Current State of Rare and Endangered Barbels of the Genus Luciobarbus Heckel, 1843 in the Aral-Syrdarya Basin (Kazakhstan) and Prospects for Their Conservation (A Review)

The current status of the barbels inhabiting the Kazakhstan section of the Syrdarya River needs special study, as has been noted since the second half of the 20th century. Stocks of commercial fish valuable in the past as barbels in the Aral-Syrdarya basin are now catastrophically reduced as a result of anthropogenic impact on the ichthyofauna and natural environment of the Aral Sea region. The study of the condition; abundance and distribution range is necessary to determine measures for their restoration in natural habitats and their breeding in fish farms. Research on the biotechnology of barbel breeding with subsequent acclimatization and reacclimatization of these fish species will not only improve the composition of the ichthyofauna of the Aral-Syrdarya basin, but also preserve the genetic potential of natural populations. At present, the only way to restore the population of the Aral barbel is stocking hatchery reared juveniles in natural environments. Under the current situation, a way forward is seen in the creation of domesticated replacement-broodstocks of barbels. As a result of the influence of anthropogenic factors, the populations of this species have come to almost complete degradation and depletion and require the development and adoption of urgent measures for their conservation and restoration through reintroduction, which is a priority and urgent task for the fisheries of the republic.

Priming European Sea Bass Female Broodstock Improves the Antimicrobial Immunity of Their Offspring

Acquiring immunocompetence is essential in the development of fish embryos, as they are exposed to environmental pathogens even before they are fertilized. Despite the importance of the antimicrobial function as the first line of defense against foreign microorganisms, little knowledge is available about its role in larval development. In vertebrates, transgenerational immune priming influences the acquisition of immunocompetence of specimens, regulating the selective allocation of nongenetic resources to their progeny and modulating their development. In this work, we primed teleost European sea bass broodstock females with a viral protein expression vector in order to evaluate the innate immunity development of their offspring. Several antimicrobial functions, the pattern of expression of gene coding for different antimicrobial peptides (AMPs), and their protein levels, were evaluated in eggs and larvae during development. Our data determined the presence of antimicrobial proteins of maternal origin in eggs, and that female vaccination increases antimicrobial activities and the transcription and synthesis of AMPs during larval development.

Growth, Health, and Gut Microbiota of Female Pacific White Shrimp, Litopenaeus vannamei Broodstock Fed Different Phospholipid Sources

Phospholipids have an important antioxidant effect on animals. The effects of different dietary phospholipid sources on the growth, antioxidant activity, immunity, and gut microbiota of female broodstock of Pacific white shrimp Litopenaeus vannamei were investigated. Four isoproteic and isolipid semi-purified diets containing 4% soybean lecithin (SL), egg yolk lecithin (EL), or krill oil (KO) and a control diet without phospholipid supplementation were fed to female broodstock of L. vannamei (34.7 ± 4.2 g) for 28 days. The growth performance, antioxidative capacity, and innate immunity of the female broodstock fed phospholipid supplemented diets were improved regardless of sources compared with the control shrimp. The effects on growth and antioxidant capacity in female shrimp fed the KO diet were highest. The innate immunity of female shrimp fed the EL and KO diets were significantly higher than shrimp fed the SL diet. Dietary phospholipid supplementation increased gut microbiota diversity and richness, and the Chao1 and ACE values in the KO group were significantly higher than in the control group. The richness of Proteobacteria, Photobacterium, and Vibrio decreased, whereas the richness of Firmicutes and Bacteroidetes increased in the shrimp fed the KO diet compared with the shrimp fed the SL and EL diets. The interactions of gut microbiota in shrimp fed the KO diet were the most complex, and the positive interaction was the largest among all the treatments. The functional genes of gut microbiota in shrimp fed the KO diet were significantly enriched in lipid metabolism and terpenoid/polyketide metabolism pathways. Spearman correlation analysis showed that Fusibacter had significantly positive correlations with antioxidant activity (total antioxidant capacity, superoxide dismutase, glutathione peroxidase), immune enzyme activity (phenoloxidase and lysozyme), and immune gene expression (C-type lectin 3, Caspase-1). All findings suggest that dietary phospholipids supplementation can improve the growth and health status of female L. vananmei broodstock. Krill oil is more beneficial in improving the antioxidant capacity and innate immunity than other dietary phospholipid sources. Furthermore, krill oil can help establish the intestinal immune barrier by increasing the richness of Fusibacter and promote the growth of female shrimp. Fusibacter may be involved in iron metabolism to improve the antioxidant capacity of female shrimp.

