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Conservation aquaculture programs that release fish to supplement wild populations can potentially capture greater genetic diversity by collecting offspring as embryos and larvae from wild spawning events than by producing them conventionally from broodstock. A conservation aquaculture program for the endangered white sturgeon population of the Upper Columbia River initially utilized wild broodstock for 14 years before fully transitioning to rearing wild-origin offspring in 2014. Here we evaluated the performance of this program in capturing the wild population’s genetic diversity since transitioning to wild-origin offspring. We analyzed genotypes of 325 tetrasomic single nucleotide polymorphism (SNP) markers in more than 5,000 offspring reared from 2014 to 2020 and over 1,000 wild adults from the population. Genetic diversity statistics were highly similar between each offspring year class and the wild adult population. We inferred sibship structure to estimate the total number of spawners (Ns) and effective number of breeders (Nb) represented within each year class and found values as high as 932.5 (95% CI 876–989) and 146.3 (95% CI 144–149), respectively, far surpassing the numbers included as broodstock. We further estimated Ns and Nb for three year classes with their individuals that died in aquaculture and found that on average, the mortality rate of 33.2% decreased Ns by 21.5% and Nb by 7.9%. Finally, we analyzed relationship coefficients to identify full-sibships spanning collection sites and found them in one year class, comprising 0.27% of all full-sibling pairs that year, demonstrating that the separate sites display negligible redundancy with respect to sibling families collected. Our results illustrate a robust performance by this program in representing the wild population’s diversity compared to broodstock approaches and support the adoption of utilizing wild-origin offspring in other conservation aquaculture programs when feasible.

While conservation fish hatchery programs can be a valuable tool providing demographic support, they can also cause domestication, risking unintended fitness consequences to both target and connected populations. When conservation hatcheries are used over a fixed amount of time, the interaction between program duration and species life history might determine the scale of fitness effects and the effectiveness of mitigation measures. We develop a mathematical model to quantify the effectiveness of approaches to mitigate unintended fitness consequences in such temporary conservation hatchery programs. We parameterize our model to represent a conservation aquaculture-based recovery program for white sturgeon (Acipenser transmontatus) in the Nechako River (British Columbia), which might impose genetic risks on the adjacent populations within the Fraser River. We find that over a period spanning 50–200 years of hatchery operation, the life history characteristics of white sturgeon, particularly late age of maturity and longevity, reduce the genetic risks of conservation hatcheries when compared to shorter-lived species. The genetic impacts of the hatchery accumulate slowly increasing the potential for adaptive management in this system.

Conservation aquaculture has prevented extirpation of Upper Columbia River white sturgeon Acipenser transmontanus, but uncertainty remains on how hatchery-origin fish move between habitats located within Canada and the United States. We describe how core and home ranges of sturgeon varied by environmental (country, season) and biological (age, sex, size) factors and determined residence at important habitats. Core range represented areas where individuals spent the majority of their time, while home range represented most areas occupied. Fidelity to specific habitats was high, with home ranges averaging 10 km2 and 50% of individuals occupied the same core range across their entire detection period. Only 12% of individuals had home ranges encompassing both countries. Core and home ranges were larger during the summer compared to winter and larger within the United States compared to Canada. Larger (>120 cm) sturgeon had increased core and home ranges. We documented spawning capable hatchery-origin males and confirmed their residence at spawning sites when spawning was detected. Results improve our understanding of species biology and directly inform adaptive management of population recovery. [ABSTRACT FROM AUTHOR]

ABSTRACT Understanding the distribution and habitat use of endangered species is essential for conservation efforts. Environmental DNA (eDNA) analysis has become a more common approach to defining species habitat occupancy through identification of residual DNA in water samples and has potential to detect populations that are in low abundance or use habitats over a large geographical range. Here, we optimized an eDNA protocol to detect the presence of the endangered white sturgeon (Acipenser transmontanus). We implemented lab‐based experiments to understand the sensitivity and persistence of white sturgeon eDNA and then applied these methods to habitats with known white sturgeon abundances categorized as high, low, or not present. Using quantitative PCR (qPCR) and a modified StrAci1N‐flap primer set, white sturgeon eDNA was detected in water collected from tanks holding white sturgeon down to a dilution of 10,000× (estimated eDNA concentration of 0.00035 μg/L—0.00176 μg/L). Following the removal of white sturgeon from the tanks, the eDNA signal decreased with time but could be detected for up to 7 days. In the field, all sites with high abundances of white sturgeon returned positive eDNA detections. We did not detect white sturgeon eDNA at sites with low abundance or in areas where they were not expected to be present. Results from this work further advance our interpretation of eDNA from wild populations and provide a noninvasive method to advance recovery efforts by identifying species presence in areas of suspected use or to guide additional inventory efforts.

Acipenserid herpesvirus 2 (AciHV-2) is a large double-stranded DNA virus in the family Alloherpesviridae that causes catastrophic outbreaks in young naive white sturgeon (Acipenser transmontanus) populations, with mortalities of up to 80%. Survivors of these infections are suspected to remain latently infected. The grampositive zoonotic bacterium Streptococcus iniae is another important sturgeon pathogen that causes severe myositis and up to 50% mortality during natural outbreaks. Throughout the last decade, co-infections of AciHV-2 and S. iniae have been reported in cultured white sturgeon in California resulting in severe presentations of piscine streptococcosis. This phenomenon of herpesvirus and streptococcus co-infection appears to span multiple taxa since in humans, it is recognized that a Human herpesvirus 3 infection (VZV) is a negative prognostic indicator for pediatric Invasive Group A Streptococcal infections (IGASI). While a decrease in humoral immunity caused by VZV has been hypothesized as a potentially important factor in IGASI cases, no natural animal model exists to study this process. Moreover, no studies have investigated these reported coinfections in white sturgeon. Therefore, the goal of this study was to investigate the effects of a recent AciHV-2 infection on the outcome of a subsequent S. iniae challenge in white sturgeon fingerlings. When fish were infected with 108 colony forming units (CFU) of S. iniae intramuscularly (IM), a statistically significant decrease in survival of 41% was detected in the co-infection group compared to the S. iniae group (p-value < 0.001). This difference was not observed when fish were infected with 106 CFU of S. iniae IM. At this lower infection dose, however, a statistically significant downregulation of tnfa was observed in the spleen of fish in the co-infection group compared to the S. iniae group (p-value = 0.0098). Analysis of serum from survivors revealed a statistically significant reduction in anti-S. iniae serum IgM and serum serotransferrin in fish from the co-infection group compared to the S. iniae group (p-value = 0.0134 and p-value = 0.0183, respectively). Further studies are indicated to determine what interactions lead to the decreased production of pathogen-specific IgM, serotransferrin, and TNFa in the host. [ABSTRACT FROM AUTHOR]

Green sturgeon (Acipenser medirostris) and white sturgeon (A. transmontanus) are closely related, sympatric species that inhabit the San Francisco estuary. Green sturgeon have a more marine life history but both species spawn in the Sacramento River and reside for some duration in San Francisco Bay. These sturgeons are of conservation concern, yet little is known about their dietary competition when they overlap in space and time. To examine evidence of dietary differentiation, we collected whole blood and blood plasma from 26 green sturgeon and 35 white sturgeon in San Francisco Bay. Using carbon and nitrogen stable isotope analyses, we compared their relative trophic levels and foraging locations along the freshwater to marine gradient. Sampling blood plasma and whole blood allowed comparison of dietary integration over shorter and longer time scales, respectively. Plasma and whole blood δ13C values confirmed green sturgeon had more marine dietary sources than white sturgeon. Plasma δ15N values revealed white sturgeon fed at lower trophic levels than green sturgeon recently, however, whole blood δ15N values demonstrated the two species fed at the same trophic level over longer time scales. Larger individuals of both species had higher δ13C values than smaller individuals, reflecting more marine food sources in adulthood. Length did not affect δ15N values of either species. Isotope analyses supported the more marine life history of green than white sturgeon and potentially highlight a temporary trophic differentiation of diet between species during and preceding the overlapping life stage in San Francisco Bay. [ABSTRACT FROM AUTHOR]

