Pseudocaranx Dentex Research Articles

Mortality events associated with microsporidian, Spraguea sp., in White Trevally culture in Japan.

In 2021, White Trevally or Striped Jack cultured in the western part of Japan exhibited mild, but chronic mortalities from late September through early October. The cumulative mortality rate was approximately 0.02% per a net pen containing approximately 50,000 fish. Although the cumulative mortality rate was not high, most of the fish in net pens showed characteristic gross signs and an abnormal swimming behaviour. The body of diseased fish became pale and the yellow lines on the lateral sides of fish body became darken. In addition, silver lines along the dorsal fin became apparent. Loss of schooling behaviour was noted during the mortality event. In addition, affected fish became lethargic and failed to swim against current, or frequently stopped swimming and sank to the bottom of net pens after feeding. The goal of this study was to identify the cause of the mortality event. To achieve the goal, we used histopathology and metatranscriptome analysis. Histopathological examination revealed that xenoma of microsporidian were frequently observed in the nerve axon in the brain and spinal cord. Spores observed in the sections were stained with a fluorescent dye, Uvitex 2B, indicating those spores are microsporidian. The data from metatranscriptome analysis indicated that the microsporidian is Spraguea sp. The microsporidian was frequently detected from diseased fish with similar symptoms collected in the same region, suggesting that the microsporidian was highly associated with abnormal swimming behaviour of fish.

Integrative Metabolomics, Enzymatic Activity, and Gene Expression Analysis Provide Insights into the Metabolic Profile Differences between the Slow-Twitch Muscle and Fast-Twitch Muscle of Pseudocaranx dentex.

The skeletal muscles of teleost fish encompass heterogeneous muscle types, termed slow-twitch muscle (SM) and fast-twitch muscle (FM), characterized by distinct morphological, anatomical, histological, biochemical, and physiological attributes, driving different swimming behaviors. Despite the central role of metabolism in regulating skeletal muscle types and functions, comprehensive metabolomics investigations focusing on the metabolic differences between these muscle types are lacking. To reveal the differences in metabolic characteristics between the SM and FM of teleost, we conducted an untargeted metabolomics analysis using Pseudocaranx dentex as a representative model and identified 411 differential metabolites (DFMs), of which 345 exhibited higher contents in SM and 66 in FM. KEGG enrichment analysis showed that these DFMs were enriched in the metabolic processes of lipids, amino acids, carbohydrates, purines, and vitamins, suggesting that there were significant differences between the SM and FM in multiple metabolic pathways, especially in the metabolism of energy substances. Furthermore, an integrative analysis of metabolite contents, enzymatic activity assays, and gene expression levels involved in ATP-PCr phosphate, anaerobic glycolysis, and aerobic oxidative energy systems was performed to explore the potential regulatory mechanisms of energy metabolism differences. The results unveiled a set of differential metabolites, enzymes, and genes between the SM and FM, providing compelling molecular evidence of the FM achieving a higher anaerobic energy supply capacity through the ATP-PCr phosphate and glycolysis energy systems, while the SM obtains greater energy supply capacity via aerobic oxidation. These findings significantly advance our understanding of the metabolic profiles and related regulatory mechanisms of skeletal muscles, thereby expanding the knowledge of metabolic physiology and ecological adaptation in teleost fish.

Comparative genome analyses of three serotypes of Lactococcus bacteria isolated from diseased cultured striped jack (Pseudocaranx dentex).

Lactococcosis, caused by members of the genus Lactococcus, represents a devastating disease inducing mass mortalities and economic losses in many fish species worldwide. The present work aimed to compare the whole genome sequences of three different serotypes of Lactococcus garvieae isolated from diseased cultured striped jack (Pseudocaranx dentex) in Ehime prefecture, Japan. The three serotypes showed different virulence in the challenge test using Japanese amberjack (Seriola quinqueradiata). The genome sequencing revealed that two of the strains (serotype I and serotype III) were identified as L. garvieae, while the third strain (serotype II) was identified as L. formosensis. The chromosome sizes of the three serotypes ranged from 1.9 to 2.0 Mb; the GC content ranges were 38.2 to 38.9%; and the numbers of predicted protein-coding sequences (CDSs) were from 1922 to 1959. Only the serotype II harbours two plasmids, sizes of around 14 kb and 9 kb. The detected virulence factors varied among the different serotypes with some shared factors like adherence, anti-phagocytosis, secretion system, toxin (haemolysin), serum resistance, antimicrobial resistance and others. The genomes also contained factors responsible for resistance to toxic compounds. The genome of the serotype III tended to encode more prophage regions than the other serotypes.

