Objective Monitoring and assessment of nongame native fishes is limited, but conservation interest in these species is growing. Freshwater Drum Aplodinotus grunniens are a wide-ranging species that serve important functional roles and could serve as an indicator for similar but less common species. Our overall objectives were to quantify and compare population dynamic rates and life history of Freshwater Drum among study reaches in the upper Mississippi and Illinois rivers and relate these metrics to hypothesized environmental and anthropogenic factors.Methods We integrated recently collected age data with monitoring data to estimate age and size distributions, growth curves, maturation schedules, mortality rates, and young-to-adult ratios of Freshwater Drum in six study reaches spanning 1,500 km of river. Principal component analyses and linear regression were used to relate environmental and anthropogenic gradients (latitude, commercial harvest, hydrologic dynamics, primary productivity) to life history traits and population dynamic rates.Results We found latitudinal gradients in life history traits and population dynamic rates whereby Freshwater Drum in upstream, higher-latitude study reaches generally exhibited later maturity, slower growth, smaller maximum size, and lower mortality rates compared with those in lower-latitude study reaches. Further, young-to-adult ratios positively corresponded with chlorophyll-a concentration. No clear relationships were apparent between population dynamic rates and hydrologic variation or commercial harvest.Conclusions Latitude is an important structuring component of life history traits and population dynamics of Freshwater Drum in the upper Mississippi and Illinois rivers likely due to both temperature seasonality and disturbance regimes. The presence of demographic structure in a widespread, common species such as Freshwater Drum suggests similar patterns likely exist in other long-lived native fishes. Latitude is a key environmental gradient driving fast versus slow life histories in Freshwater Drum in the upper Mississippi River and Illinois River. Freshwater Drum at lower latitudes matured earlier, grew faster and larger, and had higher mortality than those at higher latitudes.

Long-term monitoring indicates bluegill catch rates are relatively stable in some reaches of the Upper Mississippi River and highly variable in others, whereas in the Illinois River, catch rates have decreased. A lack of age structure information precludes understanding population processes responsible for patterns in catch rates. To build a better understanding of why catch rates have changed over time, we integrated short-term age structure information with long-term monitoring data to quantify and assess spatial patterns in bluegill population dynamics across six study reaches of these two rivers. Specifically, we estimated and compared age and size structure, growth, maturity, mortality, and recruitment. We used quantile regressions to apply age estimates to long-term data for investigating trends in age-based catch rates reflective of recruitment (age-1 catch rates), mortality (using age-1 and age-2+ catch rates), and spawning stock (age-2+). Our findings indicate trends in bluegill age-2+ catch rates increased and then stabilized across upstream study reaches, but dynamic rates, size structure, and age at maturity varied among reaches. Bluegill populations in downstream study reaches had low maximum size, early maturation, low mean age, low proportional stock density, declining recruitment, and declining age-2+ catch rates. An insufficient number of bluegills were collected from the study reach furthest downstream to adequately quantify dynamic rates. Our results support life history theory in that bluegill respond to unstable environmental conditions through life history adaptations. These findings show how integrating periodic age structure information with long-term monitoring can enhance population assessments.

Hatchery release is a common and effective practice for protecting and restoring wild resources, and the success of the practice is commonly assessed using mark-recapture technology. We investigated the use of different dimensional X-ray imaging techniques for the strontium (Sr) marking of fish fin rays for stocking. Megalobrama amblycephala juveniles were marked by culturing specimens in 800-mg/L SrCl2·6H2O solution, the cross-sections of dorsal fin rays were subsequently obtained, and the concentrations Sr was analyzed by 2D imaging using an electron probe X-ray microanalyzer. Our preliminary findings indicate that the immersion marking method is effective for the Sr marking of fin rays in experimental fish. Moreover, we generated a bird’s-eye-view 3D mesh image of the Sr concentrations, which can provide a more comprehensive information for fish stocking than that using normal 2D imaging.

The aquatic fauna of large river systems have been the cornerstones of multiple civilizations throughout human history.Today,they remain critically important as pri-mary resources for humans as well as indicators of gen-eral ecosystem structure and function.Unfortunately,nearly all large-river systems globally are at risk from over-exploitation,pollution,large-scale development,navigation,dredging,climate change,and other threats.