Five metal mixture dose–response models were used to predict the toxicity of porewater to young sturgeon at areas of interest in the Upper Columbia River (WA, USA/BC, Canada) and to evaluate these models as tools for risk assessments. Dose components of metal mixture models included exposure to free metal ion activities or metal accumulation by biotic ligands or humic acid, and links of dose to response used logistic equations, independent joint action equations, or additive toxicity functions. Laboratory bioassay studies of single metal exposures to juvenile sturgeon, porewater collected in situ in the fast‐flowing Upper Columbia River, and metal mixture models were used to evaluate toxicity. The five metal mixture models were very similar in their predictions of adverse response of juvenile sturgeon and in identifying copper (Cu) as the metal responsible for the most toxic conditions. Although the modes of toxic action and the 20% effective concentration values were different among the dose models, predictions of adverse response were consistent among models because all doses were tied to the same biological responses. All models indicated that 56% ± 5% of 122 porewater samples were predicted to have <20% adverse response, 25% ± 5% of samples were predicted to have 20% to 80% adverse response, and 20% ± 4% were predicted to have >80% adverse response in juvenile sturgeon. The approach of combining bioassay toxicity data, compositions of field porewater, and metal mixture models to predict lack of growth and survival of aquatic organisms due to metal toxicity is an important tool that can be integrated with other information (e.g., survey studies of organism populations, life cycle and behavior characteristics, sediment geochemistry, and food sources) to assess risks to aquatic organisms in metal‐enriched ecosystems. Environ Toxicol Chem 2024;43:62–73. Published 2023. This article is a U.S. Government work and is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

Traditional methods for estimating abundance of fish populations are not feasible in some systems due to complex population structure and constraints on sampling effort. Lincoln's estimator provides a technique that uses harvest and harvest rate to estimate abundance. Using angler catch data allows assumptions of the estimator to be addressed without relying on methods that could be prohibitively field-intensive or costly. Historic estimates of White Sturgeon Acipenser transmontanus abundance in the Sacramento–San Joaquin River basin have been obtained using mark–recapture methods; however, White Sturgeon population characteristics often cause violations of model assumptions, such as population closure and independent capture probabilities. We developed a version of Lincoln's estimator using a joint likelihood, estimated abundance of White Sturgeon in the Sacramento–San Joaquin River basin in 2015 using this method and empirical data and assessed accuracy and precision of estimates in a simulation study. Estimating abundance using harvest and harvest rate, as represented by our model framework, has the potential to be precise and accurate. The joint likelihood–based approach fitted using Bayesian methods is advantageous because it includes all sources of variation in a single model. Precision of abundance estimates was low with application of the model to White Sturgeon in the Sacramento–San Joaquin River basin and to similar conditions in a simulated dataset. Using simulation, precision and accuracy increased with increases in the number of high-reward and standard tags released, tag reporting rate, tag retention rate, and harvest rate. Results demonstrate potential sources of error when using this approach and suggest that increasing the number of tagged fish and tag reporting rate are potential actions to improve precision and accuracy of abundance estimates of the model. [ABSTRACT FROM AUTHOR]

Predation of fish released as part of conservation aquaculture programs may undermine conservation goals. Identification of factors influencing predation, therefore, can inform management decisions that minimize predation losses. For the endangered Nechako white sturgeon (Acipenser transmontanus Richardson, 1836), the survival of individuals released as part of a conservation aquaculture program is threatened by river otter (Lontra canadensis (Schreber, 1777)) predation. Through the recovery of sturgeon passive integrated transponder (PIT) tags from otter latrines, we set out to quantify the extent of predation, identify spatial patterns in predation including identifying predation hotspots, and understand the timing of predation. The recovery of 3.9% of PIT tags from the hatchery-released sturgeon represents a minimum predation estimate based on several identified factors. The distribution of predation hotspots varied by release cohort, with some consistent hotspots among cohorts. An apparent decrease in predation in recent years was seen in conjunction with fewer live captures and lower release numbers, suggesting some level of density-dependent predation. Results from this study can be used to contribute to management decisions related to Nechako white sturgeon recovery efforts, inform further research needs, and contribute to a growing knowledge of sturgeon predation. [ABSTRACT FROM AUTHOR]

White Sturgeon (Acipenser transmontanus), a species of concern in the San Francisco Estuary, is in relatively low abundance due to a variety of factors.  The purpose of our study was to identify the estuarine habitat used by White Sturgeon to aid in the conservation and management of the species locally and across its range. We seasonally sampled sub-adult and adult White Sturgeon in the central estuary using setlines across a habitat gradient representative of three primary structural elements: shallow wetland channels (mean sample depth = 2 m), shallow open-water shoal (mean sample depth = 2 m), and deep open-water channel (mean sample depth = 7 m). We found that the shallow open-water shoal and deep open-water channel habitats were consistently occupied by White Sturgeon in spring, summer, and fall across highly variable water quality conditions, whereas the shallow wetland channel habitat was essentially unoccupied. We conclude that sub-adult and adult White Sturgeon inhabit estuaries in at least spring, summer, and fall and that small, shallow wetland channels are relatively unoccupied.

Improving the status of endangered species can be challenging because the efficacy of conservation actions is often uncertain. Conservation aquaculture has been the main recovery action for endangered white sturgeon (Acipenser transmontanus) in the Transboundary Reach of the upper Columbia River. Using long-term mark-recapture data (2002–2018), we predicted variation in growth rates due to genetic, environmental, and competition effects to evaluate the efficacy of the aquaculture program. Environmental conditions (by season and country) and competition had the greatest effects on growth. Growth, length-at-age, weight-at-age, and condition factor were higher for fish residing in reservoir habitats (US) compared to those in riverine habitat (Canada). Growth declined over the study period but growth in length for larger fish remained higher in the US as fish > 100 cm fork length in Canada were not growing. Small differences in growth among families indicate that differences in genetics among parents spawned in the hatchery had negligible effects on growth in the wild. Our estimate of substantive negative density-dependent growth in Canada is important for management of conservation aquaculture for sturgeons. [ABSTRACT FROM AUTHOR]

Abstract Background A new technology for a self-powered acoustic tag (SPT) was developed for active tracking of juvenile fish, intended to avoid the typical battery life constraints associated with active telemetry technology. We performed a laboratory study to evaluate a subdermal tagging technique for the SPT and effects of the tag on survival, tag retention, and growth in juvenile white sturgeon (Acipenser transmontanus). Results Survival was associated with tag retention. White sturgeon implanted with the SPT (n = 30) had 93% survival and tag retention by day 28, 67% by day 101, and 38% by day 595 post-tagging. Sturgeon implanted with a passive integrated transponder (PIT) tag only (control group) had 96% survival and tag retention by day 28, and through day 101 post-tagging. Fish in the PIT group were repurposed after day 101, so no comparisons with this group were made at day 595 post-tagging. Specific growth rate (SGR) for fork length was a median of 0.25% day−1 by day 28 for the SPT group, which was significantly lower than the PIT group (median: 0.42% day−1; n = 27). The SPT and PIT groups had similar SGR fork length by day 101 post-tagging (0.22 and 0.25% day−1, respectively). SGR weight was also lower for the SPT group compared to the PIT group on day 28 (1.39 and 2.11% day−1, respectively), but the difference again dissipated by day 101 (0.79 and 0.88% day−1, respectively). Conclusion The tagging technique and placement of the SPT allowed the tag to remain upright along the flank of the sturgeon to ensure maximum battery output of the SPT; however, retention rates of the SPT were not ideal. We provided suggestions to improve the tagging technique. Suggestions included tagging fish that are > 400 mm FL, moving the incision location to extend the cavity and create a pocket for the placement of the SPT, and performing a quantitative wound-healing evaluation. Future studies are therefore recommended to evaluate these suggestions.