Tissue Distribution of mtDNA Copy Number And Expression Pattern of An mtDNA-Related Gene in Three Teleost Fish Species.

Teleosts are the most speciose vertebrates and have diverse swimming performance. Based on swimming duration and speed, teleosts are broadly divided into sustained, prolonged, and burst swimming fish. Teleosts with different swimming performance have different energy requirements. In addition, energy requirement also varies among different tissues. As mitochondrial DNA (mtDNA) copy number is correlated with ATP production, we speculated that mtDNA copy number varies among fish with different swimming performance, as well as among different tissues. In other species, mtDNA copy number is regulated by tfam (mitochondrial transcription factor A) through mtDNA compaction and mito-genome replication initiation. In order to clarify the tissue distribution of mtDNA copy number and expression pattern of tfam in teleosts with disparate swimming performance, we selected representative fish with sustained swimming (Pseudocaranx dentex), prolonged swimming (Takifugu rubripes), and burst swimming (Paralichthys olivaceus). We measured mtDNA copy number and tfam gene expression in 10 tissues of these three fish. The results showed the mtDNA content pattern of various tissues was broadly consistent among three fish, and high-energy demanding tissues contain higher mtDNA copy number. Slow-twitch muscles with higher oxidative metabolism possess a greater content of mtDNA than fast-twitch muscles. In addition, relatively higher mtDNA content in fast-twitch muscle of P. olivaceus compared to the other two fish could be an adaptation to their frequent burst swimming demands. And the higher mtDNA copy number in heart of P. dentex could meet their oxygen transport demands of long-distance swimming. However, tfam expression was not significantly correlated with mtDNA copy number in these teleosts, suggesting tfam may be not the only factor regulating mtDNA content among various tissues. This study can lay a foundation for studying the role of mtDNA in the adaptive evolution of various swimming ability in teleost fish.

Pengaruh Umur Bulan Terhadap Hasil Tangkapan Sero

Bambanipa Village is one of the villages in Palasa District, Parigi Moutong Regency, Central Sulawesi Province. Based on direct observations and interviews with local fishermen, the number of fishermen in the village of Bambanipa is 37 people. The research method used is descriptive and participatory. descriptive methods used are surveys and interviews. for data analysis using a randomized block design (RBD) model, with a mathematical formulation. During the research in the village of Bambanipa, the total number of catches was 318 individuals. With details based on the type of fish caught, namely Baronang (Siganus lineatus) 19 individuals, Grouper (Cromileptes altivelis) 1 individuals, Botana (Ctenochaetus striatus) 1 individual, Katamba (Lethrinus lentjan) 3 individuals, Dayah beard (Upeneus moluccensis) 3 individuals, Rengginan (Myripristis hexagonatus) 69 individuals, Tiger snapper (Plectorhinchus chaetodontoides) 2 individuals, Kuwe (Pseudocaranx dentex) 5 individuals, Black point snapper (Lutjanus fulviflamma) 3 individuals, Selar (Selar boops) 10 individuals, Sembilang (Euristhmus microceps) 200 individuals , 2 individuals of Cuttlefish (Sepia sp.).

Four carangid fish species as new host records for Kudoa trachuri Matsukane, Sato, Tanaka, Kamata et Sugita-Konishi, 2011 (Myxozoa: Multivalvulida), and description of a new species, Kudoa longichorda sp. n., forming pseudocysts in the muscle of Decapterus tabl Berry.

