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Objective: California Yellowtail (CYT) Seriola dorsalis are continuous spawners and rely entirely on their diet to supply nutrients like fatty acids (FAs) to their eggs to support early development. The objective of this study was to determine whether commercial diets could replace a diet consisting of fresh fishery products (FFP‐D) without compromising egg quality and biochemical composition, specifically FAs. Methods: In 2017, one broodstock group (one female and two males) was fed a formulated reference feed (REF‐D; Bio‐Oregon). This pilot experiment showed that it was possible for a minimum of one female and two male broodfish to spawn repeatedly in a tank, a finding that led to a replicated diet experiment during 2018 in which 18 CYT broodfish were divided into six replicate tanks, with one female and two males per tank. Three tanks were fed the FFP‐D as a control, and three tanks were fed a commercial diet (COM‐D; Breed‐M, INVE). For each spawning event, egg quality metrics were collected, along with samples for FA analysis. Result: The 2017 REF‐D treatment produced eggs that met arachidonic acid (ARA) and eicosapentaenoic acid (EPA) requirements and had egg metrics comparable to those obtained from the FFP‐D, with higher viability and average batch fecundity. However, the REF‐D treatment had insufficient docosahexaenoic acid (DHA) and no tank replicates. The 2018 COM‐D treatment produced eggs with large egg and oil diameters and met ARA and EPA requirements but was associated with very poor spawning and hatch success and had insufficient DHA levels. The FFP‐D treatment produced below‐average viability and batch fecundity rates and was unable to meet most essential FA requirements, but it yielded the greatest number of spawning events. Conclusion: None of the experimental treatments, including the control, was able to fully meet the nutritional requirements of CYT broodstock. These results reveal crucial data about current CYT broodstock diets that can facilitate future research for developing nutritionally complete diets, especially in terms of essential FAs. Impact statementThis study investigates three different feed types in California Yellowtail broodstock. We explored if standard fish feeds could replace a standard raw fish diet without compromising egg quality. This is especially relevant to producers because understanding the right feed for broodstock helps ensure a reliable production of high quality eggs. The replacement of a raw fish diet with commercial pellets allows producers to reduce the use of wild‐caught fish as a primary food source for these broodstock, resulting in more sustainable aquaculture practices. [ABSTRACT FROM AUTHOR]

Simple Summary: Limiting inbreeding rates in farmed populations is crucial to ensuring long-term commercial viability. This task is particularly challenging in the aquaculture of mass communal spawning species, such as the yellowtail kingfish (Seriola lalandi). This reproductive strategy often results in a skewed parental genetic contribution while introducing additional complexities in parentage determination (c.f., controlled matings). To overcome these issues, we developed a marker panel based on genotyping-by-sequencing spanning 300 SNPs for parentage determination. Panel performance was satisfactory, which advocates for its employment to increase the long-term sustainability of this aquaculture resource when implementing breeding programs. Developing sound breeding programs for aquaculture species may be challenging when matings cannot be controlled due to communal spawning. We developed a genotyping-by-sequencing marker panel of 300 SNPs for parentage testing and sex determination by using data from an in-house reference genome as well as a 90 K SNP genotyping array based on different populations of yellowtail kingfish (Seriola lalandi). The minimum and maximum distance between adjacent marker pairs were 0.7 Mb and 13 Mb, respectively, with an average marker spacing of 2 Mb. Weak evidence of the linkage disequilibrium between adjacent marker pairs was found. The results showed high panel performance for parental assignment, with probability exclusion values equaling 1. The rate of false positives when using cross-population data was null. A skewed distribution of genetic contributions by dominant females was observed, thus increasing the risk of higher rates of inbreeding in subsequent captive generations when no parentage data are used. All these results are discussed in the context of breeding program design, using this marker panel to increase the sustainability of this aquaculture resource. [ABSTRACT FROM AUTHOR]

[Display omitted] • The hypothalamic-pituitary-thyroid axis was studied in Seriola rivoliana early larvae. • Larvae at 22 °C increased more trh expression than larvae at higher temperatures. • tsh was highly expressed at hatching, and then, downregulated at any temperature. • tsh -binding occurred before hatching, and further upregulating larval thyroglobulin. • On day six after hatching, all HPT axis genes were significantly upregulated. We analyzed the expression of genes involved in the hypothalamic-pituitary-thyroid axis (HPT-axis) in the longfin yellowtail Seriola rivoliana early larva, including temperature effects (22, 26 and 28 °C) and days of development (day one, day two, and day six after hatching). We aimed to determine if egg and larval incubation at different temperatures could disrupt this critical endocrine axis, which, in an aquaculture context, it could provoke mortality during early metamorphosis. There was a significant interaction between temperature and developmental timing on the relative expression of thyrotropin releasing hormone (trh). Larvae at 22 °C was the longest and increased more trh expression than larvae at higher temperatures. Interestingly, thyrotropin stimulating hormone (tsh) was highly expressed after hatching. Subsequently, it was downregulated at any temperature at least until day four, suggesting a temporal inhibition of the HPT axis. Therefore, we suggest that tsh -binding (tshr) to follicles should have occurred from hatching, creating a further "cascade effect" of upregulation of larval thyroglobulin (tg) from day two in a temperature-dependent manner. Consequently, new thyroid hormones should have been produced after yolk sac absorption. The above may indicate a narrow window of larval survival, where the larval transition from endogenous to exogenous feeding would depend on the correct timing to synthesize tg. Temperature significantly affected the expressions of deiodinase 1 (dio1 -downregulated) and deiodinase 2 (dio2 -upregulated) after hatching. The expressions of thyroid receptors alpha (trα) and beta (trβ) remained constant after hatching without significant effects of temperature and days of development. Then, the differential expression on day six showed that all HPT-axis transcripts increased their expressions as larvae developed, which suggested a functional HPT. Finally, there was no evidence that any temperature would disrupt the endocrine's larval axis, which indicated that the longfin yellowtail has a wide temperature adaption. Nevertheless, based on tg upregulation, we suggest that larvae should be maintained around 25–26 °C after hatching for a better chance of survival and development. [ABSTRACT FROM AUTHOR]

A decision support tool was developed to aid management of problematic parasites in marine fish aquaculture. The tool provides biologically relevant treatment intervals to interrupt the life cycle of ectoparasitic flatworms that occur in global kingfish and amberjack (Seriola spp.) aquaculture. Temperature‐dependent life cycle parameters for the 'skin flukes', Benedenia seriolae and Neobenedenia girellae, and the 'gill fluke', Zeuxapta seriolae, were derived from published data and modelled using non‐linear regressions. Increasing temperatures shortened the duration of most life cycle parameters of all parasites. Salinity had no effect on the timing of life cycle parameters but limited hatching success in hypo‐ and hypersaline conditions. The tool, named BeNeZe after the first two letters of each parasite genera, enables rapid determination of treatment intervals for two consecutive medicinal immersion or 'bathing' treatments—the first to kill adult flatworms attached to fish and the second to prevent maturity of new parasite recruits. As temperature increases, the interval between treatments and the 'window' within which the second treatment should be applied is reduced. The tool can be used for multi‐species infections. The inclusion of parasite taxonomy, biology and behaviour as part of an integrated management strategy is reviewed. Available through an open access app, BeNeZe is intended to be applied in conjunction with farm biosecurity, surveillance, management measures and recognition of independent management units. BeNeZe can be used to reduce infection burdens, improve fish welfare and production and reduce treatment number and frequency. [ABSTRACT FROM AUTHOR]

Existing broodstock research has ascertained that eggs are heavily influenced by broodstock diet, but there is currently sparse information regarding the time it takes for nutrients to transfer into eggs after broodstock feeding. Thus, our study aimed to quantify this duration of broodstock to egg nutrient transfer by feeding two alternating diets. In 2021, nine California yellowtail (Seriola dorsalis) broodstock were fed alternating diets of commercial pellets (Vitalis Prima: Skretting, Norway) and cutbait (70% sardine and 30% squid). These diets were switched every 41 days and then repeated so each diet was provided twice during the study. Biochemical and biometric data from spawns were collected and statistically analyzed by grouping spawns based on diet type and diet duration. Between diet switches, we observed a selective retention of C18:3n-3 (α-linolenic acid) and C18:2n-6 (linoleic acid) from the Vitalis diet, and C20:5n-3 (eicosapentaenoic acid), from the cutbait diet. Our results showed overall fatty acids from both diets were incorporated by the eggs after 10 to 19 days of feeding. Knowing this timing of nutritional incorporation from broodstock diet to eggs will help significantly improve feed efficiency by providing producers with a specific timeframe to maximize egg quality through dietary modifications or supplements. • The lag period of fatty acid incorporation from broodstock diet to egg was within 19 days. • Specific essential fatty acids were selectively retained by eggs from their previous diets. • Vitalis diet is a potential substitute for a standard cut bait diet in California Yellowtail broodstock. [ABSTRACT FROM AUTHOR]

