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Sturgeon immunity is relevant for basic evolutionary and applied research, including caviar‐ and meat‐producing aquaculture, protection of wild sturgeons and their re‐introduction through conservation aquaculture. Starting from a comprehensive overview of immune organs, we discuss pathways of innate and adaptive immune systems in a vertebrate phylogenetic and genomic context. The thymus as a key organ of adaptive immunity in sturgeons requires future molecular studies. Likewise, data on immune functions of sturgeon‐specific pericardial and meningeal tissues are largely missing. Integrating immunological and endocrine functions, the sturgeon head kidney resembles that of teleosts. Recently identified pattern recognition receptors in sturgeon require research on downstream regulation. We review first acipenseriform data on Toll‐like receptors (TLRs), type I transmembrane glycoproteins expressed in membranes and endosomes, initiating inflammation and host defence by molecular pattern‐induced activation. Retinoic acid‐inducible gene‐I‐like (RIG‐like) receptors of sturgeons present RNA and key sensors of virus infections in most cell types. Sturgeons and teleosts share major components of the adaptive immune system, including B cells, immunoglobulins, major histocompatibility complex and the adaptive cellular response by T cells. The ontogeny of the sturgeon innate and onset of adaptive immune genes in different organs remain understudied. In a genomics perspective, our new data on 100 key immune genes exemplify a multitude of evolutionary trajectories after the sturgeon‐specific genome duplication, where some single‐copy genes contrast with many duplications, allowing tissue specialization, sub‐functionalization or both. Our preliminary conclusion should be tested by future evolutionary bioinformatics, involving all >1000 immunity genes. This knowledge update about the acipenseriform immune system identifies several important research gaps and presents a basis for future applications.

Polypodium hydriforme is a parasitic cnidarian that develops within the eggs of acipenseriform fish in the Old and New Worlds. Currently regarded as monotypic, P. hydriforme has been studied largely in the context of caviar production in Russian sturgeon species. We report the first robust epidemiological study of P. hydriforme in North American acipenseriform fish. We sampled infection prevalences (in 2017 and 2018) and intensities (in 2017) during annual surveys of American Paddlefish, Polyodon spathula, caught during spawning migration in north-eastern Oklahoma. Egg masses were characterized for the presence and intensity of P. hydriforme infection. Prevalences were similar in 2017 and 2018 (49% and 45%, respectively). Generally, a small number of eggs were infected per egg mass, but a few were heavily infected. Longer, heavier and older fish are more likely to be infected and to harbour more severe infections. In addition, infection is linked to decreases in roe fat weight independently of fish length, weight, age or roe weight. Infection thus diminishes Paddlefish energy reserves (roe fat) which could in turn impact host fitness. Our results raise questions about the impacts of infection on caviar production and Paddlefish conservation and suggest insights on infection dynamics and parasite strategies.

Excessive fishing pressure can induce population declines or complete collapse of fisheries. Unless commercial and recreational fisheries for K‐selected fishes, or those with slow growth and late maturation, are carefully managed, declines in abundance or fishery collapse is probable. Paddlefish Polyodon spathula,are a K‐selected species that experienced historical declines in abundance as a result of habitat degradation and overfishing. Mark‐recapture studies are well‐suited for long‐lived fishes by providing information on population density and vital rates. For sustainable commercial or recreational fisheries targeting species such as the paddlefish, managers require accurate estimates of population vital rates including survival, abundance, and exploitation. We used a Montana Fish, Wildlife & Parks (MFWP) mark‐recapture dataset and modified Jolly‐Seber (POPAN) models to estimate survival, recapture, probability of entry, and abundance of 8,518 tagged paddlefish over a 25‐year period. With many supporting estimates including stable survival (0.92 for females, mean of 0.82 for males), low exploitation rates (means of 2.6% for females and 2.9% for males), and stable abundance estimates (25‐year mean of 12,309 individuals for both sexes), the Fort Peck paddlefish population appears to be stable and well‐managed over the past 25 years. Presently, this is the only study focused on paddlefish in North America that has estimated survival and abundance for both male and female paddlefish using contemporary analyses. This research provided a unique opportunity to highlight that the effort exerted by management agencies to collect long‐term field data is extremely useful to our understanding of fish populations and management.

