Yellowtail Kingfish Seriola Lalandi Research Articles

Potential Role of Gastrointestinal Microbiota in Growth Regulation of Yellowtail Kingfish Seriola lalandi in Different Stocking Densities

A 90-day study was performed under three different stocking densities, including high density (10,000 fishes/cage), medium density (8000 fishes/cage), and low density (6000 fishes/cage), in a deep-sea net cage for yellowtail kingfish (Seriola lalandi). The physiological characteristics and growth performance were tested, and structural characteristics of the gastrointestinal microbiota were systematically analyzed. The results show that fishes with high density had a lower weight gain rate and a specific growth rate, as well as higher serum cortisol content. The diversity, types and numbers of dominant microbiota with significant differences, and the numbers of shared genera among the different groups all changed. Core genera in the gastrointestinal tract were obtained according to the principles of dominance, commonality, and difference. The changes in the relative abundance of the core genera might be related to the growth and physiological characteristics of the host. The ratio of Firmicutes to Bacteroidetes in the stomach and pyloric caecum, which favors the accumulation of energy by the host from the diet, was higher in the medium-density group than in the other groups. This indicates that the higher density could cause physiological stress and affect growth performance. In order to reduce the resulting growth differences, gastrointestinal microbiota might assist the host in accumulating energy, participating in the energy distribution by adjusting its structure. Based on the growth, physiology, and production practices, the medium density was the appropriate density in this study. This study provides a reference for the improvement of deep-sea culture technology and the promotion of healthy growth through the gastrointestinal microecological regulation of yellowtail kingfish.

The effect of hydrogen peroxide concentration and water temperature on yellowtail kingfish Seriola lalandi in a repeated bathing treatment

Hydrogen peroxide is routinely used in commercial yellowtail kingfish culture to treat monogenean infections. As the culture of this species expands into warmer geographical areas, this study aimed to compare the effects of a repeated exposure to different hydrogen peroxide concentrations at two rearing temperatures, 18 and 26 °C. The repeat bath occurred 14 days after the initial bath in line with commercial treatment regimes. The three concentrations tested were 85, 170 and 340 mg L−1, with bathing conducted for 30 min. Mortality occurred following the second bath at 340 mg L−1 at 26 °C.The highest hydrogen peroxide dose caused epithelial lifting in gill filaments and significantly reduced the size and abundance of common mucus cells within the skin epithelium following the repeat bath in warm water. Despite the highest dose causing gill damage and mortality in warm water, there were no significant effects of hydrogen peroxide concentration on any of the conventional blood parameters, except in moribund fish. A novel measurement of plasma thiol oxidation, however, was found to be significantly elevated at the highest bathing concentration.Whilst yellowtail kingfish appeared to be tolerant of the high concentration of hydrogen peroxide tested in the current study at ambient water temperature, these fish were not infected with monogeneans, and any such burden is likely to increase the susceptibility of the fish to the effects of hydrogen peroxide.

A Chromosome-Level Genome Assembly of Yellowtail Kingfish (Seriola lalandi)

Yellowtail kingfish (Seriola lalandi) is a pelagic marine piscivore with a circumglobal distribution. It is particularly suitable for open ocean aquaculture owing to its large body size, fast swimming, rapid growth, and high economic value. A high-precision genome is of great significance for future genetic breeding research and large-scale aquaculture in the open ocean. PacBio, Illumina, and Hi-C data were combined to assemble chromosome-level reference genome with the size of 648.34 Mb (contig N50: 28.52 Mb). 175 contigs was anchored onto 24 chromosomes with lengths ranging from 12.28 to 34.59 Mb, and 99.79% of the whole genome sequence was covered. The BUSCOs of genome and gene were 94.20 and 95.70%, respectively. Gene families associated with adaptive behaviors, such as olfactory receptors and HSP70 gene families, expanded in the genome of S. lalandi. An analysis of selection pressure revealed 652 fast-evolving genes, among which mkxb, popdc2, dlx6, and ifitm5 may be related to rapid growth traits. The data generated in this study provide a valuable resource for understanding the genetic basis of S. lalandi traits.

