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Anthropogenic modifications to the environment have had damaging effects on the wildlife that depend on those natural ecosystems. Specific to Upper Mississippi River fishes, channelization, dams, and loss of floodplain connectivity have all been purported as deleterious. In the face of these habitat modifications, understanding habitat requirements of native species is needed to help guide management and restoration efforts. Furthermore, bluegill (Lepomis macrochirus) are an important indicator species that may provide insight to habitat needs of the broader fish community (e.g., “canary in a coal mine”). Prior research suggests bluegill require a mosaic of habitats throughout all life stages (e.g., main channel to backwater connection). As such, the objective of this study was to identify the habitat needs of bluegill in the Upper Mississippi River. We evaluated bluegill habitat use via electrofishing conducted by the U.S. Army Corps of Engineers’ Long-Term Resource Monitoring (LTRM) element. Electrofishing events (n = 4868) were conducted at three field sites throughout the Upper Mississippi River from 1993 to 2017. Our analysis of catch data (n = 83,352) indicates that bluegill prefer backwater macrohabitat over main channel and side channel habitats. Bluegill abundance varied between microhabitat characteristics. Bluegill catch rates were highest in low-flow areas, with velocities ranging from 0 to 0.09 m/sec. In general, catch rates were highest across all pools in moderately shallow depths (0–1.5 m) and in silty substrates. Management efforts that focus on the preservation of backwater habitat and connectivity to the main channel should help to sustain bluegill populations in the Upper Mississippi River. The information garnered in this study can be used to help direct management efforts that not only favor bluegill, but also other members of the Upper Mississippi River fish community.

Knowledge of environments used during early life history and movement patterns of Bighead Carp (Hypophthalmichthys nobilis) and Silver Carp (H. molitrix), collectively termed bigheaded carps, in the Upper Mississippi River (UMR) would be valuable for informing control measures to limit further population expansion and impacts of these species. Lock and Dam 19 (LD19) is a high-head dam on the UMR that delineates downriver areas where bigheaded carps are well established from upriver pools where these species are less abundant and evidence of reproduction and recruitment are limited. Principal natal environments supporting recruitment of emerging bigheaded carp populations in the UMR are unknown. The objectives of this study were to (1) infer environments occupied during early-life stages by bigheaded carps collected in UMR Pools 19–21 during 2013–2014 using otolith microchemistry and stable isotope analyses, and (2) use early-life environment assignments and capture location to identify individuals that passed through LD19. Differences in multivariate water chemistry signatures (Sr:Ca, Ba:Ca and δ18O) among the UMR, its tributaries, and the Missouri and Middle Mississippi rivers enabled development of a classification model for inferring early-life environment of bigheaded carps. Multiple sources of recruits, including from tributaries, have contributed to upriver expansion of bigheaded carps in the UMR. Sustainable control of bigheaded carps upstream of LD19 will likely require efforts to control local recruitment and immigration from downriver. The frequency of bigheaded carps collected in Pool 19 that were downstream of LD19 during early life suggests that bigheaded carps upstream of LD19 still predominantly consisted of immigrants from downriver during 2013–2014. Otolith chemistry provides an approach for assessing the extent to which changes in abundance of bigheaded carps upstream of LD19 are associated with local recruitment or immigration from downriver.

The loss of spawning habitat has been identified as a limiting factor to population growth for lake sturgeon, Acipenser fulvescens, the most widely distributed species of the family in North America. While local information exists about lake sturgeon spawning habitat, a synthesis of all available data is needed across its range. Our study used meta-analytical techniques to describe the mean and range of critical spawning habitat characteristics based on data from 48 sites across all major watersheds in which lake sturgeon are found. Data were compiled into univariate habitat suitability indices to describe the spawning niche. Results indicate that peak suitability occurred at depth-averaged velocities of 0.6 m·s−1, depths of 0.55–0.85 m in small rivers (3·s−1 annual average discharge) and 0.75–5.25 m in large rivers (>100 m3·s−1), over cobble substrates (64–256 mm), and that suitable water temperatures decreased with increasing latitude. This study provides a comprehensive review of critical spawning criteria from which future habitat suitability models can be adapted.