Acipenseriformes (sturgeons and paddlefish) globally have declined throughout their range due to river fragmentation, habitat loss, overfishing, and degradation of water quality. In North America, pallid sturgeon (Scaphirhynchus albus) populations have experienced poor to no recruitment, or substantial levels of hybridization with the closely related shovelnose sturgeon (S. platorynchus). The Lower Missouri River is the only portion of the species’ range where successful reproduction and recruitment of genetically pure pallid sturgeon have been documented. This paper documents spawning habitat and behavior on the Lower Missouri River, which comprises over 1,300 km of unfragmented river habitat. The objective of this study was to determine spawning locations and describe habitat characteristics and environmental conditions (depth, water velocity, substrate, discharge, temperature, and turbidity) on the Lower Missouri River. We measured habitat characteristics for spawning events of ten telemetry‐tagged female pallid sturgeon from 2008–2013 that occurred in discrete reaches distributed over hundreds of kilometers. These results show pallid sturgeon select deep and fast areas in or near the navigation channel along outside revetted banks for spawning. These habitats are deeper and faster than nearby river habitats within the surrounding river reach. Spawning patches have a mean depth of 6.6 m and a mean depth‐averaged water‐column velocity of 1.4 m per second. Substrates in spawning patches consist of coarse bank revetment, gravel, sand, and bedrock. Results indicate habitat used by pallid sturgeon for spawning is more common and widespread in the present‐day channelized Lower Missouri River relative to the sparse and disperse coarse substrates available prior to channelization. Understanding the spawning habitats currently utilized on the Lower Missouri River and if they are functioning properly is important for improving habitat remediation measures aimed at increasing reproductive success. Recovery efforts for pallid sturgeon on the Missouri River, if successful, can provide guidance to sturgeon recovery on other river systems; particularly large, regulated, and channelized rivers.

In this study we quantified the percent CaCO3 polymorph composition in otoliths of larval and juvenile Lake Sturgeon Acipenser fulvescens via X-ray microdiffraction. Sagittal otoliths of sub-adults were primarily composed of aragonite (> 90%) while the lapilli otoliths were 100% vaterite. This is the first time the presence of aragonite in otoliths has been reported in an acipenseriform and is surprising given that the ability to form aragonite otoliths was not thought to have evolved until the separation of teleost and holostean species from other Actinopterygian fishes (e.g., sturgeon, paddlefish, gar).

Melatonin (MLT) is a well-known antioxidant and can improve sperm quality during storage in many species. In the present study, the effects of different concentration of MLT (0.1, 0.5, 1 and 5 μM) on paddlefish sperm quality and ATP content in sperm were evaluated during semen storage at 4 °C. Compared with other groups, 0.5 μM MLT supplement in semen could be more effective to improve the plasma membrane integrity, maintain the steady reactive oxygen species (ROS) level and inhibit decrease of mitochondrial membrane potential of the non-activated sperm during whole storage. To the activated sperm, the total motility, progressive motility, beat cross frequency of sperm in semen with 0.5 μM MLT was significant higher (p

This study reports the first cases of intersex (abnormal development of both male and female reproductive tissues in a gonad) paddlefish Polyodon spathula, an Acipenseriform species of large rivers in the central U.S. and in aquaculture worldwide. Despite a large, multi-decadal data set in Oklahoma, Montana, and North Dakota, intersex development was not observed until 2019, when two individuals were harvested from the Grand Lake/Neosho River stock in Oklahoma. This suggests that intersex development in mid-water, zooplanktivorous paddlefish is rarer than in bottom-dwelling sturgeons for which intersex development is regularly observed. Although contaminants are implicated in causing intersex development in other Acipenseriformes, more investigation is needed.

Although sturgeons and paddlefish represent a highly endangered species group, knowledge regarding their ecology, life history and management and restoration measures still reveals substantial gaps and uncertainties. As such, it was hypothesized that the information on overall experiences and perspectives of researchers working in the field would provide a good indication of the state of knowledge, and help identify areas for further investigation. To gain in‐depth insight into their perspectives on a variety of topics related to sturgeon life history, management and conservation, as well as opinions on issues characterized by a lack of data, a worldwide online survey was conducted among scientists specializing in sturgeon and paddlefish research. With a total of 277 respondents, the response rate was good (40.3% of those invited). The survey results indicated a high level of uncertainty with regard to various aspects of sturgeon life history, such as spawning migrations, reproduction and senescence. Responses differed largely with the origin and the research focus of the participants. Agreement on reported extreme dimensions and lifespans of sturgeons varied among species, but the level of agreement was generally higher among those scientists working on the species in question. Responses on major threats varied regionally, with dams and habitat fragmentation recognized as the major threats by researchers from North America, whereas poaching was considered the dominant threat in Europe and Asia. Sturgeon aquaculture was generally considered as having a positive effect on sturgeon protection by reducing the pressure on natural populations. The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) was recognized as the most effective instrument in international sturgeon conservation. While sturgeons are generally perceived as flagship species, especially in Europe, participants questioned their potential utilization as umbrella species. Beside providing an insight into the available scientific information and the general level of consensus regarding some of the questions tackled, the results also created a basis for further discussion within the scientific community concerning the validity, relevance, and application of the published information and future research priorities.