Invasive carp populations have purported a negative influence on native biota at high densities. These invasive fishes (i.e., bighead carp Hypophthalmichthys nobilis, silver carp Hypophthalmichthys molitrix, grass carp Ctenopharyngodon idella, and black carp Mylopharyngodon piceus) each exhibit similar life history characteristics. In the Neosho River-Grand Lake system (i.e., John Redmond Reservoir, Kansas, downstream to Grand Lake O' the Cherokees, Oklahoma), only bighead carp and grass carp have been documented to date. The distribution and status of bighead carp throughout this system were previously unknown due to limited historical data and low abundance. While few bighead carp are encountered within this system, grass carp exhibited relatively higher abundance a were used to provide insights into bighead carp. Captures of both species were used to inform management and suppression efforts. Sampling locations (n = 18) were established for environmental DNA analyses throughout the Neosho River-Grand Lake system. We sampled 13 sites using a suite of gears for standardized targeted fish sampling. All invasive carp were measured, sexed, and otoliths removed for ageing and microchemical analysis. Grass carp were processed for ploidy testing following the U.S. Fish and Wildlife Service protocol. Environmental DNA analyses generated positive results for the eDNA presence of bighead carp and silver carp. Otolith age estimates suggest fish are long lived and supported by multiple year classes. Additionally, a sampled two-year-old grass carp demonstrates spawning and recruitment potential. Otolith microchemistry suggests largescale broad movement patterns. Ploidy testing confirmed the first documented evidence of diploid grass carp in the Neosho River-Grand Lake system and revealed reproductive viability. Our results may provide future insights into locations for containment, removal, and/or eradication.

White Crappie (Pomoxis annularis) and Black Crappie (P. nigromaculatus) were studied in three southeast Kansas reservoirs to assess exploitation and determine if current regulations were conducive for sustainable populations. Trap nets were used to sample crappie in Elk City Reservoir, Big Hill Reservoir, and Parsons City Lake. Crappie measuring 210 mm and greater received Floy FD-94 tags that served as entries for rewards to encourage tag reporting. Harvest and angler demographic information were collected when tags were reported. Postcard surveys and motion-sensed cameras were used in conjunction to estimate angler effort and reporting rate on Parsons City Lake. Annual exploitation rates (i.e., percent of fish harvested) determined by tag returns and corrected for nonreporting and tag loss were 28.3%, 21.8%, and 3.9% on Elk City Reservoir, Big Hill Reservoir, and Parsons City Lake, respectively. Overfishing was not occurring, so current statewide regulations were likely appropriate, and no changes may be necessary.

Background Restocking by introducing hatchery-reared fish into wild habitats aids in the restoration of fishery aquatic ecosystems and reefs to increase the abundance of fish resources, restore the ecological balance of water bodies, and enhance ecosystem functioning. Accurately, rapidly, and effectively evaluating the success of restocking using chemical markers (e.g., strontium [Sr]) remains challenging for fisheries management. Consequently, for non-lethal fish sampling, hard tissues, such as fin rays, have received increasing attention as a target for marking method. However, data on the differences in marking different types of fin rays remain limited. Therefore, we exposed juvenile blunt snout bream individuals ( Megalobrama amblycephala ) to 0 (control group) or 800 mg/L of SrCl 2 ·6H 2 O (marked group) for 5 days and transferred them into normal aerated water for post-immersion culture. We sampled their pectoral, dorsal, ventral, anal, and caudal fin rays. The Sr marks among the fin types were sampled at 0 and 20 days post-immersion and evaluated using an electron probe micro-analyzer (EPMA) for the five-day Sr/Ca ratios, along with line transect and Sr mapping analyses. Results Sr marking signatures were observed in all fin types in the marked group, with a success rate of up to 100%. Although marking efficiency varied among the different fin ray types, the highest Sr/Ca ratios were most often detected in the dorsal fin. Cross-sectional Sr concentration maps of all fin rays sampled showed high-Sr domains in the marked group; in contrast, the entire cross-sections of the control group displayed low Sr contents, indicating successful marking efficiency. Conclusions Fin ray Sr marking is a successful method for juvenile M. amblycephala , with the advantages of non-lethality and negligible sampling injuries, facilitating the rapid and effective evaluation of Sr marking in restocking M. amblycephala .

