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Background: In aquaculture, sturgeons are generally maintained in the confined spaces, which not only hinders sturgeon movement, but also threatens their flesh quality that seriously concerned by aquaculture industry. As a typical antioxidant, resveratrol can improve the flesh quality of livestock and poultry. However, the mechanism of resveratrol's effect on the muscle of Siberian sturgeon is still unclear. Results: In this study, the dietary resveratrol increased the myofiber diameter, the content of the amino acids, antioxidant capacity markers (CAT, LDH and SOD) levels and the expression levels of mTORC1 and MYH9 in muscle of Siberian sturgeon. Further transcriptome analysis displayed that ROS production-related pathways ("Oxidative phosphorylation" and "Chemical carcinogenes-reactive oxygen species") were enriched in KEGG analysis, and the expression levels of genes related to the production of ROS (COX4, COX6A, ATPeF1A, etc.) in mitochondria were significantly down-regulated, while the expression levels of genes related to scavenging ROS (SOD1) were up-regulated. Conclusions: In summary, this study reveals that resveratrol may promote the flesh quality of Siberian sturgeon probably by enhancing myofiber growth, nutritional value and the antioxidant capacity of muscle, which has certain reference significance for the development of a new type of feed for Siberian sturgeon. [ABSTRACT FROM AUTHOR]

This study aimed to examine the effect of various live foods on the fatty acids (FAs) and amino acids (AAs) profiles in Persian sturgeon (Acipenser persicus) larvae. One thousand and two hundred larvae were cultured in circular concrete tanks, and four treatments were administered as: (1) Artemia + Daphnia, (2) Artemia, (3) Artemia + Chironomid, and (4) Chironomid. Each treatment was considered as three replicates over an 11-day period. At the end of the experiment, treatment 1 (Artemia + Daphnia) showed the highest average weight of larvae, and the lowest weight was observed in treatment 4 (Chironomid). Survival rate ranged from 83.84% to 88.86% and no significant difference was observed among the groups (P > 0.05). Among Artemia-fed larvae, the predominant FAs were docosahexaenoic acid (DHA), oleic acid (ω9), and monounsaturated fatty acids (MUFA), while saturated fatty acids (SFA) and polyunsaturated fatty acids (PUFA) (ω3 + ω6) were present in a lesser proportion (P < 0.05). In larvae fed with Artemia and Daphnia, the predominant proportions were observed in SFAs, eicosapentaenoic acid (EPA), ω3, DHA + EPA, and the n3/n6 ratio, all registering the highest percentages. Conversely, MUFA, ω6, and the DHA/EPA ratio displayed the lowest percentages (P < 0.05). Moreover, larvae fed with Artemia exhibited higher levels of ω6, PUFA (ω3 + ω6), and DHA/EPA ratio. In contrast, larvae fed with Chironomid showed lower levels of EPA, DHA + EPA, and n3/n6 ratio (P < 0.05). Among larvae fed with Chironomid, solely the DHA/EPA ratio exhibited a higher value compared to larvae fed with Artemia and Daphnia (P < 0.05). The amount of leucine in fish fed Artemia + Daphnia was more than the other treatments (P < 0.05). This study revealed a significant difference in amino acids composition among various live foods (P < 0.05), but no significant difference in AAs was observed in the body of Persian sturgeon larvae (P > 0.05). The results of this study suggest that the Persian sturgeon larvae possess the ability to maintain a balanced state of AAs. It is also evident that the FA profile of different live foods can affect the overall FA levels in the body of Persian sturgeon larvae, ultimately contributing to the enhancement of fish survival rate and growth. [ABSTRACT FROM AUTHOR]

Bisphenol A (BPA), an important component of the plastics industry, is characterized as an endocrine disrupting toxic substance for aquatic organisms. This study focused on the toxic effects of BPA on endangered Danube sturgeon larvae (Acipenser gueldenstaedtii). In the study, LC50 values for five different BPA concentrations (100, 200, 400, 800, 1200 μg/L) were observed as 803.4 μg/L, 63.1 μg/L, and 39.6 μg/L at 24th, 48th a nd 72nd hours, respectively. Especially, the lethal effect of BPA on the larvae was remarkable after the 24th hour. On the other hand, histopathological changes were examined based on the LC50 value at the 24th hour. Vacuolization symptom was noted in the gills of the larvae. In addition, vacuolization and melanomacrophage centers caused a severe degradation in liver and kidney tissues of BPA group. In the intestine, the number of goblet cells per ville was lower in the BPA group. As a result, it has been proven by LC50 and histopathological studies that BPA has high toxicity in A. gueldenstaedtii larvae. [ABSTRACT FROM AUTHOR]

Background: Monitoring movement across an organism's ontogeny is often challenging, particularly for long-lived or wide-ranging species. When empirical data are unavailable, general knowledge about species' ecology may be used to make assumptions about habitat use across space or time. However, inferences about habitat use based on population-level ecology may overlook important eco-evolutionary contributions from individuals with heterogenous ethologies and could diminish the efficacy of conservation and management. Methods: We analyzed over a decade of acoustic telemetry data to understand individual differences in habitat use of federally endangered adult Atlantic sturgeon (Acipenser o. oxyrinchus) in the Delaware and Hudson rivers during spawning season. In particular, we sought to understand whether sex or natal origin could predict patterns in habitat use, as there is a long-held assumption that adult Atlantic sturgeon seldom stray into non-natal rivers. Results: In both rivers, migration timing, spawning habitat occupancy, and maximum upstream migration distance were similar between natal and non-natal individuals. While non-natal individuals represented only 13% of fish detected in the Hudson River, nearly half of all tagged fish detected in the Delaware River were non-natal and generally occupied freshwater habitats longer than natal individuals. In both systems males had more heterogenous patterns of habitat use and longer duration of occupancy than did females. Conclusions: This study demonstrates the importance of non-natal rivers for fulfilling ontogenetic habitat requirements in Atlantic sturgeon. Our results may also highlight an opportunity to improve conservation and management by extending habitat designations to account for more heterogenous patterns in individual habitat use in non-natal freshwater environments. [ABSTRACT FROM AUTHOR]

Many teleosts possess a unique set of respiratory characteristics allowing enhanced oxygen unloading to the tissues during stress. This system comprises three major components: highly pH sensitive haemoglobins (large Bohr and Root effects), rapid red blood cell (RBC) intracellular pH (pHi) protection, and a heterogeneous distribution of membrane-bound plasma-accessible carbonic anhydrase (paCA; absence in the gills). The first two components have received considerable research effort; however, the evolutionary loss of branchial paCA has received little attention. In the current study, we investigated the availability of branchial membrane-bound CA, along with several other CA-related characteristics in species belonging to three basal actinopterygian groups: the Lepisosteiformes, Acipenseriformes and Polypteriformes to assess the earlier hypothesis that Root effect haemoglobins constrain branchial paCA availability. We present the first evidence suggesting branchial membrane-bound CA presence in a basal actinopterygian species: the Senegal bichir (Polypterus senegalus) and show that like the teleosts, white sturgeon (Acipenser transmontanus) and alligator gar (Atractosteus spatula) do not possess branchial membrane-bound CA. We discuss the varying respiratory strategies for these species and propose that branchial paCA may have been lost much earlier than previously thought, likely in relation to the changes in haemoglobin buffer capacity associated with the increasing magnitude of the Bohr effect. The findings described here represent an important advancement in our understanding of the evolution of the unique system of enhanced oxygen unloading thought to be present in most teleosts, a group that encompasses half of all vertebrates. [ABSTRACT FROM AUTHOR]