Management objectives for long-lived species are difficult to define because many taxa have delayed maturity and variable recruitment. White Sturgeon Acipenser transmontanus is an example of a species with a complex life history that complicates long-term status monitoring and establishment of management objectives. Historically, White Sturgeon in the Sacramento–San Joaquin River basin have been monitored by tracking the abundance of age-15 individuals as outlined by the Central Valley Project Improvement Act. However, infrequent recruitment complicates progress toward Central Valley Project Improvement Act management objectives because abundance of a single cohort fails to represent overall population trends. By using a Leslie population matrix, we demonstrate that the probability of reaching the Central Valley Project Improvement Act objective of 11,000 age-15 White Sturgeon is highly unlikely. We propose an alternative metric of 155,000 adults, which better represents overall population trends of White Sturgeon in the Sacramento–San Joaquin River basin, can be efficiently monitored, and can support both the goal of the Central Valley Project Improvement Act and management objectives. [ABSTRACT FROM AUTHOR]

Flavobacterium columnare represent one of the most important bacterial pathogens of cultured sturgeon. However, at present there are no commercially available vaccines to prevent infection and treatment options are limited. β-glucans have been shown to be potent immunostimulants that can provide fish protection against infectious disease. In this study, the effects of dietary β-glucan supplementation on disease susceptibility were examined by exposing 0.3% β-glucan-fed white sturgeon (Acipenser transmontanus) to Flavobacterium columnare in laboratory-controlled challenges. Morbidity and mortality were monitored for 15 days post-challenge (dpc). Additionally, transcript levels for pro-inflammatory cytokines, regulatory cytokines and acute phase proteins (APP) were investigated in the spleen and gills at different time points post-challenge. No evidence of protection was observed in β-glucan-fed fish challenged with the bacteria. Moreover, significantly greater mortalities were observed in β-glucan-fed fish challenged with F. columnare (p

The internal organs of white sturgeon in Miyazaki Prefecture are discarded during processing. Therefore, we tried to produce fish sauce using a short-term manufacturing method. The minced internal organs were autolyzed by endogenous proteases at 50 °C. During autolysis, the protein contents of the supernatant and precipitate after centrifugation were analyzed by the Kjeldahl method, and the protein size was monitored by SDS-PAGE. This analysis showed that the extraction rate was about 60% after treatment at 50 °C for 24 h. The major bands at 200 kDa, 43 kDa, and 40 kDa detected before the start of the treatment gradually disappeared over time. Fifteen components were detected as the main volatile components. These components increased sharply and then decreased during incubation at 50 °C for 24 h. The fish sauce produced had a good aroma after incubation at 50 °C for 72 h. [ABSTRACT FROM AUTHOR]

Abundances of important and imperiled fishes of the Snake River Basin continue to decline. We assessed the rationale for breaching the four lower Snake River Basin dams to prevent complete loss of these fishes, and to maximize their likelihood of recovery. We summarize the science surrounding Sockeye Salmon (Oncorhynchus nerka), Chinook Salmon (O. tshawytscha), steelhead (O. mykiss), Bull Trout (Salvelinus confluentus), White Sturgeon (Acipenser transmontanus), and Pacific Lamprey (Entosphenus tridentatus). From this, we drew ten conclusions: (1) development of the Columbia River System (including the Snake River Basin) has converted mainstem rivers into reservoirs, altering fish behavior and survival; (2) most populations currently record their lowest abundance; (3) the Columbia River System dams reduce productivity of diadromous fishes in the highest-quality spawning grounds that could buffer against future climate dynamics; (4) past actions have done little to reduce impacts or precipitate recovery; (5) the Columbia River System constrains survival and productivity of salmon, steelhead and Bull Trout; (6) Snake River Basin salmon and steelhead remain at high extinction risk; (7) eliminating migration impediments and improving mainstem habitats are essential for maintaining genetic diversity and improving Bull Trout persistence; (8) the lower Snake River Basin dams preclude passage of adult White Sturgeon, constraining gene flow and recruitment; (9) the lower Snake River Basin dams impede dramatically passage of adult and juvenile Pacific Lamprey, and (10) Snake River Basin Pacific Lamprey is at high risk of extirpation. Breaching the four lower Snake River Basin dams is an action likely to prevent extirpation and extinction of these fishes. Lessons from the Columbia River System can inform conservation in other impounded rivers.

An 8-week feeding trial was conducted to investigate the responses of juvenile white sturgeon (Acipenser transmontanus) to elevated dietary selenium (Se) based on the determination of the RNA/DNA ratio in muscle, heat shock protein 70 (Hsp70), and caspase-3/7 in muscle and/or liver tissues. Four semi-purified test diets were prepared by adding different levels of L-selenomethionine (0, 50, 100, and 200 mg/kg diet). The analytical determinations of total Se were 2.2, 19.7, 40.1, and 77.7 mg/kg diet. The sturgeon (initial body weight: 30 ± 2 g; mean ± SEM) were raised in indoor tanks provided with flow through freshwater (18-19 °C). There were three replicates for each dietary treatment with 25 fish per replicate. The liver and muscle tissues were collected at 4 and 8 weeks after feeding the test diets. A significant interaction between duration and levels of dietary Se exposures on RNA/DNA ratio in the muscle tissue was detected (P

Understanding life-history diversity in a population is imperative to developing effective fisheries management and conservation practices, particularly in degraded environments with high environmental variability. Here, we examined variation in habitat use and migration patterns of White Sturgeon (Acipenser transmontanus), a long-lived migratory fish that is native to the San Francisco Estuary, CA, United States. Annual increment profiles were combined with respective geochemical (87Sr/86Sr) profiles in sturgeon fin rays to reconstruct annual salinity chronologies for 112 individuals from 5 to 30 years old. Results indicated a complex and diverse amphidromous life history across individuals, characterized largely by estuarine residence, a general ontogenetic trend toward higher-salinity brackish habitats, and high variability in habitat use across all age groups. Hierarchical clustering based on fin ray geochemistry during the first 10 years of life, prior to sexual maturation, indicated at least four distinct migratory phenotypes which differed largely in the timing and duration of juvenile to subadult movements between fresh- and brackish-water habitats. This study provides information regarding habitat use and migration in sub-adult fish that was previously lacking. Different migratory phenotypes vary in exposure to stressors across time and space and populations. Understanding White Sturgeon habitat distributions through space and time at different life stages can help identify areas where habitat restoration would be most effective and develop management actions to reduce stressors associated with specific areas where White Sturgeon are present.