Effects of shark tourism on the daily residency and movements of a non-focal pelagic teleost

Marine wildlife tourism is increasing in popularity, with operations targeting a wide range of taxa globally. While previous studies have mostly focused on assessing the effects of provisioning from tourism on focal species, non-focal species that unintentionally feed on supplemental food sources have largely been overlooked. This study improves our understanding of the effects of shark-cage-diving tourism on the movements and behaviours of a non-focal pelagic fish. We used acoustic tracking to determine the effects of shark-cage-diving tourism on the residency and space use of 17 yellowtail kingfish Seriola lalandi at the Neptune Islands, South Australia. We revealed that while cage-diving did not affect the overall or weekly residency and space use of kingfish, daily time spent at the islands and location of kingfish was influenced by the presence of operators. Acoustic attractant did not affect kingfish behaviours, but operators using food-based attractants increased the average time spent at the Neptune Islands by ~27% (from 230.6 ± 6.8 to 293.8 ± 5.5 min). Kingfish were also observed closer to operators using food-based attractants (217 ± 4.82 m from vessel) compared to an acoustic attractant (412 ± 29.5 m from vessel). Our findings identify changes in the daily behaviour of kingfish at the Neptune Islands as a result of food-based attractants from shark-cage-diving, which demonstrates that non-focal large pelagic species can be affected by shark-diving tourism. These effects may lead to long-term effects on the physiological condition and energetic responses of these individuals.

Estimation of apparent dietary nutrient digestibility in Yellowtail Kingfish Seriola lalandi by Near-Infrared Spectroscopy (NIRS)

The apparent digestibility (AD) of dietary nutrients is an essential criterion used to improve nutrition in aquaculture. We assessed whether Near-Infrared Spectroscopy (NIRS) can assist in streamlining the process by predicting directly diet AD or the composition of diets and/or faecal nutrients and digestibility marker (yttrium oxide) concentrations collected in Yellowtail Kingfish (YTK) in vivo experiments. NIRS models were developed using up to 121 diets and 185 faecal samples, and assessed as part of a case-study investigating the accuracy of AD results for 7 validation diets using a range of prediction scenarios (S2-S5) against the benchmark analytical method (S1; all samples analysed). A large range in AD of diets was noted and results from the case-study suggested diet nutrient digestibility was significantly affected by the type of alternative ingredients used (AD dry matter ranged 45–73%; AD protein 75–85%; AD lipid 66–92%; AD energy 65–87%; AD amino acids 78–86%; AD methionine 81–90%; AD lysine 77–91%; AD taurine 70–79%). NIRS models had cross-validation R2 values ranging 0.63–0.89 and residual predictive deviation (RPD) values ranging 0.7–3.3 for diet nutrients; R2 values ranging 0.63–0.94 and RPD values ranging 1.8–4.0 for faeces. Successful NIRS models were developed for diet dry matter, ash, crude protein, total lipid, gross energy, and total amino acids; successful faeces models also included methionine and lysine but not dry matter and ash; taurine and yttrium oxide models were deemed unsuccessful for both diets and faeces. Dry matter AD based on either yttrium concentration predictions (S4) or direct prediction of diet AD (S5) were relatively inaccurate (±20% error in dry matter AD). Nonetheless S4 was relatively successful to predict lipid AD and S5 the protein AD of the seven diets with an average error of ±6.7% AD and ± 5% AD respectively compared to the benchmark. When the digestibility marker concentrations were analysed, the S2 (diet composition predicted) and S3 (diet and faeces composition predicted) scenarios could predict nutrient AD with a degree of error of ±1–3%, with the exception of lipid AD (±6–8% error), and taurine which was modelled poorly in this study. NIRS prediction of diet and faecal composition, combined with digestibility marker analysis, appears to be a cost-effective and reasonably accurate rapid method to assess diet AD in fish, reducing sample volume requirements, welfare impact and opening a range of new opportunities for fish nutrition and the development of more efficient phenotypes.