Multivalvulid myxosporeans of the genera Kudoa Meglitsch, 1947 and Unicapsula Davis, 1924 (Cnidaria: Myxozoa) are often the cause of unsightly cyst formation or postmortem myoliquefaction in the trunk muscle of commercial marine fish, which reduces the market value of infected individuals. Twenty species (18 Kudoa spp. and two Unicapsula spp.) have been recorded from carangid fish, although the majority of them, excluding polyxenous species, such as K. amamiensis Egusa et Nakajima, 1980, K. iwatai Egusa et Shiomitsu, 1983, K. nova Naidenova, 1975, K. quadratum (Thélohan, 1895) and K. yasunagai (Hsieh et Chen, 1984), are limited to a single or a few fish species. We report the occurrence of macroscopic cysts of Kudoa trachuri Matsukane, Sato, Tanaka, Kamata et Sugita-Konishi, 2011 in the trunk muscle of four new host fish species, i.e., Pseudocaranx dentex (Bloch et Schneider), Decapterus akaadsi Abe, D. muroadsi (Temminck et Schlegel) and Decapterus tabl Berry, fished from the Philippine Sea (Northwest Pacific Ocean), off southwestern of Japan. Myxospore morphology and genetic characteristics of the ribosomal RNA gene (rDNA) of these isolates were consistent with previous records of K. trachuri from Trachurus japonicus (Temminck et Schlegel) from around Japan. In addition, a new species of Kudoa that forms long filamentous pseudocysts in trunk myofibres was found in four of the six D. tabl collected in this study. We describe Kudoa longichorda sp. n. for this new isolate, based on its morphology of subquadrate myxospores with four shell valves and polar capsules and with small dimensions (length 4.3-5.5 µm, width 6.0-6.8 µm, thickness 4.8-6.3 µm, polar capsule length 2.3-3.1 µm, polar capsule width 1.1-1.7 µm), as well as 18S and 28S rDNA sequences distinct from those of known species.

The Landscape of DNA Methylation Generates Insight Into Epigenetic Regulation of Differences Between Slow-Twitch and Fast-Twitch Muscles in Pseudocaranx dentex

Skeletal muscles of teleost are mainly composed of slow-twitch muscles (SM) and fast-twitch muscles (FM) differed in contractile properties, metabolic capacities, and regeneration rate. The transcriptional regulatory mechanisms that control different muscle types have been elucidated in teleost according to transcriptome between SM and FM. However, the differences between SM and FM were affected not only by genotype but also by complicated epigenetic effects, including DNA methylation, which usually regulates genes in transcription level. To determine the essential role of DNA methylation in the regulation of different muscle types, we analyzed whole-genome methylation profiles of pelagic migratory fish Pseudocaranx dentex with abundant and well-separated SM and integrated DNA methylation profiles with the previously obtained transcriptome data. A total of 4,217 differentially methylated genes (DMGs) were identified, of which 3,582 were located in the gene body and 635 in the promoter. These DMGs mainly participated in muscle metabolite and cell junction. Enriched cell junction pathway reflected different capillary distribution between SM and FM. Through comprehensive analysis of methylome and transcriptome, 84 differentially expressed genes (DEGs) showed significant methylation variation in promoters between SM and FM, indicating that their expression was regulated by DNA methylation. Hypomethylated and highly expressed oxygen storage protein Myoglobin (myg) in SM indicated demethylation of myg promoter could upregulate its expression, thus increasing O2 supplying and meeting oxygen demands of SM. Hypermethylated and lowly expressed tnn (Troponin) and rlc (myosin regulatory light chain) in SM may be associated with low mobility of myosin cross bridges, which lead to slower and less frequent muscle contraction in SM than in FM. In addition, hypomethylated and highly expressed lbx1 (Ladybird homeobox protein homolog 1) and epo (erythropoietin) may be related to increased satellite cell numbers, and Semaphorin/Plexin genes may be related to higher rate of neuromuscular connection reconstruction, which further promote high muscle regeneration efficiency in SM. Our study elucidated the potential DNA methylation mechanisms that regulate physiological characteristics differences between SM and FM, which could facilitate our understanding of skeletal muscle adaptation in pelagic migratory fishes and further enrich the theoretical basis for the study of physiological characteristics and adaptive evolution in teleost fishes.