Developing sound breeding programs for aquaculture species may be challenging when matings cannot be controlled due to communal spawning. We developed a genotyping-by-sequencing marker panel of 300 SNPs for parentage testing and sex determination by using data from an in-house reference genome as well as a 90 K SNP genotyping array based on different populations of yellowtail kingfish (Seriola lalandi). The minimum and maximum distance between adjacent marker pairs were 0.7 Mb and 13 Mb, respectively, with an average marker spacing of 2 Mb. Weak evidence of the linkage disequilibrium between adjacent marker pairs was found. The results showed high panel performance for parental assignment, with probability exclusion values equaling 1. The rate of false positives when using cross-population data was null. A skewed distribution of genetic contributions by dominant females was observed, thus increasing the risk of higher rates of inbreeding in subsequent captive generations when no parentage data are used. All these results are discussed in the context of breeding program design, using this marker panel to increase the sustainability of this aquaculture resource.

We investigated a time-course larval transcriptional analysis (RNA-seq) in the longfin yellowtail Seriola rivoliana, from hatching to day four at 22 °C, without providing zooplankton as food. Larval starvation is a critical physiological stage that must be prevented to ensure survival. However, the transcriptional mechanisms to endure starvation have not been investigated in marine fish. Differential gene expression showed newly day-specific transcriptome events during larval development. On day 1 (yolk sac absorption), the predominant upregulated developmental processes were larval growth, muscle and vision development, cytoskeletal structure, protein synthesis, protein and fat digestion-absorption, and hormone biosynthesis, whereas the cell cycle was suppressed. On day 2 (yolk sac exhaustion), a new stage of energy regeneration (ATP) was supplied by the oil drop reserve, whereas protein digestion-absorption and growth were suppressed. On day 3 (mouth opening and starvation), stress signals and nutrition deprivation upregulated the p53 signal and triggered autophagy and the AMP-activated protein kinase (AMPK) pathways as an alternative catabolic pathway to enduring starvation, and the circadian rhythm was established. On day 4 (starving and weakened larvae condition), autophagy supported subsequent protein synthesis, activated the immune system, and promoted estrogen signaling and skeleton renovation. However, larvae suppressed muscle development, vision and carbohydrate, and fat digestion-absorption and became lethargic, evidencing limited physiological support by autophagy to maintain survival without exogenous nutrition in this species. [ABSTRACT FROM AUTHOR]

A modular land-based integrated multi-tropic recirculating aquaculture system (IMTRAS) for fish, sea cucumbers, mussels and macroalgae was established to optimize resource utilization, while reducing water requirements and nutrient discharge levels. The first module included California yellowtail (Seriola dorsalis) as the primary "fed" species and Ulva lactuca functioned as biofilters. Effluent from the fish tank was passed through a drum filter for solids removal, and then the filtered seawater entered a sump. Seawater was pumped from the sump into U. lactuca tumble culture tanks and then back to the fish tank. The second module housed Mediterranean mussels (Mytilus galloprovincialis) and warty sea cucumbers (Apostichopus parvimensis) in separate serial units. Backwashes of the drum filter occurred automatically and effluent flowed by gravity to M. galloprovincialis culture tanks, and then to A. parvimensis culture troughs. Two trials of two weeks each were conducted – one at an initial fish stocking density of 5.2 kg m−3 (Trial 1), and another at 20.9 kg m−3 (Trial 2). The seawater flow rates and aeration levels were determined based on earlier pilot studies. Yellowtail grew on average 0.36 and 0.64% d−1 with a food conversion ratio of 1.73 and 1.47, in Trial 1 and Trial 2, respectively. Ulva lactuca showed productivity of 24.39 ± 2.00 and 15.57 ± 2.47 g DW m−2 d−1 with a protein content of 15.13 ± 3.11 and 30.36 ± 1.41% DW in each trial, respectively, which resulted in nitrogen uptake rates of 0.58 ± 0.08 and 0.75 ± 0.12 g m−2 d−1. Mussels and sea cucumbers removed 16.1 to 18.9% and 16.4 to 20.4% of the total solid wastes produced daily, respectively. The condition index of mussels and sea cucumbers showed no difference between the beginning and end of trial. After calculating the nitrogen balance in this IMTRAS, the largest proportion of nitrogen was in the form of dissolved inorganic nitrogen that accumulated inside the system (31.46%), followed by the yield of S. dorsalis (24.64%) and then the harvest production of U. lactuca (14.91%). All other measured nitrogen components were <7 % combined. Nitrogen that was not directly measured (i.e. "black box" nitrogen) including nitrogen accumulated inside plumbing components and lost with the effluent discharge totaled 22.48%. Based on these results, the proper ratio of co-cultured species in this system was estimated as 20.9 kg m−3 of S. dorsalis , six tanks of U. lactuca , three tanks of M. galloprovincialis and six troughs of A. parvimensis with the same volumes and stocking densities reported in this study. Future long-term trials need to be conducted to refine the operation of this IMTRAS. • An IMTRAS was established for the culture of fish, sea cucumbers, mussels and macroalgae. • All trophic levels showed good performance with little daily seawater addition. • Considerable waste removal occurred by macroalgae and solids feeders. • More macroalgae and solids feeders were needed at high fish stocking density. [ABSTRACT FROM AUTHOR]

In pelagic fish, embryo buoyancy is a noteworthy aspect of the reproductive strategy, and is associated with overall quality, survival, and further developmental success. In captivity, the loss of buoyancy of early embryos correlates with high mortality that might be related to massive cell death. Therefore, the aim of this study was to evaluate under captivity conditions the expression of genes related to the apoptosis process during the early embryonic development of the pelagic fish Seriola lalandi, and its relationship to the buoyancy of embryos. The relative expression of bcl2, bax-like, casp9, casp8, and casp3 was evaluated by RT-qPCR and FasL/Fas protein levels by western blot in five development stages of embryos sorted as floating or low-floating. All genes examined were expressed in both floating and low-floating embryos up to 24 h of development. Expression of the pro-apoptotic factors bax, casp9, casp8, and casp3 was higher in low-floating as compared with floating embryos in a developmental stage-specific manner. In contrast, there was no difference in expression of bcl2 between floating and low-floating embryos. Fas protein was detected as a single band in floating embryos without changes in expression throughout development; however, in low-floating embryos, three higher intensity reactive bands were detected in the 24-h embryos. Interestingly, FasL was only detected at 24-h in floating embryos, whereas in low-floating samples this ligand was present at all stages, with a sharp increase as development progressed. Cell death, as evaluated by the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay, was highly increased in low-floating embryos as compared to floating embryos throughout all developmental stages, with the highest levels observed during the gastrula stage and at 24 h. The results of this study suggest that an increase in cell death, probably associated with the intrinsic and extrinsic apoptosis pathways, is present in low-floating embryos that might explain their lower developmental potential under captivity conditions.

The buoyancy of eggs and embryos is associated with successful development in pelagic fish. Buoyancy is the result of oocyte hydration, which depends on the osmotic force exerted by free amino acids (FAA) generated by yolk proteolysis, and cathepsins are the main enzymes involved in this process. Seriola lalandi is a pelagic fish whose farming has been hampered by development failure that have been partially attributed to decreased buoyancy of embryos. Therefore, the aim of this study was to compare the mRNA expression and activity of cathepsins B, D, and L, as well as the FAA content in floating and low-floating embryos at different developmental stages. The chosen stages were eggs, morula, blastula, gastrula and 24 h embryos. Complementary assessments showed that there were no differences attributed to buoyancy status in embryo and oil droplet diameters, as well as the transcriptional status at any developmental stage. Cathepsin B did not show differences in mRNA expression or activity related to buoyancy at any stage. Cathepsin D displayed higher transcript and activity levels only in low-floating eggs compared with those floating. Cathepsin L showed higher expression in floating eggs and 24 h embryos compared with that of low-floating, but the activity of this enzyme was higher in floating eggs and morula. Total FAA content constantly decreased throughout development in floating embryos, but it was always higher than low-floating embryos until gastrula stage. In 24 h embryos floating and low-floating embryos share similar quantities of FAA. In summary, differences in the expression and activity of cathepsins between floating and low-floating embryos could be revealed at specific embryonic stages, suggesting different functions of these enzymes throughout development. Besides 24 h embryos, FAA content seems to be a decisive factor for buoyancy of embryos during early development of S. lalandi. Overall, considering the main role of cathepsins and FAA in buoyancy acquisition process and therefore in both embryo quality and viability, our study identifies good marker candidates to evaluate embryo quality in the farming of this species.

