Epinephelus Polyphekadion Research Articles

Dual RNA-Seq Unveils Candidate Key Virulence Genes of Vibrio harveyi at the Early Stage of Infection in Hybrid Grouper (♀ Epinephelus polyphekadion × ♂ E. fuscoguttatus)

Vibrio harveyi is a major bacterial pathogen that causes disease in aquaculture animals worldwide. Although V. harveyi consistently harbors a range of traditional virulence genes, it remains unclear which specific genes are crucial for virulence at different infection stages. Dual RNA-seq is a cutting-edge RNA sequencing technology that is ideal for investigating the gene expression patterns of pathogens within the host, which is highly effective in identifying key virulence genes. In previous artificial infection experiments, we have identified the liver of hybrid grouper (♀ Epinephelus polyphekadion × ♂ E. fuscoguttatus) as the main target organ for pathogenic V. harveyi GDH11385 during the initial infection phase. To further explore the key virulence factors of V. harveyi at the early stage of infection, the liver of the hybrid grouper infected with strain GDH11385 was analyzed here by dual RNA-seq. The transcriptome data were compared with that of in vitro cultured bacteria. The results showed that 326 and 1140 DEGs (differentially expressed genes) were significantly up- and down-regulated, respectively, at 4 h post-infection (hpi). Further pathway enrichment analyses revealed that these up-regulated DEGs in vivo were mainly enriched in siderophore biosynthesis and transport, type VI secretion system (T6SS), flagellar assembly, glycolysis/gluconeogenesis, and ribosome. Notably, all genes involved in the metabolism and utilization of vibrioferrin (a carboxylate class of siderophore produced by Vibrio), and most of the genes within one of three T6SSs, were significantly up-regulated in vivo. This indicates that siderophore-dependent iron competition and T6SS-mediated delivery of virulence factors are vital for the successful colonization of V. harveyi at the early stage of infection. This study provides more precise clues to reveal the virulence mechanism of V. harveyi during the initial phase of infection.

Structural Equation Modeling (SEM) of the interaction between cholecalciferol treatment and external factors in the incidence of vertebrae malformations in the hybrid grouper Epinephelus fuscoguttatus X Epinephelus polypehadion

Vitamin D3(VD3), also known as cholecalciferol plays a crucial role in maintaining calcium and phosphate homeostasis and has the potential to suppress bone malformations in fish larvae. However, external factors during growth also significantly influence the development of fish larval bones. Understanding the complex interaction between VD3 treatment and these external factors is crucial for optimizing therapeutic potential and effectively treating bone anomalies. SEM (Structural Equation Modeling) offers a comprehensive framework to explore these interactions by considering multiple variables simultaneously and examining their interrelationships. This study aimed to determine the impact of VD3 and its relationship with other external factors on the incidence of bone malformations in hybrid grouper larvae (Epinephelus fuscoguttatus X Epinephelus polyphekadion, EFEP). The treatments included a dose of 1.9 IU/g of VD3 in the feed and control group without VD3. All treatments received standard enrichment ingredients including vitamin C, taurine, and commercial enrichment (*SELCO). The enrichment was applied to rotifers (3 – 25 days after hatching, DAH) and artificial feed (25 – 35 DAH). The treatment was conducted in two batches, during the dry season (batch 1) and the rainy season (batch 2), to explore the seasonal impact on bone malformations. Results indicated that VD3 reduced the incidence of bone malformations in EFEP hybrid grouper fry by 1.14–1.65 times. SEM analysis revealed that spawning timing, egg quality, and water quality significantly impacted the occurrence of bone deformities, influencing malformations directly and indirectly through bone mineral content. This study demonstrated that bone malformations can be result from deficiencies in calcium, excess potassium and sulfur, and the presence of bromine in bone.

Exploring the influence of DNA methylation and single nucleotide polymorphisms of the Myostatin gene on growth traits in the hybrid grouper (Epinephelus fuscoguttatus (female) × Epinephelus polyphekadion (male)).