Stock enhancement and releasing is one of common and effective technique in the wild resource protection and restoration. Nevertheless, missing an effective mark-recapture method makes it hard to evaluate the effect. By the benefit of non-toxic, harmless and long retention time, microchemical marking (i.e. strontium) become an effective means. Here we developed a fin ray strontium marking technique. The larvae, blunt snout bream ( Megalobrama amblycephala Yih, 1955) was marked in the 800 mg L SrCl ·6H O solution for 5 days before a 20-day recovery culture in normal water. The section of dorsal fin rays was extracted to analyze the Sr concentration distribution in the plane by using electron probe microanalysis (EPMA) with accelerating voltage of 15 kV and beam current of 0.36 μA. It showed that the determination condition of 15 kV, 0.36 μA could obtain the obviously visual and accurate distribution map of Sr concentration in the fin rays, with minimum damage. The dynamics of Sr mark in fin ray coped well with that of Sr immersing process of the experimental fish. By the meantime, a 3D mesh image was also used, which was able to reflect more details than the normal 2D mapping result. Non-lethally samplable fin ray can completely replace lethally sampled otolith for accurate evaluation the Sr marking effect by using EPMA with accelerating voltage of 15 kV and beam current of 0.36 μA. The method had immensely practical value in the experimental development of restocking methodologies with the advantages of objectivity, accuracy and visualization.

Barrier presence in river systems has been demonstrated to impair fish assemblages. Low head dams specifically are frequently occurring barriers in riverine environments. Well-supported impacts of these structures on fishes include diminished movement, reproduction, and habitat availability. Longitudinal patterns in riverine fish assemblages have long been researched to ascertain dynamics and display interactions. The need for research becomes more critical when factoring in impacts of barriers and detrimental invasive species. Knowledge of fish assemblages can inform fisheries biologists and aid in improved management practices for recreational and ecologically important species, as well as invasive species. The Neosho River system in Kansas has 14 barriers present. Little fisheries sampling has been done in the Kansas portion of this river system from the John Redmond Dam to the Oklahoma border; therefore, sampling was conducted to inform questions posed about the fish assemblages. We sought to document the fish assemblages of the system in Kansas and examine for assemblage composition distinctions by geographic region along a longitudinal gradient. The fish assemblage dataset from this research generated a wealth of knowledge on sportfish infiltration from reservoirs, imperiled fishes, and apparent impacts from low-head dams. Information from this study will aid in future management and direct new research investigating imperiled fishes.

Understanding survival probabilities is critical for the sustainable harvest of wildlife and fisheries populations. Age‐ and stage class‐specific survival probabilities are needed to inform a suite of population models used to estimate abundance and track population trends. However, current techniques for estimating survival probabilities using age‐at‐harvest methods require restrictive assumptions or incorporate potentially unknown parameters within the model. Using a Bayesian approach, we developed a flexible age‐at‐harvest model that incorporates either age‐ or stage‐structured populations, while accounting for uncertainty in age structure, population growth rates and relative selectivity. Survival probabilities can vary by age or stage class, as well as by environmental covariates, and both population growth rates and selectivity for each age or stage class can be specified as fixed and known or these parameters can be specified as informative priors, allowing for the incorporation of expert opinion. We evaluated our model with simulations and empirical data from harvested bobcats Lynx rufus and American paddlefish Polyodon spathula . Models fit to simulated age‐at‐harvest data yielded unbiased estimates of survival probability when population growth rates and selectivity were centered on the data‐generating parameter. We obtained unbiased estimates of survival probability even with biased prior estimates of selectivity and random departures from the assumed stage distribution, although the latter increased uncertainty in those estimates. We found biased estimates of survival probability when the prior distribution for population growth rate was not centered on the data‐generating value. When fit to empirical harvest data, our proposed age‐at‐harvest model produced estimates of survival probability congruent to those reported in the literature within similar geographic regions. We demonstrate the utility of a novel age‐at‐harvest model that estimates survival probability and realistically account for uncertainty in model parameters, transcending the restrictive assumptions and auxiliary data requirements of other methods. Furthermore, we advise collecting information about population trends and age structure alongside age‐at‐harvest data to help reduce bias. Although our model cannot replace more rigorous methods, we believe our model will be transformative for wildlife and fisheries practitioners who collect age‐at‐harvest data to estimate age‐ or stage‐specific survival probabilities to help inform management decisions.