Order Acipenseriformes (sturgeons and paddlefishes) is an ancient lineage of osteichthyan fishes (>200 million years old) with most extant species at conservation risk. A relatively basal species, the pallid sturgeon, Scaphirhynchus albus, is a federally endangered species native to the Mississippi and Missouri River basins. Hybridization with sympatric shovelnose sturgeon, S. platorynchus, is one of several threats to pallid sturgeon. Current molecular markers cannot reliably distinguish among pure species and multigenerational backcrosses. This information is critical for implementation of management strategies to increase populations through natural reproduction and artificial propagation. Genotypes from a large panel of unlinked single-nucleotide polymorphisms (SNPs) may provide greater resolution of the two species; however, paralogous sequence variants (PSVs) within individuals resulting from an ancient whole genome duplication event confound SNP development. The aim of this study was to produce pallid sturgeon gynogens that contain 100% homozygous DNA contributed by only the maternal parent and have enough DNA for future SNP marker development. When homozygous gynogens are sequenced, heterozygosity at a locus within an individual indicates the presence of incorrectly aligned sequences that contain PSVs; accurate identification of these multi-locus contigs can facilitate their exclusion when developing disomic markers. In this study, we attempted to produce two types of pallid sturgeon gynogens: a) haploid gynogens produced from the activation of pallid sturgeon eggs with ultraviolet-irradiated sperm from the distantly related paddlefish (Polyodon spathula), and b) doubled haploids produced from the activation of pallid sturgeon eggs with irradiated paddlefish milt followed by thermal shock to suppress the first mitotic division. Production of doubled haploids, gynogens with 100% homozygous DNA and double the genome content of haploid gynogens, was pursued because it was originally unknown if haploid gyongens would survive long enough to attain enough genetic material for SNP marker development. We performed flow cytometry and microsatellite genotyping on the specimens in order to confirm haploid and doubled haploid status. Our study was unable to successfully yield doubled haploids; however, we successfully produced haploid gynogens that contained enough nuclear DNA for our future SNP marker development study. Interestingly, this study also produced paddlefish × pallid sturgeon hybrids in the control groups in two separate years; this is the first study to report viable offspring between the paddlefish and a Scaphirhynchus sturgeon species and reflects on the malleability of the genomes of the species in this order.

Summary The objective of this study was to investigate lipid accumulation and storage in age-0 and age-1 paddlefish Polyodon spathula (Walbaum, 1792) in relation to age, stock, year, and growth. Juvenile paddlefish were collected from three locations in North Dakota and Montana, USA, during July and August of 2011 and 2012 and proximate analysis was used to determine lipid content. RNA/DNA ratios were used as an index of growth rates. Differences in age-based lipid accumulation and storage in juvenile paddlefish suggest a split allocation between growth and lipid storage, with growth being the highest initial priority and emphasis on energy storage occurring at a larger size, later in life. Differences in lipid allocation between stocks indicate that allocation is influenced by hatchery/wild rearing conditions. Differences within and between year-classes are consistent with field evidence observed in 2012 of a strong 2011 year-class, and indicate that during productive times, paddlefish may allocate energy to both body growth and lipid reserves, and that allocation differs among years. The lack of a relationship between RNA/DNA ratio and lipid does not support a physiologically exclusive allocation strategy between growth and lipid. Evidence from this and other studies suggests rather that an emphasis on growth, some energy storage, and a large rostrum size in relation to overall fish length in age-0 and age-1 fish, may be adaptive in avoiding predation while accruing necessary energy reserves for overwintering. Although this study also provides reference information regarding proximate composition of wild and hatchery origin juvenile paddlefish, much more study is needed into the relationships among growth, low and high lipid groups, lipid allocation in juvenile paddlefish as well as the existence and timing of allocation changes between growth and storage. To aid in understanding paddlefish survival and year-class strengths, these relationships also need to be linked to inter-annual differences in early rearing environments for age-0 and age-1 fish.

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...

This study sought to resolve whether sturgeon (Acipenseridae) sagittae (otoliths) contain a non-vaterite fraction and to quantify how large a non-vaterite fraction is using neutron diffraction analysis. This study found that all otoliths examined had a calcite fraction that ranged from 18 ± 6 to 36 ± 3% by mass. This calcite fraction is most probably due to biological variation during otolith formation rather than an artefact of polymorph transformation during preparation.

