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Offshore oil and gas platforms support abundant reef fish and are popular fishing sites for recreational anglers. However, the rapid decommissioning and removal of active platforms have decreased such fishing opportunities in the Gulf of Mexico, raising concerns about fisheries impacts. Conversely, planned offshore energy structures like wind turbines may offer similar habitats and fishing sites. To inform spatial planning for marine energy infrastructure in the context of recreational fisheries, we created models of fish communities associated with oil and gas platforms using existing abundance data. We employed Random Forest analysis to predict the presence‐absence and abundance of Red Snapper (Lutjanus campechanus) and Greater Amberjack (Seriola dumerili) at platforms using 47 environmental and platform variables. Nonmetric multidimensional scaling on Bray−Curtis dissimilarities explored fish species composition among 37 species. Results showed variability in Red Snapper and Greater Amberjack incidence/abundance from shore to shelf‐edge, not attributed to surrounding habitat or climatological oceanographic variables. Incidence models were more robust than abundance models. Fish species composition was significantly influenced by location gradient, with less impact from other habitat features. Our findings guide selecting areas for artificial structures to enhance angler opportunities and maintain fish diversity, but identifying the drivers of finer scale abundance variation will require further sampling. [ABSTRACT FROM AUTHOR]

Abstract Offshore oil and gas platforms support abundant reef fish and are popular fishing sites for recreational anglers. However, the rapid decommissioning and removal of active platforms have decreased such fishing opportunities in the Gulf of Mexico, raising concerns about fisheries impacts. Conversely, planned offshore energy structures like wind turbines may offer similar habitats and fishing sites. To inform spatial planning for marine energy infrastructure in the context of recreational fisheries, we created models of fish communities associated with oil and gas platforms using existing abundance data. We employed Random Forest analysis to predict the presence‐absence and abundance of Red Snapper (Lutjanus campechanus) and Greater Amberjack (Seriola dumerili) at platforms using 47 environmental and platform variables. Nonmetric multidimensional scaling on Bray−Curtis dissimilarities explored fish species composition among 37 species. Results showed variability in Red Snapper and Greater Amberjack incidence/abundance from shore to shelf‐edge, not attributed to surrounding habitat or climatological oceanographic variables. Incidence models were more robust than abundance models. Fish species composition was significantly influenced by location gradient, with less impact from other habitat features. Our findings guide selecting areas for artificial structures to enhance angler opportunities and maintain fish diversity, but identifying the drivers of finer scale abundance variation will require further sampling.

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Feeding habits and trophic level of juvenile greater amberjack, Seriola dumerili were studied using 170 specimens collected by set net fishery and lure fishing in the southern waters of Korea during July, August, September, October, and November 2022. The size of juvenile greater amberjack ranged from 17.5 to 49.9 cm in fork length. Juvenile greater amberjack was piscivorous predator that feed primarily on fish. We calculated the trophic level as 4.06 ± 0.80 for juvenile greater amberjack. Fishes were the main prey items for all size groups. Juvenile greater amberjack also showed size-related dietary shift from Japanese anchovy to jack mackerel. As the fork length of juvenile greater amberjack increase, the mean weight of prey per stomach tended to increased, while the mean number of preys per stomach was not significantly different. Fishes were the main prey items for summer and autumn. The main fish prey during summer and autumn was Japanese anchovy, but in the autumn, the Japanese anchovy portion decreased, and the jack mackerel portion increased. PERMANOVA analysis was used to examine seasonal and size-related changes in diet composition, which showed significant variations among size classes. Juvenile greater amberjack presumably feed on larger prey to meet their energy requirements. [ABSTRACT FROM AUTHOR]