The release of hatchery-reared fish fry for restocking is important for the enrichment of fishery resources; however, the effective evaluation of the success rate of marking such fish is challenging. We exposed juvenile crucian carp (Carassius carassius) to a single concentration of SrCl2·6H2O for 5 d and evaluated the efficiency of Sr marking of the fish otoliths (sagittae, asterisci, and lapilli) using an electron probe micro-analyzer. Sr marking signatures formed a peak in all otolith types, with a marking success rate of 100%. The ratio of Sr to Ca in the lapilli and sagittae was higher than that in the asterisci. It took 2 d from the beginning of immersion to the deposition of Sr on the lapilli and sagittae, and the time delay for asterisci was 1 d. For the lapilli and sagittae, it took 16 d to terminate Sr marking and fully recover to the pre-marking Sr level, whereas it was 12 d for the asterisci. The application of the Sr dose had no effect on the survival or growth of the carp. This study demonstrated that the lapilli are the most suitable otolith type for Sr marking observations in crucian carp and provides a theoretical basis and technical support for carp restocking using the Sr marking approach.

The effectiveness of chemical compounds for marking hard tissues in juvenile silver carp (Hypophthalmichthys molitrix) is not well known. We analyzed the use of alizarin complexone (ALC) as a fluorescent marker to mark the various hard structures of juvenile silver carp. Experimental fish (~2 months old) were randomly assigned to either control or marking groups, which were immersed in 0 or 100 mg/L ALC solutions, respectively, for 2 days. The otoliths, fin rays, and scales of the fish were then sampled, visualized using fluorescence microscopy, and evaluated after 10 days. The ALC treatment was effective for marking certain hard structures and the marking color was affected by the light source. There were no obvious differences in the marking efficiency of rays from pectoral, dorsal, ventral, anal, and caudal fins, but the lapilli and lateral line scales were marked most effectively from the sampled otolith and scale types, respectively. Our findings indicate that ALC immersion and fin ray and scale sampling can be used for the effective marking and non-lethal evaluation of hard structures in juvenile silver carp.

Harvest regulations are important tools that fisheries professionals use to impact fish abundance, alter population size structure, and improve fishing opportunities. Fisheries professionals often assume that specialized harvest regulations will have specific effects on target fish populations, but these predictions are not always realized because theory and practice do not always match (literature indicates that predictions are not met in about half of the cases). To identify trends that can improve the future success of harvest regulations, we reviewed a representative sample of harvest regulation evaluations for inland sport fish (i.e., 62 evaluations from 41 studies). Our review revealed gaps related to quantitative predictions, evaluation duration, statistical design, researcher–manager collaboration, and data standardization. Fisheries professionals can benefit from shared and thoughtful data collection designs and protocol standardizations. These designs can transform assessment sampling into empirical regulation evaluations that provide generality across locations and time periods with similar effort and cost.