White Sturgeon Acipenser transmontanus are cultured for human consumption as well as for conservation purposes. In this study, two commercially available portable devices for measuring glucose and lactate were compared to a benchtop analyzer and blood reference intervals were generated using heparin plasma collected from 43 healthy White Sturgeon yearlings. The generated normal ranges were used to compare plasma values collected from Veronaea botryosa‐infected White Sturgeon at 10, 20, and 30 d postchallenge (dpc). In the 43 healthy yearlings, significantly different glucose and lactate values were obtained when comparing the portable devices to the benchtop analyzer. In the portable devices, blood glucose showed a consistent bias of 12.3 mg/dL and blood lactate showed a proportional bias. The detected blood glucose values in infected sturgeon were significantly different from those in noninfected controls when using the benchtop analyzer at 20 and 30 dpc and when using the portable device at 20 dpc. However, blood glucose in infected individuals and controls was within the reference interval on either device. No significant difference was noted for lactate measurements in infected sturgeon. The results of this study indicate that portable devices for blood glucose and blood lactate evaluation in White Sturgeon may be useful in a setting where relative values are an acceptable approximation of absolute values. [ABSTRACT FROM AUTHOR]

Background: A new technology for a self-powered acoustic tag (SPT) was developed for active tracking of juvenile fish, intended to avoid the typical battery life constraints associated with active telemetry technology. We performed a laboratory study to evaluate a subdermal tagging technique for the SPT and effects of the tag on survival, tag retention, and growth in juvenile white sturgeon (Acipenser transmontanus). Results: Survival was associated with tag retention. White sturgeon implanted with the SPT (n = 30) had 93% survival and tag retention by day 28, 67% by day 101, and 38% by day 595 post-tagging. Sturgeon implanted with a passive integrated transponder (PIT) tag only (control group) had 96% survival and tag retention by day 28, and through day 101 post-tagging. Fish in the PIT group were repurposed after day 101, so no comparisons with this group were made at day 595 post-tagging. Specific growth rate (SGR) for fork length was a median of 0.25% day−1 by day 28 for the SPT group, which was significantly lower than the PIT group (median: 0.42% day−1; n = 27). The SPT and PIT groups had similar SGR fork length by day 101 post-tagging (0.22 and 0.25% day−1, respectively). SGR weight was also lower for the SPT group compared to the PIT group on day 28 (1.39 and 2.11% day−1, respectively), but the difference again dissipated by day 101 (0.79 and 0.88% day−1, respectively). Conclusion: The tagging technique and placement of the SPT allowed the tag to remain upright along the flank of the sturgeon to ensure maximum battery output of the SPT; however, retention rates of the SPT were not ideal. We provided suggestions to improve the tagging technique. Suggestions included tagging fish that are > 400 mm FL, moving the incision location to extend the cavity and create a pocket for the placement of the SPT, and performing a quantitative wound-healing evaluation. Future studies are therefore recommended to evaluate these suggestions. [ABSTRACT FROM AUTHOR]

The goal of a day-long symposium on March 3, 2015, Sturgeon in the Sacramento–San Joaquin Watershed: New Insights to Support Conservation and Management, was to present new information about the physiology, behavior, and ecology of the green (Acipenser medirostris) and white sturgeon (Acipenser transmontanus) to help guide enhanced management and conservation efforts within the Sacramento–San Joaquin watershed. This symposium identified current unknowns and highlighted new electronic tracking technologies and physiological techniques to address these knowledge gaps. A number of presentations, each reviewing ongoing research on the two species, was followed by a round-table discussion, in which each of the participants was asked to share recom-mendations for future research on sturgeon in the watershed. This article presents an in-depth review of the scientific information presented at the sympo-sium with a summary of recommendations for future research.

The migration of larval fish from spawning to rearing habitat in rivers is not well understood. This paper describes a methodology to predict larval drift using a Lagrangian particle-tracking (LPT) model with passive and active behavioural components loosely coupled to a quasi-three-dimensional hydraulic model. In the absence of measured larval drift, a heuristic approach is presented for the larval drift of two species of interest, white sturgeon (Acipenser transmontanus) and burbot (Lota lota), in the Kootenai River, Idaho. Previous studies found that many fish species prefer certain vertical zones within the water column; sturgeon tend to be found near the bottom and burbot close to the water surface. Limiting the vertical movement of larvae is incorporated into the active component of the LPT model. The results illustrate a pattern of drift where secondary flow in meander bends and other zones of flow curvature redistributes particles toward the outside of the bend for surface drifters and toward the inside of the bend for bottom drifters. This pattern periodically reinforces the intersection of drifting larvae with channel margins in meander bends. In the absence of measured larval drift data, the model provides a tool for hypothesis testing and a guide to both field and laboratory experiments to further define the role of active behaviour in drifting larvae. [ABSTRACT FROM AUTHOR]

The application of genetic markers to investigate evolutionary and ecological questions about white sturgeon, Acipenser transmontanus, has been limited due to the species’ highly duplicated nuclear genome. Here, polysomic microsatellite markers were used to 1) examine the ancestral level of genome duplication in white sturgeon, 2) examine genetic diversity and patterns of population structure within and among drainages across the species’ range, and 3) provide genetic monitoring for a conservation aquaculture program sustaining an endangered white sturgeon population. In the first chapter, we followed the inheritance of eight microsatellite markers in 15 families of white sturgeon from a commercial caviar farm to determine whether white sturgeon (~250 chromosomes) should be classified as tetraploid or octoploid. The eight microsatellite loci were detected predominantly in four or eight copies, with one locus observed in >8 copies. Numbers of alleles per locus, patterns of allele transmission, and inference of gene copy number in parents suggested that white sturgeon should be considered ancient octoploids. The discovery of dodecaploid parents and their decaploid offspring in the farm population, confirmed by flow cytometry analysis, indicated that some aspect of sturgeon aquaculture was inducing spontaneous autopolyploidy in white sturgeon.Next, microsatellite markers were applied to examine white sturgeon population structure across the species’ range. Population assignment testing was used to determine the origin of white sturgeon sampled in non-natal estuaries, or those not containing a spawning population, to evaluate marine dispersal behavior. The Sacramento-San Joaquin River system was found to contain a single white sturgeon population while the8Fraser River exhibited a hierarchical pattern of population structure. Strong levels of genetic divergence were detected above and below a natural barrier, Hells Gate, and fine-scale population substructure was identified above Hells Gate. Population structure in the Columbia River drainage (including the mainstem Columbia and Snake Rivers) was complex and suggested a pattern of isolation by distance. Net downstream gene flow also may have contributed to this pattern, with individuals migrating downstream through impoundments and over barriers with little upstream movement possible. There was no support for the current practice of managing each impounded reach on the Columbia or Snake Rivers as a separate population. Lack of population structure within historically continuous river habitat found across the species’ range suggested spawning site fidelity in white sturgeon may occur on a regional scale, with local gene flow among geographically proximate spawning sites. Population assignment of samples collected from non-natal estuaries indicated that all populations with ocean access make marine migrations, and individuals did not necessarily originate from the nearest spawning population.Finally, microsatellites were used to conduct genetic monitoring of the Kootenai Tribe of Idaho’s conservation aquaculture program (CAP) for the endangered Kootenai River white sturgeon population. Continuous recruitment failure in this population has left it entirely dependent on the CAP for reproduction. A genetic profile database of wild broodstock used in the CAP was created to monitor hatchery-induced genetic changes in the Kootenai River population. Broodstock genotypes also were used to evaluate the accuracy of parentage assignment in the Kootenai River population, as hatchery managers soon will depend on this analysis to prevent inbreeding when most sexually mature adults available for captive breeding will be derived from hatchery production. Numbers of alleles and numbers of alleles per individual per locus were calculated to monitor the amount of wild type genetic diversity captured in broodstock utilized by the CAP. Parentage analysis with 18 microsatellite markers was validated in known hatchery families from the 2010 year class. Genetic diversity in the Kootenai River population was very low relative to other populations examined, likely due to founder effects and genetic drift after isolation from the mainstem Columbia c. 10,000 YBP. In less than one sturgeon generation, 96% of Kootenai River genetic diversity has been captured in broodstock that contributed offspring that survived to release in the Kootenai River and further propagation will likely preserve additional genetic variation. The 18 microsatellite panel improved parentage assignment accuracy and allowed a greater number of assignments relative to the previous panel used for parentage analysis, suggesting that this technique may become a useful tool in the management of this vulnerable population.