Constant and oscillating egg incubation temperatures on embryonic development and early larval morphology were studied in longfin yellowtail (Seriola rivoliana Valenciennes). We investigated the effects of constant temperatures from 16 to 32°C on embryo development and larval morphology at hatch, and whether oscillating temperature during embryogenesis could lead to larval morphological variations. After hatching, larval morphology and development during yolk sac (YS) utilization were examined in larvae at constant temperatures and larvae at 25°C that had oscillating temperature during egg incubation. Hatching rates were > 75%, only decreasing to ~ 50% at 30°C. At constant temperatures, the largest larvae occurred at 22 and 24°C. The oscillating temperature did not affect the timing of embryo development but resulted in larger and smaller larvae with a smaller and bigger YS, respectively, with a similar hatching time. Therefore, a growth response occurred in embryos during a window of development before hatching, depending on the adaptive response to temperature (spawn‐specific). After hatching, most of the YS was absorbed within 24 hr in all treatments, and the growth of the larval head was a priority with an optimal development at 26°C. There was compensatory growth in smaller larvae resulting in similar sizes after YS utilization, but larvae showed variations in body structure that could be important in further aquaculture research. [ABSTRACT FROM AUTHOR]

Heat shock protein 90 family, a class highly conserved protein and important molecular chaperone and its plays a role in enhancing animal adaptability to environmental stress and improving immunity. In this study, a full-length HSP90β cDNA (ToHSP90β) sequence was identified from Trachinotus ovatus. The cDNA of ToHSP90β was 2648 base-pairs (bp) long and contained a 5'-terminal untranslated region of 130 bp, a 3'-terminal untranslated region of 334 bp, and the open reading frame length 2184 bp, which can encode 728 amino acids. The ToHSP90β has a heat shock protein 90 family signature. The ToHSP90β amino acid sequence has high homology with other fish HSP90β amino acids (92.5-99.17%) and contains five conserved signal regions and a structural feature of the cytoplasmic HSP90 family. Phylogenetic tree analysis indicated that ToHSP90β was most closely related to Seriola dumerili HSP90β. Tissues expression analysis showed that the ToHSP90β was expressed in all nine tissues of T. ovatus, and its expression was the highest in the intestine. The stocking density significantly affected the expression of ToHSP90β in the kidney and brain tissues, and its expression levels increased significantly with increasing stocking densities, indicating that it plays an important regulatory role in the process of T. ovatus' chronic stress response. After Cryptocaryon irritans infection, the mRNA expression of ToHSP90β was significantly increased in liver and kidney tissues, indicating that ToHSP90β would be involved in the immune regulatory response. This study was the first to analyze the expression pattern of HSP90β mRNA in T. ovatus tissues and their expression responses to stocking density stress and C. irritans infection. To provide a theoretical basis for further study of the function of fish HSP90 and its physiological mechanism in environmental stress and parasite infection [ABSTRACT FROM AUTHOR]

Interferon (IFN)γ is a pivotal cytokine that promotes and orchestrates innate cellular and adaptive cell-mediated immunity against intracellular pathogens. The capacity of T cells in mammals to produce IFNγ has been measured using specific antibodies in order to analyze cell-mediated immune responses against infection or immuno-stimulants. In fish, however, measurement of IFNγ protein levels has not been possible due to a lack of research tools. In the present study, therefore, we established antibodies that react with endogenous amberjack IFNγ. An enzyme-linked immunosorbent assay (ELISA) for IFNγ in amberjack species was developed using these antibodies. The ELISA could detect endogenous IFNγ at concentrations less than 100 pg/mL in PMA/ionomycin-stimulated leukocytes culture supernatant. IFNγ production was enhanced and lasted a long time following intracellular bacterial infection with Nocardia seriolae , which is thought to be targeted by cell-mediated immunity. These results demonstrate that quantification of IFNγ using the reported ELISA can be used to estimate the status of cell-mediated immunity in amberjack species. • We developed antibodies and a sandwich ELISA specific to amberjack IFNγ. • The developed antibodies could detect endogenous IFNγ in amberjack species. • IFNγ production was elevated by infection with an intracellular pathogen Nocardia seriolae , which is thought to be targeted by cell-mediated immunity. • N. seriolae –infected fish that survived exhibited a high capacity to produce IFNγ and gained long-term protection against re-infection. [ABSTRACT FROM AUTHOR]

The effects of gonadotropin‐releasing hormone agonist (GnRHa) on plasma levels of follicle‐stimulating hormone (Fsh) and luteinising hormone (Lh) are reported for female greater amberjack Seriola dumerili with post‐vitellogenic ovarian oocytes. Five females were implanted with pellets containing GnRHa (600 μg kg−1 body weight), while five other females were injected with saline. All females implanted with GnRHa‐containing pellets ovulated 36–42 h post‐implantation. The GnRHa implants elevated Lh, but not Fsh plasma levels within 42 h of GnRHa administration. [ABSTRACT FROM AUTHOR]

The article discusses the study for the diseases caused by species of genus Chilodonella hexasticha and C. piscicola in a small South American fish yellowtail tetra Astyanax lacustris. It discusses the study for diagnosis and pathological description of the parasitic disease and its impact on the mortality in a new host. The parasitological analysis of skin and gills and intense infestation by parasites were examined and presents the result of the study.

Abstract Nocardia seriolae infection is one of the most serious bacterial diseases in Seriola species in Japanese aquaculture. In this study, the absorption-enhancing effect of citric acid on oral oxytetracycline (OTC) treatment against nocardiosis was evaluated with experimentally infected juvenile yellowtail, Seriola quinqueradiata , followed by serum, kidney and spleen OTC level analysis. When 50 mg/kg body weight (BW) of OTC was administered orally in combination with 1250 mg/kg BW of citric acid, the serum OTC level increased 3-fold at 6 h post single-dose administration, while no effect was observed when the dose of citric acid was set at 50 mg/kg BW. OTC levels in the kidney and spleen were increased 2-fold when 50 mg/kg BW of OTC and 1250 mg/kg BW of citric acid were administered for 5 consecutive days. This coadministration improved the clinical efficacy of oral OTC treatment against nocardiosis by significantly reducing the mortality rate compared to that of the group that received OTC alone and the untreated control group. These results suggest that coadministration of 1250 mg/kg BW of citric acid enhanced OTC absorption and therefore improved the clinical efficacy of oral OTC treatment against nocardiosis. Highlights • Nocardiosis is one of the most serious diseases in Japanese aquaculture. • Oral treatment with OTC did not show sufficient efficacy against nocardiosis. • The coadministration of citric acid with OTC enhanced the oral absorption of OTC. • The coadministration of citric acid improved the efficacy of oral OTC treatment against nocardiosis. [ABSTRACT FROM AUTHOR]