The digestible histidine requirement of juvenile yellowtail kingfish Seriola lalandi

The Essential Amino Acid (EAA) requirements of many cultured species remains unknown and therefore aquafeeds used in new industries are often based on the requirements of similar species or those from a similar trophic level. One such example is the formulation of aquafeeds for Australian Yellowtail Kingfish Seriola lalandi (YTK), which are historically based on the published EAA requirements of Japanese Yellowtail Seriola quinqueradiata. The requirements of YTK for sulphur-amino acids as well as taurine have recently been quantified. These studies indicated that cultured YTK may have different EAA requirements to Japanese Yellowtail which has raised doubts about the adequacy of other EAAs in commercial feeds for YTK. Of these, the adequacy of histidine was considered particularly important due to concerns about cataract formation and poor growth. Therefore, the digestible histidine requirement of YTK was quantified using a dose-response design that employed a fishmeal-free basal diet containing 0.61% digestible histidine. Supplemental crystalline L-histidine was added to the basal formulation in 0.5% increments resulting in four additional diets with a digestible histidine content of 0.96, 1.32, 1.61 and 2.0%, respectively. Each dietary treatment was assigned to triplicate saltwater tanks containing 10 × 80 g YTK which were fed to apparent satiation for seven weeks at a temperature of 20 °C. Despite the incremental addition of histidine there were no differences in growth rate, feed intake, condition factor and feed conversion ratio of YTK in response to dietary treatment. In contrast, evaluation of whole carcass revealed histidine deposition rate increased in response to digestible histidine content before declining at the highest dietary level (i.e. >1.61%), suggesting YTK had reached their maximum rate of histidine deposition under our experimental conditions. A factorial analysis of the retention data from the current study was compared to and combined with previous factorial models on histidine utilisation by YTK. The combined model indicated that while the maintenance demand for histidine varied with experimental conditions, the unit cost of histidine deposition in YTK was constant at 1.99. A conservative estimate of the variable digestible histidine requirement for maintenance at temperatures between 15 and 24 °C was found to be 64.2 mg kgBW-0.7d−1. Feed ration models generated from the factorial data sets indicate YTK should be fed diets that contain between 1.6 and 2.0% digestible histidine in order to meet their daily histidine requirement. These amounts are slightly higher than generally recommended for Japanese Yellowtail.

Dispersal of yellowtail kingfish (Seriola lalandi) from a coastal embayment following a recreational fisheries enhancement stocking program: attempts to integrate aquaculture and habitat-based initiatives

Fisheries enhancement initiatives including marine stocking and artificial reef deployments are becoming increasingly common in many parts of the world. Combining the two by releasing hatchery reared fish onto artificial reefs is used in sea-ranching operations but is an approach rarely adopted for recreational fisheries. Yellowtail kingfish (Seriola lalandi) form a valuable recreational fishery in Australia and in 2018 a pilot stocking program was initiated to enhance this fishery. Fish were released onto estuarine artificial reefs in Botany Bay to evaluate if estuarine artificial reefs are suitable release habitat for juvenile yellowtail kingfish and to monitor their dispersal patterns using acoustic telemetry and a tag-recapture program. Both approaches showed similar patterns, indicating juvenile yellowtail kingfish rapidly dispersed from the release location and can travel at least 60 km during their first weeks in the wild. Twenty percent of the acoustically tagged fish entered nearby estuaries to the north and south and dart tagged fish were also recaptured in these estuaries, indicating that the estuaries provide habitat for juveniles. There was little interaction between stocked fish and two large coastal artificial reefs positioned near Botany Bay. Stocked yellowtail kingfish will likely disperse rapidly from release locations which is consistent with their pelagic life history. While this may present challenges to fisheries managers, increasing release numbers to maintain stocking densities over a broader area may provide a solution. Future releases of fish on coastal natural and artificial reefs are an important next step in refining stocking practices for this species and will help further identify key juvenile habitats.