Due to the high amounts of harvest of natural fish populations, overexploitation can occur and subsequently lead to depleted fisheries. This is especially true for commercially exploited roe-bearing species that exhibit late age at maturation and intermittent spawning. Overexploitation can create an imbalance in natural ecosystem function and in turn jeopardize the livelihood of commercial fishers. Despite the problems created by overexploitation, trends of commercial harvest on large inland river roe-bearing populations have received minimal attention. As such, we evaluated trends in commercial fishing data from 1945-2010 for two roe-bearing species (paddlefish Polyodon spathula and shovelnose sturgeon Scaphirhynchus platorynchus) from two of the largest inland rivers in North America (Mississippi River and Missouri River) adjacent to Missouri. Commercial sturgeon and paddlefish catch has varied from ∼160 to 35,150 kg over the course of the 55-year duration. Abnormally high catches corresponded to initiation of worldwide caviar markets, onset of extensive regulations on the Missouri and Mississippi rivers, and the Caspian Sea fishery collapse; respectively. Further, our results suggest that the harvest of sturgeon and paddlefish have increased since 1945 and may be influenced by local, regional, and international events. Despite the increase in harvest and the possibility of overharvest, commercial fishing regulations have not been thoroughly evaluated for effectiveness. Further evaluation of current management and regulations of these paddlefish and sturgeon fisheries is suggested, especially considering these fisheries may be influenced by local, regional, and international events. Taking potentially influential events into consideration when evaluating and implementing regulations and authorizing commercial harvest permits are vital in sustaining a long term commercial fishery and protecting the livelihood of commercial fishers.

The demographics (e.g. hatch time, growth and mortality) and habitat (macrohabitat and mesohabitat) use of age-0 blue catfish Ictalurus furcatus (Lesueur) were evaluated in the un-impounded reach of the middle Mississippi River during 2003–2010. Each year, island complexes and adjacent main river habitats were trawled, and 7,373 age-0 blue catfish (10–144 mm total length) were collected. Blue catfish hatch timing varied slightly across years and generally began in June and ended in August. Age-0 blue catfish growth rates and instantaneous mortality rates differed among years. Catch rates of age-0 blue catfish were highest in side channels and around islands, whereas main channel habitats were infrequently occupied. Regarding mesohabitat use, age-0 blue catfish frequently occupied low velocity areas (i.e. 0.3–0.4 m/s) of shallow depth (i.e. 1–4 m) and sand substratum. This study has provided insight into age-0 blue catfish population dynamics and has highlighted the importance of specific habitat characteristics in large rivers that may aid in recruitment of this species.

Silver Carp Hypophthalmicthys molitrix (Valenciennes, 1844) are an invasive species in the Mississippi River Basin and their current role in this novel ecosystem is not fully understood. Juvenile Silver Carp can and do occur in great numbers after a successful spawn. These massive schools of small Silver Carp seem to be an obvious prey source for the common predators of the Mississippi River system. The level to which native piscivores are consuming this novel prey item is unclear. Therefore, the goal of this research was to assess the diets of native piscivores collected in Pool 26 and the Open River reach of the Mississippi River. Using diet contents and catch rates of small fishes, selection or avoidance could be determined for predator prey interactions. Then a controlled laboratory experiment was conducted to determine if common predators [White Bass Morone chrysops and Largemouth Bass Micropterus salmoides (Lacepede, 1802)] would select for or against this novel prey in the presence of two native prey fish [Gizzard Shad Dorosoma cepedianum (Lesueur, 1818) and Emerald Shiner Notropis atherinoides]. Understanding how predator-prey interactions occur in a controlled laboratory experiment may provide insight to trends observed in the field. The majority of native piscivores appeared to be avoiding Silver Carp in both reaches and selecting native prey fishes. The order in which prey fish were consumed by both predators showed significant avoidance of Silver Carp. It appears that the trends observed in the field were supported by our controlled laboratory experiment. The effectiveness of different native piscivores to consume Silver Carp may have impacts on future management decisions.