Investigations into the correlation between growth characteristics and DNA methylation levels, along with genetic variations, can provide fundamental insights to enhance growth performance in groupers. The Myostatin (mstn) gene plays a vital role in regulating skeletal muscle development and growth. This study scrutinized the DNA methylation levels of the mstn gene across hybrid groupers (E. fuscoguttatus (♀) × E. polyphekadion (♂)) and their parental species, to evaluate its impact on growth attributes in grouper fish. The nucleotide sequence of the mstn gene was directly sequenced in the hybrid grouper, exhibiting different growth performance to identify the single nucleotide polymorphisms (SNPs) of the mstn gene and explore their correlation with growth characteristics. The findings revealed no significant differences in global DNA methylation levels within muscle tissue among the hybrid grouper and parents. However, significant differences in DNA methylation sites were discovered between the hybrid grouper and E. polyphekadion at sites 824 and 1521 (located at exon 2 and intron 2, respectively), and between E. fuscoguttatus and E. polyphekadion at site 1521. These variations could potentially influence the mRNA expression of the mstn gene. The study also identified that SNP g.1003 T > C in exon 2 of the mstn gene was significantly associated with various growth traits including body weight, total length, body length, head length, caudal peduncle height, and body height (p < 0.01). Specimens with the TT genotype at site 1003 demonstrated superior growth performance compared to those with the TC genotype. Furthermore, microstructural analyses of muscle tissue showed that the average area and diameter of muscle fibers in TT genotype individuals were significantly greater than those in TC genotype individuals. Therefore, this research provides robust evidence linking the DNA methylation level and polymorphisms of the mstn gene with growth traits, which could be beneficial for grouper breeding programs.

Effects of Dietary Alpha-Lipoic Acid on Growth Performance, Serum Biochemical Indexes, Liver Antioxidant Capacity and Transcriptome of Juvenile Hybrid Grouper (Epinephelus fuscoguttatus♀ × Epinephelus polyphekadion♂).

We aimed to investigate the effects of dietary alpha-lipoic acid (α-LA) on the growth performance, serum biochemical indexes, liver morphology, antioxidant capacity, and transcriptome of juvenile hybrid groupers (Epinephelus fuscoguttatus♀ × Epinephelus polyphekadion♂). Four experimental diets supplemented with 0 (SL0), 0.4 (L1), 0.6 (L2), and 1.2 (L3) g/kg α-LA were formulated and fed to three replicates of juvenile hybrid grouper (24.06 ± 0.15 g) for 56 d. The results indicated that dietary 0.4 and 0.6 g/kg α-LA significantly decreased the weight gain rate in juvenile hybrid groupers. Compared with SL0, the content of total protein in the serum of L1, L2, and L3 increased significantly, and alanine aminotransferase decreased significantly. The content of albumin in the serum of L3 increased significantly, and triglyceride, total cholesterol, and aspartate aminotransferase decreased significantly. In addition, the hepatocyte morphology in L1, L2, and L3 all showed varying degrees of improvement, and the activities of glutathione peroxidase and superoxide dismutase in the liver of L2 and L3 were significantly increased. A total of 42 differentially expressed genes were screened in the transcriptome data. KEGG showed that a total of 12 pathways were significantly enriched, including the pathway related to immune function and glucose homeostasis. The expression of genes (ifnk, prl4a1, prl3b1, and ctsl) related to immune were significantly up-regulated, and the expressions of gapdh and eno1 genes related to glucose homeostasis were significantly down-regulated and up-regulated, respectively. In summary, dietary supplementation of 0.4 and 0.6 g/kg α-LA inhibited the growth performance of juvenile hybrid groupers. A total of 1.2 g/kg α-LA could reduce the blood lipid level, improve hepatocyte damage, and increase the hepatic antioxidant enzyme activity. Dietary α-LA significantly affected the pathway related to immune function and glucose homeostasis.

Trophic and spatial patterns of contaminants in fishes from the Republic of the Marshall Islands in the equatorial Pacific

The Republic of the Marshall Islands (RMI) has been affected by marine pollution from militarization and urbanization. To address concerns raised by the Marshall Islands Marine Resources Authority, this study examined concentrations of dissolved contaminants in reef and pelagic fishes in the RMI and assessed potential associated risks. Metals, organochlorine pesticides, polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs) were examined in reef and pelagic fishes from six atolls: Kwajalein, Majuro, Jaluit, Utirik, Rongelap, and Wotje. Clear trophic patterns emerged for metals. Total arsenic was highest in higher trophic level reef fishes, particularly in the camouflage grouper (Epinephelus polyphekadion) (>100 μg g−1 total As), but inorganic arsenic was negligible in higher trophic levels and showed an inverse trend with the highest percentages present in parrotfishes and herbivores. Copper and mercury were elevated in higher trophic level reef and pelagic fishes, respectively, and the maximum mercury concentrations (6.45 μg g−1 in Gymnosarda unicolor) were among the highest reported in the Pacific. Conversely, cadmium and lead were highest in lower trophic levels, like surgeonfishes and parrotfishes. PCBs were more clearly linked to locations and were highest at two atolls with military history (Kwajalein and Jaluit) (>U.S. EPA Screening Value of 2.5 ppb). PAHs were ubiquitous across taxa (detected in 97% of samples), but the highest concentrations were in lower trophic levels. Organochlorine pesticides were detected at very low concentrations that do not likely pose a risk. We compare concentrations to established thresholds for human health and find that – for specific locations and species – contaminant concentrations may pose a risk to fish and other marine taxa, as well as human consumers. This study provides baseline information that aids the development of marine conservation and public health recommendations and addresses a data gap that persists for marine pollution throughout the Pacific Islands.