Effects and Mechanism of Different Phospholipid Diets on Ovary Development in Female Broodstock Pacific White Shrimp, Litopenaeus vannamei

Research on nutrition and feed development for the broodstock of the Pacific white shrimp, Litopenaeus vannamei, is rare, and a poor broodstock quality is a critical factor restricting the seed supply in shrimp farming. As an essential nutrient for the gonadal development of L. vannamei, one control diet (no phospholipid) and three typical phospholipids (soybean lecithin, egg yolk lecithin, and krill oil) were evaluated in a semipurified diet of 4% phospholipid for a 28-day trial (initial weight 34.7 ± 4.2 g). Dietary phospholipid supplementation significantly promoted the ovarian maturation of female L. vannamei. Compared with soybean lecithin and egg yolk lecithin, krill oil showed the best positive results. Shrimp fed with a diet krill oil has obtained a significantly higher gonadosomatic index, yolk particle deposition, lipid accumulation, and estrogen secretion than from other sources. Ovary lipidomic analysis showed that the krill oil enriched the lipid composition of the ovary. The “glycerophospholipid metabolism” and “sphingolipid metabolism” pathways were significantly varied via topological pathway analysis. Genes and hub genes, with significantly different expression levels, were significantly enriched in the “fatty acid metabolism pathway,” “glycerophospholipid metabolism,” and “arachidonic acid metabolism” pathways by transcriptomic analysis. Correlation analysis of the transcriptome and lipidomics showed that the differential gene “hormone-sensitive lipase-like” (HSL) was positively correlated with various lipids [triglycerides (TG), phosphatidic acid (PA), phosphatidylserine (P), phosphatidylethanolamine (PE), glucosylceramide (GlcCer), phosphatidylglycerol (PG), and phosphatidylinositol (PI)] but was negatively correlated with diacylglycerol (DG), lysophosphatidylethanolamine (LPE), and sphingomyelin (SM). In conclusion, the dietary phospholipids, especially krill oil as a phospholipid source, can promote the development of L. vannamei ovaries by increasing the accumulation of nutrients such as triglycerides and sterols, and the secretion of estrogen or related hormones, such as estradiol and methylfarneside, by affecting the metabolism of glycerol phospholipids and some key fatty acids.

Pharmacokinetics and bioavailability of meloxicam in rainbow trout (Oncorhynchus mykiss) broodstock following intravascular, intramuscular, and oral administrations

The pharmacokinetics and bioavailability of meloxicam were investigated after single intravascular (IV), intramuscular (IM), and oral dose of 1 mg/kg in rainbow trout broodstock at 11 ± 1.2°C. A total of 36 healthy rainbow trout (Oncorhynchus mykiss) broodstock weighing 1.40 ± 0.26 kg was used for the investigation. Plasma concentrations of meloxicam were measured with high-performance liquid chromatography-ultraviolet detection, and pharmacokinetic parameters were calculated by non-compartmental analysis. The elimination half-life for IV, IM, and oral routes was 3.63, 4.55, and 2.95 h, respectively. The IV route for meloxicam showed the total clearance of 0.05 L/h/kg and volume of distribution at a steady state of 0.20 L/kg. The peak plasma concentration was 2.97 μg/ml for the IM route and 0.84 μg/ml for the oral route. The bioavailability was 78.45% for the IM route and 21.48% for the oral route. Meloxicam following IM and oral administration displayed short t_1/2ʎz . The short t_1/2ʎz could be an advantage for the short-term use in acute conditions. The IM route with the good bioavailability can be preferred for the treatment of various conditions. However, developing new oral formulations with the good bioavailability for meloxicam is necessary to minimize stress and trauma through minimal handling in rainbow trout broodstock.