Threshold models using Gibbs sampling and machine learning genomic predictions for skin fluke disease recorded under field environment in yellowtail kingfish Seriola lalandi

Ectoparasitic infestations, such as skin fluke due to Benedenia seriolae, represent substantial fish health and welfare challenges that have caused significant industry implications. Unfortunately, existing methods used to control this disease such as bath-administered compounds or therapeutic (dietary) trials are labour intensive, costly and only temporarily effective. Genetic (genomic) methods may provide sustainable long-term solutions to improve host resistance to parasitic diseases in marine finfish species. This study thus explored possibilities for applying genomic selection to improve resistance to B. seriolae and deformity in yellowtail kingfish Seriola lalandi. Specifically, we used a total of 752 animals with individual records and 14,448 single nucleotide polymorphisms (SNPs) developed de novo from Diversity Arrays technology (DArT, a combination of genome complexity reduction methods and next generation sequencing platforms) to assess accuracy of genomic predictions for the incidence of skin fluke and deformity recorded under field (farm) condition. Our multi-locus linear and threshold mixed model analyses showed that heritabilities for the incidence of skin fluke and deformity were small (mean range h2 = 0.02–0.03). Genetic correlations of skin fluke with body weight and deformity were not significant. Our threshold Gibbs sampling and machine learning models revealed that the accuracies of genomic prediction were low for both traits (mean range from 0.151–0.432). Imputation of missing genotypes improved the prediction accuracies for skin fluke and deformity by 0.5–13.2%. Multi-trait analyses outperformed single trait models, only for deformity. Our findings suggest that genomic selection for reduced skin fluke and deformity, albeit possible in yellowtail kingfish, genetic progress made for these traits may be slow because of the low prediction accuracies across models used in this study. To enable the application of genomic selection for skin fluke or disease resistant traits recorded under field condition, it is necessary to sequence a larger number of individuals and families as well as to develop large-scale routine data recording of new phenotypes (e.g., parasite counts) to increase the prediction accuracies for these traits in the breeding program of yellowtail kingfish S. lalandi.

A Comparison of Short-Term and Continuous Exposures in Toxicity Tests of Produced Waters, Condensate, and Crude Oil to Marine Invertebrates and Fish.

Petroleum hydrocarbons can be discharged into the marine environment during offshore oil and gas production or as a result of oil spills, with potential impacts on marine organisms. Ecotoxicological assay durations (typically 24–96 h) used to characterize risks to exposed organisms may not always reflect realistic environmental exposure durations in a high‐energy offshore environment where hydrocarbons are mixed and diluted rapidly in the water column. To investigate this, we adapted 3 sensitive toxicity tests to incorporate a short‐term pulse exposure to 3 petroleum‐based products: a produced water, the water‐accommodated fraction (WAF) of a condensate, and a crude oil WAF. We measured 48‐h mobility of the copepod Acartia sinjiensis, 72‐h larval development of the sea urchin Heliocidaris tuberculata, and 48‐h embryo survival and deformities of yellowtail kingfish Seriola lalandi, after exposure to a dilution series of each of the 3 products for 2, 4 to 12, and 24 h and for the standard duration of each toxicity test (continuous exposure). Effects on copepod survival and sea urchin larval development were significantly reduced in short‐term exposures to produced water and WAFs compared to continuous exposures. Fish embryos, however, showed an increased frequency of deformities at elevated concentrations regardless of exposure duration, although there was a trend toward increased severity of deformities with continuous exposure. The results demonstrate how exposure duration alters toxic response and how incorporating relevant exposure duration to contaminants into toxicity testing may aid interpretation of more realistic effects (and hence an additional line of evidence in risk assessment) in the receiving environment. Environ Toxicol Chem 2021;40:2587–2600. © 2021 CSIRO. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

First Report of Blood Fluke Pathogens with Potential Risk for Emerging Yellowtail Kingfish (Seriola lalandi) Aquaculture on the Chilean Coast, with Descriptions of Two New Species of Paradeontacylix (Aporocotylidae).