Effects of Bacillus sp. and Lactobacillus sp. combination as a water additive on the culture pond water and growth performance of hybrid grouper (Epinephelus fuscoguttatus × Epinephelus polyphekadion)

The individual Probiotic application has become increasingly widespread in aquaculture and has been extensively studied. However, investigating probiotics as water additives in the grouper culture is still lacking. This study evaluated the functional efficacy of the Bacillus subtilis CICC 10071 (3 × 1011 CFU / g) and Lactobacillus sp. (8 × 1011 CFU / g) combination in a 1:1 ratio on the rearing water quality, water microbial community structure, and growth performance of hybrid grouper. Depending on the additive concentrations of probiotics, we designed four groups, each in triplicate: control (WT, 0g/m3), low concentration (WL, 0.038g/m3), middle concentration (WM, 0.075g/m3), and high concentration (WH, 0.113g/m3). The result shows that throughout the 22-day feeding period, the water supplementation of probiotics significantly decreased Ammonia (NH3) and nitrite (NO2-) in culture water. Final weight (FW), Specific growth rate (SGR), and Weight gain rate (WGR) in treated groups were higher than that in the control group (P&amp;lt;0.05). Analysis of water microbiota revealed that the dominant phylum Bacteroidetes, Proteobacteria, Cyanobacteria, and Actinobacteria enriched in the culture water. Furthermore, we found that the Probiotics combination could significantly reduce the abundance of Cetobacterium (phyla Fusobacteria) related to ammonia and nitrite. The Phylogenetic Investigation of Communities by Reconstruction of Unobserved States 2 (PICRUSt2) also shows that the 'metabolism of other amino acids and ‘Fatty acid biosynthesis’ functions of water microbiota were reinforced by the addition of the probiotic combination. Thus, the probiotic combination exhibited a range of advantages in the grouper culture environment, and further in-depth studies are needed.

Genetic characteristics and growth patterns of the hybrid grouper derived from the hybridization of Epinephelus fuscoguttatus (female) × Epinephelus polyphekadion (male).

Hybridization is one of the primary methods used to cultivate farmed grouper species. The hybrid grouper derived from crossing Epinephelus fuscoguttatus (♀) and E. polyphekadion (♂) exhibits growth superiority over its parents. The genetic characteristics and growth patterns of the hybrid grouper have not yet been defined. This study confirms the ploidy level of the hybrid grouper (2n=48) using chromosome count analysis and flow cytometry. The 5S rDNA family was used to evaluate genetic diversity. Only one 5S class (~400 bp) was detected in the hybrid grouper, which could be used to distinguish between two different types based on nucleotide sequences, likely representing homologous unit classes from the female and male parental species. Growth patterns of 5-8-month-old hybrid groupers were also monitored. In this phase, a positive allometric growth pattern in body mass with total length was found. Body height and body mass were significantly correlated based on correlation and path coefficient, suggesting that body height could serve as an excellent index to increase body mass. These results aid our understanding of the genetic evolution of the hybrid grouper and inform the development of improved rearing techniques.

Prevalence of Bacterial Coinfections with Vibrio harveyi in the Industrialized Flow-through Aquaculture Systems in Hainan Province: A Neglected High-Risk Lethal Causative Agent to Hybrid Grouper.

Vibrio harveyi is one of the most serious bacterial pathogens to aquatic animals worldwide. Evidence is mounting that coinfections caused by multiple pathogens are common in nature and can alter the severity of diseases in marine animals. However, bacterial coinfections involving V. harveyi have received little attention in mariculture. In this study, the results of pathogen isolation indicated that bacterial coinfection was a common and overlooked risk for hybrid groupers (♀ Epinephelus polyphekadion × ♂ E. fuscoguttatus) reared in an industrialized flow-through pattern in Hainan Province. The artificial infection in hybrid groupers revealed that coinfections with V. harveyi strain GDH11385 (a serious lethal causative agent to groupers) and other isolated pathogens resulted in higher mortality (46.67%) than infection with strain GDH11385 alone (33.33%), whereas no mortality was observed in single infection with other pathogens. Furthermore, the intestine, liver and spleen of hybrid groupers are target organs for bacterial coinfections involving V. harveyi. Based on the infection patterns found in this study, we propose that V. harveyi may have a specific spatiotemporal expression pattern of virulence genes when infecting the host. Taken together, bacterial coinfection with V. harveyi is a neglected high-risk lethal causative agent to hybrid groupers in the industrialized flow-through aquaculture systems in Hainan Province.