Spotted Wolffish Broodstock Management and Egg Production: Retrospective, Current Status, and Research Priorities

The first artificially fertilized spotted wolffish (Anarhichas minor) eggs hatched in Norway in the mid-1990s as this species was considered by Norwegian authorities to be a top candidate species for cold-water aquaculture in the North Atlantic regions. Previous research conducted in Norway (since 1992) and Canada (since 2000), focused on identifying key biological parameters for spotted wolffish cultivation which led, respectively, to the rapid establishment of a full commercial production line in northern Norway, while Québec (Canada) is witnessing its first privately driven initiative to establish commercial production of spotted wolffish on its territory. The control of reproduction can be viewed as a major requirement to achieve the development of performant strains using genetic selection tools and/or all-year-round production to bring about maximal productivity and synchronization among a given captive population. Although the basic reproduction aspects are more understood and controlled there are still some challenges remaining involving broodstock and upscaling of operations that limit the achievement of a standardized production at the commercial level. Quality of gametes is still considered a major constraint and it can be affected by multiple factors including nutrition, environmental conditions, handling practices, and welfare status. Internal insemination/fertilization and the protracted incubation period are challenging as well as the establishment of a health monitoring program to secure large-scale operations. The profound progress achieved in the control of reproduction, sperm handling, and cryopreservation methods for this species is presented and discussed. In this review, we also go into detail over the full range of up-to-date cultivation practices involving broodstock and identify areas that could benefit from additional research efforts (i.e., broodstock nutrition, health and welfare, scaling-up egg and larval production, genetics, and development of selective breeding programs).

Chorion Alterations in Eyed-Stage Salmonid Eggs Farmed in La Araucanía, Chile: A Retrospective Study

Simple Summary

The chorion (also called egg envelope) is the primary envelope that protects the fish embryo against drying, mechanical actions, and abrupt changes in the water conditions. Alterations of the chorion during the embryo incubation are not unusual, but these are scarcely reported. Increased occurrence of chorion alterations can lead to decreased reproductive performance and important losses for fish farms. Here, we described several chorion alterations observed in samples of embryonated eggs collected from different salmon and trout farms located in southern Chile over a period of 14 years. We detected four types of chorion alterations and found soft chorion as the most prevalent alteration in the years analyzed, affecting mainly Atlantic and Coho Salmon. Eggs of Rainbow Trout displayed fewer chorion alterations among the three species analyzed. As the eggs analyzed here were produced under standard industrial conditions, we conclude that these alterations are possibly linked to changes in water conditions, which need to be further investigated.

Abstract

The chorion is the primary envelop that protects the fish embryo against mechanical actions, pathogens, and abrupt changes in physical and chemicals conditions of the incubation medium. During embryo development, chorion alterations are not rare, but the occurrence of these is scarcely reported. Increased frequency of chorion alterations can result in increased embryo mortality and thus decreased reproductive performance and losses for fish farms. In this study, we characterize different chorion alterations observed in samples collected over 14 years from 12 salmon and trout farms located in the region of La Araucanía in southern Chile, which sent live eyed-stage embryos (‘eyed-eggs’) for quality analysis to our laboratory. We found soft chorion as the most common alteration observed, being present in the whole 14-year series analyzed in Atlantic Salmon (Salmo salar) and affecting up to 35.0% of the samples examined in a year. This alteration also affected up to 20.0 and 5.7% of Coho Salmon (Oncorhynchus kisutch) and Rainbow Trout (Oncorhynchus mykiss) samples analyzed in a year, respectively. We also found an increase of other chorion alterations, including perforated and white-spotted chorion in Atlantic and Coho Salmon, in the last 8 years. Among the three species, Rainbow Trout exhibited fewer chorion alterations. As the embryonated eggs analyzed here were obtained from broodstocks maintained under standard industrial conditions, these alterations might be linked to changes in environmental conditions affecting the incubation water that need to be further investigated.