Label-Free Quantitative Proteomic Analysis Provides Insight Into the Differences Between Slow-Twitch Muscle and Fast-Twitch Muscle of Pseudocaranx dentex

Fish skeletal muscles are mainly composed of two distinct types, fast-twitch and slow-twitch muscles, and they play important roles in maintaining movement and energy metabolism. The fast-twitch muscle contracts quickly and is mainly responsible for burst swimming, while the slow-twitch muscle possesses fatigue resistance and supports endurance swimming. To assess the differences in molecular composition and investigate the potential regulatory mechanisms, we performed an integrative study at both proteomic and transcriptomic levels of the fast-twitch and slow-twitch muscles in Pseudocaranx dentex, a pelagic migratory fish with distinctly differentiated skeletal muscle. Label-free proteomics revealed 471 differentially expressed proteins (DEPs), 422 upregulated and 49 downregulated in slow-twitch muscle when compared to fast-twitch muscle. These DEPs were mainly involved in myofibrillary structure and energy metabolism. Integrative analysis of proteomic and transcriptomic data showed that 757 RNA-protein pairs were positively correlated, and 191 RNA-protein pairs were negatively correlated in abundance. Meanwhile, 311 RNA-protein pairs were consistent in fold changes, and 594 RNA-protein pairs exhibited striking differences, which provided an insight into the complex regulation at both transcriptional and post-transcriptional levels that contribute to shaping the different muscle types. The specific expression of multiple myofibrillar proteins, such as myosin, actin, troponin, and tropomyosin, suggested that the distinction in contraction characterizations between slow-twitch and fast-twitch muscles is related to different protein isoforms. Muscle-type specific expression of gene-encoding key enzymes in fatty acid metabolism, glycolysis, tricarboxylic acid (TCA) cycle, and oxidative phosphorylation pathways, such as carnitine palmitoyltransferase (CPT2), phosphofructokinase (Pfkm), pyruvate kinase (Pkmb), citrate synthase (CS), isocitrate dehydrogenase (IDH), and 2-oxoglutarate dehydrogenase complex (Ogdh), may be the molecular basis responsible for the differences in energy metabolism. Overall, this global view of protein and RNA expression levels in P. dentex fast-twitch and slow-twitch muscles reveals the essential roles of transcriptional and post-transcriptional regulation in maintaining muscle structure and function. The identified potential genes that may cause the differences in physiological characteristics will greatly improve our understanding on the molecular basis of skeletal muscle contraction, metabolism, and regulation in teleost.

Expression profiles and transcript properties of fast-twitch and slow-twitch muscles in a deep-sea highly migratory fish, Pseudocaranx dentex.

Fast-twitch and slow-twitch muscles are the two principal skeletal muscle types in teleost with obvious differences in metabolic and contractile phenotypes. The molecular mechanisms that control and maintain the different muscle types remain unclear yet. Pseudocaranx dentex is a highly mobile active pelagic fish with distinctly differentiated fast-twitch and slow-twitch muscles. Meanwhile, P. dentex has become a potential target species for deep-sea aquaculture because of its considerable economic value. To elucidate the molecular characteristics in the two muscle types of P. dentex, we generated 122 million and 130 million clean reads from fast-twitch and slow-witch muscles using RNA-Seq, respectively. Comparative transcriptome analysis revealed that 2,862 genes were differentially expressed. According to GO and KEGG analysis, the differentially expressed genes (DEGs) were mainly enriched in energy metabolism and skeletal muscle structure related pathways. Difference in the expression levels of specific genes for glycolytic and lipolysis provided molecular evidence for the differences in energy metabolic pathway between fast-twitch and slow-twitch muscles of P. dentex. Numerous genes encoding key enzymes of mitochondrial oxidative phosphorylation pathway were significantly upregulated at the mRNA expression level suggested slow-twitch muscle had a higher oxidative phosphorylation to ensure more energy supply. Meanwhile, expression patterns of the main skeletal muscle developmental genes were characterized, and the expression signatures of Sox8, Myod1, Calpain-3, Myogenin, and five insulin-like growth factors indicated that more myogenic cells of fast-twitch muscle in the differentiating state. The analysis of important skeletal muscle structural genes showed that muscle type-specific expression of myosin, troponin and tropomyosin may lead to the phenotypic structure differentiation. RT-qPCR analysis of twelve DEGs showed a good correlation with the transcriptome data and confirmed the reliability of the results presented in the study. The large-scale transcriptomic data generated in this study provided an overall insight into the thorough gene expression profiles of skeletal muscle in a highly mobile active pelagic fish, which could be valuable for further studies on molecular mechanisms responsible for the diversity and function of skeletal muscle.