The objectives of this study were to characterize relationships between water and paddlefish Polyodon spathula dentary Sr:Ca, δ18 O and stable hydrogen isotope ratio (δD) to determine the accuracy with which individual P. spathula could be assigned to their collection locations using dentary-edge Sr:Ca, δD and δ18 O. A laboratory experiment was also conducted to determine whether dentary Sr:Ca in age 0 year P. spathula would reflect shifts in water Sr:Ca to which fish were exposed. Significant linear relationships between water and dentary Sr:Ca, δD and δ18 O were observed, although the relationship between water and dentary δ18 O was weaker than those for Sr:Ca and δD. Classification success for individual fish to collection locations that differed in water Sr:Ca, δD and δ18 O ranged from 86 to 100% based on dentary-edge Sr:Ca, δD and δ18 O. Dentary Sr:Ca increased significantly in laboratory-reared age 0 year P. spathula following 4 weeks of exposure to elevated water Sr:Ca; dentary Sr:Ca of fish held in water with elevated Sr:Ca was also significantly higher than that of control fish reared in ambient laboratory water. Results indicated that P. spathula dentaries reflect water signatures for commonly-applied natural chemical markers and strongly suggest that dentary microchemistry and stable-isotopic compositions will be applicable for reconstructing P. spathula environmental history in locations where sufficient spatial differences in water chemistry occur.

The American paddlefish, Polyodon spathula (Walbaum), is an endangered acipenserid fish. Its wild populations are supplemented with stocking material that is obtained by conducting artificial spawning in aquaculture conditions. When fish are bred in captivity, it is important to select breeding pairs that will produce the most genetically diverse progeny, since this permits maintaining the fitness of wild populations. Breeding pairs of land animals are selected successfully based on the polymorphism of their microsatellite loci. This theoretical paper asks how to adapt this technique to fish so that American paddlefish spawners can be paired with the aim of producing restocking material in aquaculture that maintains genetic variation. To test our calculating techniques, we used actual data on the polymorphism of the microsatellites from paddlefish broodstock at the Pogorze fish farm (Poland). The data enabled us to do calculations that showed which spawner pairs would create the most genetically diverse offspring and how to assemble sets of spawning pairs that would be best for maintaining genetic variation. The method presented in this paper can be used for breeding fish in aquaculture to help conserve species. It could also be used in a computer program which would automate calculations and present them in easy-to-read tables and graphs. CORRESPONDING AUTHOR: D. Kaczmarczyk [+] Department of Environmental Biotechnology University of Warmia and Mazury in Olsztyn, ul. Sloneczna 45G, 10-718 Olsztyn, Poland, e-mail: d.kaczmarczyk@uwm.edu.pl

Nonnative bigheaded carps are established in the Mississippi River and there is substantial concern about their potential entry into the interconnected Laurentian Great Lakes. While electrical barriers currently exist as a preventative measure, there is need for additional control mechanisms to promote barrier security through redundancy. We tested the effectiveness of infused carbon dioxide gas (CO2) as a tool to influence the movement and behavior invasive bigheaded carps, namely Bighead Carp Hypophthalmichthys nobilis and Silver Carp H. molitrix, as well as native Bigmouth Buffalo Ictiobus cyprinellus, Channel Catfish Ictalurus punctatus, Paddlefish Polyodon spathula, and Yellow Perch Perca flavescens in an experimental pond. Individuals were monitored with acoustic telemetry before, during, and after CO2 addition to the pond. We noted distinct changes in fish behavior following CO2 addition. Each species except Paddlefish maintained farther distances from the CO2 infusion manifold relative to ...

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.

The role of gastrointestinal microbiome has long been proven to be crucial in the nutrition uptake and metabolism of host. In paddlefish (Polyodon spathula), a greater proportion of Gammaproteobacteria, Fusobacteriia, Clostridia, Alphaproteobacteria were found in esophagus and stomach, whereas intestine was predominated by Fusobacteriia, Gammaproteobacteria, and Bacteroidia detected by 16s RNA sequencing. Shannon diversity index and microbial richness decreased along the digestive tract, and a significantly higher proportion of Cetobacterium was observed in intestine, following by a remarkable alteration in the structure of microbial community in intestine compared to esophagus and stomach. Through species-species interactions, microbiome formed unique ecological networks to adapt the distinct physicochemical conditions in esophagus, stomach, and intestine, and dominant microflora was the major component of these networks. Within these networks, many bacterial strains from the dominant microbiota served important ecological roles such as module hubs or connectors, which contributed in maintaining the stability of the microbial community. The microbial cooperative interactions predominated along the digestive tract, and the lowest proportion of competitive interactions was observed in stomach. Microbial function composition in intestine, predicted by function analysis, significantly differed from that in esophagus and stomach. Specially, in terms of nutrition metabolism, the intestinal microbial community exhibited a high capacity in carbohydrate fermentation compared with that in esophagus and stomach. These results suggested that the microbial composition and function in intestine were significantly different from that in esophagus and stomach of paddle fish. Moreover, complex species-species interactions may promote the adaptation of microbiome to the physiological environment of the host.