Haematological and metabolic profiles associated with age and sex in giant kokopu (Galaxias argenteus) (Gmelin 1789) broodstock

This study characterized selected peripheral blood (PB) haematological parameters, liver, serum and muscle metabolic features in 3- and 5-year-old male and female giant kokopu (Galaxias argenteus) broodstock reared indoor at 16°C. Sex and age did not affect PB total cell count and haematocrit values. Nonetheless, higher erythrocytes in 5-year-old fish, elevated thrombocyte and lymphocyte counts in 3-year-old fish indicate age-specific cellular regulation. Higher thrombocyte counts in female fish suggest sex-specific regulation. At a metabolic level, liver abundance for long chain saturated fatty acids (FAs) was higher in males, whereas females had elevated levels of polyunsaturated FAs. Essential and non-essential amino acids (AAs) in liver and serum were also elevated in females compared to males. These findings suggest differential allocation of FAs and AAs to reflect requirements for gonadal, development and provisioning. Similarly, age significantly resulted in higher liver and serum abundances of some non-essential AAs in 3-year-olds compared to 5-year-old fish, suggesting higher metabolism in younger fish. Overall, results enhance our understanding of sex- and age-based differences in fish haematology, muscle, liver, and serum metabolite profiles in healthy G. argenteus. Future studies should carefully consider potential age- and sex-specific differences in metabolic responses.

Pharmacokinetics and Bioavailability of Carprofen in Rainbow Trout (Oncorhynchus mykiss) Broodstock

The aim of this study was to determine the pharmacokinetics of carprofen following intravenous (IV), intramuscular (IM) and oral routes to rainbow trout (Oncorhynchus mykiss) broodstock at temperatures of 10 ± 1.5 °C. In this study, thirty-six healthy rainbow trout broodstock (body weight, 1.45 ± 0.30 kg) were used. The plasma concentrations of carprofen were determined using high-performance liquid chromatography and pharmacokinetic parameters were calculated using non-compartmental analysis. Carprofen was measured up to 192 h for IV route and 240 h for IM, and oral routes in plasma. The elimination half-life (t1/2λz) was 30.66, 46.11, and 41.08 h for IV, IM and oral routes, respectively. Carprofen for the IV route showed the total clearance of 0.02 L/h/kg and volume of distribution at steady state of 0.60 L/kg. For IM and oral routes, the peak plasma concentration (Cmax) was 3.96 and 2.52 μg/mL with the time to reach Cmax of 2 and 4 h, respectively. The bioavailability was 121.89% for IM route and 78.66% for oral route. The favorable pharmacokinetic properties such as the good bioavailability and long t1/2λz for IM and oral route of carprofen suggest the possibility of its effective use for the treatment of various conditions in broodstock.

Modulation of Energy Metabolism and Epigenetic Landscape in Rainbow Trout Fry by a Parental Low Protein/High Carbohydrate Diet

Simple Summary

While the effects of parental diets on their progeny have been highly described in mammals, such studies are lacking in fish. To explore such a question in a high trophic level teleost fish, two-year old male and female rainbow trout were fed either a control diet (0% carbohydrate and 63.89% protein) or a high-carbohydrate diet (35% carbohydrate and 42.96% protein), for a complete reproductive cycle for females and for a period of 5 months for males. Neither the maternal nor the paternal high-carbohydrate diet alone had induced significant effects on their progeny. Nevertheless, when both parents were fed the high-carbohydrate diet, the energy metabolism and mitochondrial dynamics of their progeny were altered. Moreover, the epigenetic landscape was also highly affected. Even though, offspring growth was only slightly affected at the early stage of life; the effect of parental high-carbohydrate diet should be explored over the long term.