Motilin is a gastrointestinal hormone that is mainly produced in the duodenum of mammals, and it is responsible for regulating appetite. However, the role and expression of motilin are poorly understood during starvation and the weaning stage, which is of great importance in the seeding cultivation of fish. In this study, the sequences of Yangtze sturgeon (Acipenser dabryanus Motilin (AdMotilin)) motilin receptor (AdMotilinR) were cloned and characterized. The results of tissue expression showed that by contrast with mammals, AdMotilin mRNA was richly expressed in the brain, whereas AdMotilinR was highly expressed in the stomach, duodenum, and brain. Weaning from a natural diet of T. Limnodrilus to commercial feed significantly promoted the expression of AdMotilin in the brain during the period from day 1 to day 10, and after re-feeding with T. Limnodrilus the change in expression of AdMotilin was partially reversed. Similarly, it was revealed that fasting increased the expression of AdMotilin in the brain (3 h, 6 h) and duodenum (3 h), and the expression of AdMotilinR in the brain (1 h) in a time-dependent manner. Furthermore, it was observed that peripheral injection of motilin-NH2 increased food intake and the filling index of the digestive tract in the Yangtze sturgeon, which was accompanied by the changes of AdMotilinR and appetite factors expression in the brain (POMC, CART, AGRP, NPY and CCK) and stomach (CCK). These results indicate that motilin acts as an indicator of nutritional status, and also serves as a novel orexigenic factor that stimulates food intake in Acipenser dabryanus. This study lays a strong foundation for the application of motilin as a biomarker in the estimation of hunger in juvenile Acipenser dabryanu during the weaning phase, and enhances the understanding of the role of motilin as a novel regulator of feeding in fish. [ABSTRACT FROM AUTHOR]

The Chinese sturgeon (Acipenser sinensis) is a critically endangered aquatic fish. Health monitoring and welfare assessments are critical for the conservation of Chinese sturgeon. In this study, biochemical parameters of serum and skin mucus in Chinese sturgeon were examined to evaluate the potential biomarkers. Serum and mucous samples were obtained from Chinese sturgeon, and the levels of total protein (TP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), creatine kinase (CK), lactic acid (LD), acid phosphatase (ACP), lysozyme (LYZ), glucose (GLU), and cortisol were determined. The concentrations of ALT, AST, cortisol, and LYZ were significantly higher in the mucous group than those in the serum group (p < 0.05). In addition, the concentrations of ALP, ACP, LD, LDH, CK, and TP were significantly higher level in the serum group than those in the mucous group (p < 0.05). Moreover, the correlations between serum and mucous biochemical parameters were established. Statistical analysis showed a positive correlation between serum and skin mucous markers (ACP, cortisol, and LYZ). AST versus ALT in serum and mucus showed a significant positive correlation (p < 0.01). A significant positive correlation was found between cortisol and CK in mucus (p < 0.01). Moreover, LD versus LDH in serum showed a significant but weak positive correlation (p < 0.01). Principal component analysis revealed a complete separation between the serum and mucous groups, with the biomarkers that contributed the most being ALP, TP, ALT, and AST. This study provides baseline data and reference intervals for serum and mucous biochemical parameters in presumably healthy Chinese sturgeons. The current study has important implications for the development of conservation strategies and the conservation status of critically endangered species. [ABSTRACT FROM AUTHOR]

This study was performed to assess the impacts of introducing diets containing different levels of soybean meal (SBM) to sterlet sturgeon (Acipenser ruthenus) larvae on growth performance, body composition, and molecular responses in the juvenile stage. The sterlet larvae (57.68 ± 0.66 mg) were weaned onto the formulated diets as follows: a control diet containing 60% fishmeal (FM), and three experimental diets with replacement levels of 15% (SBM15), 30% (SBM30), and 45% (SBM45) of FM with SBM. Then, a total of 260 fish (initial weight: 323.33 ± 11.76 mg) were fed the four different diets for 28 days in triplicates (phase 1, nutritional programming, NP). All treatments were then fed with the FM diet in phase 2 (common phase), and in phase 3 (challenge phase), all experimental groups (6.14 ± 0.08 g) were transitioned to SBM45 for 28 days. At the end of phases 1 and 2, growth performance showed no significant differences among the groups (P > 0.05), while significantly improved in SBM45 than the control at the end of phase 3 (P < 0.05). No significant differences were found among the groups in any phases for whole body composition (P > 0.05). Additionally, the total saturated fatty acids were significantly higher in SBM-based diets than FM at the end of phase 3 (P < 0.05). The mRNA of GH, IGF-I was significantly affected by variation of FM replacement level (P < 0.05). The expression level of Ghrelin was up-regulated in fish fed SBM at the end of phase 3 (P < 0.05). Our findings revealed that NP can positively enhance the adaptation of juvenile sterlet sturgeon to 45% SBM when exposed to the same diets at the larval stage. Further research is being carried out to provide valuable insights into the underlying mechanisms of digestive performance for this species. [ABSTRACT FROM AUTHOR]

Chemical analysis of samples of ovarian fluid (OF), a secondary product of breeding of the two common species of Acipenseridae family in Russian aquaculture, was carried out in order to assess its nutritional and possible medicinal value. It has been established that the dominant organic component of OF of both species is a water-soluble or water-dispersible protein easily absorbed by the digestive tract. Proteomic analysis of the samples has shown that the main component of the protein fraction of OF is a highly nutritious protein vitellogenin. Amino acid analysis has shown that 350 g of dried sturgeon OF or 245 g of dried sterlet OF satisfy the needs of an adult human in all essential amino acids per one day. Eighty-five grams of dried sturgeon OF or 55 g of dried sterlet OF covers the daily requirement of an adult for vitamins C, B1, B2, B3 (PP) and B6, a number of macroelements (Na, K, Ca, Mg) and microelements (Fe, Cu, Mn, Zn, Cr). Furthermore, Cu content is significantly higher in sturgeon OF, and Fe content is significantly higher in sterlet OF, which is partly confirmed by the relative content of Cu and Fe carrier proteins, ceruloplasmin and transferrin, respectively. In addition, a number of proteins of physiological significance for fish were identified. The possible medicinal value of OF consists, among other things, in significant content of various antioxidant proteins in OF of both species. The use of OF as a food supplement could improve the profitability of sturgeon breeding by producing an additional valuable product, and would also expand the range of natural dietary supplements on the market. [ABSTRACT FROM AUTHOR]

Sturgeon farming is rapidly expanding in Europe, where Italy ranks first in farmed caviar production. A major threat to sturgeon health in captivity is infection with Acipenser European Iridovirus (AcIV-E), a viral disease definitively identified in 2016. Here we present data on the occurrence of AcIV-E in 482 sturgeons (age ≤ 12 months, species of the genus Acipenser and the species Huso huso) collected from sturgeon farms in northern Italy between January 2021 and December 2023. The health status of each specimen was determined by necroscopy and virological assay. Virological analysis was performed on gill samples and real-time PCR specific to the MCP gene of the iridovirus viral capsid. Molecular analysis revealed positivity to the virus in 204 samples (42.68% of the total), while anatomopathological examination of nearly all fish with positive real-time PCR disclosed swollen abdomen, hepatic steatosis, splenomegaly, and increased gill volume. Two challenges to timely diagnosis are the absence of pathognomonic symptoms and the inability to isolate the virus on cell monolayers. Continuous and widespread health monitoring is therefore crucial for disease management and to effectively control spread of the virus. [ABSTRACT FROM AUTHOR]

Chinese sturgeon Dmrt gene family was identified and characterized for the first time. A total of 5 putative Dmrt genes were identified. The gene structure, conserved protein domain and the phylogenetic relationship of Dmrt gene family were systematically analyzed. The expressed profile of Chinese sturgeon Dmrt genes in gonad, pituitary and hypothalamus in the male and female were investigated. The results indicated that the accumulation of Dmrt genes was involved in different tissues, and the expression profile also differed among each Dmrt genes. ASDmrt1A, ASDmrt2, ASDmrt3, and ASDmrtA1 were highly expressed in the testis in comparison with other tissue. This result showed that ASDmrt1A, ASDmrt2, ASDmrt3, and ASDmrtA1 played an important role in the development of testicle, and may be useful tool in distinguishing between male and female of Chinese sturgeon. Our study will provide a basis for additional analyses of Chinese sturgeon Dmrt genes. This systematic analysis provided a foundation for further functional characterization of Dmrt genes with an aim of study of Chinese sturgeon Dmrt gene family. [ABSTRACT FROM AUTHOR]

