Bird's Point-New Madrid floodway, a 55 000-ha, agriculturally dominated, leveed area. Water entered the floodway at flows >1 m s−1 through two crevasses created in the upper portion of the levee and exited through a crevasse at the lower end. During the month, the floodway was inundated; we quantified discharge, water chemistry, primary production and fish production in the floodway and the adjacent river. Water entering the floodway was retained

In many populations, males compete for mates and contribute to genetic diversity, but are assumed to have little impact on population growth rates and density, because one father is all that is necessary to fertilize a large number of eggs and sire a potential cohort. A factor affecting male reproductive output is exposure to contaminants that either disrupt endocrine function or mimic hormones. Polychlorinated biphenyls (PCBs) persist in aquatic ecosystems and may interfere with the reproductive contribution of male fish to populations. We quantified 28 PCB congeners in adult male bluegills across eight Illinois lakes. In spring 2011 and 2012, mature male bluegills from lakes with conspecifics with PCB whole‐body residues ranging from undetectable to high (2,000 ng/g dry mass total PCBs) were placed in experimental ponds with mature females containing no detectable PCB body residues and allowed to reproduce in spring under natural conditions. The presence of PCBs in fish had no effect on the presence of intersex or other gonadal deformities in adult males nor was gonad size, lipid concentration, and survival affected. Males with high PCBs were heavier than those from lakes with low PCB concentrations. The relative density of juvenile bluegills produced in ponds by fall, a fitness endpoint in this species, was negatively related to contaminant concentration in fathers. Contaminant exposure and other factors that affect male reproduction may not only suppress the relative contribution of males to genetic diversity, but also the overall density of cohorts within populations.

The St. John's Bayou water control structure near New Madrid, MO, connects the main Mississippi River to two large backwater areas called the New Madrid Floodway and St. John's Bayou. While this area has been altered, the New Madrid Floodway and St. John's Bayou account for the only substantial portion of the historic Mississippi River floodplain that remains and provides the only critical connection between backwater/floodplain habitat and the river. Fish passage was evaluated during April–December 2010 using ultrasonic telemetry. Stationary receivers were placed strategically at five locations above and below the structure in St. John's Bayou, in the floodway and the outlet to the Mississippi River. A total of 100 individuals representing 14 species were tagged. Total number of detections during an 8-month period was 1 264 717. Fifteen individuals representing five species moved into the Mississippi and Ohio rivers; seven individuals returned to St. John's Bayou. Thirteen of the 14 species moved upstream through the structure. Of the 85 individuals that stayed in the bayou, 29 fish passed through the structure for a total of 92 passage events. The downstream : upstream passage was roughly 50:50. Passage was correlated with river rise, with frequency of passage being higher in spring, but passage occurred each month during the study. Copyright © 2015 John Wiley & Sons, Ltd.

Modification and homogenization of habitat in large-river ecosystems have led to the reduction of >50% of native fish species. Rehabilitating these complex ecosystems to recover fish populations requires an understanding of habitat availability and selection at multiple scales. Habitat selection by river fishes is typically assessed at the functional unit scale (100–10 000 m2). For example, in large, sand-dominated rivers of the Central USA, alluvial islands are critical functional units for endangered sturgeon. Functional units, however, can be subdivided into mesohabitats (

Identifying the appropriate scale at which habitat is biologically relevant to riverine fishes in large, sand-dominated rivers is a challenge. Alluvial islands are important to several of these fishes throughout the central USA, but there is a paucity of information on island habitat features that restoration efforts should try to replicate. We determined the physical characteristics of two island complexes in the middle Mississippi River that facilitate the settlement and survival of age-0 shovelnose sturgeon Scaphirhynchus platorynchus at relatively large (mean 39,000 m2) and small (mean 320 m2) scales. Depth (m), flow rate (m s−1), substrate (sand, rock, silt) and vegetation were quantified at these two scales using hydroacoustic techniques (split-beam sonar and acoustic Doppler current profiler). Abiotic attributes in the surrounding littoral zone of the island complexes were highly correlated but differed depending on location. At the coarse spatial scale, vegetation was positively related to shovelnose sturgeon abundance. At the fine spatial scale, age-0 shovelnose sturgeon were restricted to flow rates