Abstract

It is now recognized that parental diets could highly affect offspring metabolism and growth. Studies in fish are, however, lacking. In particular, the effect of a parental diet high in carbohydrate (HC) and low in protein (LP) on progeny has never been examined in higher trophic level teleost fish. Thus, two-year old male and female rainbow trout (Oncorhynchus mykiss) were fed either a control diet (0% carbohydrate and 63.89% protein) or a diet containing 35% carbohydrate and 42.96% protein (HC/LP) for a complete reproductive cycle for females and over a 5-month period for males. Cross-fertilizations were then carried out. To evaluate the effect of the parental diet on their offspring, different phenotypic and metabolic traits were recorded for offspring before their first feeding and again three weeks later. When considering the paternal and maternal HC/LP nutrition independently, fry phenotypes and transcriptomes were only slightly affected. The combination of the maternal and paternal HC/LP diets altered the energy metabolism and mitochondrial dynamics of their progeny, demonstrating the existence of a synergistic effect. The global DNA methylation of whole fry was also highly affected by the HC/LP parental diet, indicating that it could be one of the fundamental mechanisms responsible for the effects of nutritional programming.

Short-Term Effect of a Low-Protein High-Carbohydrate Diet on Mature Female and Male, and Neomale Rainbow Trout

Rainbow trout are considered as a poor user of dietary carbohydrates, displaying persistent postprandial hyperglycaemia when fed a diet containing high amounts of carbohydrates. While this phenotype is well-described in juveniles, less attention was given to broodstock. Our objective was to assess for the first time the short-term consequences of feeding mature female and male, and neomale trout with a low-protein high-carbohydrate diet on glucose and lipid metabolism. Fish were fed for two days with a diet containing either no or 32% of carbohydrates. We analysed plasma metabolites, mRNA levels and enzymatic activities of glycolysis, gluconeogenesis, de novo lipogenesis and β-oxidation in the liver. Results demonstrated that the glucose and lipid metabolism were regulated by the nutritional status in all sexes, irrespective of the carbohydrate intake. These data point out that carbohydrate intake during a short period (5 meals) at 8 °C did not induce specific metabolic changes in broodstock. Finally, we demonstrated, for the first time, sex differences regarding the consequences of two days of feeding on glucose and lipid metabolism.

Influence of Genetic Selection for Growth and Broodstock Diet n-3 LC-PUFA Levels on Reproductive Performance of Gilthead Seabream, Sparus aurata

Simple Summary

Gilthead seabream (GSB) broodstock were genetically selected based on their growth trait either high growth (HG) or low growth (LG) to evaluate the reproductive performance of these both traits under either fish oil (FO) or vegetable oil (VO) based diets feeding regime. The egg and larval quality were significantly improved by the broodstock selected for HG trait fed under FO based diet. This indicates that broodstock selected with HG trait has positive influence on the improving sperm, egg and larval quality in gilthead seabream.

Abstract

Genetic selection in gilthead seabream (GSB), Sparus aurata, has been undertaken to improve the growth, feed efficiency, fillet quality, skeletal deformities and disease resistance, but no study is available to delineate the effect of genetic selection for growth trait on GSB reproductive performance under mass spawning condition. In this study, high growth (HG) or low growth (LG) GSB broodstock were selected to evaluate the sex steroid hormones, sperm, egg quality and reproductive performance under different feeding regime of commercial diet or experimental broodstock diet containing either fish oil (FO) or vegetable oil (VO) based diet. Under commercial diet feeding phase, broodstock selected for either high growth or low growth did not show any significant changes in the egg production per kg female whereas egg viability percentage was positively (p = 0.014) improved by the high growth trait broodstock group. The experimental diet feeding results revealed that both growth trait and dietary fatty acid composition influenced the reproductive performance of GSB broodstock. In the experimental diet feeding phase, we observed high growth trait GSB males produced a higher number of sperm cells (p < 0.001) and also showed a higher sperm motility (p = 0.048) percentage. The viable egg and larval production per spawn per kg female were significantly improved by the broodstock selected for high growth trait and fed with fish oil-based diet. This present study results signifies that gilthead seabream broodstock selected on growth trait could have positive role in improvement of sperm and egg quality to produce viable progeny.

Development of EST-Molecular Markers from RNA Sequencing for Genetic Management and Identification of Growth Traits in Potato Grouper (Epinephelus tukula)

Simple Summary

The potato grouper is a novel aquaculture species in Taiwan. Due to the lack of genetic information concerning this species, we have developed molecular markers based on transcriptome sequencing and further characterized their association with gene diversity and growth traits of this species. Ultimately, these markers could be utilized as accurate and efficient tools for genetic management and marker-assisted selection of potato grouper with distinct growth traits.