Identification of the male sex-linked DNA sequence of cultured white trevally Pseudocaranx dentex

Identification of the male sex-linked DNA sequence of cultured white trevally Pseudocaranx dentex

The Effects of Silkworm-Derived Polysaccharide (Silkrose) on Ectoparasitic Infestations in Yellowtail (Seriola quinqueradiata) and White Trevally (Pseudocaranx dentex)

The effect of silkworm-derived polysaccharide silkrose on fish ectoparasites was investigated. When juvenile yellowtail (Seriola quinqueradiata) fed diets containing silkrose were artificially infected with Benedenia seriolae, a fish ectoparasite, the numbers of parasitized B. seriolae were significantly lower compared to that in fish in the control group without silkrose treatment. Furthermore, when juvenile yellowtails were severely infected with B. seriolae, no mortality was observed in the silkrose-treated group, compared to more than 60% in the control group. In field studies carried out at a fish farm with yellowtail and white trevally (Pseudocaranx dentex), oral treatment with silkrose significantly reduced B. seriolae parasitism in yellowtail and Caligus longipedis and Neobenedenia girellae parasitism in white trevally. Silkrose treatment also reduced blood levels of cortisol, a stress hormone in both species. The changes in gene expression in the epidermis of yellowtail by silkrose treatment were also investigated, showing that the expression of various genes, including factors involved in immunity, stress response, and wound healing, was changed by the treatment. These findings indicate that silkworm-derived silkrose effectively prevents infection by external parasites in yellowtail and white trevally.

Effect of additional heating of fish meal on in vitro protein digestibility and growth performance of white trevally ( Pseudocaranx dentex ) juveniles

Fish meal (FM) used in fish farming is prepared by steaming, squeezing, defatting, drying and crushing raw fish material. However, how drying affects protein digestibility has not been systematically studied. Herein, we evaluate the effect of additional heating of FM on in vitro FM protein digestibility and growth performance of white trevally (Pseudocaranx dentex) juveniles. We heated conventional steam-dried Chilean FM from 50–200°C for 1 h to prepare additionally heated FM (AHFM). In-vitro AHFM protein digestibility started to decrease significantly above 150°C, along with substantial reduction in the protein digestion speed. Five isonitrogenous/isolipidic experimental diets were prepared by substituting different proportions of FM with AHFM produced by heating FM to 180°C. In-vitro protein digestibility and digestion speed of the experimental diets decreased linearly with increasing AHFM content. After a 33-d feeding trial, the final bodyweight, specific growth rate, weight gain and feed efficiency of white trevallies decreased linearly and/or quadratically with increasing dietary AHFM levels. These findings indicate that in vitro protein digestibility of AHFM decreases linearly at temperatures above 150°C, and the growth and feed efficiency of white trevallies are negatively affected by dietary inclusion of AHFM processed at 180°C.

Complete Mitochondrial Genome of Pseudocaranx dentex (Carangidae, Perciformes) Provides Insight into Phylogenetic and Evolutionary Relationship among Carangidae Family.

Pseudocaranx dentex (white trevally) which belongs to the Carangidae family, is an important commercial fishery and aquaculture resource in Asia. However, its evolution and population genetics have received little attention which was limited by the mitogenome information absence. Here, we sequenced and annotated the complete mitochondrial genome of P. dentex which was 16,569 bp in length, containing twenty-two tRNAs (transfer RNAs), thirteen PCGs (protein-coding genes), two rRNAs (ribosomal RNAs), and one non-coding region with conservative gene arrangement. The Ka/Ks ratio analysis among Carangidae fishes indicated the PCGs were suffering purify selection and the values were related to the taxonomic status and further influenced by their living habits. Phylogenetic analysis based on the PCGs sequences of mitogenomes among 36 species presented three major clades in Carangidae. According to the phylogenetic tree, we further analyzed the taxonomic confusion of Carangoides equula which was on the same branch with P. dentex but a different branch with Carangoides spp. We inferred Kaiwarinus equula should be the accepted name and belong to the independent Kaiwarinus genus which was the sister genus of Pseudocaranx. This work provides mitochondrial genetic information and verifies the taxonomic status of P. dentex, and further helps to recognize the phylogenetic relationship and evolutionary history of Carangidae.

Gorgorhynchoides pseudocarangis n. sp. (Acanthocephala: Isthmosacanthidae) from Pseudocaranx dentex (Carangidae) in southeast Queensland, Australia, with comments on the Isthmosacanthidae.