Studies have demonstrated the importance of the synergistic relationship between large rivers and adjacent floodplain connectivity. The majority of large rivers and their associated floodplain have been isolated through a series of expansive levee systems. Thus, evaluations of the relative importance of floodplain connectivity are limited due to the aforementioned anthropogenic perturbations. However, persistent elevated river levels during spring 2011 at the confluence of the Mississippi River and Ohio River prompted the U.S. Army Corps of Engineers to create large gaps in the levee system producing an expansive floodplain (i.e. the New Madrid Floodway). Specifically, the New Madrid Floodway (approximately 475 km2) in southeast Missouri was created to divert part of the Mississippi River flow during catastrophic floods and thus alleviate flood risk on nearby population centers. Given the historic flooding of 2011, the floodway was opened and provided an unprecedented opportunity to evaluate the influence of floodplain inundation on fish species diversity, relative abundance, and growth. We sampled the floodplain and the adjacent river at three stratified random locations with replication biweekly from the commencement of inundation (late May) through early October. Overall, we found that species diversity, relative abundance, and growth were higher in the floodplain than the main river. Our data support previous examinations, including those outside North America, that suggest floodplain inundation may be important for riverine fishes. Given these apparent advantages of floodplain inundation, restoration efforts should balance benefits of floodplain inundation while safeguarding priority needs of humans.

Telemetry is valuable for understanding animal ecology and assessing conservation priorities. Sturgeon species worldwide are imperiled and telemetric methods have been applied to adults, but the feasibility of using this methodology on age-0 sturgeon remains unclear. The pallid sturgeon (Scaphirhynchus albus) is a federally endangered species in the central United States and little is known about its early life ecology. The use of telemetry on age-0 pallid sturgeon would greatly increase understanding of their early life ecology. We assessed growth, survival, and swimming performance of age-0 pallid sturgeon tagged with 0.2 g, nonfunctioning radio telemetry tags to determine whether radio telemetry can be used on such small sturgeon. Tags were surgically implanted internally and attached externally, with a control group that only experienced handling. Age-0 sturgeon with internally implanted tags grew slowly and had low survival, while counterparts within the control group and those with external...

Dams have been implicated in the alteration of natural river processes. Quantifying spatial and temporal movement and passage patterns of large river fishes are critical for determining the extent of restricted passage and the needs for fish passage improvements. However, limited information regarding this topic exists because of the inherent difficulties associated with large river systems and assumptions associated with movement studies. Because of this lack of information, we investigated broad scale passage patterns of several riverine fish species through seven locks and dams complexes of the Upper Mississippi River using telemetry. Over the course of our 5-year evaluation, we observed species-specific movement and passage patterns, and how these trends were affected by factors such as water level and lock and dam management. Stationary receivers placed in a monitoring array detected a total of 1036 passage events. Eighty-four percent of the passage occurred through all but one of the lock and dam structures during both open and closed river conditions. While 70% of the passage occurred during open river conditions, further investigation of passages that occurred during closed river conditions (when gates are extended into the water column at some level) revealed that the majority of passage occurred when the average opening for all gates ranged from 0.6 to 1.2 m. Lock usage was also quantified, and most species were not routinely using the lock chambers for passage. Ultimately, these data have shown that individuals of each study species were able to negotiate most of the locks and dams during open and closed river conditions in both directions. Copyright © 2013 John Wiley & Sons, Ltd.

The lack of an immediate-release sedative (i.e., one for which no postsedation holding or withdrawal period is required) jeopardizes fish and fisheries research and poses considerable risk to those involved in aquatic resource management and the operation of public hatcheries and commercial fish farms. Carbon dioxide may be used as an immediate-release sedative, but it is slow-acting and difficult to apply uniformly and effectively. Tricaine methanesulfonate (MS-222) is easier to apply but requires a 21-d withdrawal period. The lack of an immediate-release sedative approved by the U.S. Food and Drug Administration (FDA) is a consequence of numerous factors, including the complexities of the approval process, the substantial human and monetary resources involved, and the specialized nature of the work. Efforts are currently underway to demonstrate the safety and effectiveness of benzocaine- and eugenol-based products as immediate-release sedatives. However, pursuing approvals within the current fr...