The present study was conducted to investigate the effects of dietary fish oil replacement with a mixture of vegetable oils and probiotic supplementation on plasma biochemical parameters, oxidative stress, and antioxidant ability of Seriola dumerili. Specimens with an initial weight of 175 g were used. Four feeds were formulated with 0% (FO-100), 75% (FO-25), and 100% (FO-0 and FO-0+ with the addition of Lactobacillus probiotics) substitution of fish oil with a mixture of linseed, sunflower, and palm oils. After 109 days, no significant differences were observed in the activity of antioxidant enzymes in the liver, foregut, and hindgut, only glucose-6-phosphate dehydrogenase activity in the liver was higher in the fish fed the FO-100 diet than in those fed the FO-0 diet. No significant differences were observed in the total, reduced, and oxidized glutathione and the oxidative stress index in the liver. In addition, lipid peroxidation in the liver and red muscle values were higher in the fish fed the FO-100 diet than in the fish fed the FO-0+ diet, however, the foregut of the fish fed the FO-100 diet presented lower values than that of the fish fed the FO replacement diet, with and without probiotics. There were significant differences in cholesterol levels in the FO-100 group; they were significantly higher than those observed with the fish diets without fish oil. To sum up, fish oil can be replaced by up to 25% with vegetable oils in diets for Seriola dumerili juveniles, but total fish oil substitution is not feasible because it causes poor survival. The inclusion of probiotics in the FO-0+ diet had no effects on the parameters measured. [ABSTRACT FROM AUTHOR]

Greater amberjack (Seriola dumerili) is an important commercial fish for its high growth rate and excellent flesh quality. However, its sensitivity to variations of water salinity poses challenges to the cage culture. In this study, the greater amberjack were reared in the optimum salinity (30 ppt, CK) and undesired regimes (10 and 40 ppt) for 72 hours. The molecular adaptive mechanisms to salinity stress were revealed by the comparative transcriptome analysis for the gills and kidneys. In gills, a total of 445 and 423 differentially expressed genes (DEGs) were identified in 10 and 40 ppt salinity stress groups, respectively. Those DEGs were involved in cartilage and skeletal development, ions transport, and immune response. The major ion secretion and osmoregulation transport proteins gene slc12a2/nkcc1 and cftr expression levels were significantly down-regulated at 10 ppt, but slightly activated at 40 ppt, compared with the control group. The expression changes in response to the Na+, K+ movement, and Cl- ion secretion reduced under the hypo-osmotic exposure and ion excretion boost upon hyper-salinity stress. Meanwhile, the cartilage and skeletal development were enhanced in the gills by hypo- or hyper-salinity stimuli, which is critical for maintaining gill structures and improving respiration and osmoregulation under salinity stress. In kidneys, 600 and 539 DEGs were identified in 10 and 40 ppt groups, respectively. Those DEGs were enriched in oxygen transport, pronephros development, regulation of growth, blood coagulation, ion transmembrane transport, and immune response. While the known renal Na+/Cl– co-transporter gene slc12a3/ncc expression level was significantly down-regulated at 10 ppt, the organic cation transporter 2 gene slc22a2, ammonium transmembrane transport gene rhd and rhag expression levels were overexpressed under the hyper-salinity condition at 40 ppt, contributing to the salts secretion and ammonium transport regulation, to combat the osmotic influx of salts following the drink of seawater and elevated ammonia production upon high salinity stress. These findings advance our knowledge of adaptative mechanisms to the salinity stress and provide theoretical guidance for the optimal breeding mode for the aquaculture of greater amberjack.