This study inferred that the majority of shovelnose sturgeon Scaphirhynchus platorynchus captured in the upper Mississippi River probably originated from locations outside the upper Mississippi River (Missouri River, middle Mississippi River); whereas, lake sturgeon Acipenser fulvescens exhibit infrequent movement outside of the upper Mississippi River, but may move throughout these interconnected large rivers at various life stages. By using pectoral fin-ray microchemistry (a non-lethal alternative to using otoliths), it is suggest that interjurisdictional cooperation will probably be needed to ensure sustainability of the S. platorynchus commercial fishery and the success of A. fulvescens reintroduction in the upper Mississippi River. Additionally, fin-ray microchemistry can provide invaluable data to make informed management decisions regarding large river fishes, that cross jurisdictional boundaries or that move outside of closure zones, without causing further mortality to compromised fish populations (e.g. threatened and endangered species).

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.

Summary Lake sturgeon Acipenser fulvescens are considered rare and were nearly extirpated in the Mississippi River in Missouri by 1931 as a result of overfishing and habitat fragmentation. Propagation efforts have been implemented by the Missouri Department of Conservation since 1984 as means to restore the lake sturgeon population. Although recent population increases have been observed, a formalized evaluation to determine if lake sturgeon are self-sustaining in the Missouri portion of the Mississippi River has not been completed. Therefore, the objectives of this study were to: (i) determine the proportion of reproductive individuals, (ii) evaluate seasonal movement patterns of adults, and (iii) validate purported spawning locations within the Mississippi River in Missouri. Lake sturgeon catch data indicated that approximately 11 percent of the population are reproductively mature. Additionally, telemetry data confirms that the greatest movement by adult lake sturgeon occurs during spring, which suggests spawning behavior. Finally, it was possible to document lake sturgeon embryos and emergent fry larvae below Melvin Price Locks and Dam 26 in the Upper Mississippi River near St. Louis, Missouri. Water velocity, depth, and substrate size were measured at this location and embryos were collected and hatched in the laboratory. River gage data suggest that spawning behavior may have been elicited by a large influx of water during a drawdown period of water above the dam. This study represents the first documented spawning of A. fulvescens in the Mississippi River and highlights the success of recovery efforts in Missouri.

Summary Pallid sturgeon Scaphirhynchus albus relative condition has been observed to be declining along the Nebraska reach (rkm 1212.6–801.3) of the Missouri River over the past several years; therefore, pallid sturgeon capture data was synthesized from the entire Missouri and Middle Mississippi rivers to document and compare how pallid sturgeon condition varies spatially and temporally throughout much of their current range. The study area was subdivided into four river reaches based on a priori statistical differences for pallid sturgeon catches from 2003 to 2015. Pallid sturgeon in the Middle Mississippi River (Alton Dam [rkm 321.9]) to the confluence of the Ohio River (rkm 0.0) were in the best condition while pallid sturgeon in the Middle Missouri River (Fort Randall Dam [rkm 1416.2]) to the Grand River confluence (rkm 402.3) were in the poorest condition. Furthermore, pallid sturgeon condition in the Upper Missouri River (Fort Peck Dam [rkm 2850.9] to the headwaters of Lake Sakakawea [rkm 2523.5] and lower Yellowstone River) and the Lower Missouri River (Grand River confluence to the Mississippi River confluence [rkm 0.0]) were significantly less than in the Middle Mississippi River but significantly higher than the Middle Missouri River. Temporally, pallid sturgeon condition was highly variable. Relative condition in the Middle Mississippi River was consistently above average (Kn = 1.1). Comparatively, Kn throughout the Missouri River rarely exceeded “normal” (Kn = 1.0), with Kn in the middle and lower reaches of the Missouri River having declined to the lowest observed. As pallid sturgeon recovery efforts continue, understanding the range-wide differences and effects on condition could be critical, as poor condition may cause maturation delays, reproductive senescence or even mortality, which affects the likelihood of natural reproduction and recruitment.

Autochthonous material has been found to be an important base in large river food webs. However, a spatial understanding of primary production in large rivers is lacking. We modeled primary productivity and community respiration (CR) during a low water period in two types of off-channel habitat present in the Middle Mississippi River, side channels and wing dike fields. Wing dike fields are constantly connected to the main channel and are well mixed along most of their length, while side channels are typically connected only at the top and mouth. Gross primary production (GPP) in wing dike fields ranged from 0.0 to 8.9 g O2 m−2 D−1 and in side channels GPP ranged from 0.4 to 33.5 g O2 m−2 D−1. Both habitat types experienced periods of positive net ecosystem production (NEP) especially in the late summer and early fall. Correlations between metabolic rates and ecosystem characteristics differed between habitat types. Discharge was negatively correlated to NEP in wing dike fields but was not associated with metabolic rates in side channels. Light was positively correlated with GPP and CR at both site types and with NEP in side channels. These areas are protected from high velocity and likely experience greater light penetration, allowing more photosynthesis to take place especially during low water periods. This study demonstrates the potential for high productivity in off-channel habitats that are permanently connected to the main channel. Copyright © 2016 John Wiley & Sons, Ltd.