Simple Summary: Tachykinin1 (tac1) gene products participate in the regulation of hormone secretion in the pituitary of Dabry's sturgeon. Two products of tac1 gene, Substance P (SP) and neurokinin A (NKA), were initially confirmed to regulate the gene expression of two gonadotropins (lh and fsh) in the Dabry's sturgeon pituitary tissue by intraperitoneal injection in vivo and co-culture of primary cells in vitro. This research presents the initial investigation into the reproductive role of SP and NKA in Dabry's sturgeon, offering a valuable insights for advancing efficient ripening techniques in artificial breeding of sturgeon. As an ancient and endangered species unique to the Yangtze River in China, the wild population of the Dabry's sturgeon has become scarce. Due to the long time till the first sexual maturity of Dabry's sturgeon, the population of artificially bred Dabry's sturgeon recovered slowly. As a member of the tachykinin family, TAC1 has been reported to have a variety of functions in mammals such as pain control, smooth muscle contraction and reproductive cycle regulation, but the function of Tac1 in fish has been rarely reported. In this study, we synthesized two tac1 gene products, Substance P (SP) and neurokinin A (NKA), and further verified the effect of two tac1 gene products on the secretion of related hormones in the pituitary of Dabry's Sturgeon by intraperitoneal injection and co-culture of primary cells. Expression studies revealed that the newly cloned tac1 were mainly distributed in the hypothalamus and pituitary tissue of the brain. In prepubertal Dabry's sturgeon, this study showed that the two gonadotropins' mRNA levels in pituitary tissue can be significantly increased by SP and NKA through intraperitoneal injection, and the LH protein level in serum was also increased. Further study showed that both NKA and SP could promote the two gonadotropins' mRNA expression in pituitary cells of Dabry's sturgeon. In addition, we explored the optimal dose and time of SP and NKA on pituitary cells is 24 h and over 10 nM. These results, as a whole, suggested that tac1 gene products play an important role in gonadotropin release and gonadal development in prepubertal Dabry's sturgeon. [ABSTRACT FROM AUTHOR]

Simple Summary: The objective of this study was to investigate the correlation between juvenile Acipenser sinensis density and the eDNA content in a controlled laboratory aquarium environment. The results obtained from fluorescent quantitative PCR indicated an overall increasing trend in the eDNA content, which tended to stabilize after three days. Furthermore, a significant positive linear correlation was observed between the density of juvenile A. sinensis and eDNA content at different time points (R2 = 0.768~0.986). When the juvenile A. sinensis were removed at a density of 0.114 ind./L, there was a negative correlation between eDNA content and time. Based on AIC and BIC analyses, a power function model was employed to illustrate the degradation relationship between eDNA content and time. Since the construction of the Gezhouba Dam, Chinese sturgeon (Acipenser sinensis) numbers have gradually declined, rendering this species critically endangered according to the International Union for the Conservation of Nature. Environmental DNA (eDNA) technology plays an important role in monitoring the abundance of aquatic organisms. Species density and biomass have been proven to be estimable by researchers, but the level of accuracy depends on the specific species and ecosystem. In this study, juvenile A. sinensis, an endangered fish, were selected as the research target. Under controlled laboratory conditions in an aquarium, one, two, four, six, and eight juvenile A. sinensis were cultured in five fish tanks, respectively. Water samples were filtered at eight different time points for eDNA content analysis. Additionally, eDNA yield was tested at six different time points after a 0.114 ind./L density of A. sinensis was removed, and the employed degradation model was screened using the Akaike information criterion (AIC) and the Bayesian information criterion (BIC). The results showed that eDNA content remained stable after 3 days and exhibited a significant positive linear correlation with the density of A. sinensis (R2 = 0.768~0.986). Furthermore, eDNA content was negatively correlated with the 3-day period after the removal of A. sinensis. The power function had the smallest AIC and BIC values, indicating better fitting performance. This study lays a momentous foundation for the application of eDNA for monitoring juvenile A. sinensis in the Yangtze Estuary and reveals the applicability of eDNA as a useful tool for assessing fish density/biomass in natural environments. [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]

Sturgeons belong to the family Acipenseridae, the most species‐rich extant family of Acipenseriformes, a basal actinopterygian group of key importance in assessing the early radiations of the actinopterygians. At the same time, acipenseriforms display unique specializations in the morphology of the snout and jaws which make them a valuable model for studying evolutionary novelties. However, despite a long history of research, the homologies of the snout and the mandibular arch of acipenseriforms remain uncertain preventing further studies on the evolutionary origin of their unique snout and jaw structure, and in particular, of the upper jaw symphysis, the key apomorphy of the group and the preoral snout. In the present study, a detailed description of the upper jaw morphology and development in sturgeons is provided in order to address its composition in terms of the common actinopterygian archetype. Based on the obtained results, the upper jaw of acipenseriforms is assumed to have lost the autopalatine portion, which most likely is represented by the separate cartilages supporting the tentacles. Also, the conventional interpretation of the sturgeon's maxilla as dermopalatine is rejected on the grounds of this bone structure and development. Paedomorphosis is proposed to be the most likely mechanism explaining the evolutionary origin of the upper jaw symphysis and supposed modifications of the snout in sturgeons. [ABSTRACT FROM AUTHOR]

Simple Summary: Heat is a common stressor in aquatic environments and can cause damage to organs such as the kidneys, which in turn affects normal physiological functions in aquatic animals. The effects of heat stress on the kidney of Siberian Sturgeon (Acipenser baerii) were investigated using histologic observation, flow cytometry assay, and RT-qPCR technique. Heat stress caused damage to the kidneys, leading to inflammatory cell infiltration, a significant increase in apoptosis as well as a significant increase in plasma creatinine, and induced significant expression of the heat shock protein GRP75 mRNA. However, the mRNA expression levels of inflammatory factors (IL-1β and TNF-α) and heat shock protein (HSP70 and HSP90) did not change significantly. Chronic heat stress caused by global warming can have serious implications for fish survival. The kidney plays a central role in many homeostatic functions, including water and electrolyte regulation. However, there is limited knowledge about the effect of heat stress on fish kidneys. In this study, water temperatures were increased from 20 °C to 24 °C and 28 °C in 8 days at a warming rate of 1 °C/d, and then maintained for 12 days. We investigated the effects of mild heat stress (24 °C) and high heat stress (28 °C) on Siberian Sturgeon (Acipenser baerii) kidneys using histological observation, flow cytometry detection, and RT-qPCR. Our histological observations revealed that heat stress caused significant infiltration of inflammatory cells in the kidney, especially at 28 °C. The flow cytometry assay demonstrated a significant increase in the number of apoptotic cells after heat stress at 28 °C compared to a control group at 20 °C (p = 0.033). The level of plasma creatinine was significantly increased in the 28 °C group compared to the control group (p = 0.001). In addition, the mRNA expression levels of heat shock protein GRP75 increased (p = 0.009). The results indicate that heat stress at 28 °C caused damage to the kidneys of A. baerii and triggered the protective response of heat shock proteins. In conclusion, this study contributes to the understanding of the coping strategies of the kidney of A. baerii for chronic heat stress. [ABSTRACT FROM AUTHOR]

Lysozyme (Lys) is one of the most vital antibacterial proteins of the innate immune system that neutralizes pathogens. This work described Lys-c gene expression in cDNA from the liver, spleen, pancreas, and anterior kidney of male and female Acipenser persicus matured for the first time globally. In this respect, tissue samples were taken from eight male and eight female fish after artificial breeding. Frozen tissues were used to extract total RNA. A complete cDNA synthesis was carried out. Real-time quantitative RT-PCR was used to compare and evaluate Lys-c expression. According to the findings, Lys-c was present in all experimental tissues. The highest and lowest Lys-c expressions were displayed in the spleen and pancreatic tissues, respectively (p < 0.01). However, Lys-c expression in male species was significantly higher compared to females (p < 0.01). Based on the obtained results, we conclude that the levels of Lys-c expression in individuals of mature A.persicus breeding can be affected by various circumstances, with the possibility of implications requiring further investigation. [ABSTRACT FROM AUTHOR]