Influences of ferulic acid on intestinal digestive and antioxidant enzymes, immune, antioxidant gene and tight junction protein expression and microbiota in hybrid grouper (Epinephelus fuscoguttatus♀× Epinephelus polyphekadion♂)

The current study was performed to assess the effects of dietary administration of ferulic acid (FA) on digestive enzyme activities, antioxidant capacity, morphology, immunity, and microbiota in the gut of hybrid grouper (Epinephelus fuscoguttatus♀ × Epinephelus polyphekadion♂). A total of 630 fish (9.51 ± 0.01 g) were allocated randomly to seven dietary treatments, each with three replicates. Experiment diets supplemented with FA at the levels of 0, 40, 80, 160, 320, 640, and 1280 mg kg−1 (FA0 (control), FA40, FA80, FA160, FA320, FA640, and FA1280), were fed to fish for 70 days. The results showed that dietary 80–160 mg kg−1 FA intake considerably augmented the enzymes activities of digestion (lipase, trypsin, amylase, and pepsin) and antioxidation (superoxide dismutase, glutathione peroxidase, and catalase) and the values of immune parameters (Immunoglobulin, C3 and lysozyme), as well as reduced malondialdehyde content, with respect to the control group (P < 0.05). Furthermore, a significant increase in the intestinal fold height, fold width, and muscular thickness was detected in fish fed the diets containing 80–160 mg kg−1 FA (P < 0.05). For gut genes expression, dietary supplementation of 80–160 mg kg−1 FA significantly upregulated the transcriptional levels of the immune-related genes (interleukin 1β, interleukin 8, tumor necrosis factor-alpha, interleukin 10, and transforming growth factor-beta 1), the antioxidation-associated genes (superoxide dismutase, copper/zinc superoxide dismutase, and nuclear factor erythroid 2-related factor 2-like 2), and tight junction proteins genes (zonula occludens 1, Occludin, and Claudin-3), whereas downregulated kelch like ECH associated protein 1 (P < 0.05). Regarding the intestinal microbiota, the FA-supplemented diets with 80 and 1280 mg kg−1 significantly increased the alpha diversity indexes (Simpson and Shannon) and the relative abundances of Firmicutes and Bacteroidetes, as well as lowered the relative abundance of Proteobacteria (P < 0.05). Additionally, the ratio of Firmicutes to Bacteroidetes was remarkably reduced, following the diet supplemented with 80 mg kg−1 FA, which also exhibited the decreased relative abundance of Acinetobacter and the increased relative abundances of Lactobacillus and Bifidobacterium (P < 0.05). Taken together, these results signified that the appropriate FA inclusion in diets could serve as a nutritional strategy to improve the intestinal health of hybrid grouper.

Hepatic transcriptome profiles reveal the hepatoprotective effects of dietary quercetin and sodium quercetin-5′-sulfonates supplementation in hybrid grouper (Epinephelus fuscoguttatus♀ × Epinephelus polyphekadion♂)

Plant flavonoids, such as quercetin (QE), are traditionally used to treat liver injuries. Given the limited bioavailability of quercetin, sodium quercetin-5′-sulfonates (QS) were synthesised and characterised. Although beneficial effects of QE on the fatty liver are observed in vertebrates, the exact mechanism is still unclear, particularly in fish livers. As a result, RNA-sequencing was conducted on hepatic libraries from hybrid groupers (Epinephelus fuscoguttatus♀ × Epinephelus polyphekadion♂) after QE and QS exposure for 56 d. In total, 49,411 unigenes were generated with a control group (FM, 0 mmol/kg), QE (QE, 3.2 mmol/kg), and QS (QS, 3.2 mmol/kg) supplementation group. The N50 for the unigenes is 2047 bp, whereas the mean length is 1198.55 bp. Compared with FM, we identified 788 and 848 differentially expressed unigenes (DEGs) in the liver in response to QE and QS, including 423 up- and 365 down-regulated in the QE group and 402 up- and 446 down-regulated in the QS group. Furthermore, ten genes were selected for real-time quantitative PCR to verify the reliability of our transcriptome data, and the result has shown that both up-and down-regulated genes were consistent with the RNA-seq results. Results showed that QE down-regulated hepatic genes involved in the steroid biosynthesis pathway, while QS up-regulated genes related to polyamine synthesis. More importantly, glutaminase1 (GLS1) is the initial and rate-limiting enzyme responsible for glutamine catabolism, down-regulated by QE and QS exposure. Our results will provide valuable information to help understand the underlying molecular mechanism for QE and QS preventing fatty liver of grouper.