Management of migratory fishes is a difficult task for fishery managers because fish cross jurisdictional boundaries and encounter differing regulations. States within the Mississippi River basin have differing commercial and recreational regulations for riverine Paddlefish Polyodon spathula populations, and the current population dynamics have not been evaluated on a system-wide basis. The objective of this study was to simulate the current reproductive potential of the population using various harvest scenarios. At the current exploitation rate of all locations pooled (u = 14.8%), the population may experience recruitment overfishing at a 610 mm minimum length limit and has the potential to experience recruitment overfishing at a 710 mm length limit (u = ∼20%). Any added stressors (e.g., Asian carp) may cause further mortality; thus, adopting a precautionary approach is necessary to maintain sustainable Paddlefish fisheries. At an 810 mm length limit, the population would not realistically experience re...

Habitat management is a crucial aspect of fisheries management. Without knowledge of habitat associations, fisheries scientists are unable to effectively make habitat conservation or restoration recommendations. This becomes especially prominent when trying to manage commercially harvested populations and protect threatened or endangered species. To determine juvenile fishes habitat associations in the Middle Mississippi River, we analysed mini-trawl catch data of six common juvenile fish species: blue catfish (Ictalurus furcatus), channel catfish (Ictalurus punctatus), channel shiner (Notropis wickliffi), freshwater drum (Aplodinotus grunniens), paddlefish (Polyodon spathula), and shovelnose sturgeon (Scaphirhynchus platorynchus). Overall, we conducted 2251 mini-trawl sampling efforts between 2002 and 2013, resulting in the capture of 23,742 target specimens. Catch per unit effort was evaluated by structural habitat (i.e. velocity, depth, and substrate). Overall, these data suggest that juvenile fish species are more prevalent in shallow water and slower velocities. Ultimately the information garnered during this evaluation should be incorporated when considering habitat modifications, especially those modifications that impact the availability of shallow-low velocity habitats. Copyright © 2016 John Wiley & Sons, Ltd.

Natural resource professionals have frequently criticized universities for poorly preparing graduates to succeed in their jobs. We surveyed members of the American Fisheries Society to determine which job skills and knowledge of academic topics employers, students, and university faculty members deemed most important to early-career success of fisheries professionals. Respondents also rated proficiency of recently hired, entry-level professionals (employers) on how well their programs prepared them for career success (students and faculty) in those same job skills and academic topics. Critical thinking and written and oral communication skills topped the list of important skills and academic topics. Employers perceived recent entry-level hires to be less well-prepared to succeed in their careers than either university faculty or students. Entry-level hires with post-graduate degrees rated higher in proficiency for highly important skills and knowledge than those with bachelor's degrees. We conclude that a...

Fisheries science is a diverse field that requires individuals to be knowledgeable in many disciplines in addition to fisheries (e.g., economics, sociology, political science, chemistry; Kelso and ...

Worldwide large rivers have been severely modified by human intervention. Many modifications result in disconnection of the river from floodplain and off-channel habitats generally characterized by lower velocities and Copyright © 2016 John Wiley & Sons, Ltd. shallower depths relative to the main channel, conditions vital to many organisms. Extensive levees on the Middle Mississippi River (MMR) have cut off backwater systems and disconnected the river from 80% of its floodplain. However, the system is characterized by large side channels associated with islands. We examined a long term data set for differences in physical (e.g. depth and velocity) and water quality metrics (e.g. temperature, suspended solids, dissolved oxygen, chlorophyll, % organic matter) between the main and side channels of a 128-km reach of the MMR. We compared variability between main and side channels using the coefficient of variation (COV). All metrics differed between habitats. Side channels were shallower with lower velocities and had greater mean and COV of % organic matter and more variable dissolved oxygen concentrations. Velocity, temperature, and suspended solids were similar in the spring. COVs were lowest in both habitats during the spring for all metrics except temperature and DO. Resource management in the MMR tends to focus on maintaining existing side channels because of the difficulty of working in the heavily used navigation channel. This study shows that these actions protect areas that function differently than the main channel for most of the year. However, our results also highlight the need for restoration activities aimed at restoring floodplain connectivity, especially during the spring. Copyright © 2016 John Wiley & Sons, Ltd.