Empirical evidence suggests that marine animals perceive and orient to local distortions in the earth's natural magnetic field. Magnetic fields (MFs) generated by electrified underwater cables may produce similar local distortions in the earth's main field. Concern exists that these distortions may impact migration movements of MF-sensitive animals. The Trans Bay Cable (TBC) is a ± 200-kV, 400-megawatt, 85-km high-voltage direct current transmission line buried through San Francisco Bay (37° 56′ 8.81″ N, 122° 27′ 0.19″ W). Detections of adult green sturgeon implanted with acoustic transmitters were used from six cross-bay receiver arrays from 2006 to 2015 to investigate how inbound and outbound migration movements through lower portions of their route to/from upstream breeding grounds are related to the TBC's energization status (off/on) and other local environmental variables. Here, we assess how these variables impacted transit success, misdirection from the migration route, transit times, and migration path locations within stretches between the Bay's mouth and the start of the Sacramento River. Overall, there was varied evidence for any effect on migration behavior associated with cable status (off/on). A higher percentage of inbound fish successfully transited after the cable was energized, but this effect was nonsignificant in models including temperature. Outbound fish took longer to transit after cable energization. Inbound and outbound migration path locations were not significantly influenced by cable energization, but results suggest a potential subtle relationship between energization and both inbound and outbound paths. Overall, additional migration-based studies are needed to investigate the impact of anthropogenic cables on marine species. [ABSTRACT FROM AUTHOR]

The white sturgeon (Acipenser transmontanus) is the largest freshwater fish in North America. Because of the unique life history characteristics of sturgeon, including longevity, late maturation and long spawning intervals, their aquaculture can be a significant investment of resources. As a result of habitat loss and overharvesting, natural populations of white sturgeon are threatened and there is a growing effort to improve conservation aquaculture programs. Germ cell transplantation is an innovative technology previously demonstrated in a variety of fish species to be able to produce a surrogate broodstock. The technique relies upon optimal donor germ cell recovery and transplantation into a recipient fish. In this study, we developed and optimized the harvest of donor cells for germline transplantation and evaluated methods for ovary cryopreservation for the first time in the white sturgeon. We found that harvesting gonads from juveniles between the ages of 1.5 and 2.5-years resulted in reliably high proportions of pre-meiotic cells regardless of sex, a critical feature for using white sturgeon for transplantation studies since the species shows no distinguishing external sex characteristics. From the viable cells, we identified germline cells using immunolabeling with the antibody DDX4, a marker specific to the germline. For in vivo tracking of donor cells during transplantations, gonadal cells were stained with a long half-life non-toxic cell membrane dye, PKH26, and microinjected into the peritoneal cavity of newly hatched white sturgeon larvae. Larvae were reared until 3 months post-transplantation to monitor for colonization and proliferation of PKH26-labeled cells within the recipient larval gonads. Furthermore, viable cell detection, assessment of germline-specificity, and transplantation was determined for cells recovered from cryopreserved ovarian tissue from sexually immature females. Transplantations using cells cryopreserved with media supplemented with dimethyl sulfoxide (DMSO) rather than ethylene glycol (EG) demonstrated the highest number of PKH26-labeled cells distributed along the gonadal ridges of the larval recipient. Determining optimal methods of tissue cryopreservation, and germ cell recovery and transplantation are foundational to the future development of germ cell transplantation as a strategy to improve the aquaculture and conservation of this species. Our study demonstrates that conservation actions, such as surrogate breeding, could be utilized by hatcheries to retain or improve natural gamete production without genetic modification, and provide an encouraging approach to the management of threatened sturgeon species. [ABSTRACT FROM AUTHOR]

The experiment was to study the effect of compound Chinese herbal medicine on the immunity, antioxidant and disease resistance of juvenile Acipenser dabryanus. A total of 360 juvenile Acipenser dabryanus with a body weight of (537.68 ± 25.47) g and a body length of (46.27 ± 5.71) cm were randomly divided into four groups, with three replicates in each group and 30 fish in each replicate. The fish in the control group were fed with a basic feed, and the experimental groups were fed with a basic feed supplemented with 0.5%, 1.0% and 1.5% compound Chinese herbal medicine, respectively. The experiment lasted for 21 d. On 14 and 21 d of the experiment, 20 juvenile Acipenser dabryanus were randomly selected from each group, and Aeromonas hydrophila was used for challenge test. The results showed that compared with the control group, the serum IgM content in the 1.5% experimental group was significantly increased on 7 d (P<0.05). On 14 d, serum IgG and IgM content in the 1.0% experimental group and the 1.5% experimental group were significantly increased (P<0.05). On 21 d, the content of IgG and IgM in the 1.5% experimental group were higher than those in the control group. Compared with the control group, the content of serum complement C4 and AMP and the activitiy of LSZ and AKP in the 1.5% experimental group were significantly increased on 2 7, 14 d (P<0.05). On 21 d, the serum AMP content of the 1.5% experimental group was still significantly higher than those in the control group (P<0.05). Compared with the control group, the serum SOD activity of the 1.5% experimental group was significantly increased on 7, 14, 21 d (P<0.05). On 14 d, the activitiy of CAT and POD in the serum of the 1.5% experimental group was significantly increased (P<0.05), while the content of MDA was significantly decreased (P<0.05). On 14, 21 d, the serum GSH-Px activity of the 1.5% experimental group was significantly increased (P<0.05). On 7, 14 d, serum T-AOC in the 1.5% experimental group was significantly increased (P<0.05). The mortality of the 1.0% experimental group and the 1.5% experimental group on 14, 21 d was significantly lower than that of the control group. The study indicates that the compound Chinese herbal medicine can improve the immunity, antioxidant and disease resistance of juvenile Acipenser dabryanus, and a course of treatment with a 1.5% supplement for 14~21 d is more effective. [ABSTRACT FROM AUTHOR]

Aquatic environments face frequent exposure to organophosphate pesticides, such as diazinon, which are frequently utilized in agriculture. The goal of this study was to evaluate the effects of diazinon exposure on fish and to investigate the potential of the HSP inducer (HSPi) in developing a defense mechanism. To achieve this, several factors were analyzed, including the HSP70 gene expression, levels of immunity markers (lysozyme, IgM, and C3), antioxidant status, and the activity of acetylcholine esterase (AChE). Stellate sturgeon (Acipenser stellatus) fry, was exposed to diazinon (25, 50, and 75% of 96h-LC50) for 6 days after pre-treatment with an HSP inducer (HSPi), TEX-OE® (a prickly pear cactus extract), for 4 hours. Two HSPi concentrations, 100 and 200 mg.L-1, were used. Pre-treatment with HSPi significantly enhanced HSP70 gene expression in the gill and liver, as well as immune markers in the blood of Acipenser stellatus. Diazinon-treated groups exhibited higher antioxidant activities of SOD, CAT, and T-AOC. Increased activity also observed in control fish pre-treated with HSPi. However, stellate sturgeon receiving both diazinon and HSPi+diazinon experienced a significant decrease in AChE activity in comparison with control group. Cortisol levels were elevated in the fish that were subjected to diazinon. Those subjected to diazinon after receiving HSPi showed a significant decrease in cortisol levels. In conclusion, the study suggests that HSPi-mediated HSP70 induction may have a protective effect. The presence of an HSP inducer offers a potential strategy to mitigate the consequences of diazinon exposure in stellate sturgeon. [ABSTRACT FROM AUTHOR]

Sturgeon is known as a primitive fish with the ZZ/ZW sex determination system and is highly prized for its valuable caviar. Exploring the molecular mechanisms underlying gonadal differentiation would contribute to broadening our knowledge on the genetic regulation of sex differentiation of fish, enabling improved artificial breeding and management of sturgeons. However, the mechanisms are still poorly understood in sturgeons. This study aimed to profile expression patterns between female and male gonads at morphologically undifferentiated and early differentiated stages and identify vital genes involved in gonadal sex differentiation of sturgeons. The sexes of Yangtze sturgeon (Acipenser dabryanus) juveniles were identified via the sex-specific DNA marker and histological observation. Transcriptome analyses were carried out on female and male gonads at 30, 80 and 180 days post-hatching. The results showed that there was a total of 17 overlapped DEGs in the comparison groups of between female and male gonads at the three developmental stages, in which there were three DEGs related to ovarian steroidogenesis, including hsd17b1, foxl2 and cyp19a1. The three DEGs were highly expressed in the female gonads, of which the expression levels were gradually increased with the number of days after hatching. No well-known testis-related genes were found in the overlapped DEGs. Additionally, the expression levels of hsd17b1 and cyp19a1 mRNA were decreased with the knockdown of foxl2 mRNA via siRNA. The results further suggested that foxl2 should play a crucial role in the ovarian differentiation of sturgeons. In conclusion, this study showed that more genes involved in ovarian development than testis development emerged with sexually dimorphic expression during early gonadal sex differentiation, and it provided a preliminary understanding of the molecular regulation on gonadal differentiation of sturgeons. [ABSTRACT FROM AUTHOR]