Blood flukes are digeneans that infect wild and farmed fish that can cause a severe and potentially lethal disease in farmed fish. These parasites are undetectable in the larval stage based on macroscopic observations in the definitive host with the infection becoming evident when eggs accumulate in the branchial vessels. There are nine known species of the genus Paradeontacylix and seven exclusively parasitize Seriola spp. from several geographical areas. Seriola lalandi aquaculture farms are emerging at various localities in northern Chile. Here, we report, for the first time, two blood fluke species parasitizing S. lalandi in the Southeastern Pacific (Chile). In the laboratory, the gills and heart of fish were removed. The retained blood flukes were separated according to the infection site, fixed in 70% or 95% ethanol for taxonomic and molecular analysis, respectively. Morphometrical differences among the fluke species were evaluated with a principal component analysis (PCA) using proportional body measurements. Phylogenetic trees were constructed based on 28S rDNA, cox1 mDNA using Bayesian inference (BI), and maximum likelihood (ML). Based on morphology, morphometry, and molecular analyses, two new species are proposed: P. humboldti n. sp. from the gills and P. olivai n. sp. from the heart of S. lalandi. Both were clearly distinguished from other species of Paradeontacylix by a combination of morphologic features (posterior tegumental spines, testes arrangement, body size). The genetic distance (based on cox1) among species was >10%. P. humboldti n. sp. and P. olivai n. sp. are sister species (with a common ancestor) independent of P. godfreyi from S. lalandi in Australia. The newly identified parasites may pose a risk to farmed S. lalandi as aporocotylids have been the cause of diseases in farmed fish from other geographical areas. In addition, some cages of S. lalandi are currently maintained in an open circulating system, which could favor the transmission of these parasites (if involved hosts are present in the environment).

The interaction of feeding regime and dietary specification on growth and nutrient utilisation in Yellowtail Kingfish Seriola lalandi

Feeding regimes on fish farms are often disrupted for logistical reasons or adverse environmental conditions. Issues such as these are commonplace with respect to the sea pen culture of Yellowtail Kingfish Seriola lalandi (YTK) in Australia. These disruptions represent periods of feed restriction which lead to reduced productivity. However, production losses may be ameliorated using different feeding strategies or the use of nutrient dense aquafeeds. To examine the potential of these options we conducted an eight-week experiment with sub-adult YTK (stocking weight ~ 0.80 kg) investigating three feeding regimes crossed with two dietary specifications. The feeding regimes were selected following industry consultation; feeding once daily 7 days per week (control), once daily Monday to Friday (economic) or once daily on randomly selected days of the week (random). Regardless of regime all feed was offered to apparent satiation. A standard specification (Std-Spec; 386 g DP kg−1, 15.1 MJ DE kg−1) and high specification diet (High-Spec; 460 g DP kg−1 and 19.2 MJ DE kg−1) were formulated using a similar suite of ingredients. Each of the 6 treatment combinations was fed to three replicate tanks of fish and results were examined using two-way ANOVA. There was a general absence of interaction between the main effects for most production indices. Specific growth rate (SGR) and relative feed intake (RFI) were significantly better in YTK fed 7 days per week than in YTK fed under more restricted regimes, but feeding regime did not affect FCR. The SGR, FCR and condition factor of YTK were significantly better when fed the High-Spec diet than in YTK fed the Std-Spec diet. The RFI of fish fed under restricted regimes was significantly lower than YTK fed 7 days per week, irrespective of diet specification, indicating YTK were not capable of hyperphagia. However, the RFI of YTK fed the Std-Spec diet was significantly higher than YTK fed the High-Spec diet, confirming nutrient or energy density was likely controlling feed intake. Examination of data on digestible protein, fat and energy intake indicated YTK were eating primarily to satisfy their protein requirement and sub-optimal energy intake was indirectly limiting growth. Our results demonstrate YTK have a limited capacity to increase their feed intake as a means of overcoming moderate feed restriction in order to meet nutrient and energy demands. We recommend feeding YTK of this size a high specification diet to apparent satiation once per day 7 days a week in order to maximize their growth, feed efficiency and physical condition.