Abstract Single nucleotide polymorphisms (SNPs) have been used for quantitative traits and evolutionary studies, but only recently have they been applied to identify family relationships and construct pedigrees. Pedigree assignments can be challenging for mass spawning, polygamous marine species due to the large number of half-sib families arising from mass spawning, and small size of larvae, so genetic markers are required in order to achieve a highly accurate pedigree assignment. In the present study, sibship and parentage in yellowtail kingfish (Seriola lalandi) were obtained from SNPs and the results were compared with those obtained from DNA microsatellite data. The accuracies of pedigrees formed using COLONY and a more recently developed program, Sequoia, the latter designed to optimize speed of processing large data sets, were compared. We also considered the impact of choosing SNPs with varying minor allele frequencies (MAF from 0.05 to 0.50), varying the actual numbers of SNPs used in a given analysis (from 50 to 1000+) and varying assigned SNP genotyping error rates (0% to 10%). Accuracy of assignment, relative to DNA microsatellites, tended to increase with increasing MAF, and increased, up to a point, with increasing SNP number, but did not change with assigned genotyping error rates up to 10%. Both COLONY and Sequoia analyses, with moderate number of SNPs (500 SNPs) and MAF values (0.20–0.30), were able to predict full-sib pairs of which >95% were also predicted by DNA microsatellites, i.e. the concordance between SNP and microsatellite pedigrees was high; processing speeds were faster with Sequoia albeit with some minor reductions in accuracy. When parental data were included in the analyses, 98% of the individuals assigned to parents using SNPs were also assigned to the same parents using DNA microsatellites. Overall, the present study provides guidance as to the parameters (minor allele frequencies, number of SNPs, SNP genotyping error rates) that optimize accuracy, and once optimized, SNPs can be used efficiently for sibship and parentage assignments for polygamous species such as yellowtail kingfish in comparison to pedigrees obtained from traditional microsatellite markers. Highlights • Successful pedigree assessment for polygamous aquaculture species using SNPs • Optimized parameters for SNP pedigree assessments • Assessment of sibship using SNPs without parental data in kingfish [ABSTRACT FROM AUTHOR]

Abstract A well-balanced diet adapted to fulfil the specific nutritional requirements of greater amberjack (Seriola dumerili) would contribute to optimize reproduction and spawning quality. The main objective of the present study was to examine the effects of supplemental histidine, taurine and protein in broodstock diets, on egg quality of greater amberjack. Twelve broodstocks were distributed in three 40 m3 circular tanks and fed three different diets, one high in histidine, another in taurine and the third one in protein contents. Overall the best spawning quality was obtained histidine levels were elevated from 1 to 1.5%, increasing the relative fecundity, fertilization rates, egg viability, hatching rates, larval survival, egg protein contents, and egg and larval size, denoting the importance of this amino acid for embryo and larval development. The increase of taurine from 0.3 to 1.1% in diets for greater amberjack increased the relative fecundity in comparison to fish fed higher protein levels. Fertilization rates tend to increase with the elevation of dietary taurine and were not significantly different from those of broodstock fed higher histidine levels. Besides, dietary taurine increased egg diameter and taurine contents. Increase in dietary protein contents from 51 to 56% lead to an increase protein content in egg, as well as a larger yolk sac volume, but did not improve any of the spawning quality parameters. In conclusion, the results of this study have pointed out the importance of raising histidine contents in broodstock diets from 1 to 1.5% to optimize the reproductive performance of greater amberjack. Besides, the study showed that taurine levels in broodstock diets increased fecundity, maintaining good fertilization rates, but further studies must be conducted to determine the optimum taurine dietary levels. Highlights • The importance of raising histidine contents in broodstock diets from 1 to 1.5% to optimize reproductive performance of greater amberjack, particularly to improve egg and larval quality. • Taurine levels in broodstock diets increased fecundity, maintaining good fertilization rates. • Increasing protein contents over 51% lead to the lowest number of egg and larvae produced. [ABSTRACT FROM AUTHOR]

This study examines the effects of swim bladder inflation failure, a common developmental abnormality in finfish aquaculture, on the energy allocation, growth, and development of California Yellowtail ( Seriola dorsalis ). Health and fitness metrics including oxygen consumption, aerobic scope, critical swimming speed, feed conversion ratio, and growth rate, were monitored over a 32-week growout period in three groups of S. dorsalis : aquaculture-reared fish that failed to inflate their swim bladders (uninflated), aquaculture-reared fish with properly inflated swim bladders (inflated), and wild-caught individuals (wild). After the growout period, the uninflated fish had significantly lower body mass (636.1 ± 80.4 g vs. 758.6 ± 92.7 g inflated), shorter body length (36.5 ± 1.9 cm vs. 39.6 ± 2.0 cm inflated), and smaller girth (21.5 ± 1.2 cm vs. 23.2 ± 1.1 cm inflated) than the inflated fish. In addition, the uninflated fish had the least efficient feed conversion ratio (2.08 uninflated vs. 1.49 inflated, 1.41 wild), needing 39.8% more feed than the inflated fish, and 47.8% more feed than the wild fish to gain equivalent mass. These differences in growth and feed conversion appear to be primarily attributed to differences in energy allocation. Measures of oxygen consumption using a swim tunnel respirometer at two time points during the growout period showed that uninflated fish had significantly higher metabolic costs than both the inflated and wild groups over a large range of the swimming speeds tested. In addition, the uninflated fish were often observed swimming faster in their growout tank, likely to generate enough lift to compensate for the lack of a buoyant swim bladder. The wild-caught fish had the lowest feed conversion ratios and had significantly lower metabolic costs than both the inflated and uninflated aquaculture-reared fish at the beginning of the growout period (shortly after capture from the wild). The results of this study show that rearing S. dorsalis without a functional swim bladder is not economically feasible based on their poor growth and feed conversion ratios, and suggest that there is room for improvement in the metabolic efficiency of cultured S. dorsalis with properly inflated swim bladders. [ABSTRACT FROM AUTHOR]

Highlights • Greater amberjack sex ratio in the Gulf of Mexico may differ from 1:1. • Sex-specific fishing mortality rates can theoretically alter amberjack sex ratios. • Altered sex ratios influence could influence population dynamics of amberjack. • Incorrect sex ratio assumptions could lead to management issues. • Should incorporate a range of realistic sex ratios into future stock assessments. Abstract The US Gulf of Mexico stock assessment of greater amberjack Seriola dumerili assumes a 1:1 male:female sex ratio. However, the observed sex ratio in the landed catch is 1:1.8, and for fish >1 m fork length is 1:2.4. To theoretically explore whether this female-skewed sex ratio may arise due to differential fishing mortality between the sexes, we used a sex-specific age- and size-based model to investigate how different fishing mortality rates could create a female-skew in the landed catch as well as its subsequent effects on reproductive potential. When fishing mortality rates in the model were equal between the sexes, the sex ratio of the landed catch was approximately 1:1 for all legal-sized fish, and approximately 1:2.4 for fish >1 m FL. However, reproductive potential decreased in comparison to the corresponding scenario with equal fishing mortality rates when fishing mortality rates between the sexes were changed to create the 1:1.8 sex ratio observed in the landed catch. This modeling study demonstrates one possible route that could explain the female-skewed sex ratios observed in the landed catch, and indicates that sex ratio values other than 1:1 should be considered in future stock assessments for Gulf of Mexico greater amberjack. [ABSTRACT FROM AUTHOR]

Highlights • Previtellogenic greater amberjack were exposed to short or long photoperiods. • Plasma Fsh, but not Lh, was higher in the long-photoperiod group on days 10 and 30. • Pituitary fshb and lhb elevated in the long-photoperiod group on day 30. • Increase in plasma Fsh may be a key factor that mediates photoperiodic effects. Abstract In Seriola species, exposure to a long photoperiod regime is known to induce ovarian development. This study examined photoperiodic effects on pituitary gene expression and plasma levels of follicle-stimulating hormone (Fsh) and luteinizing hormone (Lh) in previtellogenic greater amberjack (Seriola dumerili). The fish were exposed to short (8L:16D) or long (18L:6D) photoperiod. The water temperature was maintained at 22 °C. Compared with the short-photoperiod group, plasma Fsh levels were higher on days 10 and 30 in the long-photoperiod group, but plasma Lh levels did not significantly differ. On day 30, pituitary Fsh- and Lh-β subunit gene expressions were also higher in the long-photoperiod group than the short-photoperiod group, whereas α-subunit gene expressions were higher on days 20 and 30. Throughout the experiment, average gonadosomatic index and plasma E2 levels did not significantly differ between the two groups. This study clearly demonstrated that a long photoperiod induced Fsh release in the previtellogenic fish followed by upregulation of pituitary Fsh and Lh subunit gene expressions. An increase in plasma Fsh levels may be a key factor that mediates the photoperiodic effect on the initiation of ovarian development. [ABSTRACT FROM AUTHOR]

Communal spawning behaviour in marine aquaculture species often results in a few individuals contributing disproportionate amounts of gametes. This can lead to a reduction in genetic variability and increases the risk of inbreeding among successive generations. Therefore, long term sustainability of captive breeding programmes for such species partly depends upon maintaining a sufficiently high proportion of parents contributing high quality gametes during spawning. The current study was conducted to evaluate if the use of slow-release gonadotropin-releasing hormone analog (GnRHa) implants could increase the number of females spawning high quality gametes, and thus increase genetic variation in a captive population of yellowtail kingfish Seriola lalandi (Valenciennes, 1833). Broodstock fish received implants with or without 500 μg of GnRHa during the spawning season. GnRHa treatment was associated with a higher proportion of females contributing to spawning. However, compared to eggs from non-GnRHa-treated broodstock, GnRHa significantly decreased the floating rate, fertilisation rate, number of viable eggs and egg oil globule diameter. Overall, the use of slow-release GnRHa implants is a useful tool to increase parental contribution to spawning, but this benefit must be carefully balanced against lower egg quality.