Abstract

The accuracy and efficiency of marker-assisted selection (MAS) has been proven for economically critical aquaculture species. The potato grouper (Epinephelus tukula), a novel cultured grouper species in Taiwan, shows large potential in aquaculture because of its fast growth rate among other groupers. Because of the lack of genetic information for the potato grouper, the first transcriptome and expressed sequence tag (EST)-derived simple sequence repeat (SSR) and single nucleotide polymorphism (SNP) markers were developed. Initially, the transcriptome was obtained from seven cDNA libraries by using the Illumina platform. De novo transcriptome of the potato grouper yielded 51.34 Gb and 111,490 unigenes. The EST-derived SSR and SNP markers were applied in genetic management, in parentage analysis, and to discover the functional markers of economic traits. The F₁ juveniles were identified as siblings from one pair of parents (80 broodstocks). Fast- and slow-growth individuals were analyzed using functional molecular markers and through their association with growth performance. The results revealed that two SNPs were correlated with growth traits. The transcriptome database obtained in this study and its derived SSR and SNP markers may be applied not only for MAS but also to maintain functional gene diversity in the novel cultured grouper.

Testicular leiomyoma and spermatogenic failure syndrome in a seabass from broodstock

Testicular leiomyomas and gonadal dysfunctions are not commonly reported in teleost and particularly in broodstock fish. In the present work, a testicular leiomyoma related to an unusual case of spermatogenic failure syndrome, in a broodstock seabass coming from an Italian aquaculture farm, is reported. At gross pathology, the circumscribed neoplasia showed several white nodular masses, originating from the gonad, deforming the anatomo-physiological shape. From light microscopy, the presence of neoplastic tissue islands with spindle cells with a whirling pattern and the low presence of connective tissue were evident and originated from smooth muscle cells. Seminiferous tubules showed severe azoospermia with the absence of sperm cells even closer to the neoplastic area. Immunohistochemical analysis was positive for alpha-SMA, desmin and vimentin but negative for S-100, confirming a diagnosis of leiomyoma. This is the first report of spermatogenic failure syndrome associated with a testicular leiomyoma in fish from broodstock. More efforts should be made in studying broodstock fish pathologies related to fish maintenance and hormonal treatments that could economically affect aquaculture production.

Broodstock development and captive maturation of hilsa (Tenualosa ilisha) in a brackishwater pond-based system

Successful captive broodstock development of clupeid fish, hilsa, is one of the major challenges for the artificial propagation of this economically valued fish. The present study provides novel insights into the pond-reared captive broodstock development of hilsa using artificial feed. In the present study, wild collected hilsa fry (weight 1.35 ± 0.13 g, length 53.84 ± 0.95 mm) were reared in grow-out ponds for 6 months followed by maintaining them as broodstock in other ponds using formulated feed in both cases. After 6 months of pond rearing, the average body weight and length of fish were 66.76 ± 4.53 g and 184.75 ± 3.65 mm, respectively. In broodstock ponds, hilsa subadults fed with formulated feed (crude protein 41.06%) ensured significant advancement in ovarian maturity with gonado somatic index of 9.09%, enhanced secondary yolk stage oocytes of 91.66% and enlargement of oocyte diameters up to 570 μm. The broodstock reached somatic growth such as average body weight and average body length of 383.80 ± 27.38 g and 339.33 ± 9.68 mm, respectively, with a condition factor of 1.06 ± 0.15. Gut content analysis revealed the better acceptability of the artificial feed. Lipid profiling of muscle and ovary during gonadal maturation revealed mobilization of fat from muscle to ovary and selective retention of some fatty acids (i.e., C14:0, C18:0, C20:5, C22:6 and C20:4) in the ovary, which might help in gonadal maturation. STATEMENT OF SIGNIFICANCE: Successful rearing of wild-caught hilsa juvenile in captive condition using formulated feed showed its potential as aquaculture species in low saline conditions. Advance stage of maturation in low saline captive conditions showed the possibility for induced breeding of hilsa, a high priced anadromous fish. Mobilization of fat from muscle to ovary and selective retention of some fatty acids in the ovary showed the scope of dietary manipulation for broodstock development of hilsa.