The internal organs of white sturgeon in Miyazaki Prefecture are discarded during processing. Therefore, we tried to produce fish sauce using a short-term manufacturing method. The minced internal organs were autolyzed by endogenous proteases at 50 °C. During autolysis, the protein contents of the supernatant and precipitate after centrifugation were analyzed by the Kjeldahl method, and the protein size was monitored by SDS-PAGE. This analysis showed that the extraction rate was about 60% after treatment at 50 °C for 24 h. The major bands at 200 kDa, 43 kDa, and 40 kDa detected before the start of the treatment gradually disappeared over time. Fifteen components were detected as the main volatile components. These components increased sharply and then decreased during incubation at 50 °C for 24 h. The fish sauce produced had a good aroma after incubation at 50 °C for 72 h.

Keywords: otter; PIT tag; predation; radio tag; white sturgeon EN otter PIT tag predation radio tag white sturgeon 780 784 5 12/21/20 20201201 NES 201201 INTRODUCTION White sturgeon ( I Acipenser transmontanus i ) in the Nechako River, British Columbia, Canada have experienced recruitment failure since 1967 (McAdam et al., 2005) and this population was listed as endangered under the Species at Risk Act (SARA) in 2006 (Fisheries & Oceans Canada, 2014). Sturgeon radio tags were collected in suspected otter feeding sites and sturgeon PIT tags were collected from otter latrine sites. It is difficult to be confident that all radio-tagged sturgeon mortalities are a result of river otter predation, however there is evidence that at least a proportion of radio-tag mortalities were caused by otters. [Extracted from the article]

Streptococcus iniae is a zoonotic pathogen and one of the major aetiologic agents of streptococcosis. In White Sturgeon Acipenser transmontanus, S. iniae infection typically presents as a necrotizing and heterophilic myositis, causing 30–50% mortality in infected fish. To gain a better understanding of the pathogenesis of streptococcosis in White Sturgeon, and to identify the experimental route of infection that most closely mimics the natural disease, fingerlings were challenged with a single dose of 1.3 × 108 cells/fish of S. iniae that was administered via intracoelomic/intraperitoneal (IC) or intramuscular (IM) routes. Acute mortalities were present only in the IM‐challenged fish, with first mortality occurring 4 d postchallenge and the mortality rate reaching 18.3% after 9 d. The challenged fish presented erratic swimming, ulcerative skin lesions, and hemorrhages in the liver and swim bladder. Streptococcus iniae was recovered from the kidney and brain tissues of moribund and dead fish. Histopathologic analysis of fish that died acutely revealed massive proliferation of bacteria in the muscle at the injection site and within vascular organs such as the heart and spleen, with variable amounts of tissue necrosis including a necrotizing myositis. Fish that died closer to 9 d postchallenge demonstrated more pronounced multifocal to locally extensive granulomatous inflammation of skeletal muscle at the injection site, liver, kidney, and spleen. No mortality, clinical signs, or gross changes were observed in the control or IC‐challenged fish. Postmortem evaluation of 10 survivors in each treatment was performed to determine carrier status in the brain and posterior kidney tissues. The prevalence of S. iniae in survivors was 10% and 0% in the IM‐ and IC‐challenged groups, respectively. The results from this study suggest that IM‐injection challenge methods are suitable for inducing streptococcosis in White Sturgeon, and they may be the preferred method for studying the pathogenesis of the naturally occurring disease in this species. [ABSTRACT FROM AUTHOR]

Temperature differentially influences developmental trajectories of traits during early life stages that can affect survival and recruitment. Experiments were conducted to quantify temperature-induced developmental responses of White Sturgeon (Acipenser transmontanus) yolk-sac larvae (YSL) reared at temperatures encountered across the species' range (12.5, 14.0, 15.5, and 17.0 °C). We quantified effects of temperature on timing of transitions between sequential developmental stages from hatch to initiation of exogenous feeding. Rate of development significantly increased at warmer compared to cooler temperatures; no significant difference was observed between 15.5 and 17.0 °C or 12.5 and 14.0 °C. When standardized by relative timing of development (RTi), developmental rate was not significantly different among treatments. Morphological traits (total length; body area; yolk-sac area; head area; gill filament area; mouth area; pectoral fin area) were measured daily, though only data for YSL reared at 12.5 and 17.0 °C was used to quantify phenotypic variation. Morphological traits (excluding yolk-sac area) were generally larger 48+ hours post hatch for YSL reared at 17. 0 °C compared to 12.5 °C. In contrast, these same traits, with the exception of gill filament area, were larger in 12.5 °C reared YSL when considered as a function of developmental stage. These opposing results suggest trade-offs associated with allocating resources to a particular trait depended on rearing temperature. Our results provide the ability to estimate timing of critical early life stages (i.e., hatch, emergence) as a function of temperature which is an important management tool to understand how early life development contributes to recruitment processes and adaptability in thermally altered systems. [ABSTRACT FROM AUTHOR]

Outbreaks of an infectious disease affecting cultured white sturgeon (Acipenser transmontanus) were investigated. Clinical signs included erratic swimming, arching of the back and mortality. Necropsy findings included poorly demarcated yellow to dark‐red and friable lesions in the epaxial muscle, ulcerative skin lesions and haemorrhages in the swim bladder and coelomic wall. Histological evaluation revealed areas of necrotizing and heterophilic myositis with aggregates of bacterial cocci. The lumen of blood vessels in the dermis, under ulcerated areas, and in the posterior kidney, was occluded by fibrin thrombi. Aggregates of Gram‐positive cocci were observed in the muscle lesions and within the fibrin thrombi in the dermis and kidney. Genetically homogeneous Streptococcus iniae strains were recovered from affected fish from different outbreaks. The isolates shared high degree of similarity at gene locus (gyrB) with previously characterized S. iniae from cultured fish in California, confirming the emergence of this particular strain of S. iniae in US aquaculture. [ABSTRACT FROM AUTHOR]

Vitellogenin (Vg), the estrogen inducible protein precursor to egg yolk, serves as an indicator of exposure to estrogen mimicking environmental contaminants. Vg was isolated by size exclusion and ion exchange chromatography from plasma of California halibut (Paralichthys californicus) treated with estrogen. MALDI TOF mass spectrometry (MS) analysis resulted in a molecular mass of 188 kDa. MS/MS de novo sequencing provided evidence that California halibut has more than one form of Vg. Similar analysis on white sturgeon (Acipenser transmontamus) Vg did not reveal adequate evidence to suggest that sturgeon has more than one Vg. The potential of using other MS methods to understand the structure and function of Vg are discussed.An ELISA for measurement of California halibut plasma Vg was optimized and validated using a commercially available antibody developed for another flatfish species, turbot. Inclusion of overnight preincubation was critical for low detection limits. Increasing the amount of Tween-20 to 0.05% in buffers was most effective for improving recoveries of spiked plasma samples. At the IC50, the average recovery of spiked plasma samples was 104% and the interplate CV was 12%. The working range of the assay was 33-1000 ng/mL, while the detection limit in a plasma sample is 2.2 µg/mL. The response to the model compounds 17beta-estradiol and/j-nonylphenol show that this is a suitable model for further studies of estrogen mimicking contaminants.White sturgeon are native to the Sacramento River and subject to agricultural, municipal and industrial waste water effluents that likely contain different classes of endocrine-disrupting contaminants. Reductions in 17beta-estradiol-induced vitellogenin levels were observed in white sturgeon co-injected with beta-naphthoflavone (BNF, 50 mg/kg), an Ah receptor agonist. The inhibition was maximal when the compounds were injected simultaneously versus prior treatment offish with BNF. This timing of the effect compared to increases in ethoxyresorufin-O-deethylase (EROD) activity suggests that the effect is not directly due to enhanced estrogen metabolism by the Ah receptor-induced enzymes. Results of this study will be relevant for those with monitoring programs who measure vitellogenin, as it is important to understand how Ah (dioxin) receptor active environmental contaminants can influence this endpoint.