The white sturgeon (Acipenser transmontanus) is the largest freshwater fish in North America. Because of the unique life history characteristics of sturgeon, including longevity, late maturation and long spawning intervals, their aquaculture can be a significant investment of resources. As a result of habitat loss and overharvesting, natural populations of white sturgeon are threatened and there is a growing effort to improve conservation aquaculture programs. Germ cell transplantation is an innovative technology previously demonstrated in a variety of fish species to be able to produce a surrogate broodstock. The technique relies upon optimal donor germ cell recovery and transplantation into a recipient fish. In this study, we developed and optimized the harvest of donor cells for germline transplantation and evaluated methods for ovary cryopreservation for the first time in the white sturgeon. We found that harvesting gonads from juveniles between the ages of 1.5 and 2.5-years resulted in reliably high proportions of pre-meiotic cells regardless of sex, a critical feature for using white sturgeon for transplantation studies since the species shows no distinguishing external sex characteristics. From the viable cells, we identified germline cells using immunolabeling with the antibody DDX4, a marker specific to the germline. For in vivo tracking of donor cells during transplantations, gonadal cells were stained with a long half-life non-toxic cell membrane dye, PKH26, and microinjected into the peritoneal cavity of newly hatched white sturgeon larvae. Larvae were reared until 3 months post-transplantation to monitor for colonization and proliferation of PKH26-labeled cells within the recipient larval gonads. Furthermore, viable cell detection, assessment of germline-specificity, and transplantation was determined for cells recovered from cryopreserved ovarian tissue from sexually immature females. Transplantations using cells cryopreserved with media supplemented with dimethyl sulfoxide (DMSO) rather than ethylene glycol (EG) demonstrated the highest number of PKH26-labeled cells distributed along the gonadal ridges of the larval recipient. Determining optimal methods of tissue cryopreservation, and germ cell recovery and transplantation are foundational to the future development of germ cell transplantation as a strategy to improve the aquaculture and conservation of this species. Our study demonstrates that conservation actions, such as surrogate breeding, could be utilized by hatcheries to retain or improve natural gamete production without genetic modification, and provide an encouraging approach to the management of threatened sturgeon species. [ABSTRACT FROM AUTHOR]

The Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) has been listed under the Endangered Species Act since 2012, with the Chesapeake Bay distinct population segment listed as endangered. We tracked the timing of occupancy and movement in Chesapeake Bay of adult Atlantic sturgeon from the York River to best identify when Atlantic sturgeon are likely to interact with anthropogenic threats. We monitored 84 adult (40 male and 44 female) Atlantic sturgeon from August 2013 through January 2020 by using acoustic telemetry. Both spawning and non-spawning fish regularly utilized Chesapeake Bay, with females and males arriving as early as 27 February (when the mean water temperature was 7.7°C) and 4 March (6.5°C) and departing as late as 24 January (6.3°C) and 27 January (6.5°C), respectively. Peak occupation of the bay by Atlantic sturgeon occurred from 1 April to 31 August and again from 15 October to 1 December. Females of above average size (>1880 mm in fork length) spent significantly longer in the bay (>113 d) than smaller females and all males before spawning; therefore, the females capable of producing the most eggs were disproportionately exposed to anthropogenic threats. Although changes in arrival and departure dates are not statistically significant, during the 7 years of this study, both males and females generally arrived earlier and departed later each year than the previous year, increasing residency in Chesapeake Bay by a month in that time. [ABSTRACT FROM AUTHOR]

Evaluating population trends in dynamic estuarine environments can be challenging, especially when survey data include a high percentage of zero observations. In fishery‐independent surveys, zeros that come from reduced susceptibility to sample gears and reduced availability of the population to the survey impact survey catchability and negatively bias relative abundance indices. A zero‐inflated negative binomial model was used to standardize a juvenile Atlantic Sturgeon (Acipenser oxyrinchus oxyrinchus) relative abundance index (Hudson River, New York) that included a high proportion (42%) of zero observations and intra‐ and interannually variable covariates. Reduced susceptibility was related to low water temperature, with the percentage of zeroes increasing rapidly below 7°C. Availability was influenced by temperature and distance to salt front, as catch rates increased with temperature and peaked in mesohaline waters ~27 km downstream of the predicted salt front. An alternative index suggested significant population growth (r = 0.15; p‐value = 0.007) occurred from 2004 to 2015. The zero‐inflated model helped better understand Hudson River juvenile Atlantic Sturgeon ecology and relative trends in abundance, to better inform future management and monitoring decisions along the Atlantic Coast. [ABSTRACT FROM AUTHOR]

Simple Summary: Aeromonas salmonicida represents an important cause of mortality in a broad diversity of fish species, in which it has been extensively reported. Nevertheless, aeromoniasis in sturgeons is far from being fully understood. Four juvenile sturgeons from a mortality outbreak in a farm located in the north of Spain were submitted to the VISAVET Health Surveillance Centre. Aeromonas salmonicida was isolated from the bacteriological culture. They were found to suffer from a hyperacute form of the disease (almost no clinical signs and non-specific gross or histological lesions), thus confirming the susceptibility of sturgeons to this pathogen. The findings described here hope to provide a better understanding of this potentially fatal disease in the industries of aquaculture and caviar. Aeromonas salmonicida is one of the major threats to world aquaculture, causing fish furunculosis and high mortality rates in cultured fish, particularly salmonids. Although Aeromonas spp. is a thoroughly studied pathogen, little is known regarding aeromoniasis in sturgeons. After a mortality outbreak, four juvenile sturgeons (Acipenser baerii) were submitted for autopsy and tissue samples were collected for histopathological and microbiological studies. The external examination revealed size heterogenicity, skin hyperpigmentation and reduced body condition of sturgeons. Within the abdominal cavity, mild hepatomegaly and splenomegaly were observed, as well as generalized organic congestion. Histology revealed severe multifocal haemorrhagic and ulcerative dermatitis, mainly localized in the dorsal and latero-ventral areas of fish. The histological study also showed moderate to severe inflammation of gills and organic lesions compatible with septicaemia. Bacterial isolates were identified as Aeromonas salmonicida subsp. salmonicida using MALDI-TOF MS and PCR. Overall, the lesions first described here are consistent with those previously reported in other cultured fish species and contribute to a better understanding of the pathogenesis of Aeromonas salmonicida subsp. salmonicida in the Siberian sturgeon, aside from providing new diagnostic tools for bacterial diseases impacting the fast-growing industry of caviar. [ABSTRACT FROM AUTHOR]

Freezing is the most commonly used technology to preserve the quality of fish and extend its shelf-life. The fish subjected to freezing and thawing processes could be sold as unfrozen ones. In this study, the ability of mid-infrared spectroscopy (MIR) to differentiate between fresh Sevruga (Acipenser stellatus) samples (F) kept up to 13 days at 4 °C from: (i) frozen–thawed (2 weeks at − 20 °C), then refrigerated up to 10 days at 4 °C (F-T R), and (ii) refrigerated up to 13 days at 4 °C, then frozen–thawed (2 weeks at − 20 °C) (R F-T) Sevruga samples was investigated. The application of factorial discriminant analysis (FDA) to the concatenated three spectral regions in the MIR (3000–2800 cm−1, 1700–1500 cm−1 and 1500–900 cm−1) allowed to distinguish clearly between samples according to their storage time, regardless of the quality of raw Sevruga samples since correct classification rate amounting to 92.16% was obtained. The electrophoresis analysis indicated that proteins undergo oxidation and degradation during storage impacting their secondary structure. For example, the level of the α-helix for Sevruga samples aged 1 day was 11.93%, 12.13%, and 11.83% for respectively F, F-T R, and R F-T groups that decreased throughout storage attaining on days 10 amounts of 11.90%, 11.70%, and 11.76%, respectively. It could be concluded that MIR spectroscopy could be used as a rapid screening tool to discriminate rapidly between fresh and frozen–thawed Sevruga fish, since 92.16% of correct classification was obtained. [ABSTRACT FROM AUTHOR]