Hepatic Metabolomics Analysis of Hybrid Grouper (Epinephelus fuscoguttatus♀×Epinephelus polyphekadion♂) Fed With Quercetin and Sodium Quercetin-5′-Sulfonates

Combining feeding trials and metabolomics analyses of tissues and biofluids could shed light on nutrient effects and changes in feed intake. In the present study, hybrid grouper (F1 hybrid Epinephelus fuscoguttatus♀×Epinephelus polyphekadion♂) was used as the marine fish model to quantify the impacts of quercetin and sodium quercetin-5′-sulfonates on serum biochemistry and the status of hepatic lipid accumulation and the changes of metabolites in the liver using ultra-performance liquid chromatography-electrospray triple quadrupole mass spectrometry (UPLC-QTRAP/MS/MS). The study shows that total protein, albumin, alkaline phosphatase and glucose were not significantly different among the three groups (P &amp;gt; 0.05). Total cholesterol, triglyceride, and alanine aminotransferase of fish fed quercetin, and sodium quercetin-5′-sulfonates were significantly lower than fish fed without additives (P &amp;lt; 0.05). Low-density lipoprotein cholesterol and aspartate aminotransferase of fish fed quercetin were significantly lower than that of fish fed without additives and sodium quercetin-5′-sulfonates (P &amp;lt; 0.05). The high-density lipoprotein cholesterol of fish fed quercetin, and sodium quercetin-5′-sulfonates were significantly higher than that of fish fed without additives (P &amp;lt; 0.05). Lipid accumulation in the quercetin and sodium quercetin-5′-sulfonates groups decreased significantly. Quercetin and sodium quercetin-5′-sulfonates were effective by increasing hypolipidemic and hepatoprotective compounds that are known for reducing blood lipid levels and liver fat accumulation. As a result of this study, we provide international data for metabolic adaptations during the additives feeding using the fish liver as the study model. By understanding the metabolic effects of these feed additives, this study provides a first step toward understanding the molecular mechanisms of these additives and how they function.

Evaluating Age and Growth Relationship to Ciguatoxicity in Five Coral Reef Fish Species from French Polynesia

Ciguatera poisoning (CP) results from the consumption of coral reef fish or marine invertebrates contaminated with potent marine polyether compounds, namely ciguatoxins. In French Polynesia, 220 fish specimens belonging to parrotfish (Chlorurus microrhinos, Scarus forsteni, and Scarus ghobban), surgeonfish (Naso lituratus), and groupers (Epinephelus polyphekadion) were collected from two sites with contrasted risk of CP, i.e., Kaukura Atoll versus Mangareva Island. Fish age and growth were assessed from otoliths’ yearly increments and their ciguatoxic status (negative, suspect, or positive) was evaluated by neuroblastoma cell-based assay. Using permutational multivariate analyses of variance, no significant differences in size and weight were found between negative and suspect specimens while positive specimens showed significantly greater size and weight particularly for E. polyphekadion and S. ghobban. However, eating small or low-weight specimens remains risky due to the high variability in size and weight of positive fish. Overall, no relationship could be evidenced between fish ciguatoxicity and age and growth characteristics. In conclusion, size, weight, age, and growth are not reliable determinants of fish ciguatoxicity which appears to be rather species and/or site-specific, although larger fish pose an increased risk of poisoning. Such findings have important implications in current CP risk management programs.

Effects of dietary supplementation of ferulic acid on growth performance, antioxidant ability, non-specific immunity, hepatic morphology and genes expression related to growth and immunity in juvenile hybrid grouper (Epinephelus fuscoguttatus♀ × Epinephelus polyphekadion♂)