• Identification of putative miRNAs regulating molecular markers for follicular atresia in teleost fish. • Identification of miRNAs related to follicular atresia, apoptosis and cell death. • Novel and new miRNA with potential function related to dysfunctional gonad maturation. • Distinct miRNA profiles between different ovarian maturation stages. Gonad maturation is critical for the reproductive success of any organism, and in fish, captivity can significantly affect their reproductive performance, leading to maturation incompetence and spawning failure. The greater amberjack (Seriola dumerili), a fish species recently introduced to aquaculture fails to undergo oocyte maturation, ovulation, and spawning when reared in aquaculture facilities. Since confinement has been shown to influence gonad maturation and completion of the reproductive cycle, investigations into epigenetic mechanisms may shed light on the reasoning behind the reproductive dysfunctions of fish under captivity. Among the known important epigenetic regulators are small non-coding RNAs (sncRNAs), and in particular microRNAs (miRNAs). In this study, immature, maturing (late vitellogenesis), and spent ovaries of captive greater amberjack were collected, and the differential expression of miRNAs in the three different ovarian development stages was examined. Expression patterns of conserved and novel miRNAs were identified, and potential targets of highly differentially expressed miRNAs were detected. Additionally, read length distribution showed two prominent peaks in the three different ovarian maturation stages, corresponding to miRNAs and putative piwi-interacting RNAs (piRNAs), another type of ncRNAs with a germ-cell specific role. Furthermore, miRNA expression patterns and their putative target mRNAs are discussed, in relevance with the different ovarian maturation stages of captive greater amberjack. Overall, this study provides insights into the role of miRNAs in the reproductive dysfunctions observed in fish under captivity and highlights the importance of epigenetic mechanisms in understanding and managing the reproductive performance of economically important fish species. [ABSTRACT FROM AUTHOR]

The combined effect of ε-polylysine (PL) and modified atmosphere packaging (MAP; 60% CO2/40% N2) on the bacterial community of greater amberjack filets and their physicochemical properties was evaluated at 4°C. The total viable counts (TVC), psychrotrophic bacterial count, sensory index, texture analysis, and total volatile basic nitrogen (TVB-N) revealed that PL, MAP, and MAP + PL treatment delayed the deterioration of greater amberjack filets. These treatment groups also showed decreased accumulation of biogenic amines. High-throughput 16S rRNA gene sequencing results indicated that these treatments suppressed the growth of Pseudomonas in greater amberjack filets. Furthermore, the MAP + PL treatment group was observed to be more effective than the PL and MAP groups, extending the shelf life of greater amberjack filets by 6 days. This investigation showed that the combination of PL and MAP has the potential to retain the quality and extend the shelf life of greater amberjack.

Potato protein concentrate (PPC) is a potential fish meal (FM) substitute. We replaced FM in greater amberjack diets with low-temperature air-dried PPC (LT-PPC) and high-temperature rotary-dried PPC (HT-PPC) to investigate their effects on growth and feed utilization. Four experimental and one control diet was prepared. The control diet comprised FM, wherein the experimental diets were prepared by replacing 20 and 40% of FM in the control diet with LT-PPC (LP20 and LP40) or HT-PPC (LP20 and LP40). Following an 8-week growth trial, the final mean body weight, specific growth rate, and feed intake of HP40 diet-fed fish were significantly lower than those of control diet-fed fish (p < 0.05). However, these parameters in LT-PPC and HP20 diet-fed fish did not differ significantly from those of the control diet-fed fish (p > 0.05). In vitro relative protein digestibility did not differ between LT-PPC (91.1%) and HT-PPC (89.5%) (p > 0.05); however, the digestion speed of LT-PPC was higher (63.8%) than that of HT-PPC (46.8%) (p < 0.05). In conclusion, the findings demonstrate that LT-PPC and HT-PPC could be used to replace up to 40 and 20% of FM in greater amberjack diets, respectively, without compromising growth performance. [ABSTRACT FROM AUTHOR]

The complete genome sequence of Lactococcus garvieae KN22525, isolated in May 2022 from a diseased greater amberjack ( Seriola dumerili ) with a gross indication of body surface redness in Nomi Bay, Japan, was determined. Multilocus sequencing typing revealed that KN22525's genotype was sequence type ST95., Competing Interests: The authors declare no conflict of interest.