Black Carp (Mylopharyngodon piceus) was imported to the USA to control aquaculture pond snails. This species has escaped captivity and occurs in parts of the Mississippi River, several tributaries, and floodplain lakes, which is concerning due to potential competition with native fishes and predation on native mussels, many of which are imperiled. However, Black Carp captures have primarily been incidental by commercial fishers, and evidence of reproduction in the wild is limited. The objectives of this study were to assess relative abundance of aquaculture-origin and wild Black Carp using ploidy and otolith stable isotope analysis, identify spatial extent of natural reproduction using otolith microchemistry, assess age distributions of wild and aquaculture-source Black Carp to infer years in which natural reproduction occurred and timing of aquaculture escapement or introductions, and estimate size and age at maturation to assess whether recruitment to adulthood has occurred. Results revealed that Black Carp are established in parts of the Mississippi River basin based on findings that: (1) non-captive Black Carp primarily consist of fertile, naturally-reproduced fish, (2) reproduction has occurred in several rivers, (3) multiple year classes of wild fish are present, and (4) wild fish have recruited to adulthood. Multiple introductions or escapements of aquaculture-source fish into the wild, including both fertile and functionally sterile individuals, were also inferred. Individual growth appears to be rapid, although considerable variation was observed among fish. Additional study is suggested to refine understanding of where and when Black Carp reproduction is occurring in the Mississippi River basin.

Despite potential importance of tributaries to Shovelnose sturgeon populations and historical declines range wide, limited population demographic and sampling efficiency information exists on shovelnose sturgeon populations in tributaries of the Upper Mississippi River. As such, we sought to evaluate the catch statistics of boat electrofishing, drifted trammel netting, and otter trawling for assessing shovelnose sturgeon populations on the Cedar River in Iowa. Trammel nets did not provide the highest estimate of CPUE or number of fish captured, however did provide the lowest CV of CPUE and thus required the least amount of effort needed to detect changes in relative abundance. Trammel netting also captured the widest size range of fish and most proportionate male:female ratio. If goals were to evaluate trends in relative abundance, male:female ratio, and spawning periodicity of females with the least amount of effort, trammel nets appear to be best suited. However, when sampling objectives require a large number of fish to be collected, the use of multiple gears may be appropriate. Our study highlights the need for an adaptive multi-gear sampling approach to properly evaluate shovelnose sturgeon in tributaries across the Upper Mississippi River.

Recruitment is one of the most important dynamic rate functions (i.e., recruitment, growth, and mortality). Often, recruitment can be heavily dependent on overwinter survival. Wintertime presents thermal and metabolic challenges to fish. Studies have suggested that overwinter survival and mortality is correlated to lipid content before entering winter. Inadequate lipid reserves are related to poor condition and may lead to overwinter mortality. Young fish need to accumulate adequate lipid reserves before entering winter. In the Mississippi River, where silver carp Hypophthalmichthys moltrix Valenciennes, 1844 are hyper abundant, silver carp are not experiencing recruitment issues. As such, we evaluated lipid levels and size as potential silver carp recruitment regulators. Silver carp were collected by the Long Term Resource Monitoring element in 2015 on the middle Mississippi River using mini fyke nets; total lengths ranged from 34-177 mm. Lipid levels of whole carp were determined using the phosphovanillin assay. No difference in lipid levels (mg/g) was observed between spring and fall fishes. Additionally, we observed no relation between total length and lipid levels. Size structure did not significantly differ between fall age-0 and spring age-1 silver carp. Our results suggest there may not be a size dependent overwinter mortality/survival in silver carp in the middle Mississippi River. Additionally, lipids may not be a driving factor in overwinter mortality/survival. Our research suggests silver carp in the Mississippi River basin do not follow most early life history paradigms and may explain the successful nature of the silver carp invasion.

North American Journal of Fisheries ManagementVolume 41, Issue 4 p. 889-890 Special Section: 4th Mississippi-Yangtze River Basins Symposium Introduction to a Special Section: 4th Mississippi–Yangtze River Basins Symposium Yushun Chen, Corresponding Author Yushun Chen yushunchen@ihb.ac.cn State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072 ChinaCorresponding author: yushunchen@ihb.ac.cnSearch for more papers by this authorQuinton Phelps, Quinton Phelps Department of Biology, Missouri State University, 901 South National Avenue, Springfield, Misssouri, 65897 USASearch for more papers by this author Yushun Chen, Corresponding Author Yushun Chen yushunchen@ihb.ac.cn State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072 ChinaCorresponding author: yushunchen@ihb.ac.cnSearch for more papers by this authorQuinton Phelps, Quinton Phelps Department of Biology, Missouri State University, 901 South National Avenue, Springfield, Misssouri, 65897 USASearch for more papers by this author First published: 27 August 2021 https://doi.org/10.1002/nafm.10684Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume41, Issue4Special Section: 4th Mississippi–Yangtze River Basins SymposiumAugust 2021Pages 889-890 RelatedInformation