The current study was conducted to investigate the influences of ferulic acid (FA) as a dietary addition on growth performance, serum biochemical indices, liver morphology, antioxidant capacity, non-specific immunity, and expression of genes related to growth, immunity, apoptosis, and antioxidation in juvenile hybrid grouper (Epinephelus fuscoguttatus♀ × Epinephelus polyphekadion♂). Seven experimental diets added with 0 (Diet1), 40 (Diet2), 80 (Diet3), 160 (Diet4), 320 (Diet5), 640 (Diet6), and 1280 (Diet7) mg/kg FA, were formulated and fed to triplicate groups of 30 fish (9.51 ± 0.01 g) respectively for 10 weeks. The results exhibited that fish fed the diets with FA supplementation of 80 mg/kg presented the best growth performance and feed utilization, whereas the inclusion of 1280 mg/kg FA was the worst respect to Diet1 (control) (P < 0.05). The levels of serum low-density lipoprotein cholesterol, alanine aminotransferase, aspartate aminotransferase, total cholesterol, triglycerides, and alkaline phosphatase were significantly decreased, and high-density lipoprotein cholesterol level was increased following the FA-containing (80–160 mg/kg) diets (P < 0.05). Meanwhile, dietary 80–160 mg/kg FA administration provided an increase in the contents of complement 3, immunoglobulin M, and lysozyme (P < 0.05). The antioxidant-related parameters of superoxide dismutase, catalase, glutathione peroxidase, and total antioxidant capacity were outstandingly elevated, while malondialdehyde content was significantly reduced in 80–160 mg/kg FA treatment (P < 0.05). Additionally, dietary FA intake of 40–320 mg/kg could ameliorate hepatic morphology. Regarding genes expression, the transcriptional levels of immune-related genes (IL-1β, IL-8, TNF-α, IFN-γ) were considerably upregulated in the liver, head kidney, and spleen of fish fed the diets added with 80–160 mg/kg FA, which also significantly enhanced the expression of hepatic genes related to growth and antioxidation (GH, IGF-1, GHR1, GHR2, Nrf2, Cu/ZnSOD, and MnSOD). In contrast, the genes expression of apoptosis (Caspase-3 and p53) and keap1b were downregulated (P < 0.05). To sum up, dietary supplementation of FA at the optimal dosage (80 mg/kg) could enhance growth, antioxidant status, and immunity, as well as ameliorate liver morphology and health of fish. Interestingly, the high dosage (over 640 mg/kg) of FA had adverse effects on hybrid grouper, particularly for growth performance.

The development of the reproductive organs of the hybrid grouper cantik (Epinephelus fuscoguttatus x E. polyphekadion)

Observation of the reproductive organs of the hybrid grouper cantik was carried out. Cantik grouper is the result of cross-breeding between female tiger grouper Epinephelus fuscoguttatus and male camouflage grouper E. polyphekadion. This study aimed to determine the development of the reproductive organs of cantik grouper. The observed test fishes were 3 fishes of Cantik grouper with a total length of 42 - 49 cm and a bodyweight of 1.45 - 2.26 kg. The parameters observed were the concentarion of estradiol and testosterone in the blood using the ELISA kit, gonad development, and histological maturity level of the gonads. The results showed that the hormone testosterone found in the sample cantik no 1 was 9353 pg/ml, while the hormone estradiol was found in all samples of beautiful grouper in the range of 291 - 1133 pg/ml. From the dissected fish, the gonads had developed and weighed 3.12 - 56.01 g and one sample had a fecundity of 265,800 eggs with an egg diameter of 360-520 micron. Gonadal histology shows oosit development at maturity levels I, II, and IV. This indicates that the crossbreeding between female tiger grouper and male camouflage grouper produces hybrid grouper cantik that are fertile, which is shown by their reproductive organs to have developed well.

Aligning fisheries management with life history in two commercially important groupers in Chuuk, Federated States of Micronesia

Abstract Camouflage grouper, Epinephelus polyphekadion (Bleeker, 1849), and squaretail coralgrouper, Plectropomus areolatus (Rüppell, 1830), are commercially important medium‐bodied groupers that aggregate at specific sites and times to spawn and are highly vulnerable to fishing during these events. Populations of both species are in decline globally, such that management specifically targeting these species is warranted. A 12‐month fish market survey in Chuuk, Federated States of Micronesia, provided an opportunity to examine age‐based reproductive life history of these two groupers and assess whether current management acts to conserve them. Life history characteristics of both E. polyphekadion and P. areolatus include a functionally gonochoristic sexual pattern and rapid growth particularly during early life history. P. areolatus demonstrated early maturity (2.8 years) and a relatively brief lifespan (10 years), while delayed maturity (4.5 years) and higher longevity (25 years) was shown for E. polyphekadion. The spawning seasons for E. polyphekadion and P. areolatus were 2 and 3 months, respectively, which fall entirely within the January–April grouper sales, catch, and export ban period for Chuuk. Marketed catch included 22% E. polyphekadion and 15% P. areolatus juveniles, suggesting that size limits may aid in the conservation of these species. Findings from this and recent grouper life history studies suggest that the current 4‐month ban in Chuuk be applied only to grouper species known to reproduce during these months to minimize economic impacts to fishers and market owners, and prevent shifts in fishing pressure to more vulnerable species, such as those with low population turnover times, slow growth, or late maturity. Size limits for catch, sale and export are also warranted as an additional management option.