This document discusses the challenges faced by White Sturgeon in California, including droughts, habitat loss, and warming water conditions. The California Department of Fish and Wildlife conducted a rescue and monitoring effort to relocate sturgeon from the Tuolumne River to the San Joaquin River to protect their health and reduce the risk of poaching. Acoustic monitoring was used to track the sturgeon's movements after relocation. The document also provides information on a separate monitoring effort in the San Joaquin River and its tributaries, where three sturgeon were tagged and monitored to understand their habitat use and migration patterns. The document acknowledges the individuals and organizations involved in the monitoring effort and provides additional references for further research. [Extracted from the article]

An 8-week growth trial was conducted to determine the sensitivity of white sturgeon (Acipenser transmontanus) to the toxicological effects of elevated dietary selenium (Se). Juvenile white sturgeon were fed diets supplemented with Se in the form Of L-selenomethionine (SeMet), resulting in dietary concentrations of 0.4, 9.6, 20.5, 41.7, 89.8, and 191.1 mu g Se/g diet on a dry weight basis. Effects of dietary SeMet on survival, swimming activity, growth, whole-body proximate composition, tissue Se concentrations, and histopathology were determined. Sturgeon survival among treatment groups did not differ significantly with a mean survival rate of 99 +/- 0.43% across all groups. A significant decrease (p < 0.05) in swimming activity and growth rate was observed in sturgeon fed at or above 41.7 mu g Se/g diet. Dietary SeMet concentrations were negatively correlated with whole-body protein and lipid content, but positively correlated with ash and moisture content. Selenium accumulated. in the kidney, muscle, liver, gill, and plasma tissues in a dose-dependent manner. Histopathological alterations in the liver and kidney were observed in sturgeon fed above 20.5 mu g Se/g diet. The threshold dietary Se toxicity concentration for white sturgeon was estimated to lie between 10 and 20 jig Se/g diet based on the histopathological alterations in the kidney. Research examining the consequences of elevated dietary Se concentrations on more sensitive life stages and the interactive effects of Se with other chemical or physical stressors are needed in order to determine if dietary threshold should be lowered to minimize the potential impacts of Se on white sturgeon in the San Francisco Bay-Delta. (c) 2006 Elsevier B.V. All rights reserved.

An 8-week growth trial was conducted to study carbohydrate utilization by white sturgeon fed diets containing glucose or hydrolyzed potato starch (HPS). Four diets supplemented with 15% or 30% of glucose or HPS and a control diet with no added carbohydrate were each fed to triplicate groups of fish. The diets were processed by a 3-min 80 degrees C microwave moist heating, followed by 1-h 70 degrees C drying. Feeding rates varied from 1.7% to 3.2% body weight day(-1) so that all treatment groups were fed the same amount of dietary protein and lipid. The HPS groups showed the highest (P

Genetics professor Dr. Bernie May of the University of California at Davis and Sea Grant Trainee Dr. Jeff Rodzen were funded to develop a breeding program for broodstock at Stolt Sea Farm, the state’s largest producer of white sturgeon caviar. The goal of the project was twofold: to develop a breeding plan for slowing the rate of inbreeding of offspring and to investigate whether commercially desirable traits—superior growth rates, enhanced caviar yield and early sexual maturity—can be selectively bred.

The overall intent of this project was to develop a breeding plan for white sturgeon, using Stolt Sea Farm California LLC as a model system for broodstock management and selection using molecular markers. While the title of this project implies the function of the breeding plan to be of maintaining existing genetic variation as inferred from nuclear DNA markers, it is in the best interest of those parties involved in commercial production of this species to evaluate the feasibility of directed selection for economic traits such as growth rate. Thus, this project involves the estimation of quantitative genetic variation in addition to developing specific applications of molecular markers to broodstock management. Recommendations for their integration into a breeding plan and an overview of our research will be summarized in a manuscript being prepared (Rodzen et al. in prep4).

Nine tetramer [GATA]n microsatellite systems were developed for use in the white sturgeon, Acipenser transmontanus. We report inheritance patterns for these nine systems, which range from one possible disornic system to tetrasomy and octosomy, with some systems containing null alleles. Due to the complex modes of inheritance underlying these systems and the highly duplicated nature of the genome, we propose each allele be scored as its own dominant marker, similar to AFLPs or RAPDs. The utility of this method is validated by the observation that individual alleles within a microsatellite system generally fit the expectation for independent transmission and fit the expected transmission frequency for single copy nuclear markers.