Embryo Buoyancy and Cell Death Gene Expression During Embryogenesis of Yellow-Tail Kingfish Seriola lalandi.

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.

Shallow seamounts represent speciation islands for circumglobal yellowtail Seriola lalandi

Phenotypic plasticity in life-history traits in response to heterogeneous environments has been observed in a number of fishes. Conversely, genetic structure has recently been detected in even the most wide ranging pelagic teleost fish and shark species with massive dispersal potential, putting into question previous expectations of panmixia. Shallow oceanic seamounts are known aggregation sites for pelagic species, but their role in genetic structuring of widely distributed species remains poorly understood. The yellowtail kingfish (Seriola lalandi), a commercially valuable, circumglobal, epipelagic fish species occurs in two genetically distinct Southern Hemisphere populations (South Pacific and southern Africa) with low levels of gene-flow between the regions. Two shallow oceanic seamounts exist in the ocean basins around southern Africa; Vema and Walters Shoal in the Atlantic and Indian oceans, respectively. We analysed rare samples from these remote locations and from the South African continental shelf to assess genetic structure and population connectivity in S. lalandi and investigated life-history traits by comparing diet, age, growth and maturation among the three sites. The results suggest that yellowtail from South Africa and the two seamounts are genetically and phenotypically distinct. Rather than mere feeding oases, we postulate that these seamounts represent islands of breeding populations with site-specific adaptations.

Alternative Feed Raw Materials Modulate Intestinal Microbiota and Its Relationship with Digestibility in Yellowtail Kingfish Seriola lalandi

Gut microbiota plays a crucial role in nutrient digestibility and fish health. This study aimed to investigate the effects of alternative feed raw materials on the bacterial communities in the distal intestine and its relationship with nutrient digestibility in yellowtail kingfish (YTK), Seriola lalandi. Two 4-week digestibility trials were conducted to evaluate fish meal (FM), two sources of poultry by-product meal (PBM-1 & PBM-2), blood meal (BLM), faba bean meal (FBM), corn gluten meal (CGM), soy protein concentrate (SPC) and wheat flour (WH). The nutrient digestibility value was determined using the stripping fecal collection method. Bacterial communities were characterized by high-throughput sequencing based on V3-V4 region of the 16S rRNA gene. The most abundant phylum identified in the present study was Proteobacteria. A significant change in the distal intestine was observed in fish fed diets containing CGM and BLM, characterized by a reduction of species richness and diversity. Additionally, significant correlation between nutrient digestibility and intestinal microbiota was observed. Allivibrio, Vibrio, Curvibacter, Ruminococcaceae, and Clostridium were positively correlated, whereas Ralstonia genus was negatively correlated with nutrient digestibility. This study demonstrated that intestinal microbiota could be a useful tool for evaluating the digestibility of feed raw materials; however, further culture-based study is needed to confirm this observation.

Development of SNP markers for yellowtail kingfish (Seriola lalandi) by 2b-RAD simplified genome sequencing

Yellowtail kingfish, Seriola lalandi, is a globally distributing pelagic marine fish species. In recent years, the wild population has suffered drastic decline due to overfishing and environmental deterioration. Thus, the sustainable utilization and conservation management for this species should be implemented urgently. In the present study, we developed SNP markers using 2b-RAD sequencing method from 33 individuals of yellowtail kingfish. Wherein, 100 high-quality SNP markers were obtained based on high throughput sequencing and stringent SNP filter process. The minor allele frequency of these SNPs ranged from 0.0126 to 0.4957. The observed heterozygosity and expected heterozygosity ranged from 0 to 0.9914 and 0.0249 to 0.5000, respectively. The inbreeding coefficient varied from − 0.9828 to 0.7882. Among these SNPs, 10 loci deviated significantly from Hardy–Weinberg equilibrium after Bonferroni correction. These novel SNP markers will serve as valuable tools for population genetics evaluation and natural resources conservation of yellowtail kingfish.