The mitochondrial genomes of Seriola quinqueradiata and S. lalandi were 16,539 and 16,535 base pairs long, respectively, whose organizations were similar to those of other bony fishes. The sequence similarity of two species was 93% in the mitochondrial whole genome. Between each coding gene, rRNA, and control region, the highest similarity was 98% in ATP8 and lowest similarity was 87% in the control region. Phylogenetic analysis of Carangidae mt 12 protein-coding genes showed that Seriola and Carangoides do not form a monophyletic genus.

Abstract: This study investigated the effect of intermittent feeding on the water quality, occurrence of skin parasites, feed consumption, and growth performance of juveniles (102.7 ± 5.1 g) longfin yellowtail, Seriola rivoliana. Fish were exposed for 89 days to six different feeding regimes: continuous daily feeding fed one or twice a day (treatment 24R1 and 24R2); 2‐day fasting and refed once or twice a day for 1 day (treatment 48R1 and 48R2); and 3‐day fasting and refed once or twice a day for 1 day (treatment 96R1 and 96R2). Water quality was not affected by feeding strategies. Likewise, condition factor was not affected by fasting up 48 hr. On the other hand, lowest survival in 96R1 was not related with abundance of skin parasites (Neobenedenia girellae). Specific growth rate, feed intake, feed efficiency, and morphological indices were not statistically different (p > 0.05) between 2 days fasted fish and continuously fed fish. Partial compensatory growth in 48R2 could be attributed to a hyperphagic consumption (8.2 ± 1.1 g day−1 fish−1) and feed conversion efficiency (0.61 ± 0.03). A feeding strategy based on cyclical 48 hr of starvation followed by 1 day of refeeding twice may be used for on‐growing juvenile longfin yellowtail without reduction in growth or welfare of fish. [ABSTRACT FROM AUTHOR]

Abstract: Production of sufficient high‐quality eggs of greater amberjack (Seriola dumerili) still constitutes the main bottleneck for commercial production of this species. The main objective of this study was to compare the quality of spontaneous spawn of greater amberjack with those obtained by either GnRHa injection or GnRHa implant protocols. Captive amberjack broodstock were distributed in three circular tanks of 40 m3. Broodstock from Tank 1 were not hormonally induced and spawned spontaneously, whereas those of Tank 2 were intramuscularly injected with GnRHa (20 µg/kg body weight) and those of Tank 3 were given EV‐500 µg GnRHa implants. The number of eggs per spawn obtained in the broodstock without hormonal treatment was larger than in those obtained with injections or implants. Egg quality was best in broodstock with spontaneous spawn, followed by GnRHa‐injected fish and then GnRHa implants. Besides, size of larvae from control and injected broodstock was similar between them and significantly higher (p < 0.01) than those from GnRHa implant spawn. Overall, this study showed that it is possible to obtain very high‐quality spontaneous spawn in greater amberjack, providing the adequate conditions. Furthermore, GnRHa weekly injections lead to similar egg viability and hatching rates than spontaneous spawn and higher fertilization rates than GnRHa hormonal implants, which is better than in previous studies. [ABSTRACT FROM AUTHOR]

This study was carried out to estimate total catches extracted from the offshore areas of northeastern Brazil by recreational fishers from offshore operations, daily activities, and fishing competitions. It also aimed at providing a first estimate of expenditure by anglers in the region. The basis for this analysis was the data supplied by the only offshore fishing operator established in Paraíba State. The available logbooks allowed for the first estimate of total catches by anglers in Paraíba State, which was extrapolated to the entire region using information provided in a database of recreational fishers' licenses. By combining these data with catch data from fishing competitions, we were able to estimate that a peak of about 90 ton was extracted in 2011. This catch is low when compared with commercial catches, but the associated economic impacts, assessed via the expenditure by recreational fishers at US$1.5 million in 2014, is high. Moreover, catches are concentrated mainly on a small number of species, mostly Thunnus spp. and Seriola spp. in waters off Paraíba State. No information is available on the current status of these amberjacks (Seriola spp.). However, some of the snappers (Fam. Lutjanidae) included in the top species caught by recreational fishers are considered overexploited in the region. [ABSTRACT FROM AUTHOR]

Abstract: A 154‐day trial was performed to assess the use of an alternative protein blend (corn gluten, krill and meat meal) as a substitute for fishmeal in diets for juvenile yellowtail, using four isolipidic (140 g/kg) and isoenergetic diets (24 MJ/kg) with the same digestible protein content (50%). The control diet was FM100, without replacement, and in FM66, FM33 and FM0, fishmeal was replaced at 33 g/kg, 66 g/kg and 100 g/kg, respectively. At the end of the experiment, no differences in growth parameters were observed. Fish fed the FM0 diet exhibited the lowest survival (23%). This high mortality may be due to different factors, such as a dietary amino acid imbalance or some antinutrient factors contained in the alternative ingredients. Feed intake, feed conversion ratio, digestible protein intake and protein efficiency ratio were similar in all diets. However, digestible energy intake and protein efficiency retention were lowest in fish fed the FM0 diet. Apparent digestibility coefficients for protein, energy and amino acids diminished as a substitution for fishmeal increased. Significant differences were observed in the diet whole‐fish body profile amino acid retention (AAR) ratio for the seven essential amino acids. In summary, total fishmeal replacement by the blend assayed was not feasible for yellowtail. The FM66 diet resulted in good growth, high survival and good nutrient efficiency. [ABSTRACT FROM AUTHOR]

Since 2011, high mortality rates and symptoms consistent with vibriosis have been observed in farmed amberjack (Seriola dumerili) in Japan. To identify 41 strains isolated from diseased amberjack, a multilocus sequence analysis using nine concatenated genes (ftsZ, gapA, gyrB, mreB, pyrH, recA, rpoA, topA and 16S rRNA) was conducted. Twenty-seven strains were identified as Vibrio harveyi, suggesting an epidemic of V. harveyi infection in amberjack farms. Other strains were identified as Vibrio anguillarum, Vibrio owensii and Photobacterium damselae subsp. damselae. To develop an efficient diagnostic method for vibriosis in amberjack, a multiplex PCR system was developed to identify V. anguillarum, V. harveyi and P. damselae subsp. damselae. The method successfully discriminated between these three bacterial species, with amplification products of 350 bp for V. anguillarum, 545 bp for V. harveyi and 887 bp for P. damselae subsp. damselae and can be used for diagnosis in aquaculture farms. [ABSTRACT FROM AUTHOR]

Abstract: Five isoproteic (54.8%) and isolipidic (24.1%) microdiets, which varied in their docosahexaenoic acid (DHA) content (0.25%, 0.75%, 1.64%, 1.99% and 3.17%; dw), were manufactured to determine its effects on longfin yellowtail Seriola rivoliana larvae in terms of fish biological performance, whole body fatty acid profile and incidence of skeletal anomalies from 30 dah (11.31 ± 1.79 Total Length, TL) to 50 dah (19.80 ± 0.58 mm TL). The inclusion of dietary DHA up to 3.17% (dw) improved larval resistance to air exposure, although DHA did not significantly affect fish final growth or final survival. Indeed, high levels of dietary DHA (1.99% and 3.17%, dw) tended to increase the incidence of skeletal anomalies in S. rivoliana larvae, albeit no significant differences were observed. Furthermore, the occurrence of severe anomalies such as kyphosis and lordosis, was mainly associated to the larvae fed the highest levels of dietary DHA. In terms of survival, increasing dietary DHA levels did not significantly affect longfin yellowtail survival rate, despite a tendency for enhanced survival. The results of the present study proved that the inclusion of dietary DHA in inert diets up to a 3.17% (dw) and a DHA/EPA ratio above 3.1 increased the final survival and stress resistance in S. rivoliana larvae. [ABSTRACT FROM AUTHOR]