Significant progress has been achieved during the past several years in understanding endocrine control of reproduction in white sturgeon, Acipenser transmontanus (Moberg et al., 1995; Doroshov et al., 1997), however the regulation of prespawning oocyte development and the effects of environmental factors on this phase have been inadequately studied. Field and experimental observations suggest that the thermal regime of rivers plays a pivotal role in environmental control of tinal ovarian maturation (FOM) and spawning of wild sturgeon (Dettlaff et al., 1993), and constant, elevated temperatures have been found to result in decreased plasma sex steroid concentrations, a high incidence of ovarian atresia, and spawning failure in cultured sturgeon (Webb et al., 1999). Chapter l reviews our current knowledge of sturgeon reproductive endocrinology and the effects of environmental factors, specifically temperature, on the late phase of oogenesis.The effects of environmental temperature, ultimately mediated y brain-pituitary secretions, can be tested at the level of the ovary by observations on sex steroid secretion correlated with oocyte development. The objectives of this project were l) to determine baseline steroidogenic profiles in prespawning female sturgeon exposed to seasonal temperature, 2) to identify native steroid hormones involved in oocyte maturation, and 3) to examine and compare ovarian development, acquisition of maturational competence, and plasma sex steroid profiles in gravid females reared in warm water and transferred to cold water in the late fall or early spring.Chapter 2 characterizes the baseline plasma steroid profile and in vitro ovarian steroid secretion in two females held at seasonal temperatures throughout FOM and ovulation. Ovarian follicles were incubated with or without pregnenolone (P5), and concentrations of testosterone (T), 11-ketotestosterone (KT), estradiol (E2), and 17a, 208-dihydroxy-4-pregnen-3-one (17, 208-P) were measured by radioimmunoassay in the incubation media. The follicles of both females reached maturational competence (the ability to undergo germinal vesicle breakdown, GVBD, in response to a progestin in vitro), and ovulation was induced by hormonal treatment. Female 1 responded with oocyte maturation (GVBD), but did not ovulate. Female 2 underwent the normal sequence of oocyte maturation and ovulation. Lower in vitro production of T, KT, and 17, 208-P and elevated E2 were detected in Female 1 compared to Female 2. A surge in plasma 17, 20B-P was found in Female 2 at the onset of oocyte maturation before ovulation. No such surge was detected in the plasma of Female 1. High performance liquid chromatography (HPLC) analysis of plasma at the actual or expected time of ovulation revealed several C21 steroids present in the plasma of Female 2 that were absent in Female 1 These results suggest that it may be possible to assess follicular health during FOM through plasma steroid concentrations or follicular steroidogenesis as a means to select females for hormonal induction of ovulation or estimate the spawning potential of wild females.The ovarian follicles collected from Females 1 and 2 after a priming injection with pituitary extracts were used to determine the putative maturation-inducing steroid (MIS) involved in GVBD (Chapter 3). Follicles were incubated in the presence of a radiolabelled precursor eH-P5). Steroids were extracted from media and intact follicles, and the extracts were analyzed and fractionated by HPLC. The fractions were used in a bioassay to determine the potency of the endogenous steroid products. The results revealed production of C 19 and C2l steroids by the ovarian follicles of primed females, and several of these steroids were found to be physiologically active in the induction of GVBD in oocytes collected from ripe sturgeon females. However, only two fractions, containing a steroid with the same isopolarity as the authentic steroid 11-deoxycortisol (S) on HPLC and a steroid positively identified as 17, 208-P (HPLC and gas chromatography-mass spectrometry), were found to stimulate the resumption of meiosis at the shortest time of oocyte incubation. These steroids, produced in large quantities in vitro by the follicles undergoing GVBD, may be potential putative MISs in white sturgeon.The in vitro effects of steroids on oocyte maturation in sturgeon were further investigated using synthetic hormones matching native C19 and C21 steroids produced in vitro during GVBD (Chapter 4). Ovarian follicles from four mature sturgeon females were incubated with the synthetic steroids at different concentrations and exposure times. At the highest concentration (>1 J.Lg/rnl), all of the C21 steroids tested (progesterone, P4; 17a­ hydroxyprogesterone, 170HP; 17a, 20B, 21-trihydroxy-4-pregnen-3-one, 20B-S; cortisol, F; 17, 20B-P, and S) and T induced maturation at 14 and 22 hrs. At 6 hrs, only P4 and 17, 20B-P induced maturation at the highest concentration. At 14 and 22 hrs, S was the most potent steroidal inducer of GVBD followed closely by P4 and 170HP. The C21 steroids induced oocyte maturation at lower concentrations compared to the C19 steroid T. Calculation of the mean effective concentration that induced 50% GVBD (EC50) revealed the following order of potencies: S > P4 > 170HP > 17, 20B-P > 20B-S >> F > T. These results, together with previous findings on the in vitro production of native steroids, indicate that more than one steroid has a biological role in the resumption of meiosis in sturgeon follicles and provides empirical evidence for S, 17. 20B-P, P4, and 170HP as the most potent steroid inducers of GVBD.The objective of Chapter 5 was to examine and compare ovarian development, acquisition of maturational competence, and plasma sex steroid profiles in gravid sturgeon females reared in warm water and transferred to cold water in the late fall or early spring. Eighteen gravid females that had been raised under natural photoperiod at water temperatures of 16-20°C were randomly assigned to two groups (n=6 in Group 1 and n=12 in Group 2). Group 1 was transferred from warm water to cold water (12±1°C) in November 1997, while Group 2 was held in ambient water temperatures (10-19°C). Both groups were sampled in March 1998. Half of the fish in Group 2 had regressed ovaries, but the remaining females (n=6) had intact ovarian follicles and were transported to the cold water one week after the sampling. Ovarian follicles and blood were collected from October 1997 to November 1998, and the reproductive development was monitored until each female reached the stage of spawning readiness (oocyte polarization index s 0.10 and ovarian follicles had acquired maturational competence in vitro) or until atretic follicles were detected. Chonic exposure of gravid sturgeon females to elevated water temperature from October to March led to a decrease in plasma sex steroids and a high incidence of ovarian atresia in 50% of the females. It appears that the temperature-sensitive phase in ovarian development occurs during the transition from vitellogenic growth to FOM. The degree and timing of sensitivity to environmental temperature in the broodstock population are dependent on the female endogenous rhythms. Normal ovarian development occurred in the majority (83%) of females with intact follicles transferred to cold water in the fall or early spring. Though holding gravid females in cold water has extended the spawning season, the majority of females in our study reached the stage of spawning readiness by June. Several females, however, did retain maturational competence until early fall. A decrease in plasma T and KT was evident five weeks to several months prior to visual signs of atresia indicating that aquaculturists and conservationists may be able to screen potential sturgeon spawners based on androgen concentrations.Understanding ovarian steroidogenesis during FOM and ovulation elucidates the hormonal regulation of late oogenesis in sturgeon and provides useful information for environmental studies in aquaculture and in the wild. For example, baseline plasma steroid data may be used in the analysis of normal and abnormal gonad function of fish exposed to adverse environmental conditions during spawning migrations or holding in captivity. Characterization of the temperature-sensitive stage in late oogenesis of sturgeon enables aquaculturists and conservationists to determine the best timing of exposure of maturing females to cool water and ensure that environmental temperature is not a limiting factor influencing follicular development and spawning of sturgeon.

Highlights • Effects of catch-and-release (C&R) angling on wild white sturgeon stress physiology and immediate post-release behaviour are unknown. • Results support the general C&R literature with concentrations of lactate increasing and plasma potassium decreasing with fight time duration. • Tri-axial acoustic accelerometer transmitters were calibrated to identify relative activity for white sturgeon. • Wild accelerometer-tagged white sturgeon were located <75 m from release site and readings showed a decrease in activity 10 min after release. • All 7 accelerometer-tagged sturgeon were located closer to shore after release – suggesting a possible refuge-seeking recovery behaviour. Abstract White sturgeon (Acipenser transmontanus) are anadromous and the largest fish occurring in fresh-water habitats in North America. The largest population is found in the lower Fraser River (LFR), British Columbia, Canada where anglers target the species in a catch-and-release (C&R) recreational fishery. Yet, little is known about the consequences of C&R on these wild fish. Sixty-three angled sturgeon had blood samples taken to assess the physiological stress response relative to fight times. Seven sturgeon were also fitted with acoustic transmitters equipped with accelerometer sensors to assess immediate post-release locomotor behaviour. To understand the relationship between accelerometry and fish behaviour, we calibrated the tags in a lab before deploying them in the field. A physiological stress response was apparent (i.e., increased whole-blood lactate and reduced plasma potassium) and was influenced by fight time. Post-release activity profiles showed a general decrease in activity over time. Post-release displacement was 2–75 m from the release site and all 7 sturgeon were relocated closer to shore. The possible preference we identified for nearshore areas after release should be examined in greater detail in the future as this may lend insight into optimal release locations for white sturgeon. Although C&R mortality rates are low for this species, there is some evidence of transient sub-lethal effects emphasizing the need to refine C&R practices to further improve fish welfare. [ABSTRACT FROM AUTHOR]

Predation and reduced energetic intake have been highlighted as potential mechanisms of recruitment failure in sturgeon populations. These two factors may interact, as foraging carries with it costs of increased predation risk, requiring behavioral trade-offs. We expect that juvenile sturgeon should express predator avoidance behaviors while they are within vulnerable size ranges, yet these behaviors should be modified by nutritional state. To evaluate behavioral trade-offs of juvenile white sturgeon, we designed an experiment to test the interacting effects of acute nutritional state and predation risk on the spatial distribution and movement of small groups (n = 6). Groups were assigned to one of four treatments, designed as a full factorial of nutritional state (well-fed or starved 24-h) and predation risk (largemouth bass present or absent), and eight replicates were conducted for each treatment. Juvenile sturgeon displayed a predicted and adaptive response to predation risk and predator aggression levels by reducing activity levels and displaying marked freezing behavior. Sturgeon responded strongly to nutritional deprivation through increased activity and increased near-neighbor distance, which was likely an adaptive response to increase encounter rates with benthic food items. Both of these responses to starvation were suppressed in the presence of predators. This study has provided experimental evidence that predators can abruptly reduce the foraging activity of white sturgeon, possibly reducing growth rates and extending the period of juvenile vulnerability. Future conservation planning should consider the interacting effects of multiple stressors experienced by sturgeon at early life-stages, as introduced predators and degraded foraging habitats may have interacting effects. [ABSTRACT FROM AUTHOR]