Inventory of commercially important coral reef fishes in Tawi-Tawi Islands, Southern Philippines: The Heart of the Coral Triangle

Tawi-Tawi, Southern Philippines, which has over 300 islands and huge reef systems, is geographically located at the heart of the Coral Triangle, the global center of coral reef biodiversity. In this study, we conducted an inventory survey of market fishes in Tawi-Tawi from October 2015 to December 2018. We considered 11 major commercially important coral reef fishes, namely, surgeonfish (family Acanthuridae), parrotfish (subfamily Scarinae, family Labridae), snapper (family Lutjanidae), grouper (subfamily Epinephelinae, family Serranidae), sweetlips (family Haemulidae), goatfish (family Mullidae), emperor (family Lethrinidae), triggerfish (family Balistidae), coral bream (family Nemipteridae except genus Nemipterus), fusilier (family Caesionidae) and rabbitfish (family Siganidae). We further compared the results with published reports from Palawan and Panay Island which are also located along the Sulu Sea, the region with the highest coral reef fish diversity in the Philippines. Overall, we recorded a total of 266 species of reef fish in Tawi-Tawi with Epinephelinae (48 species), Lutjanidae (40 species) and Acanthuridae (33 species) as the most speciose groups. Further investigation showed that the average relative abundance of the three most abundant species in each family/subfamily is about 64.5% (range, 51.6% for Acanthuridae to 87.6% for Balistidae) of their respective groups. Based on the status assessment of the International Union for Conservation of Nature, one species (Scarus hypselopterus) was considered as Near Threatened (NT), four species (Bolbometopon muricatum, Epinephelus fuscoguttatus, Epinephelus polyphekadion and Plectropomus areolatus) as Vulnerable (VU) while the majority were considered as Least Concern (LC). The number of species recorded in Tawi-Tawi was much higher than in Palawan and Panay Island which had a total of only 159 species and 139 species, respectively. Moreover, Tawi-Tawi had about five times more unique species than either of the two other areas. Our study indicates the importance of the reefs of Tawi-Tawi and the Sulu Archipelago in general as the richest in the Philippines in terms of commercially important coral reef fish species diversity. Various factors that explain the high diversity of reef fishes on the reefs of Tawi-Tawi and the importance of conserving these valuable ecosystems are discussed.

Declining grouper spawning aggregations in Western Province, Solomon Islands, signal the need for a modified management approach.

Globally, groupers (Epinephelidae) that form fish spawning aggregations (FSAs) are highly vulnerable to overfishing and often require site-specific approaches to management. Over 5-years (2009–2013), we conducted underwater visual censuses (UVC) at a well-known spawning site at Njari Island, Gizo, Western Province, Solomon Islands, that supports aggregations of squaretail coralgrouper (Plectropomus areolatus), camouflage grouper (Epinephelus polyphekadion) and brown-marbled grouper (E. fuscoguttatus). Findings show that while there were species-specific variations in the duration and timing of the spawning season, aggregation densities peaked from March to June, representing the main spawning season for all three species. For P. areolatus, gonad analysis from samples taken from 2008 to 2011 confirmed reproductive activity in support of density trends observed through UVC. Over the 5-year UVC monitoring period, FSA densities declined for P. areolatus and E. polyphekadion. Conversely, following the first year of monitoring, E. fuscoguttatus densities increased. These inter-specific differences may reflect variable responses to fishing as shown elsewhere, or for example, differences in recruitment success. In response to known declines in FSAs of these species, in 2018 the Solomon Islands government placed a nationwide ban on these species’ harvest and sale between October and January. As this study shows, this ban does not encompass the peak aggregation period at Njari and will offer limited protection to other FSAs of these species that are known to vary in reproductive seasonality across the Solomon Islands. A more biologically meaningful and practical management strategy would be to implement a nationwide ban on the harvest and sale of these groupers each month between full and new moons when these FSAs form consistently throughout the country. Since effective management of FSAs typically requires a combined approach, spatial management that protects both spawning sites and reproductive migratory corridors is warranted.