Effect of temperature and dietary lipid proportion on gut microbiota in yellowtail kingfish Seriola lalandi juveniles

Gut microbiota plays a determining role in the health status of the host. In general, a beneficial bacterial community, associated with a greater metabolic capacity and wellbeing, shows high values of species richness and relative abundance. Because environmental temperature is a regulating factor in fish physiological and metabolic processes, it is very important to understand the effect of environmental temperature on diversity and richness of gut microbiota in poikilothermic organisms. This study analysed the reciprocal diet-temperature correlations in the faecal microbiota diversity in Seriola lalandi. Juveniles were acclimated at 20 °C and 26 °C for 30 days; in addition, the fish were fed three diets with three levels of lipid inclusion (7%, 14% and 21%). Faecal microbiota in S. lalandi was characterized using the high-throughput sequencing approach based on the V3 region of the 16S rRNA gene. The most abundant phyla identified in this study were Proteobacteria, Actinobacteria, Bacteroidetes and Firmicutes. A significant change was observed in faecal microbiota in relation to acclimation temperature. The results indicated that species richness was modified in relation to the environmental temperatures; the Operational Taxonomic Units (OTUs) identified in fish acclimated at 26 °C belonged to the families Pseudomonadacea, Alcaligenaceae and Microbacteriaceae whereas those identified at 20 °C were Micavibrio, Comamonadaceae and Saprospiraceae. Furthermore, significant differences were observed between the OTUs identified in the dietary treatments, in which Actinobacteria (7% lipid), Gammaproteobacteria (14% lipid), Betaproteobacteria (21% lipid), and Flavobacteria (skretting diet) were the phyla preferentially identified from each treatment. The results obtained in this study demonstrated the importance of environmental temperature to maintain a balance in intestinal microbiota, as well as the effects of diet composition on proliferation of different microbial groups with respect to thermal induction.

Ocean warming has a greater effect than acidification on the early life history development and swimming performance of a large circumglobal pelagic fish.

Ocean warming and acidification are serious threats to marine life; however, their individual and combined effects on large pelagic and predatory fishes are poorly understood. We determined the effects of projected future temperature and carbon dioxide (CO2 ) levels on survival, growth, morphological development and swimming performance on the early life stages of a large circumglobal pelagic fish, the yellowtail kingfish Seriola lalandi. Eggs, larvae and juveniles were reared in cross-factored treatments of temperature (21 and 25°C) and pCO2 (500 and 985μatm) from fertilisation to 25days post hatching (dph). Temperature had the greatest effect on survival, growth and development. Survivorship was lower, but growth and morphological development were faster at 25°C, with surviving fish larger and more developed at 1, 11 and 21dph. Elevated pCO2 affected size at 1dph, but not at 11 or 21dph, and did not affect survival or morphological development. Elevated temperature and pCO2 had opposing effects on swimming performance at 21dph. Critical swimming speed (Ucrit ) was increased by elevated temperature but reduced by elevated pCO2 . Additionally, elevated temperature increased the proportion of individuals that responded to a startle stimulus, reduced latency to respond and increased maximum escape speed, potentially due to the more advanced developmental stage of juveniles at 25°C. By contrast, elevated pCO2 reduced the distance moved and average speed in response to a startle stimulus. Our results show that higher temperature is likely to be the primary driver of global change impacts on kingfish early life history; however, elevated pCO2 could affect critical aspects of swimming performance in this pelagic species. Our findings will help parameterise and structure fisheries population dynamics models and improve projections of impacts to large pelagic fishes under climate change scenarios to better inform adaptation and mitigation responses.

First High-Density Linkage Map and Single Nucleotide Polymorphisms Significantly Associated With Traits of Economic Importance in Yellowtail Kingfish Seriola lalandi.