Gorgorhynchoides pseudocarangis n. sp. (Isthmosacanthidae), is described from the intestine of the white trevally Pseudocaranx dentex (Bloch & Schneider) (Carangiformes: Carangidae) collected in Moreton Bay, Queensland, Australia. The new species has a proboscis armature of 27-28 rows of 16-17 hooks. It is most similar morphologically to Gorgorhynchoides bullocki Cable & Marafachisi, 1970 and Gorgorhynchoides gnathanodontos Smales, 2014 but differs from the former in having a longer proboscis with more rows of hooks, ventral hooks 6/7-12 with notched tips and trunk spines which do not extend onto the anterior bulbous swelling, and from the latter in having a longer proboscis, ventral hooks 6/7-12 with notched tips, more circles of trunk spines, larger eggs and a proboscis armature with all hooks lacking manubria. Previous molecular phylogenetic analyses have shown that the genus Serrasentis Van Cleave, 1923 is sister to Gorgorhynchoides Cable & Linderoth, 1963, although some have failed to resolve these two lineages in separate monophyletic clades. We performed novel single-gene and concatenated phylogenetic analyses using cox1 mtDNA, 18S and 28S rDNA gene-sequences, resolving Gorgorhynchoides and Serrasentis in monophyletic sister clades and demonstrating that Gorgorhynchoides pseudocarangis n. sp. is phylogenetically distinct from related species for which molecular sequence data are available. We view the previous amendment of the Isthmosacanthidae to include the genera Golvanorhynchus Noronha, Fabio & Pinto, 1987, Gorgorhynchoides, Isthmosacanthus Smales 2014 and Serrasentis, and the transfer of the family to the Polymorphida, as the most satisfactory classification at present, although additional molecular evidence would provide greater stability.

Suitable light intensity during the ontogenetic development of white trevally, Pseudocaranx dentex (Bloch and Schneider, 1801), larvae

Three experiments were conducted to elucidate the most suitable rearing light intensity during the ontogenetic changes in white trevally (Pseudocaranx dentex) larvae. In Experiment 1, larvae were reared under 1000, 3000 or 9000 lx. At 10 days post hatching (dph), larval growth was significantly higher in the 1000 lx treatment than in the other treatments. In Experiment 2, larvae were reared under 30, 100, 300, 1000, 3000, and 9000 lx, and 300 lx was revealed to be the most suitable light intensity for larval growth and survival until 10 dph. However, light intensities higher than 1000 lx may promote larval growth after 10 dph when the larval retina has developed prior to the metamorphic stage. In Experiment 3, larvae were exposed to increasing light intensities (i.e. from 300 lx to 1000, 3000 and 9000 lx) from 10 to 18 dph. Our results indicated that the most suitable rearing light intensity was 300 lx during the first week of development and at the commencement of feeding, and between 1000 and 3000 lx when the larvae approached the metamorphic stage. The rearing light intensity should, therefore, be adapted throughout the ontogenetic development of white trevally to promote larval growth and production efficiency.

Analysis of biological aspects of Scottish seine net catches in Mamuju waters, West Sulawesi

The decree of the Minister of Maritime Affairs and Fisheries No. 2 of 2015 has disturbed many fishermen in Indonesia, including Scottish seine fishermen. In that decree, the government concludes that the Scottish seine is not selective in catching fish and tends to disrupt the sustainability of small pelagic fish resources. This study aimed to analyse the biological aspects of fish caught with Scottish seine nets during the west monsoon season in the waters of Mamuju, South Sulawesi, Indonesia. The study was carried out from January to March 2016 with a case study of 1 unit during 30 fishing trips. The data collected included the type of fish caught, the weight and length of each fish by species. Data on fish taxa and size were analysed graphically and descriptively. The composition of the fish caught during the study was: shortfin scads (38%), bigeye scads (18%), sardines (14%), mackerel tuna (9%), Indian mackerel (7%), torpedo scads (6%), white trevally (3%), and other species (5 %). The length of shortfin scads, bigeye scads, sardinella, and mackerel tuna ranged from 9.9 - 18.2 cm; 8.5 - 19.5 cm; 10 - 12.5 cm; and 10-15 cm, respectively. In general, the fish caught were still classified as immature and not suitable for capture. To support sustainable fishing, it is necessary to limit fishing in the period from January to March.