The paddlefish (Polyodon spathula) was first introduced to Europe in 1974, mainly due to its potential for rearing in natural polyculture ponds and large temperate reservoirs. The information on the history of paddlefish aquaculture efforts in Europe is scarce, as well as data on current paddlefish aquaculture status and trends. In addition, there is a lack of data on its presence and potential establishment in the wild, while its invasive potential and associated risks and impacts are largely unknown. In order to evaluate its current status in Europe, we conducted a survey among scientists, aquaculture producers and other stakeholders, and reviewed literature and data on the Internet. Based on the results obtained, we discuss the potential and the challenges in European paddlefish aquaculture development, and analyze paddlefish invasive potential and risks associated with its naturalization. Paddlefish aquaculture is well established only regionally in Europe, but offers relatively high potential for further development in pond farms. Nevertheless, future development will require careful planning, especially regarding market development and improved marketing strategies. While paddlefish likely represents a low-risk invader, improved control and reporting on trade and intentional and unintentional releases will be required. Given the lack of knowledge on potential impacts following its introduction, due caution seems highly advisable. This is the peer reviewed version of the following article: Jarić I, Bronzi P, Cvijanović G, Lenhardt M, Smederevac-Lalić M, Gessner J. Paddlefish (Polyodon spathula) in Europe: An aquaculture species and a potential invader. J Appl Ichthyol. 2018, which has been published in final form at [http://doi.org/10.1111/jai.13672]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.

Intensive production of ictalurid catfish in the USA has increased over the past several years, and a better understanding of the amount of organic carbon (OC) and dissolved oxygen (DO) in these culture environments is needed. Budgets for OC and DO were estimated over a production season (March to November) for an in-pond raceway system for channel catfish, Ictalurus punctatus, and hybrid catfish (channel catfish × blue catfish, Ictalurus furcatus), with co-culture of paddlefish, Polyodon spathula, and Nile tilapia, Oreochromis niloticus. Feed input ranged from 45 to 263 kg/ha/d with an overall average of 80 kg/ha/d. Production of each kilogram of live catfish required 1.5 kg of feed and released into the water 0.70 kg of OC, and led to the synthesis of an additional 3.36 kg of OC by photosynthesis. Consequently, production of 1 kg of live catfish resulted in 4.06 kg OC, and harvest of catfish accounted for only 29.5% of OC applied from the feed. Removal of OC increased to 34.3% with the additional harvest of paddlefish and tilapia. OC was consumed in respiration, and some OC accumulated in sediment. Total respiration within the system exceeded the DO produced by photosynthesis, while diffusion and mechanical aeration aided in maintaining suitable DO levels for fish production.

Dams have many effects on river systems, including impeding the migratory movements of fishes. However, locks associated with lock-and-dam structures may be useful for passing fish during their migrations. We investigated the potential to facilitate fish passage at dams through two navigational lock structures on the Alabama River, Alabama—Millers Ferry Lock and Dam (L&D) and Claiborne L&D—using targeted, nonnavigational lock operations. The movements of Paddlefish Polyodon spathula with implanted ultrasonic tags and/or radio tags were tracked via both manual receivers and submersible ultrasonic receivers (SURs) deployed inside of the lock chambers and above and below each dam to quantify migration characteristics and determine whether fish passage occurred. We tagged a total of 96 fish (79 received sonic tags, 4 received radio tags, and 13 received both types of tag), and we recorded over 275,000 SUR detections of 84 individuals and 91 manual detections of 39 individuals. Although nonnavigational...

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 ...