The genetic resources available for the commercially important fish species Yellowtail kingfish (YTK) (Seriola lalandi) are relative sparse. To overcome this, we aimed (1) to develop a linkage map for this species, and (2) to identify markers/variants associated with economically important traits in kingfish (with an emphasis on body weight). Genetic and genomic analyses were conducted using 13,898 single nucleotide polymorphisms (SNPs) generated from a new high-throughput genotyping by sequencing platform, Diversity Arrays Technology (DArTseqTM) in a pedigreed population comprising 752 animals. The linkage analysis enabled to map about 4,000 markers to 24 linkage groups (LGs), with an average density of 3.4 SNPs per cM. The linkage map was integrated into a genome-wide association study (GWAS) and identified six variants/SNPs associated with body weight (P < 5e-8) when a multi-locus mixed model was used. Two out of the six significant markers were mapped to LGs 17 and 23, and collectively they explained 5.8% of the total genetic variance. It is concluded that the newly developed linkage map and the significantly associated markers with body weight provide fundamental information to characterize genetic architecture of growth-related traits in this population of YTK S. lalandi.

Inducing Subacute Enteritis in Yellowtail Kingfish Seriola lalandi: the Effect of Dietary Inclusion of Soybean Meal and Grape Seed Extract on Hindgut Morphology and Inflammation

AbstractIn this 42‐d trial, grape seed extract (GSE) was evaluated as a potential treatment for subacute enteritis in Yellowtail Kingfish Seriola lalandi induced by soybean meal (SBM) at winter water temperatures (12–15°C). Four diets were investigated: a fish meal control diet (46% fish meal, 0% SBM), a SBM diet (30% SBM with 0 mg/kg GSE), and two 30% SBM diets containing either 20 mg/kg or 40 mg/kg GSE. Yellowtail Kingfish growth performance was significantly reduced when fed 30% SBM. Fish fed 30% SBM exhibited a significant enlargement of the lamina propria, a sign of subacute enteritis, and a significant decrease in myeloperoxidase (MPO) activity, compared with those fish fed the control diet. Dietary inclusions of GSE did not affect growth performance, intestinal morphology, or MPO activity. We recommend that SBM be excluded from Yellowtail Kingfish diets. We also recommend future studies investigate higher dietary GSE inclusions, other potential dietary additives, or more refined soy products, to alleviate subacute enteritis in Yellowtail Kingfish.

Applying acoustic telemetry to understand contaminant exposure and bioaccumulation patterns in mobile fishes

Contamination in urbanised estuaries presents a risk to human health, and to the viability of populations of exploited species. Assessing animal movements in relation to contaminated areas may help to explain patterns in bioaccumulation, and assist in the effective management of health risks associated with consumption of exploited species. Using polychlorinated dibenzodioxin and polychlorinated dibenzofuran (PCDD/Fs) contamination in Sydney Harbour estuary as a case study, we present a study that links movement patterns resolved using acoustic telemetry to the accumulation of contaminants in mobile fish on a multi-species basis. Fifty-four individuals across six exploited species (Sea Mullet Mugil cephalus; Luderick Girella tricuspidata; Yellowfin Bream Acanthopagrus australis; Silver Trevally Pseudocaranx georgianus; Mulloway Argyrosomus japonicus; Yellowtail Kingfish Seriola lalandi) were tagged with acoustic transmitters, and their movements tracked for up to 3years. There was substantial inter-specific variation in fish distribution along the estuary. The proportion of distribution that overlapped with contaminated areas explained 84–98% of the inter-specific variation in lipid-standardised biota PCDD/F concentration. There was some seasonal variation in distribution along the estuary, but movement patterns indicated that Sea Mullet, Yellowfin Bream, Silver Trevally, and Mulloway were likely to be exposed to contaminated areas during the period of gonadal maturation. Acoustic telemetry allows examination of spatial and temporal patterns in exposure to contamination. When used alongside biota sampling and testing, this offers a powerful approach to assess exposure, bioaccumulation, and potential risks faced by different species, as well as human health risks associated with their consumption.