Molecular evidence of three species in the Pseudocaranx dentex complex (Carangidae) in Australian waters

The discovery and identification of species is fundamental to the documentation, conservation and management of biodiversity. The taxonomy of the antitropical Pseudocaranx dentex complex (Carangidae) is confused and inconsistently reported. Previous morphological analyses concluded that this complex consisted of three species, namely P. sp. ‘dentex’, P. georgianus and P. dinjerra, in Australian waters. This study used genetic (COI sequence) and morphological data to evaluate the validity of this conclusion. The COI data showed the presence of three discrete lineages within this complex, which appear to correspond to the above-mentioned three species. They also suggested that P. sp. ‘dentex’ is closely related to, and possibly the same species as, P. dentex from southern Africa and the Mediterranean Sea. Also, the extent of morphological and geographical overlap between P. georgianus and P. dinjerra was greater than previously documented which, uncorrected, could lead to identification errors and present challenges for monitoring and management of harvested stocks of these species. By answering important taxonomic questions, our results will facilitate the proper interpretation of the results of past studies and the design of future studies of the P. dentex complex. They have also highlighted the value of molecular data for identifying species in morphologically conservative taxa.

New records of two carangid species from the south-east coast of Sicily (Ionian Sea) and considerations about their presence and abundance

New records of Pseudocaranx dentex (Bloch & Schneider, 1801) and Seriola fasciata (Bloch, 1793) are reported from the Mediterranean Sea. During the period 2013-2017, we have collected several records of both species from the south-east coast of Sicily (Ionian Sea). On the basis of our and published data, we can consider S. fasciata as a relatively common species in the area, commonly caught with purse seine around FADs in summer and autumn; while, P. dentex remains basically a rare species, occasionally caught with trammel nets or gillnets. This work represents the first well-documented records of both carangid species in the south-east coast of Sicily.

Quality parameters of wild white trevally (Pseudocaranx dentex) natural spawn kept in captivity

The white trevally (Pseudocaranx dentex Bloch & Schneider, 1801) is a widely distributed carangid, commercially exploited in both the Pacific and eastern Atlantic. Most published works refer to the use of hormonal induction with gonadotropin-releasing hormone for egg supply with generally low fecundities and of poor quality. This study aimed to contribute for a better knowledge on the husbandry conditions that allow for natural spawning of white trevally in captivity. Wild white trevallies were kept in captivity for four years until natural spawning occurred. Nine breeders were kept in a 10m3 concrete tank at a density of 5 Kg/m3, under natural photoperiod and natural water temperature fluctuations. Spawning started when water temperature reached 19 °C and lasted for two months. Viability rates varied between 35 and 79% and the average number of spawned eggs per female was of 280 × 103. Egg total lipids (16%DW) and fatty acid profile (expressed as a % total detected) remained constant throughout the spawning season and were not correlated with any egg viability parameters. Neutral lipids, a major energy source in marine fish eggs and larvae, accounted for 50% of lipid classes, followed by glycolipids and phospholipids. Within lipid fractions, the neutral lipids presented high amounts of monounsaturated fatty acids followed by equally high contents of polyunsaturated fatty acids. Docohexaenoic acid (DHA) was mainly found in the phospholipids fraction, though it was present in high amounts in all lipid classes. However, no significant correlations were observed between the DHA content and the egg viability parameters. The percentage of arachidonic acid (Ara) (<0.1%) was low, possibly due to a deficiency of this fatty acid in the broodstock diet. Polyunsaturated fatty acids content, mostly represented by DHA and eicosapentaenoic acid (EPA), was positively correlated with hatching rate. Correlations observed between chemical composition of the eggs and viability parameters highlight the fact that egg quality is deeply influenced not only by environmental factors but also by broodstock management techniques.

Nalazi novih vrsta riba na ušću rijeke Neretve: potencijalna prijetnja priobalnom jadranskom rastilištu

Specimens of the three new fish species were recorded during 2015 and 2016 in the River Neretva Estuary. These species are: White trevally, Pseudocaranx dentex (Bloch and Schneider, 1801), Pilotfish, Naucrates ductor (Linnaeus, 1758) and White grouper, Epinephelus aeneus (Geoffroy Saint–Hilaire, 1817). The characteristics of caught specimens and their history of records in Adriatic Sea are described. Potential impact of new species invasion in the Neretva Estuary as a major Eastern Adriatic nursery habitat is discussed.