Aspects of swimming and metabolic physiology were measured in aquaculture-reared California Yellowtail ( Seriola dorsalis ) in comparison to wild-caught individuals in order to examine potential differences in health and fitness associated with captive rearing, and to help identify areas for targeted improvement in Seriola aquaculture. Incremental swimming velocity trials using a swim tunnel respirometer on small yellowtail (mean body length = 18.9 cm, mass = 80.1 g) showed that aquaculture-reared fish had a significantly slower mean maximum sustainable swimming speed ( U crit ) (4.16 ± 0.62 BL s −1 ) in comparison to that of wild-caught fish (4.80 ± 0.52 BL s −1 ). In addition, oxygen consumption ( Ṁ O 2 ) measurements at varying swimming speeds allowed for estimation of standard metabolic rate, which was significantly higher in aquaculture-reared yellowtail (7.31 ± 2.32 vs. 3.94 ± 1.60 mg O 2 kg −1 min −1 at 18 °C). Aquaculture fish also had a lower aerobic scope (9.20 ± 3.44 mg O 2 kg −1 min −1 ) in comparison to wild-caught yellowtail (15.80 ± 5.78 mg O 2 kg −1 min −1 ), which likely contributed to their reduced capacity for fast sustainable swimming. Reduced physical fitness is commonplace in aquaculture-reared fishes, and the examination of wild-caught yellowtail in this study provides baseline metrics that can be used to gauge the health and fitness of future S . dorsalis production. In particular, the lower standard metabolic rate and higher aerobic scope of wild-caught fish represent desirable metabolic characteristics that if achievable in aquaculture through better-rearing practices could allow for increased feed conversion efficiencies and potentially faster growth. At a minimum, a 35–40% reduction in metabolic costs at low swimming speeds (to those observed for wild-caught yellowtail) should result in substantial cost savings for feed in aquaculture operations. [ABSTRACT FROM AUTHOR]

In aquaculture of species with a large body size, such as tuna and yellowtail, a major profitability concern is that broodstock management for egg collection incurs high feeding costs and labor. In order to reduce feeding costs, development of restricted feeding techniques without affecting the reproductive performance may be useful. To gain a better understanding of the potential significance of capital energy in reproduction of large fish with income breeding patterns, we examined the effects of long-term restricted feeding prior to the onset of oocyte development on reproductive performance in female yellowtail ( Seriola quinqueradiata ). A control group was fed to satiety, while experimental groups were restricted to 50 and 25% of the ration administered to the control group from July to December. The females subjected to restricted feeding had lower ovary weight and smaller ovarian follicles than did the control females in February. Moreover, plasma 17β-estradiol levels in food-restricted females were significantly lower than those in normally fed females in January and February. Furthermore, we found that food-restricted females had lower pituitary gene expression levels of gonadotropins (follicle-stimulating hormone and luteinizing hormone) in January. These results suggest that severe food restriction during the immature phase delays initiation of oocyte development via an alteration in pituitary gonadotropin production in yellowtail females. Once food intake was sufficient after switching to the satiation feeding regime, however, oocyte development rapidly advanced, resulting in the production of fully functional eggs. Overall, these findings demonstrate that the yellowtail displays a mixed strategy of capital-breeding patterns at the onset of sexual maturation, but stronger income-breeding patterns with its progression in reproduction with energy acquired during the vitellogenic phase. Additionally, food deprivation over 6 months by 50% of the amount of food required for satiation during the immature phase did not change reproductive performance in female yellowtail, although the females in the 25% feeding group showed a lower percentage of normally hatching eggs. Therefore, a 50% restricted feeding regime before the onset of sexual maturation is acceptable for reducing feeding costs in broodstock management without affecting reproductive performance. [ABSTRACT FROM AUTHOR]

Abstract: This study was undertaken to assess the effects of fish oil (FO) substitution by a mixture of alternative vegetable oils (VO) on Seriola dumerili culture performance. A 154‐day feeding experiment was conducted using juveniles (39.2 ± 1.6 g average weight). Three isolipidic and isoenergetic meal‐based diets were formulated varying their lipid component. The control diet contained 100% FO (FO100), whereas diets VO50 and VO100 included 1/2 of oil blend and all the oil from blend of palm oil (PO) and linseed oil (LO) as substitute for FO, respectively. Dietary regime did not significantly affect growth performance, biometric indices, feed efficiency, plasma chemistry and liver and muscle lipid contents. Nonetheless, dietary VO inclusion impacted on the fatty acid profile of target tissues, especially in the liver. Fatty acid profiles of the fillets reflected those of the dietary oils except that there was apparent selective utilization of palmitic acid (C16:0) and oleic acid (C18:1n‐9) and apparent selective retention of long‐chain polyunsaturated fatty acids, especially eicosapentaenoic acid (EPA, C20:5n‐3) and docosahexaenoic acid (DHA, C22:6n‐3). The nutritional value and the potential ability to prevent the development of coronary heart diseases of the flesh lipid fraction decreased with gradual FO substitution. [ABSTRACT FROM AUTHOR]

Abstract: A 60‐day feeding trial to determine the nutritional value of marine by‐product meals in diets for longfin yellowtail Seriola rivoliana juveniles (48.1 ± 0.6 g initial weight) was conducted. Five diets were evaluated: a reference diet (RD; 500 g kg−1 CP, 130 g kg−1 L), containing 500 g kg−1 of fish meal (FM); three experimental diets with 125 g kg−1 of shrimp head (SM), Catarina scallop viscera (CM) or Pen shell viscera (PM) meals; and one diet (SCP) containing 125 g kg−1 of each of the experimental meals, to partially replace FM. Survival was not significantly affected by any treatment. Individual weight gain per day was high for the PM (5.3 ± 0.51 g d−1) and SM (4.7 ± 0.32 g d−1) diets, being significantly higher than the RD (3.5 ± 0.23 g d−1) and the other treatments (<1.2 g d−1). Feed intake was high in PM and SM diets, and very low in SCP and CM diets. Biochemical and haematological parameters were similar among treatments RD, PM and SM, while fish fed CM and SCP exhibited lower levels of total protein, cholesterol, haematocrit and haemoglobin. The results indicate that SM or PM can be used to partially replace FM in diets for yellowtail juveniles. [ABSTRACT FROM AUTHOR]

Background: Genomic prediction using Diversity Arrays Technology (DArT) genotype by sequencing platform has not been reported in yellowtail kingfish (Seriola lalandi). The principal aim of this study was to address this knowledge gap and to assess predictive ability of genomic Best Linear Unbiased Prediction (gBLUP) for traits of commercial importance in a yellowtail kingfish population comprising 752 individuals that had DNA sequence and phenotypic records for growth traits (body weight, fork length and condition index). The gBLUP method was used due to its computational efficiency and it showed similar predictive performance to other approaches, especially for traits whose variation is of polygenic nature, such as body traits analysed in this study. The accuracy or predictive ability of the gBLUP model was estimated for three growth traits: body weight, folk length and condition index. Results: The prediction accuracy was moderate to high (0.44 to 0.69) for growth-related traits. The predictive ability for body weight increased by 17.0% (from 0.69 to 0.83) when missing genotype was imputed. Within population prediction using five-fold across validation approach showed that the gBLUP model performed well for growth traits (weight, length and condition factor), with the coefficient of determination (R²) from linear regression analysis ranging from 0.49 to 0.71. Conclusions: Collectively our results demonstrated, for the first time in yellowtail kingfish, the potential application of genomic selection for growth-related traits in the future breeding program for this species, S. lalandi. [ABSTRACT FROM AUTHOR]