Ram suspension-feeding fishes swim with an open mouth to force water through the oral cavity and extract prey items that are too small to be pursued individually. Recent research has indicated that, rather than using a dead-end mechanical sieve, American paddlefish (Polyodon spathula Walbaum) employ vortical cross-step filtration. In this filtration mechanism, vortical flow that is generated posterior to the branchial arches organizes crossflow filtration processes into a spatial structure across the gill rakers. Despite the known impact of locomotor kinematics on fluid flow around the bodies of swimming fish, the effects of locomotor kinematics on filtration mechanisms in ram suspension feeders are unknown. Potential temporal organization of filtration mechanisms in ram suspension-feeding fish has not been studied previously. We investigated the effects of locomotor kinematics associated with undulatory swimming on intra-oral flow patterns and food particle transport. A mechanized model of the oral cavity was used to simulate the swimming kinematics of suspension-feeding paddlefish. We recorded fluctuations of flow speed and pressure within the model, which occurred at a frequency that corresponded with the frequency of the model's strides. Using the mechanized model in a flow tank seeded with Artemia cysts, we also showed that swimming kinematics aided the transport of this simulated food to the posterior margins of the gill slots, although the time scale of this transport is expected to vary with prey parameters such as size and concentration. Dye stream experiments revealed that, while stable vortical flow formed due to flow separation downstream of backward-facing steps in control trials, vortical flow structures in mechanized trials repeatedly formed and shed. These findings suggest strong integration between locomotor and feeding systems in ram suspension-feeding fishes.

The effects of dietary supplementation of probiotics on digestive enzymes activities, intestinal morphology and microbiota in juvenile paddlefish (Polyodon spathula) were studied. A total of 400 fish were reared in two cages and fed with a basal diet (control group, CG) or diet supplemented with commercial probiotics (treatment group, TG) for 80 days. Enzymes activities analysis indicated that protease and α-amylase activities increased (P

Spawning of the federally endangered Pallid Sturgeon Scaphirhynchus albus is known to occur in the upper Missouri River basin, but progeny from natural reproductive events have not been observed and recruitment to juvenile or adult life stages has not been documented in recent decades. Identification of Pallid Sturgeon progeny is confounded by the fact that Shovelnose Sturgeon S. platorynchus occurs throughout the entire range of Pallid Sturgeon and the two species are essentially indistinguishable (morphometrically and meristically) during early life stages. Moreover, free embryos of sympatric Paddlefish Polyodon spathula are very similar to the two sturgeon species. In this study, three single-nucleotide polymorphism (SNP) assays were employed to screen acipenseriform free embryos and larvae collected from the upper Missouri River basin in 2011, 2012, and 2013. A mitochondrial DNA SNP discriminates Paddlefish from sturgeon, and specific multilocus genotypes at two nuclear DNA SNPs occurred in 98...

Summary The food preferences of paddlefish (Polyodon spathula) in polyculture with bighead carp (Aristichthys nobilis) are unknown. Three consecutive analyses of gastrointestinal contents of paddlefish and bighead carp were conducted at 3d, 11d and 19d after introduction into the non-fed ponds. The objectives of this study were to test for competitive interactions between bighead carp and paddlefish, and to document their preferred prey when the two species have a limited food resource. The results showed that paddlefish and bighead carp are basically competitive in their diets. When they were cultured in one pond at the same density, paddlefish fed more quickly and efficiently, depleting the food resources for bighead carp; however, bighead carp were able to switch and trap small food items with the decrease in available food resources. Moreover, larger zooplankton abundance declined in ponds after fish were introduced.

Gillnetting and radiotelemetry were used to evaluate the reintroduction of Paddlefish Polyodon spathula into Allegheny Reservoir, New York–Pennsylvania. Gillnetting produced 86 total captures over 6,943 h of effort in the spring and early summer of 2008–2011. Forty-four of these individuals received implanted radio transmitters and were tracked from May 2008 to August 2011. Paddlefish showed a strong preference for reservoir sections where depths ranged from 6 to 18 m; only one individual was located in water greater than 18 m in depth. One sexually mature Paddlefish was identified, but telemetry data showed no evidence of reproduction, with only one individual making use of available riverine habitat that was predicted to be ideal for spawning. Paddlefish were susceptible to passage through Kinzua Dam: 46% of radio-tracked individuals left the reservoir during the study period. Continued efforts to evaluate Paddlefish reintroduction in Allegheny Reservoir should now focus on (1) assessing natural...

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.