The Relationship between the Expression of Fatty Acyl Desaturase 2 (fads2) Gene in Peripheral Blood Cells (PBCs) and Liver in Gilthead Seabream, Sparus aurata Broodstock Fed a Low n-3 LC-PUFA Diet

The principle aim of this study is to elucidate the relationship between the fatty acid desaturase 2 gene (fads2) expression pattern in peripheral blood cells (PBCs) and liver of gilthead seabream (GSB), Sparus aurata broodstock in order to determine the possible use of fads2 expression as a potential biomarker for the selection of broodstock. This selection could be utilized for breeding programs aiming to improve reproduction, health, and nutritional status. Passive Integrated Transponder (PIT)-tagged GSB broodstock (Male-1.22 ± 0.20 kg; 44.8 ± 2 cm and female-2.36 ± 0.64 kg; 55.1 cm) were fed a diet containing low levels of fish meal and fish oil (EPA 2.5; DHA 1.7 and n-3 LC-PUFA 4.6% TFA) for one month. After the feeding period, fads2 expression in PBCs and liver of both male and female broodstock were highly significantly correlated (r = 0.89; p < 0.001). Additionally, in male broodstock, liver fads2 expression was significantly correlated (p < 0.05) to liver contents in 16:0 (r = 0.95; p = 0.04) and total saturates (r = 0.97; p = 0.03) as well as to 20:3n–6/20:2n–6 (r = 0.98; p = 0.02) a Fads2 product/precursor ratio. Overall, we found a positive and significant correlation between fads2 expression levels in the PBCs and liver of GSB broodstock. PBCs fads2 expression levels indicate a strong potential for utilization as a non-invasive method to select animals having increased fatty acid bioconversion capability, better able to deal with diets free of fish meal and fish oil.

Demonstration of the Use of Environmental DNA for the Non-Invasive Genotyping of a Bivalve Mollusk, the European Flat Oyster (Ostrea edulis)

Accurate SNP (single nucleotide polymorphism) genotype information is critical for a wide range of selective breeding applications in aquaculture, including parentage assignment, marker-assisted, and genomic selection. However, the sampling of tissue for genetic analysis can be invasive for juvenile animals or taxa where sampling tissue is difficult or may cause mortality (e.g. bivalve mollusks). Here, we demonstrate a novel, non-invasive technique for sampling DNA based on the collection of environmental DNA using European Flat Oysters (Ostrea edulis) as an example. The live animals are placed in individual containers until sufficient genetic material is released into the seawater which is then recovered by filtration. We compared the results of tissue and eDNA derived SNP genotype calls using a PCR based genotyping platform. We found that 100% accurate genotype calls from eDNA are possible, but depend on appropriate filtration and the dilution of the sample throughout the workflow. We also developed an additional low-cost DNA extraction technique which provided >99% correct SNP genotype calls in comparison to tissue. It was concluded that eDNA sampling can be used in hatchery and selective breeding programs applicable to any aquatic organism for which direct tissue sampling may result in animal welfare concerns or mortality.

Bayesian latent class analysis of ELISA and RT-rPCR diagnostic accuracy for subclinical Renibacterium salmoninarum infection in Atlantic salmon (Salmo salar) broodstock