The justification for incorporating environmental effects into fisheries stock assessment models has been investigated and debated for a long time. Recently, a state-space age-structured assessment model which includes the stochastic change in the environmental covariate over time and its effect on recruitment was developed for Southern New England-Mid Atlantic yellowtail flounder ( Limanda ferruginea). In this paper, we first investigated the correlations of environmental covariates with Southern New England-Mid Atlantic yellowtail flounder recruitment deviations. The covariate that was most strongly correlated with the recruitment deviations was then incorporated into the state-space model and alternative effects on the stock-recruit relationship were estimated and compared. For the model that performed best as measured by Akaike information criterion, we also compared the estimates and predictions of various population attributes and biological reference points with those from an otherwise identical model without the environmental covariate in the stock-recruit function. We found that the estimates of population parameters are similar for the two models but the predictions differed substantially. To evaluate which model provided more reliable predictions, we quantitatively compared the prediction skill of the two models by generating two series of retrospective predictions. Comparison of the retrospective prediction pattern suggested that from an average point of view, the environmentally explicit model can provide more accurate near-term recruitment predictions especially the one year ahead recruitment prediction. However, the accuracy of the near-term recruitment prediction from the environmentally explicit model was largely determined by the accuracy of the corresponding environment prediction the model provides. [ABSTRACT FROM AUTHOR]

This work contributes basic knowledge on larval development of Seriola rivoliana. A histological study describes the development of the digestive tract and accessory glands in S. rivoliana larvae reared under laboratory conditions at 24 °C from hatching to 30 days post-hatching (DPH). At hatching (2.6 ± 0.12 mm), larvae had an undifferentiated digestive tract with a closed straight tube and a large yolk sac with an oil globule. The liver and pancreas were observed at 1 and 2 days, and the mouth and anus opened at day 2. Enriched rotifers were visible in their digestive tract. At the beginning of the pre-flexion stage, a mixed nutritional period was observed. At day 3, exogenous feeding began; the digestive tract became differentiated into the buccopharynx, esophagus, an undifferentiated stomach, and the intestines. Zymogen granules were visible in the exocrine pancreas. At day 4, supranuclear vacuoles were present in the posterior intestine, indicating the beginning of intracellular digestion. At day 5, goblet cells were present in the esophagus and became functional at day 7 in the esophagus and intestine. The buccopharynx goblet cells developed at day 15. The presence of gastric glands and differentiation of the stomach in the fundic, cardiac, and pyloric regions during the post-flexion stage occurred at day 20. This was the onset of the juvenile period and the beginning of weaning; however, a long co-feeding phase is recommended. Pyloric caeca were observed at day 30 (13.6 ± 1.6 mm). These results provide valuable information on S. rivoliana larvae biology and digestive physiology, which should be useful to improve cultivation techniques and identify ecological features involved in ontogeny. [ABSTRACT FROM AUTHOR]

Seriola lalandi is an economically important species that is globally distributed in temperate and subtropical marine waters. Aquaculture production of this species has had problems associated with intensive fish farming, such as disease outbreaks or nutritional deficiencies causing high mortalities. Intestinal microbiota has been involved in many processes that benefit the host, such as disease control, stimulation of the immune response, and the promotion of nutrient metabolism, among others. However, little is known about the potential functionality of the microbiota and the differences in the composition between wild and aquacultured fish. Here, we assayed the V4-region of the 16S rRNA gene using high-throughput sequencing. Our results showed that there are significant differences between S. lalandi of wild and aquaculture origin (ANOSIM and PERMANOVA, P < 0.05). At the genus level, a total of 13 genera were differentially represented between the two groups, all of which have been described as beneficial microorganisms that have an antagonistic effect against pathogenic bacteria, improve immunological parameters and growth performance, and contribute to nutrition. Additionally, the changes in the presumptive functions of the intestinal microbiota of yellowtail were examined by predicting the metagenomes using PICRUSt. The most abundant functional categories were those corresponding to the metabolism of cofactors and vitamins, amino acid metabolism and carbohydrate metabolism, revealing differences in the contribution of the microbiota depending on the origin of the animals. To our knowledge, this is the first study to characterize and compare the intestinal microbiota of S. lalandi of wild and aquaculture origin using high-throughput sequencing.

Little is known about mechanisms of resistance to parasitic diseases in marine finfish. Benedenia disease is caused by infection by the monogenean parasite Benedenia seriolae . Previous quantitative trait locus (QTL) analyses have identified a major QTL associated with resistance to Benedenia disease in linkage group Squ2 of the Japanese yellowtail/amberjack Seriola quinqueradiata. To uncover the bioregulatory mechanism of Benedenia disease resistance, complete Illumina sequencing of BAC clones carrying genomic DNA for the QTL region in linkage group Squ2 was performed to reveal a novel C-type lectin in this region. Expression of the mRNA of this C-type lectin was detected in skin tissue parasitized by B. seriolae . Scanning for single nucleotide polymorphisms (SNPs) uncovered a SNP in the C-type lectin/C-type lectin-like domain that was significantly associated with B. seriolae infection levels. These results strongly suggest that the novel C-type lectin gene controls resistance to Benedenia disease in Japanese yellowtails. [ABSTRACT FROM AUTHOR]

In aquaculture of species with a large body size such as tuna and yellowtail, a major problem still is that broodstock management for egg collection requires high feeding cost and labor. In order to reduce feeding costs, development of restricted feeding techniques without affecting the reproductive performance may be useful. To gain a better understanding of reproductive responses to food supply, we examined the effect of restricted feeding during the previtellogenic and vitellogenic phases on sexual maturation in female yellowtail, Seriola quinqueradiata . Restricted feeding during the vitellogenic phase tended to reduce ovary weight relative to normally fed controls at the end of the experiment. Histological observations revealed that both restricted feeding regimes do not affect the percentage of atretic follicles as compared to the control group. Nevertheless, the mean diameter of the most advanced follicles of the females subjected to restricted feeding during the vitellogenic phase was significantly smaller to normally fed controls. These results suggest that reduced food intake during the vitellogenic phase is likely to delay oocyte growth, and lead to low ovarian weight. Endocrine analyses showed that restricted feeding during the vitellogenic phase reduced plasma 17β-estradiol levels, but not plasma and pituitary gene expression levels of gonadotropins (follicle-stimulating hormone and luteinizing hormone) at the end of the experiment. Transcripts for ovarian steroidogenesis-related genes, such as P450 side-chain cleavage ( cyp11a1 ) and 3β-hydroxysteroid dehydrogenase ( hsd3b ) after food restriction during the vitellogenic phase tended to be high. Therefore, the effects of restricted feeding on reproduction would not be mediated by alterations in circulating gonadotropin levels, but rather through direct effects on the ovarian steroid production in yellowtail females. [ABSTRACT FROM AUTHOR]

Amberjack Seriola dumerili (Carangidae) and yellowtail S. quinqueradiata are important commercial fish species in Japan; however, they are susceptible to skin and gill monogeneans. Recently, a treatment of 75 ppm hydrogen peroxide (H 2 O 2 ) for 30 min was found to effectively eliminate these monogeneans. However, histological analyses of the host fish subjected to treatments with lower H 2 O 2 concentrations have not been performed to determine the influence of these treatments on fish. Therefore, we investigated the influence of a 100 ppm H 2 O 2 treatment at 25 °C on the survival, swimming behavior, feeding behavior and the histopathology of S. dumerili and S. quinqueradiata compared with the 300 ppm treatment at 25 °C, which is the conventional concentration. We then evaluated the susceptibility of both species to infestations of the skin monogenean Neobenedenia girellae after the administration of a 75 ppm H 2 O 2 bath treatment relative to the susceptibility after the administration of the conventional procedure (300 ppm for 3 or 4 min) at 25 °C. Both species suffered severe effects when exposed to 300 ppm H 2 O 2 ; however, when exposed to 100 ppm H 2 O 2 for 60 min, the survival, appetite, and swimming behavior were unaffected. Histopathological changes were not observed during the examination of the skin, gills, and internal organs of the fish in the control group and the group treated with 100 ppm H 2 O 2 for 60 min, whereas histopathological changes were observed in the skin, gills and liver of the fish treated with 300 ppm H 2 O 2 for 60 min, and the changes in S. dumerili became more pronounced with increasing exposure time. Furthermore, the fish treated with 75 ppm H 2 O 2 baths for 30 or 40 min did not show increased N. girellae infestation levels relative to the untreated controls; however, the fish treated with the 300 ppm H 2 O 2 baths for 4 min showed significantly increased N. girellae infestation levels relative to the untreated controls ( P < 0.05). These results show that treating fish with 75 ppm H 2 O 2 for 30 min, which effectively eliminates the monogeneans infecting S. dumerili , would be presumably safe for the use in the higher water temperatures; however, the exposure time at higher H 2 O 2 concentrations, i.e., 300 ppm, must be strictly managed. Statement of relevance To eliminate B. seriolae and N. girellae , Z. japonica , fish may be fed praziquantel-supplemented feed, submerged in a freshwater bath for 2- to 5- min, or placed in a hydrogen peroxide bath. However, none of these measures simultaneously dislodge B. seriolae , N. girellae , and Z. japonica . Orally administered praziquantel is ineffective against N. girellae infestations in Seriola species, and the freshwater treatment is not effective when the fish are infected with Z. japonica . Additionally, H 2 O 2 treatment at a concentration of 300 ppm (conventional concentration in Japan) negatively affects fish health and viability, especially in the summer when water temperatures are higher and the parasite doubling and maturation rates are increase. Thus, any parasite control measure must be performed frequently during the summer. A bath treatment with 75 ppm H 2 O 2 for 30 min effectively eliminates these parasites and the fish survival, appetite and swimming behavior were unaffected when exposed to 75 ppm H 2 O 2 for 6 h at 25 °C. Therefore, treatment with 75 ppm H 2 O 2 for 30 min is not expected to adversely affect S. dumerili . However, histological analyses of lower H 2 O 2 concentrations have not been performed to determine the effects on the host fish, and experimental proof of the safety of different concentrations is important for the use of this treatment in aquaculture. [ABSTRACT FROM AUTHOR]