Sturgeon (Acipenser baerii and A. gueldenstaedtii) specimens, native to the northern hemisphere, were reported in different environments of the La Plata Basin (South America). The objectives of this study were to provide the first insights into the natal origin and habitat use of these sturgeon species in the La Plata Basin through geochemical analysis (87Sr/86Sr) of fin spines and to review historical catch reports. Spine core‐to‐edge 87Sr/86Sr ratios were measured by LA‐MC‐ICPMS. A Quadratic Discriminant Analysis model based on water 87Sr/86Sr baseline of the La Plata Basin was run to infer the natal origin. The isotopic profiles indicate a common origin, compatible with the location of the fish farms in the Uruguay Basin. The A. baerii isotopic time series suggested that the fish moved towards the Paraná Basin months before capture, while A. gueldenstaedtii would have survived a longer time (perhaps years). Seventeen reports of sturgeons were recorded and preserved in museum collections between 1998 and 2020. Sturgeons were collected from Río de la Plata Estuary, Paraná and Uruguay basins and Atlantic coastal lagoons. It is recommended to closely monitor sturgeon catches, paying special attention to the appearance of specimens of reproductive age, in order to generate management and management plans if necessary. [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]

A large number of studies have indicated that Chinese herbaceous polysaccharides possessed immune-promoting effects in animal husbandry. However, the function of Salvia miltiorrhiza polysaccharides (SMP) in fish remains poorly understood. In the present study, juvenile hybrid sturgeons (Acipenser baerii♀ × Acipenser schrenckii♂) were studied to assess the effects of SMP on growth performance, antioxidant capacity, non-specific immunity, and resistance to Streptococcus iniae. The results showed that weight gain rate, specific growth rate, and daily growth coefficient had no difference from those of the control group, but 0.1% SMP significantly increased the thickness of muscle layer and height and number of intestinal villus (P < 0.05). 0.5% and 0.7% SMP could significantly increase the T-AOC activity in the liver and valvular intestine, along with 0.5% SMP that significantly decreased the MDA content in the liver (P < 0.05). Moreover, all experimental groups could significantly increase serum TP and GLO contents. After infection with S. iniae, the survival rate of the experimental groups was higher than that of the control group, especially in 0.5% SMP group. In conclusion, dietary supplementation of SMP could enhance the antioxidant and non-specific immune capacity of hybrid sturgeon, thus improving disease resistance and promoting the healthy breeding of juvenile hybrid sturgeon. Our findings provide novel recommendations for the application of SMP supplementation in farmed fish. [ABSTRACT FROM AUTHOR]

Flavobacterium psychrophilum affects many cultured fish species and is considered one of the most important bacterial pathogens causing substantial economic losses in salmonid aquaculture worldwide. Here, F. psychrophilum was identified by matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) and nested PCR as the aetiological agent causing mortality in diseased juvenile Siberian sturgeons (Acipenser baerii) reared on a freshwater fish farm. Diseased sturgeons were lethargic and displayed dark skin pigmentation, increased mucus production and the presence of skin ulcerations and haemorrhages specially on the ventral side and the base of fins. The histological examination of fish revealed proliferative branchitis, ulcerative and necrotizing dermatitis and myositis, lymphoid tissue atrophy, liver and kidney degeneration and thrombosis. To the best of our knowledge, this is the first report describing the infection of Siberian sturgeons by F. psychrophilum. The detection of F. psychrophilum in diseased Siberian sturgeons and the description of the pathological findings observed during the outbreak may contribute to a better understanding of the bacterium pathogenicity and the range of fish species susceptible to infection. [ABSTRACT FROM AUTHOR]

The experiment aimed to evaluate the plasticity of juvenile Russian sturgeon (Acipenser gueldenstaedtii, J. F. Brandt & Ratzeburg, 1833) reared in a floating cage located on a pond. The biological material was 1400 juvenile Russian sturgeon with a mean weight of 9 g/fish and 40 days of age. The intensive rearing system was a 5x5x3 m floating cage in a pond. The fish were fed NUTRA MP-L extruded feed containing 52% crude protein and 20% fat three times a day. The experimental results showed a 64% survival of Russian sturgeon juveniles and the evaluation of productive bioindicators demonstrates high technological plasticity at 50% of the tested group. From the analysis of rearing conditions (environmental and technological), it was concluded that Russian sturgeon juveniles show a certain degree of plasticity depending on the adaptability of the Russian sturgeon to the different environmental conditions which depend principally on the anatomy and physiology of the species Acipenser gueldenstaedtii. [ABSTRACT FROM AUTHOR]

This paper aimed to evaluate the effect of a diet supplemented with fermented products on the meat quality of Siberian sturgeon (Acipenser baerii) reared in a recirculation aquaculture system. The fermented product was made by combining artisanal cultures of Kombucha and milk kefir granules grown up in sucrose, black tea, and bovine colostrum. Four experimental groups were established: V1 - a control group that received a commercial diet with 54% crude protein, and V2 to V4 groups, which received the same diet supplemented with 1 g/kg, 2 g/kg, and 3 g/kg of fermented product, respectively. After 35 days of diet administration, the biochemical composition of fresh meat was analysed. The results showed that the addition of fermented products significantly influenced the water, ash, and lipid content of A. baerii meat (p < 0.05), while the protein content was not influenced (p > 0.05) by the administrated diet. In conclusion, it is evident that adding the fermented product in A. baerii meat has an improving effect on body composition [ABSTRACT FROM AUTHOR]

This study aimed to explore the applicability of DNA barcoding for assessing the authenticity of caviar on the Chinese market. A set of universal COI primers and two sets of designed primers based on COI and D-loop genes were used to identify maternal species of samples from 21 batches of caviar. The results showed that the PCR products from three sets of primers had more than 98% similarity to the sequences in database. The COI gene could not distinguish sturgeons with closed genetic relationships, while D-loop gene could effectively improve the accuracy of DNA barcoding and was more suitable to the identification of interspecific sturgeon than the COI gene. The neighbor-joining dendrogram further confirmed the applicability and accuracy of COI and D-loop genes in identifying maternal relatives of caviar (Acipenser baerii/Acipenser gueldenstaedtii/Acipenser schrenckii/Huso dauricus/Huso huso). Despite the limitations of mitochondrial DNA in identifying hybrid sturgeon species, the presence of counterfeit caviar of non-sturgeon ingredients could be excluded. All the caviar samples were identified successfully as sturgeon species, but the mislabeling rate of species was 33.4%, indicating that there were illegal phenomena such as disorderly labeling, mislabeling, and adulteration on the market. [ABSTRACT FROM AUTHOR]

Ship sturgeon (Acipenser nudiventris) is a critically endangered fish that is listed on the International Union for Conservation of Nature's Red List of Threatened Species. Sixteen individuals from the Chinese section of the Ili River were genotyped using genome re-sequencing technology. By applying a genomic relatedness estimation with 1,527,694 genome-wide SNP markers, we found that the coancestry coefficients showed a high level of relatedness between individuals. The effective population sizes over 500 generations were estimated, and this showed that the effective population sizes began to dramatically decline from about 14,840 to 171 individuals when going back four generations from the current population. Artificial reproduction techniques guided by genomic relatedness may be a valuable approach to the conservation of this critically endangered fish species. [ABSTRACT FROM AUTHOR]

The Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) is a anadromous fish found along the east coast of North America and is listed under the Endangered Species Act of the United States. Decades of overfishing and habitat degradation have caused range-wide population declines, and the population status of this species in many rivers is unclear. Quantifying annual recruitment is one way to assess the status of sturgeon populations, but such assessments are few. The objective of this study was to quantify recruitment of juvenile Atlantic sturgeon in the Savannah, Ogeechee, and Satilla Rivers in Georgia. Because we used identical methods in 3 rivers simultaneously, we were able to directly compare recruitment among these populations with that of other populations observed in contemporaneous studies in other rivers. We conducted mark-recapture sampling during 2014-2017 and used Huggins closed population models to estimate annual recruitment. Because there are no historical data for comparison, we evaluated the 3 populations in terms of recruit abundance, variation, and consistency. The Savannah River annually had relatively large numbers of recruits (639-937 individuals). Fewer recruits were produced in the Ogeechee (27-57 individuals) and Satilla (51-134 individuals) Rivers; recruitment occurred in only some years in those rivers. Populations that produce few recruits or do not have regular recruitment may be experiencing bottlenecks preventing recovery. [ABSTRACT FROM AUTHOR]