The environmental characteristics of the Taiwan Strait (TS) have been linked to variations in the abundance and distribution of greater amberjack (Seriola dumerili) populations. Greater amberjack is a commercially and ecologically valuable species in ecosystems, and its spatial distribution patterns are pivotal to fisheries management and conservation. However, the relationship between the catch rates of S. dumerili and the environmental changes and their impact on fish communities remains undetermined in the TS. The goal of this study was to determine the spatiotemporal distribution pattern of S. dumerili with environmental characteristics in the TS from south to north (20°N–29°N and 115°E–127°E), applying generalized additive models (GAMs) and spatiotemporal fisheries data from logbooks and voyage data recorders from Taiwanese fishing vessels (2014–2017) as well as satellite-derived remote sensing environmental data. We used the generalized linear model (GLM) and GAM to analyze the effect of environmental factors and catch rates. The predictive performance of the two statistical models was quantitatively assessed by using the root mean square difference. Results reveal that the GAM outperforms the GLM model in terms of the functional relationship of the GAM for generating a reliable predictive tool. The model selection process was based on the significance of model terms, increase in deviance explained, decrease in residual factor, and reduction in Akaike's information criterion. We then developed a species distribution model based on the best GAMs. The deviance explained indicated that sea surface temperature, linked to high catch rates, was the key factor influencing S. dumerili distributions, whereas mixed layer depth was the least relevant factor. The model predicted a relatively high S. dumerili catch rate in the northwestern region of the TS in summer, with the area extending to the East China Sea. The target species is strongly influenced by biophysical environmental conditions, and potential fishing areas are located throughout the waters of the TS. The findings of this study showed how S. dumerili populations respond to environmental variables and predict species distributions. Data on the habitat preferences and distribution patterns of S. dumerili are essential for understanding the environmental conditions of the TS, which can inform future priorities for conservation planning and management. [ABSTRACT FROM AUTHOR]

Female greater amberjack, Seriola dumerili reared in tanks have been inconsistent in entering or completing vitellogenesis. As a result, established spawning induction protocols employing gonadotropin-releasing hormone agonist (GnRHa) fail to induce oocyte maturation, ovulation and spawning. Males also exhibit reproductive dysfunctions resulting in low sperm production of relatively low quality. To ameliorate these problems, homologous Seriola dumerili single-chain recombinant Follicle stimulating hormone (sdrFsh) and Luteinizing hormone (sdrLh) were produced and administered to adult 4.8-year-old hatchery-produced (F1 generation) greater amberjack held in tanks, in order to enhance gametogenesis and increase reproductive performance (fecundity and fertilization success) upon spawning induction with GnRHa. Beginning at the onset of gametogenesis (27 April 2022), injections of sdrFsh and sdrLh were given for 6 consecutive weeks (a total of 7 treatments) in different combinations in males and females, and increasing doses. All fish treated with sdrFsh/Lh underwent complete gametogenesis, with females having oocytes in post-vitellogenesis and males producing releasable sperm at the time planned for the GnRHa spawning induction (6 June 2022). Furthermore, five of the six females initiated oocyte maturation prior to the GnRHa treatment, and at least one female also spawned spontaneously earlier (week 4). All but one untreated Control females did not complete vitellogenesis and exhibited follicular apoptosis/atresia, making them ineligible for GnRHa-induced spawning. Untreated Control males completed spermatogenesis and produced releasable sperm, but of somewhat lower spermatozoa density and significantly lower motility percentage and velocity compared to sdrFsh/Lh-treated males. GnRHa-induced spawning of the sdrFsh/Lh-treated fish enhanced mean daily relative fecundity and fertilization success, with embryo and larval survival >50%. These results are encouraging, and we expect that further optimization of dosage and administration timing can provide a reliable protocol for enhancing gametogenesis and promoting maturation in dysfunctional greater amberjack broodstocks maintained in aquaculture indoor facilities. • Untreated females did not complete vitellogenesis and underwent follicular atresia. • Seriola dumerili recombinant (sdr) Fsh and Lh promoted vitellogenesis and ovulation. • sdrFsh and sdrLh enhanced sperm motility and velocity. • Administration of GnRHa increased relative fecundity and fertilization. • sdrFsh and sdrLh may alleviate reproductive dysfunctions in greater amberjack. [ABSTRACT FROM AUTHOR]