Reclaimed water is treated wastewater that has received at least secondary treatment and basic disinfection and is reused for beneficial purposes. The goal of this study was to develop a safe and reliable sustainable aquaculture system for producing stocker fish using reclaimed water in decommissioned wastewater treatment plants (WWTP) in Kentucky. The specific objectives were (1) to monitor paddlefish, Polyodon spathula, growth and survival and water quality in experimental tanks with static or flow-through reclaimed water, (2) to evaluate the use of decommissioned tanks for large-scale production of phase II paddlefish, and (3) to biomonitor paddlefish grown in reclaimed water for contaminants. Phase I paddlefish (11 ± 2.6 g) were produced by feeding live Daphnia collected daily from the clarifier tanks with hand-pulled nets for 27 d. Phase II paddlefish were produced in four replicated 5600-L experimental tanks with static and flow-through reclaimed water. Paddlefish from the flow-through system were significantly larger (199.2 ± 61 g) and had better feed conversion ratios (2.8 ± 2.1) than those from the static system (135.5 ± 51 g; 4.1 ± 1.6). For the large-scale trial, two 1125 m3 decommissioned digester tanks were stocked with 50,000 paddlefish larvae per tank. One tank was treated as a flow-through system with reclaimed water flowing at a rate of 280 L/min, while the other tank was treated as a static system where water was just added to replace that lost by evaporation. Survival rate (40%) and weight (194.1 ± 25.4 g) from the flow-through system were significantly different from those of the static system (31%; 147.1 ± 6.5 g). This difference could be linked to better water quality in the flow-through systems. Analyses for 38 contaminants were conducted on Daphnia, prepared diets, and paddlefish. All the concentration levels detected were at levels well below the FDA action limits and their permissible limits in edible food. The result from this project showed that paddlefish can be successfully produced in large-scale as stocker fish using reclaimed water in decommissioned tanks at WWTP.

Virtual population analysis (i.e., cohort analysis) was conducted on the Yellowstone–Sakakawea paddlefish Polyodon spathula stock to evaluate recruitment patterns using a combined Montana–North Dakota dataset from the recreational snag fishery over the period 1993–2012. Distinct differences were found in the pattern of reconstructed virtual population sizes of the sexes. There existed a sharp increase in virtual male population size related to first recruitment only for the 1995 year-class. A much smaller increase was found in the female virtual population sizes because the female fish had just begun to recruit as of 2012. Episodic paddlefish recruitment seen in this study and elsewhere (e.g., Oklahoma) is probably common in other Acipenseriform stocks and may have an adaptive basis. However, adequate sex-specific age structure information is not available in many stocks for recruitment variations to be confirmed. Evidence suggests that episodic recruitment in the Yellowstone–Sakakawea paddlefish and othe...

Many fish of aquacultural importance including sturgeon and paddlefish have a history of polyploidy in their evolutionary lineages. Spontaneous autopolyploids have been detected in several sturgeon species in culture despite the fact that the induction of triploidy is not a management tool in farming sturgeon for meat and caviar. In 2010, we discovered two female spontaneous autopolyploid white sturgeon (Acipenser transmontanus) on a commercial caviar farm that had successfully produced offspring of intermediate ploidy in crosses with normal males. Here we use flow cytometry and microsatellite genotyping to screen a second aquaculture program for the presence of spontaneous autopolyploids. Flow cytometry of female parents and their progeny in the 2011 year class created by the Kootenai River white sturgeon conservation aquaculture program revealed that wild caught females used as dams possessed normal ploidy (8N). Five of ten families sampled from the 2011 year class contained spontaneous autopolyploids possessing DNA content consistent with dodecaploidy (12N). The percent of autopolyploid individuals sampled ranged from 0 to 33% per family, and the total number of spontaneous autopolyploids in the 2011 year class was 12/150 (8%). Microsatellites were not useful in detecting spontaneous autopolyploids in the conservation aquaculture program due to low levels of genetic diversity in the endangered Kootenai River population. The two families with the highest incidence of spontaneous autopolyploids (33% and 26% of offspring sampled) were sired by a single male, suggesting a paternal effect on the generation of spontaneous autopolyploids in white sturgeon.

For effective conservation, it is important to explore the environmental cues initiating the spawning activities of a fish species. Based on monitoring data gathered between 1998 and 2011, the relationships between spawning activities of the Chinese sturgeon, Acipenser sinensis, and several environmental cues were analyzed using the rare events logistic regression Relogit' method, which indicated that water temperature, 1-day -discharge, and atmospheric pressure were among the key spawning cues for A.sinensis (P

Equilibrium yield models predict the total biomass removed from an exploited stock; however, traditional yield models must be modified to simulate roe yields because a linear relationship between age (or length) and mature ovary weight does not typically exist. We extended the traditional Beverton–Holt equilibrium yield model to predict roe yields of Paddlefish Polyodon spathula in Kentucky Lake, Tennessee–Kentucky, as a function of varying conditional fishing mortality rates (10–70%), conditional natural mortality rates (cm; 9% and 18%), and four minimum size limits ranging from 864 to 1,016 mm eye-to-fork length. These results were then compared to a biomass-based yield assessment. Analysis of roe yields indicated the potential for growth overfishing at lower exploitation rates and smaller minimum length limits than were suggested by the biomass-based assessment. Patterns of biomass and roe yields in relation to exploitation rates were similar regardless of the simulated value of cm, thus indic...