Turtles face unique conservation challenges in modern modified river systems. Despite their ecological importance, gaps in knowledge still exist that may hinder their conservation. Turtle by-catch data from the US Army Corps of Engineers' Long-Term Resource Monitoring Program were analyzed for 5 turtle species (false map turtle, Graptemys pseudogeographica; red-eared slider, Trachemys scripta; common snapping turtle, Chelydra serpentina; smooth softshell turtle, Apalone mutica; and spiny softshell turtle, Apalone spinifera) to better understand macrohabitat and mesohabitat use. These species demonstrated differences in habitat use between various macrohabitats, substrata, velocity classes, and depth classes. Common snapping turtles and spiny softshell turtles were captured most often in tributaries, whereas red-eared sliders were captured most often in tributaries and closed side channels. Smooth softshell turtles used open side channels and unstructured main-channel borders most often. False map...

River modifications have had detrimental effects on biota that depend on river systems; therefore, information is needed to understand these effects and direct management efforts. Channel catfish (Ictalurus punctatus) are important recreationally, commercially, and ecologically in the Middle Mississippi River (MMR), but few studies have examined their habitat requirements, and food habits have not been evaluated in the MMR. Information about habitat use and food habits could help direct management efforts for channel catfish. To more thoroughly understand the synergistic relation between channel catfish and the associated habitat, we used data from the United States Army Corps of Engineer’s Long-Term Resource Monitoring Program to evaluate channel catfish use of large-scale river features (i.e., macrohabitats) and more fine scale mesohabitats (i.e., substrate type, depth, and velocity). Stomach contents from channel catfish were identified and quantified to determine the relative importance of sp...

The invasion of non-native fishes has caused a great detriment to many of our native fishes. Since the introduction of invasive carps, such as Silver, Bighead, Common and Grass Carp, managers and researcher have been struggling to remove these species while also hypothesizing the detriment of further invasion. This study developed a food web model of four locations on the Mississippi River and used those models to assess the impacts of two scenarios: carp removal and carp invasion. In the Middle Mississippi River where these invasive carps are already present, the models found that it would take a sustained exploitation of up to 30% of initial biomass over an extended period to remove Grass Carp and up to 90% removal of initial biomass to remove Silver and Bighead Carp. In the locations where Silver, Bighead, and Grass Carp are not yet established (i.e., Pools 4,8, and 13) the invasion of these species could cause declines from 10 to 30% in initial biomass of native fishes as well as already established nonnative invasive species.

Harvest regulations are important for fishes that are both commercially and recreationally sought after such as Channel catfish (Ictalurus punctatus) throughout the Middle Mississippi River. Monitoring total harvest and understanding Channel catfish population dynamics (i.e., recruitment, growth, and mortality) are crucial for managing a sustainable population. Total commercial harvest and current harvest regulations in the Middle Mississippi River have not recently been evaluated. Thus, we evaluated total commercial harvest reports from 1945–2012 along with commercial fishing effort, population dynamics for the Middle Mississippi River Channel catfish population, and simulated the effects of various length limits on the reproductive potential and yield per recruit of the Channel catfish population. Overall, total commercial harvest has drastically declined from 1990–2012, while commercial effort has remained relatively constant. We speculate overexploitation as a possible cause to the decline in harvest ...