Nucleotide-binding and oligomerization domain-like receptors (NOD-like receptors, NLRs) can regulate the inflammatory response to eliminate pathogens and maintain the host's homeostasis. In this study, the head kidney macrophages of Siberian sturgeon were treated with lipopolysaccharide (LPS) to induce inflammation by evaluating the expression of cytokines. The high-throughput sequencing for macrophages after 12 h treatment showed that 1224 differentially expressed genes (DEGs), including 779 upregulated and 445 downregulated, were identified. DEGs mainly focus on pattern recognition receptors (PRRs) and the adaptor proteins, cytokines, and cell adhesion molecules. In the NOD-like receptor signaling pathway, multiple NOD-like receptor family CARD domains containing 3-like (NLRC3-like) were significantly downregulated, and pro-inflammatory cytokines were upregulated. Based on the transcriptome database, 19 NLRs with NACHT structural domains were mined and named in Siberian sturgeon, including 5 NLR-A, 12 NLR-C, and 2 other NLRs. The NLR-C subfamily had the characteristics of expansion of the teleost NLRC3 family and lacked the B30.2 domain compared with other fish. This study revealed the inflammatory response mechanism and NLRs family characterization in Siberian sturgeon by transcriptome and provided basic data for further research on inflammation in teleost. [ABSTRACT FROM AUTHOR]

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]

An analysis of Polish historical sources indicates that there are no references to sturgeon in the Warta River basin before 1810. It is hypothesized that there was no autochthonic sturgeon population in this river in historic times. The occasional occurrence of fish in the Warta River stemmed from their straying from the Oder River, especially during high waters. The situation changed in the second half of the nineteenth century because increasing pollution in the Oder River meant increasing numbers of fish entered the Warta River. Peak catches by fishers in Poznań were in the 1880s and early 1890s, after which the population collapsed and never recovered. Overfishing in this period stemmed primarily from the effects of regulating the Warta River for navigation. The data presented herein might have implications for the current sturgeon reintroduction program being conducted in the Warta River basin. [ABSTRACT FROM AUTHOR]

Understanding the reproductive strategy of an organism is important in conservation ecology as it directly affects the population performance under changing environmental conditions. Chinese sturgeon (Acipenser sinensis) are the largest anadromous fish in the Yangtze River, China. Currently, the species has only one spawning ground and has failed to spawn in recent years, leading it to the brink of extinction. To develop effective conservation measures, a further understanding of its reproductive strategy is needed. In our study, we conducted kinship analyses by using mitochondrial and microsatellite DNA data from 216 wild juveniles collected over nine years (2006-2013, 2015) to understand the mating system, breeding interval, effective number of breeding adults, and reproductive success. The results from these analyses suggested polygynandry, with some parents contributing up to eight half-sibling juvenile genotypes. Although the spawning ground was restricted to a limited area, genetic diversity was maintained at a relatively high level (observed heterozygosity from 0.698 to 0.787 and expected heterozygosity from 0.763 to 0.787) and inbreeding coefficients in each year-class ranged from -1% to 9% (low to modest detrimental effects on offspring). A parental inference analysis revealed that Chinese sturgeon have a breeding interval of 2-6 years, indicating that it has the potential to feed, accumulate nutrition in the ocean, and then migrate back to the Yangtze River for iteroparous reproduction. The annual effective number of breeders in the Yangtze River ranged from 14 to 161 during the study period, and it decreased by 62.1% from the 2011-2014 year-classes. This sharp population decline likely contributes to the reproduction failure. However, the ratios of effective to census population size (Ne/Nc) were all larger than 0.20 after the 2010 year-class, indicating relatively even reproductive success. Based on these results, a suggested approach to protect this species is to restock parent fish to increase the reproductive stock size and optimize the discharge of the Three Gorges Dam to reduce the unsuitable hydrological conditions and rehabilitate spawning ground habitats. [ABSTRACT FROM AUTHOR]

Simple Summary: Cottonseed protein concentrate (CPC) is a high-protein product derived from widely available cottonseed flakes, but its use is limited by the presence of anti-nutritional components (gossypol, etc.). This study investigated the potential of using CPC as a substitute for fishmeal in the diet of sturgeon (Acipenser schrenckii). The study found that completely replacing fishmeal with CPC had negative effects on the growth and physiology of the sturgeon, as shown by reduced weight gain, feed efficiency, and essential amino acids. Additionally, there was a decrease in digestive enzyme activity and an upregulation of genes linked to metabolism in the liver. The research concluded that CPC should not completely replace fishmeal in the diet of the sturgeon. This study provides important data for the development of better aquafeeds and the evaluation of diet performance in sturgeon using molecular methods. Although plant proteins such as CPC can reduce production costs in aquaculture, their excessive consumption can lead to the loss of growth performance and digestion due to anti-nutritional components. This study estimated the effect of substituting fishmeal completely with cottonseed protein concentrate (CPC) in the diet of sturgeon (Acipenser schrenckii) on growth, digestive physiology, and hepatic gene expression. A control diet containing fishmeal and an experimental diet based on CPC was designed. The study was conducted for 56 days in indoor recirculating aquaculture systems. The results showed that weight gain, feed efficiency, and whole-body essential amino acids (EAAs) all decreased significantly in the experimental group, while whole-body non-essential amino acids (NEAAs) and serum transaminase activity increased (p < 0.05). The activity of digestive enzymes in the mid-intestine was significantly reduced (p < 0.05), and liver histology revealed fatty infiltration of hepatocytes. The hepatic transcriptome revealed an upregulation of genes linked to metabolism, including steroid biosynthesis, pyruvate metabolism, fatty acid metabolism, and amino acid biosynthesis. These findings indicate that fully replacing fishmeal with CPC harms A. schrenckii growth and physiology. This study provides valuable data for the development of improved aquafeeds and the use of molecular methods to evaluate the diet performance of sturgeon. [ABSTRACT FROM AUTHOR]

BACKGROUND: The production of Russian sturgeon is expanding rapidly in China but it is necessary to adopt measures to extend the shelf life of sturgeon meat. Previous studies found that sous vide cooking (SVC) at 60 °C increased the protein and lipid oxidation. The addition of antioxidant substances reduced the acceptance of the product. The effect of combination SVC and ultrasound pretreatment was therefore investigated. RESULTS: Results showed that SVC at 50 °C combined with ultrasound effectively restrained the growth of total viable counts (TVC) in samples. Meanwhile, the main dominant genera changed from Pseudomonas to Carnobacterium and the number of microbial species decreased. The odor profile of Russian sturgeon meat was more stable and the lipoxygenase (LOX) activity decreased more rapidly after treating with SVC and ultrasound. Importantly, more stable protein aggregates were formed in samples treated by SVC 50 °C together with ultrasound pretreatment, so the protein and lipid oxidation were slowed during storage. Higher springiness values were obtained and the color of sturgeon meat was lighter under these conditions. CONCLUSION: The combination of SVC 50 °C and ultrasound pretreatment effectively inhibited the microbial growth of Russian sturgeon meat at lower oxidation levels. These findings theoretically support the preservation and development of sturgeon meat, and the application of SVC technology. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