Channel Catfish Ictalurus punctatus were collected during 2018 and 2019 from the Monongahela River in West Virginia using hoop nets to estimate population dynamics. Length, weight, sex, fecundity, and age data were obtained from collected individuals. Population characteristics (e.g., relative abundance, size structure, age structure, growth, etc.) were modeled under three proposed length limits of 300, 375, and 450 mm. Simulation results indicated that growth overfishing may occur when exploitation rates reach 36% under a 300-mm minimum length limit. Furthermore, recruitment overfishing began to occur at 40% exploitation under a 300-mm minimum length limit. Additionally, simulations suggest that no recruitment or growth overfishing occur at minimum length limits of 375 mm or 450 mm until extremely high exploitation levels (>90%) are reached. Thus, future consideration should be given for implementation of a 375-mm minimum length limit of Channel Catfish in the Monongahela River to prevent growth and recruitment overfishing while also ensuring anglers are still able to harvest Channel Catfish.

Channel catfish are important to the Mississippi River (i.e., ecologically, commercially, and recreationally). The dynamic rate functions (recruitment, growth, and mortality) of the population are important to proper management. However, different gears can produce varying estimates of these vital rates (e.g., size selectivity or age selectivity). We evaluated the effectiveness of three commonly used gear types for sampling channel catfish. Sampling was completed following United States Army Corps of Engineers' Long-Term Resource Monitoring (LTRM) element sampling protocol; pulsed direct current daytime electrofishing, baited 37 mm hoop nets (large hoop net), baited 18 mm hoop nets (small hoop net), and a tandem hoop net set that included one large and one small hoop net. A total of 65,222 channel catfish were collected from 1993 to 2017. Channel catfish catch rates were lowest using daytime electrofishing and large hoop nets, while tandem hoop nets and small hoop nets had higher catch per unit effort (CPUE). Furthermore, tandem hoop nets collected a broader size distribution of channel catfish in comparison to daytime electrofishing, large hoop nets, and small hoop nets. As such, we recommend that tandem hoop nets should be used to evaluate channel catfish populations in the Upper Mississippi River as well as other riverine systems.

Macroinvertebrates are important prey to various fishes at all life stages and in particular, Scaphirhynchus sturgeon species. Specifically, shovelnose sturgeon and pallid sturgeon survival and growth may be influenced by macroinvertebrate availability. We examined macroinvertebrate catch rates longitudinally (i.e., upstream to downstream), laterally (i.e., across the width of the river), and vertically (i.e., in the water column) to assess spatiotemporal drift patterns. A total of 3,414 samples were collected from April 15 to June 14 in 2018. Overall, 362,000 m(3) of Missouri and Mississippi River water was filtered during sampling, and 72,216 macroinvertebrates were captured. Trichoptera comprised 75% of the total macroinvertebrate drift sampled, while Diptera (9%), Ephemeroptera (13%), and Plecoptera (2%), comprised a much smaller portion. The average number per day of drifting invertebrates (i.e., Diptera, Ephemeroptera, Plecoptera, and Trichoptera) ranged from 6.8 million/d to 36.4 million/d. We found that catch rates of drifting macroinvertebrates differed among site, dates, and position in the water column. Furthermore, of the five a priori models that we developed, the interaction of spatial variables coupled with the temporal variable best describes variability in macroinvertebrate catch rates throughout our study. Efforts to increase macroinvertebrate habitat may provide additional prey resources for Scaphirhynchus sturgeon. Previous studies have demonstrated greater macroinvertebrate diversity and density in unchannelized rivers. The section of river from the Missouri River confluence downstream to the Mosenthein Island complex is unchannelized and may be a good candidate for habitat restoration. Increasing macroinvertebrate abundance and diversity may positively influence Scaphirhynchus sturgeon.