Management of silver carp Hypophthalmichthys molitrix has become a growing concern for multiple state and federal entities. Commercial fishing may have the greatest potential to control silver carp. However, for a management action to be successful, the level of exploitation required to reduce silver carp populations must be quantified. Therefore, silver carp were collected from Midwestern U.S. rivers (i.e., Upper, Middle, and Lower Mississippi, Missouri, Illinois, Ohio, and Wabash rivers) to obtain population dynamics (i.e., recruitment, growth and mortality). Parameters obtained from population demographics were used to simulate exploitation levels using a spawning potential ratio (SPR) approach to determine target size and the amount of exploitation needed to recruitment overfish silver carp within each river system. Overall, we determined that silver carp populations (regardless of river) must be exploited at a small size (i.e., 27–33% of population exploited at ≥300 mm or 33–44% exploited at ≥400 mm), in order to reduce SPR to 0.2, which is identified as a threshold for recruitment overfishing. However, an understanding of the impacts of small mesh sizes on native species and an incentive program for commercial fisherman to promote catch of small fish is needed. This study provides federal and state agencies levels of exploitation and a target size required to effectively reduce silver carp populations in multiple rivers.

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

Lake of the Ozarks, Harry S. Truman Reservoir, and Table Rock Lake in Missouri contain important recreational trophy Paddlefish fisheries. These three reservoirs have been created by damming major rivers. Because of river modifications, Paddlefish natural reproduction is thought to be limited, and subsequently, populations have been maintained through supplementation and harvest regulations. However, these fisheries have not been thoroughly assessed and the applicability of management actions (e.g., supplementation and minimum length limits) has not been fully evaluated. Population simulations indicated changes in the amount of trophy sized fish and broodstock remaining of each population were similar, with larger minimum length limits resulting in a greater proportion of mature and trophy sized individuals. However, the number of Paddlefish that could be harvested at Harry S. Truman Reservoir and Lake of the Ozarks was much greater than at Table Rock Lake. These disparities are likely attributed ...

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

Summary Here we contrast the relative influence of the commercial and recreational harvest sectors on the Middle Mississippi River paddlefish Polyodon spathula (Walbaum, 1792) population. We performed a creel survey of randomly selected commercial fishers and recreational anglers to gather characteristic harvest information to make comparisons between sectors. We found that the commercial sector harvested predominately large, mature paddlefish. Conversely, the recreational sector tended to harvest a greater proportion of small, immature paddlefish. Because these sectors are harvesting different portions of the population, the relative influence on the dynamic rate functions and potential conflict between sectors must be taken into account for fishery management decisions. One approach would be to increase the minimum length limit, to allow for equal harvest between the commercial and recreational harvest sectors. Ultimately, this will allow for both harvest sectors to harvest the same portion of the population, as well as increase the reproductive potential of the population. Additionally, obtaining an accurate assessment of the catch and effort for both sectors is imperative for the management and allocation of a shared resource.

Rivers worldwide have experienced changes through habitat modifications and are likely further exacerbated with the onset of climate change. The coupling of these anthropogenic disturbances has reduced the ability of river ecosystems and associated biota to adjust. The aforementioned human-induced habitat perturbations coupled with high summer river temperatures have been associated with an increased frequency of fish kills. Recently, shovelnose sturgeon Scaphirhynchus platorynchus have experienced numerous events of excessive summer mortality in rivers across the USA. During the summer of 2012, multiple fish kills occurred on the lower Des Moines River. During one of these events, we collected numerous dead or dying shovelnose sturgeon (N = 132) to explore factors causing mortality. Water temperatures were exceedingly high (29–35°C), while dissolved oxygen levels varied between 4 and 10 mg L−1. Based on population simulation modelling, only ~14% mortality would need to occur to reduce the reproductive potential below sustainable levels, which was likely exceeded. The results of our controlled experiment demonstrate that the high temperature in the Des Moines River was likely the mechanism initiating mortality. Future climate projections indicate that increases in temperature on the Des Moines River are possible; thus, the population may be at risk in the future. Through our microchemistry investigation, immigration from the Upper Mississippi River appears to be common and may be a source population to the Des Moines River. Despite immigration, the influence that these mortality events have on the Upper Mississippi River is unknown. Thus, proactive management efforts are needed to ensure sustainability of this population. Copyright © 2014 John Wiley & Sons, Ltd.

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.