Renibacterium salmoninarum infection causes bacterial kidney disease (BKD) in salmonid freshwater and saltwater life stages, with potentially severe financial loss for the aquaculture industry. Preventing vertical transmission, from infected broodstock to eggs, is key to disease management. As there is no perfect reference standard for detecting R. salmoninarum, we used Bayesian latent class analyses to compare real-time reverse transcriptase PCR (RT-rPCR, mRNA target) and enzyme-linked immunosorbent assay (ELISA; p57 antigen target) diagnostic accuracy for detection in Atlantic salmon broodstock from British Columbia, Canada, and assessed ELISA repeatability. In 2016, 4,544 Atlantic salmon broodstock (no clinical signs of BKD or gross lesions) were sampled for ELISA testing of kidney tissue. Two groups of ELISA positives (n = 132) and two groups of a random sample of ELISA negatives (n = 137) were then tested with RT-rPCR, and ELISA testing was repeated. ELISA testing of broodstock provided the best diagnostic sensitivity (DSe; less chance of false-negative results). The use of joint RT-rPCR and ELISA testing improved DSe over that from each test alone, if a sample was considered positive when either test result was positive. Using these testing schemes in combination with management practices can decrease the likelihood of vertical transmission from subclinically infected broodstock.

SNP panel development for genetic management of wild and domesticated white bass (Morone chrysops)

White bass (Morone chrysops), striped bass and their interspecific hybrid are important game fishes, whereas the hybrid striped bass is an important aquaculture species in the US. Numerous state, federal and private hatcheries, therefore, rear these species for stocking purposes as well as for food fish. Although striped bass populations (both wild and domesticated) have been extensively evaluated, relatively little effort has been directed toward the study and improvement of white bass. In this study, we developed SNP resources to examine the genetic relationships among a long-term domesticated white bass line and five potential founder stocks for selective breeding collected from drainages in Arkansas, Texas and Alabama. Using genotyping-by-sequencing, we generated 13 872 genome-wide SNP loci across the six populations. Stringent filtering of SNP-calling parameters identified 426 informative SNP loci. Population genetic and structure analyses using these loci revealed only moderate genetic differentiation between populations (global F_st  = 0.083) and indicated two major genetic clusters. A final 57-SNP assay was successfully designed and validated using the MassARRAY system. The developed SNP panel assigned 96 additional genotyped individuals to their population of origin with 100% accuracy. The SNP resources developed in this study should facilitate ongoing efforts in selective breeding and conservation of white bass.

Morphometric Characteristics of Asian Catfish, Hemibagrus wyckii (Bleeker, 1858) (Bagridae), from the Riau Province of Indonesia

BACKGROUND AND OBJECTIVE

Asian Catfish (Hemibagrus wyckii) is an important fish having both food and a high price in the market. These species are categorized as a carnivorous freshwater finfish native in Indonesia and is vulnerable to endangered status. This study was carried out to identify the morphometric characteristics of Hemibagrus wyckii (H. wyckii) from the Koto Panjang Reservoir, Kampar Kanan and Kampar Kiri rivers.

MATERIALS AND METHODS

Twenty-five fish were collected from each sampling site. The morphometric characteristics were analyzed using the truss morphometric method. Twenty-nine characteristics were measured to obtain the morphometric characteristics of this species. Morphometric data of H. wyckii were analyzed using one-way ANOVA (SPSS version 17.0). Principal component analysis (PCA) was used to evaluate the relationship between different factors and morphometric characteristics. The distribution across different habitats was measured by component canonical analysis (CCA) and genetic distance was analyzed by hierarchical cluster.

RESULTS

The average standard lengths of H. wyckii from the Koto Panjang Reservoir, Kampar Kanan and Kampar Kiri rivers (Mean±SD) were 428±15.78, 432.52±66.11 and 425.86±50.41 mm, respectively. Twenty-nine morphometric characteristics were measured. There was a 68.96% difference obtained in samples collected at the Koto Panjang Reservoir and Kampar Kanan river. There was a 95.55% difference obtained in the Koto Panjang Reservoir, Kampar Kiri river and a 100% difference obtained in the Kampar Kanan and Kampar Kiri rivers. The main differences in morphometric characteristics included inter orbital distance, length of adipose-fin base, predorsal length, length of front dorsal fin-front pelvic and depth of caudal peduncle. The Mahalanobis distance between fish from the Koto Panjang Reservoir and Kampar Kanan river demonstrated that both types originated from a single population.

CONCLUSION

It was concluded that more favorable morphometric characteristics of H. wyckii were found in the Kampar Kanan river compared to those from the Koto Panjang Reservoir and Kampar Kiri river.