This study sought to characterize the effect of density stress on greater amberjack (Seriola dumerili) survival to determine an optimal transport density. To achieve this, this experiment simulated the transport conditions of fish (body length: 4.09 ± 1.00 cm; weight: 0.9 ± 0.05 g) using closed oxygen transport at 5 different densities (D1 = 1.125 kg/m3, D2 = 2.25 kg/m3, D3 = 3.375 kg/m3, D4 = 4.5 kg/m3, and D5 = 6.75 kg/m3) for 8 hours, after which biochemical indicators, stress, metabolism, and antioxidant capacity were evaluated. After 8h, only the D1 and D3 groups exhibited survival rates above 90%. The pH of the water decreased with density, whereas the ammonia nitrogen and nitrite increased with density. Cortisol (COR) levels were not significantly different among all the groups, but tended to increase with increasing density. In this study, COR is a relatively stable index with the increase in density, but in D3 group, the change of COR will not cause the change of immune-related genes, so COR can inhibit the expression of immune genes within a certain density. The D3 density group exhibited the highest catalase (CAT) and glutathione peroxidase glutathione peroxidase (GSH‐PX) levels. In addition, the expression levels of immune related factor interleukin-1β (IL-1β), tumor necrosis factor (TNF-α), major histocompatibility complex (MHC-1) and nuclear factor kappa-B (NF-KB1) were the lowest in D3 density group. The density of fish during transportation significantly affects water quality, metabolism, and immunity. During transportation, assuming that the plastic bags are airtight to ensure aerobic conditions and that the transportation time is within 8 h, transport density should be maintained at approximately 3.375 kg/m3.

• Females reared in captivity lagged behind in reproductive development compared to the wild. • Multiple handling of the rearing cage at the DEVELOPING phase affected negatively reproductive development in both sexes. • Males exhibited a pronounced dysfunction when reared in captivity, even without any handling. We compared the endocrine status of the pituitary-gonad axis of wild and captive-reared greater amberjack (Seriola dumerili) during the reproductive cycle (April – July), reporting on the expression and release of the two gonadotropins for the first time in the Mediterranean Sea. Ovaries from wild females were characterized histologically as DEVELOPING in early May and SPAWNING capable in late May-July, the latter having a 3 to 4-fold higher gonadosomatic index (GSI). SPAWNING capable wild females exhibited an increase in pituitary follicle stimulating hormone (Fsh) content, plasma testosterone (T) and 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P), while almost a 10-fold increase was observed in pituitary luteinizing hormone (Lh) content. An increasing trend of plasma 17β-estradiol (E 2) was also recorded between the two reproductive stages in wild females. Captive-reared females sampled during the reproductive cycle exhibited two additional reproductive categories, with REGRESSED females having extensive follicular atresia and fish in the REGENERATING stage having only primary oocytes in their ovaries. Pituitary content of Fsh and Lh, fshb and lhb expression and plasma levels of Fsh and Lh remained unchanged among the four reproductive stages in captive females, in contrast with plasma E 2 and T that decreased in the REGENERATING stage, and 17,20β-P which increased after the DEVELOPING stage. In general, no significant hormonal differences were recorded between captive-reared and wild DEVELOPING females, in contrast to SPAWNING capable females, where pituitary Lh content, plasma Fsh and T were found to be lower in females in captivity. Overall, the captive females lagged behind in reproductive development compared to the wild ones and this was perhaps related to the multiple handling of the sea cages where all the sampled fish were maintained. Between wild males in the DEVELOPING and SPAWNING capable stages, pituitary Lh content, plasma T and 17,20β-P, and GSI exhibited 3 to 4-fold increases, while an increasing trend of pituitary Fsh content, lhb expression levels and plasma 11-ketotestosterone (11-KT) was also observed, and an opposite trend was observed in plasma Lh. Captive males were allocated to one more category, with REGRESSED individuals having no spermatogenic capacity. During the SPAWNING capable phase, almost all measured parameters were lower in captive males compared to wild ones. More importantly, captive males showed significant differences from their wild counterparts throughout the reproductive season, starting already from the DEVELOPING stage. Therefore, it appears that captivity already exerted negative effects in males prior to the onset of the study and the multiple handling of the cage where sampled fish were reared. Overall, the present study demonstrated that female greater amberjack do undergo full vitellogenesis in captivity, albeit with some dysfunctions that may be related to the husbandry of the experiment, while males, on the other hand, may be more seriously affected by captivity even before the onset of the study. [ABSTRACT FROM AUTHOR]