The overall aim of this project was to understand the mode of sex determination mechanism operates in chondrostean species. The following hypotheses were tested: i) white sturgeon has a genetic sex determination system, ii) one of the sexes in sturgeon is heterogametic, and iii) sex-specific DNA polymorphisms exist between the sexes.Several experimental approaches derived from the fields of transmission, molecular, and cytogenetics were used to examine the nature of the sex determination process.In the first series of experiments (Chapter 2) ploidy manipulation techniques were used  to produce gynogenetic and polyploid white sturgeon. A novel random amplified polymorphic DNA (RAPD)-based technique was developed to rapidly assess the overall success of treatments designed to induce gynogenesis, and measuring erythrocyte nuclei size with a Coulter Counter was found to be a rapid and accurate technique for ploidy analysis in sturgeon. Both sexes were observed in 23-24 month old gynogenetic progeny groups derived from four different females supporting the hypothesis that white sturgeon has a female heterogametic (ZW:ZZ) genetic sex determination system. The proportion of males in diploid (48%), gynogenetic (18%), and triploid (14%) progeny groups derived from the same female suggested that the sex-determining element on the W chromosome segregates independently of the centromere. In the second series of experiments (Chapter 3) various molecular techniques were used in an attempt to isolate genetic markers for the identification of sex in white sturgeon. Subtractive hybridization, representational difference analysis and bulked segregant analysis were used, in conjunction with genetically unique groups of sturgeon, which were specifically developed  to increase the probability of isolating sex-specific DNA sequences. DNA sequences associated with sex in white sturgeon were not identified. These results suggest that either 1) there are no sex-specific sequences in sturgeon, or 2) the sex-specific DNA is comprised of unusual sequences which were not complementary to the 1200 random decamer primers or the recognition sequence of the restriction endonucleases used in this set of experiments, or 3) the sex-specific sequences comprise a very small portion of the genome.Chapter 4 details a synaptonemal complex (SC) analysis of white sturgeon spermatocytes. Synaptonemal complex analyses have not been previously reported for any sturgeon species and this study was initiated to determine if it was possible to directly identify heteromorphic sex chromosomes in meiotic prophase SC spreads. No bivalent consistently exhibited asynaptic behavior or had axes of unequal length suggesting that heteromorphic sex chromosomes are not present in white sturgeon spermatocytes which concurs with the findings of Chapter 2. Pachytene nuclei had varying numbers of univalents, self-paired foldback elements with no obvious centromeric region (1-7), and other SC peculiarities. No consistent evidence of alignment or pairing involving more than two lateral elements was found indicating that the process of diploidization is now complete in this ancient polyploid. The SC number was 139 (± 3.4) with both between and within animal variation.The final series of experiments (Chapter 5) involved mitotic analyses of metaphase chromosome spreads from four white sturgeon individuals of each sex. Conventional mitotic analyses provided no evidence for a heteromorphic sex chromosome pair or any sex-related chromosomal polymorphism. Likewise fluorescence in situ hybridization of labeled male and female sturgeon genomic DNA to metaphase chromosome spreads of each sex did not reveal a chromosome that was seen to be specifically hybridizing only to the genomic DNA of one sex. The average chromosome number was 271 (range 265-276) which concurred with the meiotic count found in Chapter 4. An  improved C-banding technique using propidium iodide and epifluorescence microscopy revealed between animal variation (2-7) in the number of entirely heterochromatic metacentric chromosomes. These heterochromatic chromosomes and the self-pairing elements observed in  Chapter 4 were approximately equal in number and relative size and they may represent accessory B chromosomes. In combination these results suggest that white sturgeon has a female heterogametic ZW:ZZ genetic sex determination system, and that the sex-determining element segregates independently ofthe centromere. No evidence of a heteromorphic sex chromosome pair was found in meiotic analyses of white sturgeon spermatocytes supporting the hypothesis of male homogamety in this species.  The inability to identify sex-specific DNA sequences despite evidence of a genetic sex determination system suggests that sex-specific DNA is rare, making up a very small portion of the genome. Mitotic analyses provided no evidence for a heteromorphic sex chromosome pair suggesting that the accumulation of sex chromosomal rearrangements is insufficient to be visible at the cytogenetic level. All of these results support the contention that white sturgeon sex chromosomes are at an early stage of differentiation.

Veronaea botryosa is the etiological agent of a systemic phaeohyphomycosis known as "fluid belly" in white sturgeon (Acipenser transmontanus). Fluid belly is a critical disease affecting sturgeon aquaculture and the caviar industry for which there are no commercially available vaccines or approved antifungal treatments to manage outbreaks. The primary aim of this study was to investigate the effect of a V. botryosa [conidia], a V. botryosa [mold], and a Saccharomyces cerevisiae [yeast] formalin-killed vaccine on sturgeon immune responses to fungal challenge. Immunization consisted of an initial intracoelomic injection with one of the three treatment preparations, followed by a vaccine booster four weeks later by the same route and dose. Experimental challenge by intramuscular injection with a virulent V. botryosa conidia suspension followed after another four weeks. Non-challenged control fish received injections of PBS. The inactivated vaccines proved safe for white sturgeon fingerlings. Sturgeon immunized with either V. botryosa [mold] or S. cerevisiae [yeast] exhibited a significantly different pro-inflammatory response upon challenge with V. botryosa compared to non-immunized fish. Challenged fish developed clinical signs similar to those reported during natural outbreaks of fluid belly. Positive control treatments (those not immunized but challenged with V. botryosa) experienced the highest mortality; however, survival curves were similar amongst all treatments (p < 0.05). Furthermore, the S. cerevisiae [yeast] vaccine resulted in comparatively lower fungal persistence and fewer lesions following histological analysis. Further efforts evaluating the potential of Saccharomyces spp. as a vaccine candidate against fluid belly are warranted. • Inactivated vaccines against V. botryosa were safe for white sturgeon fingerlings. • Mold and yeast vaccines induced a significant inflammatory response upon challenge. • S. cerevisiae has potential as a vaccine candidate against fluid belly. [ABSTRACT FROM AUTHOR]

An 8-week feeding trial was conducted to investigate the responses of juvenile white sturgeon (Acipenser transmontanus) to elevated dietary selenium (Se) based on the determination of the RNA/DNA ratio in muscle, heat shock protein 70 (Hsp70), and caspase-3/7 in muscle and/or liver tissues. Four semi-purified test diets were prepared by adding different levels of L-selenomethionine (0, 50, 100, and 200 mg/kg diet). The analytical determinations of total Se were 2.2, 19.7, 40.1, and 77.7 mg/kg diet. The sturgeon (initial body weight: 30 ± 2 g; mean ± SEM) were raised in indoor tanks provided with flow through freshwater (18–19 °C). There were three replicates for each dietary treatment with 25 fish per replicate. The liver and muscle tissues were collected at 4 and 8 weeks after feeding the test diets. A significant interaction between duration and levels of dietary Se exposures on RNA/DNA ratio in the muscle tissue was detected (P