With the growing sophistication of cloning technology, rescuing cell resources is of great significance for the protection of endangered animals. The Yangtze sturgeon (Acipenser dabryanus), one of the three Acipenseriformes species in the Yangtze River, is critically endangered. Natural reproduction of the Yangtze sturgeon has not been detected since 2000. Less than 20 wild individuals are kept in husbandry, and all are too old to breed. Therefore, it is urgent to rescue the genetic resources of every wild Yangtze sturgeon. Here, we isolated and preserved viable cells from critically endangered postmortem Yangtze sturgeon for the first time. Attempts to rescue and preserve cell resources were carried out from 8 tissues, brain, kidney, gonad, fin, liver, skin, spleen, and muscle of an over 35-year-old female wild Yangtze sturgeon between 11 and 14 hours after death at 19.8°C in an outdoor concrete pond, and only muscle tissue cells could be successfully subcultured and preserved. Furthermore, the cultured cells showed high post-thaw cell viability and normal growth with a population doubling time of 52.98 h. Moreover, they were fibronectin- and desmin-positive, characterizing them as fibroblastic confirmed muscle cells with fibroblastic properties and myogenic origin. Tests for microbial contamination of the cell lines were negative. Chromosome analysis demonstrated that muscle cells possess a modal polyploid chromosome number of 264. The mitochondrial sequence data of COI genes and 12S rRNA confirmed that the developed cell line originated from A. dabryanus. Furthermore, transfection results indicate that muscle cells could be used for gene manipulation and functional studies. These results suggest that viable muscle cells could also be successfully isolated and cryopreserved from the wild Yangtze sturgeon in a short time after death. This report is not only of great significance for the germplasm rescue of critically endangered Yangtze sturgeon but also provides some scientific reference for the germplasm preservation of other endangered fish. [ABSTRACT FROM AUTHOR]

The primary goal in aquaculture is to maximize the growth and survival of farmed fishes at a minimal cost, which requires an understanding of the changes in metabolism undergone by different fish breeds during development. In particular, highly intensive aquaculture production systems, such as recirculating aquaculture systems, require a better understanding of oxygen consumption. Ontogenetic phase shifts (i.e., sudden changes) in metabolism have been observed in several aquaculture species during early development, and such metabolic phase shifts may help to predict the oxygen consumption of aquaculture species during different stages of their development. Here, I analyzed the pattern of metabolic changes in the F2 hybrid sturgeon, the bester (Huso huso × Acipenser ruthenus; hereafter, referred to as the F2 bester), during its early development. I observed ontogenetic phase shifts in metabolism in the F2 bester at body mass values of about 0.2 and 0.8 g. Thus, the F2 bester undergoes ontogenetic phase shifts in metabolism during early development, which can help to characterize oxygen consumption at a specific developmental period. Therefore, oxygen can be appropriately adjusted and replenished during breeding. [ABSTRACT FROM AUTHOR]

Background: Maintaining osmotic equilibrium plays an important role in the survival of cold-water fishes. Heat stress has been proven to reduce the activity of Na+/K+-ATPase in the gill tissue, leading to destruction of the osmotic equilibrium. However, the mechanism of megatemperature affecting gill osmoregulation has not been fully elucidated. Results: In this study, Siberian sturgeon (Acipenser baerii) was used to analyze histopathological change, plasma ion level, and transcriptome of gill tissue subjected to 20℃, 24℃and 28℃. The results showed that ROS level and damage were increased in gill tissue with the increasing of heat stress temperature. Plasma Cl− level at 28℃ was distinctly lower than that at 20℃ and 24℃, while no significant difference was found in Na+ and K+ ion levels among different groups. Transcriptome analysis displayed that osmoregulation-, DNA-repair- and apoptosis-related terms or pathways were enriched in GO and KEGG analysis. Moreover, 194 osmoregulation-related genes were identified. Amongst, the expression of genes limiting ion outflow, occluding (OCLN), and ion absorption, solute carrier family 4, member 2 (AE2) solute carrier family 9, member 3 (NHE3) chloride channel 2 (CLC-2) were increased, while Na+/K+-ATPase alpha (NKA-a) expression was decreased after heat stress. Conclusions: This study reveals for the first time that the effect of heat stress on damage and osmotic regulation in gill tissue of cold-water fishes. Heat stress increases the permeability of fish's gill tissue, and induces the gill tissue to keep ion balance through active ion absorption and passive ion outflow. Our study will contribute to research of global-warming-caused effects on cold-water fishes. [ABSTRACT FROM AUTHOR]

Chondroitin sulfate (CS) and undenatured type II collagen (Col II) are the two major, biological macromolecules of cartilage-related tissues. In this study, a new extraction. process was developed to obtain CS and Col II simultaneously. By this process, CS. and undenatured Col II were extracted from sturgeon notochord with the yields of 5.34, ± 0.74% and 45.25 ± 5.25%, respectively. The SEC-RI-MALLS result showed that the, average molecular weight of notochord CS was 38.4 kDa. FTIR NMR, and SAX-HPLC, results indicated the notochord CS was mainly composed of CS-A. The new extraction, process had no effect on the triple helical structure of Col II. To analyze the interaction, between the two macromolecules, the effect of CS on Col II fibril formation was, examined using turbidity assay and SEM observation. CS accelerated the completion, of Col II self-assembly and inhibited the lateral aggregation of fibrils. The results of this, study suggested that the sturgeon notochord is a valuable source of CS and Col II. The. new extraction method not only improves the utilization rate of sturgeon notochord, but,also reduces the waste of aquatic resources. CS and Col II derived from sturgeon, notochord have the potential for use in biomedical materials [Display omitted] • Chondroitin sulfate (CS) and collagen (Col II) extraction method was developed. • Yields of CS and Col II from sturgeon notochord were suitable for industrialization. • Sturgeon notochord CS was mainly composed by CS-A with molecular weight of 38.4 kDa. • The method had no effect on secondary structure and fibril-forming ability of Col II. • CS bound on Col II fibrils and inhibited the lateral aggregation of fibrils. [ABSTRACT FROM AUTHOR]

As an endangered animal species, the Chinese sturgeon (Acipenser sinensis) has been artificially cultured during recent years. In the present experiment, the performance of a common formulated feed and a mixed natural feed on the growth and blood physiology of Chinese sturgeon were compared during one year of indoor culture. In terms of specific growth rate, the formulated diet group showed a higher value (4.2%) compared with the natural food group (−1.8%) during one year of indoor culture. Alanine aminotransferase activities of the sturgeons in formulated diet group was significantly higher than that in the natural food group throughout whole experiment period (p < 0.05). The total protein albumin, albumin and globulin contents of the natural food group were significantly higher than that of the formulated diet group in February and May (p < 0.05). The C-reactive protein contents of the formulated diet group were significantly higher than that of natural food group in May and August (p < 0.05). The activities of total cholesterol, high-density cholesterol, and low-density cholesterol were significantly higher in the natural food group than those in the formulated diet group (p < 0.05). The activities of triglycerides were significantly higher in the natural food group than those in the formulated diet group in February and May (p < 0.05). Almost half of the biochemical indicators examined show significant seasonal fluctuations, indicating that seasons have a substantial impact on the Chinese sturgeon. Overall, these results indicate that natural food exerted a positive impact on physiological indicators compared to the formulated diet. [ABSTRACT FROM AUTHOR]

Sturgeons have a complex free‐embryo period extending from hatch to the initiation of exogenous feeding. Although available for some sturgeon species of the genus Acipenser, descriptions of the developmental stages of free embryos of the genus Scaphirhynchus are lacking. We characterised the ontogenetic development of pallid sturgeon (Scaphirhynchus albus) and shovelnose sturgeon (S. platorynchus) free embryos from hatch through melanin plug expulsion. The rate of development was similar between Scaphirhynchus species among free embryos from 4 pallid sturgeon and 7 shovelnose sturgeon crosses reared separately in the laboratory at a mean temperature of 17.8°C. Free embryos required a mean of 18.2 days postfertilisation (DPF; 323.5 cumulative thermal units; CTU) to reach melanin plug expulsion for pallid sturgeon and 17.9 DPF (318.3 CTU) for shovelnose sturgeon. Free embryos of both species showed overlap in lengths among developmental stages indicating that length of free embryos alone is insufficient to estimate age. Description of pallid sturgeon and shovelnose sturgeon free‐embryo development provides a template to develop more sophisticated models incorporating length and stage to estimate the age of field‐collected specimens. Improved estimates of free‐embryo developmental stage and age may aid in the identification of timing and location of spawning and better inform flow manipulation and habitat management actions tailored to increase survival of early life‐stage pallid sturgeon. [ABSTRACT FROM AUTHOR]