English

Many factors contribute to the underdevelopment of oceanic aquaculture. The most significant factor of the development of hybrid grouper culture is the supply of satisfactory quantities of fast growing juveniles to stock grow-out systems at a minimized cost. In order to evaluate the growth hormone status of hybrid grouper (Epinephelus fuscoguttatus ♀&times; Epinephelus polyphekadion ♂), cDNA encoding growth hormone from the liver of juvenile fish was cloned and characterized. qPCR method was used to determine the expression of the growth hormone in the tissues. Relative expression of growth hormone in the brain was found to be highest (290.91 folds) and lowest in the stomach (1.35 folds). Bioinformatics tools were used to analyze the growth hormone proteins and prediction of its physicochemical properties, and amino acid compositions, as well as Gene Ontology, GO term predictions. The cloned hybrid grouper growth hormone gene sequence was found to be clustered monophyletically with solid bootstrap backing. It was found to be close to the Cromileptes altivelis growth hormone gene sequence and is positioned in the identical clade and consequential from the identical family. The expression pattern is comparable to that comprehended in other fishes and provides extra data for molecular biological studies on hybrid grouper fish. Key words: Growth hormone, bioinformatics analysis, tissue expression, gene ontology, hybrid grouper &nbsp;

Passive monitoring of phenological acoustic patterns reveals the sound of the camouflage grouper, Epinephelus polyphekadion

Abstract Passive acoustic monitoring (PAM) is a non‐invasive technique that uses hydrophones to monitor populations and ecosystem dynamics. Although many applications of PAM have been developed in recent years, it has never been used to identify a calling marine species. The south pass of Fakarava Atoll, French Polynesia, hosts spawning events of many reef fish species, including the camouflage grouper Epinephelus polyphekadion, with a spawning aggregation abundance exceeding 17 000 individuals during the full moons of June and July. The current study aimed to use PAM to distinguish camouflage grouper sounds among the vocal activities of all fish recorded during the aggregation periods. Audio recordings analysis resulted in the identification of 29 sound types, some of which showed diel and lunar patterns. Temporal analysis of these sounds in relation to spawning activities allowed the identification of camouflage grouper calls. These calls can be described as a single pulse or a series of ‘boom(s)’ with a pulse duration of ~44 ms and a low dominant frequency of 103 ± 31 Hz. Video recordings show that the camouflage grouper produces the ‘booms’ to initialize spawner ascent and to promote synchronous gamete release into the water column. The study highlights for the first time that PAM can be used to identify the previously unknown sound of a fish species. Moreover, we can use it to understand the phenology of some biological activities for improving the resolution of fish biodiversity assessments.

Reproductive Biology of Three Important Threatened/Near-Threatened Groupers (Plectropomus leopardus, Epinephelus polyphekadion and Plectropomus areolatus) in Eastern Indonesia and Implications for Management.

Simple SummaryIndonesia needs basic data on the reproductive dynamics of economically important fishery species, including groupers, in order to support sustainable fisheries management. Data from the histological examination of grouper gonad samples were combined with data from: participatory mapping and interviews with fishermen, monitoring data from known spawning aggregation sites, and analyzed descriptively to provide basic data on the size at first maturity and seasonal reproductive patterns of three economically important groupers. We suggest management measures including size limits, temporal spatial closures, and a trading ban during the peak spawning season (November–December).The three grouper species most heavily fished for the live reef fish trade (LRFT) in Indonesia are Plectopomus leopardus (greatest catch volume), and two species classified as Vulnerable on the International Union for Conservation of Nature (IUCN) Red List: Plectropomus areolatus and Epinephelus polyphekadion. Understanding the reproductive biology of these fishes is essential for sustainable management, but relevant data are limited. This study aimed to determine reproductive dynamics, so as to inform management measures to maintain the reproductive capacity of these groupers. Grouper gonad samples collected from fish caught for the LRFT were analyzed histologically. Data were also collected from participatory mapping and interviews with fishermen, and underwater monitoring of three known spawning aggregation sites in the Wakatobi National Park, Eastern Indonesia. Based on observed gonad development, the respective lengths and weights at first maturity were: 37.7 cm and 759 g (P. leopardus); 36.65 cm and 771.2 g (P. areolatus); 36.95 cm and 889.9 g (E. polyphekadion). The mean weight of the groupers market-based sampled was higher than the size at first sexual maturity. Sex transition was observed in P. leopardus; sex reversal was not observed in E. polyphekadion, and the sex pattern of P. areolatus was unresolved. Based on the fisher surveys and spawning aggregation monitoring, spawning occurs around the new moon from September to April, with reproductive peaks in November and December. Fisheries management measures that are suggested to sustain grouper stocks include enforcing appropriate size limits, temporal spatial closures (spawning aggregation sites), and a trading ban during the peak spawning season (November–December).