Attempts to mitigate lack of formal interjurisdictional paddlefish management have been made in the United States through the Mississippi River Interstate Cooperative Resource Association (MICRA). We used 1988–2009 data from the MICRA paddlefish (Polyodon spathula) stock assessment database—a database containing mark-recapture and biometric information on more than 30,000 individually marked wild paddlefish and more than 2 million hatchery origin paddlefish—to estimate survival and movement across large and potentially biologically relevant spatial scales. Paddlefish frequently moved between political jurisdictions with differing conservation strategies and harvest regulations and showed differences in survival parameter estimates throughout their range. We argue that the degree of interjursidictional movements, spatially variant survival rates, and conservation concerns associated with paddlefish necessitate more cohesive interjurisdictional management. Based on criteria used to establish flyway...

Most large rivers within the range of paddlefish Polyodon spathula are fragmented by dams. However, little research has been done to determine if population characteristics (e.g., growth, mortality, density) vary among impoundments within river systems and how this may influence the risk of overfishing. Population characteristics and the potential for commercial overfishing were assessed for paddlefish in three impoundments of the Arkansas River, Arkansas (Pool 13, Ozark Lake, and Lake Dardanelle). Paddlefish (n = 751) were collected with gill nets from November 2003 to March 2005. Paddlefish from the most lentic and most heavily fished pool, Lake Dardanelle, had the lowest catch rate, grew fastest, and had the highest mean condition factor, weight, fecundity, and total annual mortality (67%). In contrast, paddlefish from the most lotic impoundment that was less intensively fished, Pool 13, had the highest catch rate, slowest growth, and the lowest mean condition, weight, fecundity, and total ann...

The lesser-spotted dogfish (Scyliorhinus canicula) and the North American paddlefish (Polyodon spathula) are two emerging model systems for the study of vertebrate craniofacial development. Notably, both of these taxa have retained plesiomorphic aspects of pharyngeal endoskeletal organization, relative to more commonly used models of vertebrate craniofacial development (e.g. zebrafish, chick and mouse), and are therefore well suited to inform the pharyngeal endoskeletal patterning mechanisms that functioned in the last common ancestor of jawed vertebrates. Here, we present a histological overview of the condensation and chondrogenesis of the most prominent endoskeletal elements of the jaw, hyoid and gill arches - the palatoquadrate/Meckel's cartilage, the hyomandibula/ceratohyal, and the epi-/ceratobranchial cartilages, respectively - in embryonic series of S. canicula and P. spathula. Our observations provide a provisional timeline and anatomical framework for further molecular developmental and functional investigations of pharyngeal endoskeletal differentiation and patterning in these phylogenetically informative taxa.

Summary The aim of the study was to determine whether location and sex affected the age precision estimates between two southern, reservoir populations of paddlefish [Polyodon spathula (Walbaum, 1792)]. From 589 paddlefish collected in Grand Lake and Keystone Lake, Oklahoma in 2011, ages from dentaries were estimated using three independent readers and precision was compared with coefficient of variation between locations and sexes. Ages were more precisely estimated from Grand Lake and from females.

Summary Spawning activity of paddlefish Polyodon spathula in the Missouri River, Montana in 2008–2009 was examined to delineate spawning sites and times in relation to discharge, water temperature and turbidity. One hundred thirty-six eggs were collected at water temperatures ranging from 12.0 to 20.7� C (mean, 16.3� C; SD, 2.5). Only 12 of 89 (13%) congregations of radio-tagged adults observed during the spawning period coincided with egg captures. Six larvae were collected at water temperatures ranging from 19.1 to 21.7� C (mean, 20.5� C; SD, 0.86). Peak discharge in 2008 (903 m 3 s )1 on 14 June) was approximately 30% greater in magnitude and occurred 11 days later than peak discharge in 2009 (612 m 3 s )1 on 3 June). Despite these differences in the hydrograph, no significant differences in egg CPUE were found between years (ANOVA, F = 0.69, P = 0.56). Logistic regression identified no significant river condition variables associated with the presence or absence of eggs (P > 0.14 for all variables). However, in both years maximum egg CPUE was recorded within 3 days of the hydrograph peak and at similar water temperatures (17.5� C in 2008, 16.8� C in 2009). These results suggest an overall association of peaking discharge and seasonally warming water temperatures with egg deposition. Higher catches of eggs and larvae than observed in this study may be necessary to clarify short-term (day-to-day) effects of environmental changes on spawning activity. Continued investigation of the relationship between short-term changes in river conditions and paddlefish spawning activity is needed to understand the mechanics underlying the reproductive success of this species.