Many studies have shown that negative interactions exist between the invasive silver carp Hypophthalmichthys molitrix and the associated native fish community. The primary negative effect relates to the filter feeding capacity of Asian carp and thus dietary overlap and decreased fitness of native planktivorous fishes. However, from a nutrient transfer perspective, an alternative feedback loop may exist between invasive Asian carps and native fishes. We postulate that silver carp consuming small planktonic particles with low assimilation efficiency can subsequently egest larger, nutrient rich fecal pellets consumable by other fauna, which may have otherwise been unavailable. To evaluate this feedback loop, we extracted fecal pellets from the hindgut of silver carp. Fecal pellets were fed to age-0 channel catfish Ictalurus punctatus and blue catfish Ictalurus furcatus (i.e., < 130 mm) in a controlled laboratory setting. Both species of catfish consumed the fecal pellets and subsequently survived and increased in body mass (i.e., weight) over the 20-day trial period. These results suggest that a potential alternative feedback loop may exist between silver carp and members of the benthic community and therefore provide a pathway by which nutrients are translocated between habitats (i.e., pelagia to benthos). We suggest that undigested plankton consumed by silver carp can be converted into nutrient packed pellets and may provide an additional food source to benthic organisms such as age-0 channel catfish and age-0 blue catfish.

American eel populations are declining and have recently become a species of interest by the United States Fish and Wildlife Service to list as a threatened species. However, the American eel population in the largest inland lotic waterway in North America (Mississippi River) has received little attention despite the apparent relevance. Because of the lack of information on the Mississippi, we evaluated trends in relative abundance and habitats occupied by American eel using long-term data collected on the Mississippi River (i.e., Upper Mississippi River Restoration – Environmental Management Program). During the 18 y study, a total of 92 American eels were collected throughout the Upper Mississippi River (Lake City, Minnesota downstream to Cape Girardeau, Missouri) with a relatively fewer individuals captured as of recent. Across macrohabitats, unstructured and structured (i.e., diked) main channel borders had the greatest number of American eels captured; however, eels were infrequently capture...

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...

Smallmouth buffalo (Ictiobus bubalus (Rafinesque)) are an important component of the Middle Mississippi River commercial fishery. Despite their commercial importance, limited contemporary information is available regarding population age and growth. Therefore, the objective of this study was to determine age and growth of Middle Mississippi River smallmouth buffalo. To fulfill this objective, 125 individuals collected during routine Long-Term Resource Monitoring element hoop net surveys were aged via lapilli otoliths (mean age = 17.9 years; SD = 8.3), and a von Bertalanffy growth model (Lt = 730.289[1 - e-0.086(t-5.051)]) was used to evaluate growth. Our results indicate Middle Mississippi River smallmouth buffalo can achieve maximum ages beyond 20 y despite commercial harvest. Ultimately, we hope our results catalyze future research which seeks to understand other aspects of smallmouth buffalo biology and ecology.

Mortality is a key parameter in understanding the dynamics of any fish population. We examined three methods to evaluate Shovelnose Sturgeon Scaphirhynchus platorynchus mortality (e.g., ratio of first year recruits to all recruits [Heincke's method], a linearized weighted catch curve, and an open system mark–recapture mortality approach). The Mississippi River was sampled in two distinct but connected geomorphic sections: upper Mississippi River (UMR; river kilometer 323–587) and the middle Mississippi River (MMR; river kilometer 0–322). All analyses were pooled across these areas due to potential emigration or immigration throughout both study reaches. Heincke's method estimated annual mortality at 16.9% for the full range of ages (9–23 years) with generally increasing estimates with decreasing age ranges considered (10–23, 11–23, 12–23, and so on). A linearized weighted catch curve that considered increasing estimates of mortality for the shorter age ranges generated an annual mortality estimat...

To combat the potential deleterious effects that Silver Carp Hypophthalmichthys molitrix have on native populations, management of this species is essential. Before developing population-level models, a determination of which aging structure for estimating the age of Silver Carp is needed. To our knowledge, no consensus has been reached on which structure should be used for estimating Silver Carp ages. We collected 120 Silver Carp from the Illinois, Mississippi, Missouri, and Ohio rivers via electrofishing to evaluate aging structures. Removal time, processing time, and discernible annuli were evaluated for scales, opercles, vertebrae, pectoral fin rays, postcleithra, and asterisci and lapilli otoliths. Asteriscus otolith, opercle and scale annuli were difficult to discern and not evaluated further. Total processing times for postcleithra (246.1 s) and lapilli (251.2 s) were the most time-efficient; pectoral fin rays and vertebrae were more time intensive. Between-reader precision and agreement r...