Seriola lalandi is an economically important species that is globally distributed in temperate and subtropical marine waters. Aquaculture production of this species has had problems associated with intensive fish farming, such as disease outbreaks or nutritional deficiencies causing high mortalities. Intestinal microbiota has been involved in many processes that benefit the host, such as disease control, stimulation of the immune response, and the promotion of nutrient metabolism, among others. However, little is known about the potential functionality of the microbiota and the differences in the composition between wild and aquacultured fish. Here, we assayed the V4-region of the 16S rRNA gene using high-throughput sequencing. Our results showed that there are significant differences between S. lalandi of wild and aquaculture origin (ANOSIM and PERMANOVA, P < 0.05). At the genus level, a total of 13 genera were differentially represented between the two groups, all of which have been described as beneficial microorganisms that have an antagonistic effect against pathogenic bacteria, improve immunological parameters and growth performance, and contribute to nutrition. Additionally, the changes in the presumptive functions of the intestinal microbiota of yellowtail were examined by predicting the metagenomes using PICRUSt. The most abundant functional categories were those corresponding to the metabolism of cofactors and vitamins, amino acid metabolism and carbohydrate metabolism, revealing differences in the contribution of themicrobiota depending on the origin of the animals. To our knowledge, this is the first study to characterize and compare the intestinalmicrobiota of S. lalandi of wild and aquaculture origin using high-throughput sequencing. [ABSTRACT FROM AUTHOR]

Bacterial haemolytic jaundice caused by Ichthyobacterium seriolicida has been responsible for mortality in farmed yellowtail, Seriola quinqueradiata, in western Japan since the 1980s. In this study, polymorphic analysis of I. seriolicida was performed using three molecular methods: amplified fragment length polymorphism ( AFLP) analysis, multilocus sequence typing ( MLST) and multiple-locus variable-number tandem repeat analysis ( MLVA). Twenty-eight isolates were analysed using AFLP, while 31 isolates were examined by MLST and MLVA. No polymorphisms were identified by AFLP analysis using Eco RI and MseI, or by MLST of internal fragments of eight housekeeping genes. However, MLVA revealed variation in repeat numbers of three elements, allowing separation of the isolates into 16 sequence types. The unweighted pair group method using arithmetic averages cluster analysis of the MLVA data identified four major clusters, and all isolates belonged to clonal complexes. It is likely that I. seriolicida populations share a common ancestor, which may be a recently introduced strain. [ABSTRACT FROM AUTHOR]

The fat content and fatty acid profile of commercially important Seriola fasciata (Lesser amberjack) was determined in samples of muscle, liver and gonads of both genders at pre-spawning and spawning stage. Results indicated that edible muscle of pre-spawning fish had high fat content (>8%), lowering to medium fat (4–8%) content during spawning stage. Livers and gonads presented more constant and relatively high lipid contents. Saturated fatty acids constituted the majority of the fatty acids, followed by monounsaturated fatty acids, with palmitic acid and oleic acid as the major fatty acid in all tissues. EPA and DHA content increased in spawning females and highest amounts were observed in the ovaries (222 and 1440 mg/100 g respectively). Livers presented lowest PUFAs content regardless of maturity stage and Σ n −6/Σ n −3 ratio was influenced by gender in this organ. Σ n −3/Σ n −6 was gender related during pre-spawning stage, increasing in spawning maturation stage. Results highlight variations in the nutritional value of the different tissues according to maturity stage and gender, emphasizing the need for consumer awareness of these changes. [ABSTRACT FROM AUTHOR]

In pelagic species such as Seriola lalandi , survival of both the eggs and embryos depends on yolk processing during oocyte maturation and embryo development. The main enzymes involved in these processes are the cathepsins, which are essential for the hydration process, acquiring buoyancy and nutrition of the embryo before hatching. This study aimed to investigate the mRNA expression profiles of cathepsins B, D and L ( catb, catd and catl ) and the activity of these enzymes during early development in S. lalandi . We included previtellogenic oocytes (PO). All three enzymes were highly expressed in PO, but the expression was reduced throughout development. Between PO and recently spawned eggs (E1) the transcript to catb and catd decreased, unlike catl . Cathepsin B activity, showed stable levels between PO until blastula stage (E4). High activities levels of cathepsins D and L were observed in E1 in comparison with later developmental stages. Cathepsin L activity remained constant until E1, consistent with observations in other pelagic spawners, where its participation in a second protolithic cleavage of the yolk proteins, has been proposed for this enzyme. Their profiles of both mRNA expression and enzymatic activity indicate the importance of these enzymes during early development and suggest different roles in egg yolk processing for the hydration process and nutrition in early embryos in this species. [ABSTRACT FROM AUTHOR]

The visual environment of several aquaculture species has been shown to be crucial for increased survival and growth. However, very little is known about the visual system of the increasingly popular Seriola genus and its developmental changes. We investigated the ontogenetic changes in colour vision and spatial resolution in the yellowtail kingfish, S. lalandi and discuss them in relation to past behavioural feeding experiments. Microspectrophotometry was used to measure the spectral sensitivities of photoreceptor visual pigments in larvae and sub-adults. The yellowtail kingfish larva has a broad spectral range including ultraviolet-sensitive (UVS) single cones, middle-wavelength-sensitive (MWS) single cones, MWS twin cones and long-wavelength-sensitive (LWS) twin cones. The overall spectral range narrows during development through the loss of the LWS twin cones and a general short-wavelength shift in the spectral sensitivities of the other photoreceptor types. As a sub-adult the yellowtail kingfish also gains a short-wave-sensitive (SWS) single cone. This suggests that different lighting conditions will be optimal for larvae and sub-adults. No changes are observed in retinal ganglion cell (RGC) distribution between juveniles and sub-adults. A temporal concentric increase in RGC density and a weak horizontal band of medium RGC density (30% of the peak density) are present at both stages. This suggests that no changes in the feeding behaviour will occur throughout growth although the sub-adult possesses 1.6 times higher spatial resolution which would increase feeding accuracy at higher pellet densities. Research into the spectral properties of feed types combined with the data obtained here will allow for better contrast between prey and background by optimising lighting conditions. [ABSTRACT FROM AUTHOR]

The larval rearing performance of California yellowtail ( Seriola lalandi) and white seabass ( Atractoscion nobilis) was compared between larvae fed taurine-supplemented rotifers ( Brachionus plicatilis) and Artemia ( Artemia franciscana) and control groups fed live feeds with no taurine enhancement. Results from the S. lalandi trial demonstrated that when fed taurine-supplemented rotifers, survival was significantly higher than the control group (20.1% vs. 9.1%, P < 0.01) as was notochord length (5.43 mm vs. 5.13 mm, P < 0.005). No larval performance differences were detected between experimental and control treatments of A. nobilis. Biochemical analyses demonstrated that taurine concentrations were significantly elevated in both S. lalandi (23.7 vs. 2.7 mg g−1, P < 0.001) and A. nobilis (33.0 vs. 21.0 mg g−1, P < 0.005) when live feeds were supplemented with taurine. Results suggest that taurine is a limiting nutrient in the larviculture of S. lalandi but may not be for A. nobilis. [ABSTRACT FROM AUTHOR]