The present study was conducted to investigate the effects of dietary fish oil replacement with a mixture of vegetable oils and probiotic supplementation on plasma biochemical parameters, oxidative stress, and antioxidant ability of Seriola dumerili. Specimens with an initial weight of 175 g were used. Four feeds were formulated with 0% (FO-100), 75% (FO-25), and 100% (FO-0 and FO-0+ with the addition of Lactobacillus probiotics) substitution of fish oil with a mixture of linseed, sunflower, and palm oils. After 109 days, no significant differences were observed in the activity of antioxidant enzymes in the liver, foregut, and hindgut, only glucose-6-phosphate dehydrogenase activity in the liver was higher in the fish fed the FO-100 diet than in those fed the FO-0 diet. No significant differences were observed in the total, reduced, and oxidized glutathione and the oxidative stress index in the liver. In addition, lipid peroxidation in the liver and red muscle values were higher in the fish fed the FO-100 diet than in the fish fed the FO-0+ diet, however, the foregut of the fish fed the FO-100 diet presented lower values than that of the fish fed the FO replacement diet, with and without probiotics. There were significant differences in cholesterol levels in the FO-100 group; they were significantly higher than those observed with the fish diets without fish oil. To sum up, fish oil can be replaced by up to 25% with vegetable oils in diets for Seriola dumerili juveniles, but total fish oil substitution is not feasible because it causes poor survival. The inclusion of probiotics in the FO-0+ diet had no effects on the parameters measured.

Greater amberjack (Seriola dumerili) is an important fishery resource with a circumglobal distribution from tropical to temperate waters. Here, we investigated the spawning migration and habitat utilization of S. dumerili in the East China Sea (ECS). Archival tags were attached to 22 adult fish to examine their horizontal and vertical movements and estimate the spawning ground. S. dumerili were captured and released in the coastal waters of eastern Taiwan on November of 2016 and 2017. Information from seven pop‐up satellite archival tags and seven depth–temperature recorders was recovered. Almost all of the fish stayed in the Taiwanese exclusive economic zone. Most individuals moved from released site to the southern edge of the ECS and showed behavior associated with the topographic features in winter (November to December). These phenomena may be related to foraging and be driven by oceanographic features such as the seasonal monsoon and the Kuroshio. The fish then migrated to the south offshore area of Taiwan in January and February. During their southward migration, the fish experienced a slowly elevated water temperature regime (SETR), which is one of the environmental factors that induce final oocyte maturation. In the spawning season (February to April), tagged females exhibited continuous diel vertical movements (DVMs) after experiencing the SETR. These continuous DVMs were observed over a wide geographic range from north to south in the Kuroshio off eastern Taiwan. Our study demonstrated that the putative spawning ground of S. dumerili must extend further in a north–south direction than predicted in a previous study. [ABSTRACT FROM AUTHOR]

An 8‐week feeding trial was conducted to determine the dietary lysine requirement of greater amberjack, Seriola dumerili. Six experimental diets resulting from a practical basal formulation were produced to containing mainly plant ingredients (25% fish meal) were supplied with graded levels of crystalline L‐lysine‐HCl and the analysed lysine concentration in each diet was found to be 1.93 (basal diet; CL1.93), 2.01 (CL2.01), 2.11 (CL2.11), 2.15 (CL2.15), 2.20 (CL2.20) and 2.29 (CL2.29) g/100 g diet respectively. Seriola dumerili of 32.8 g ± 3.0 (mean ± SD) were randomly assigned to 18 experimental small cages, and each was stocked with 25 fish per cage in triplicates. The fish were hand‐fed with the experimental diets twice daily (09:00 h and 15:00 h) to apparent satiation, 6 days a week for 56 days. No significant differences were observed in weight gain (WG), daily growth index (DGI), specific growth rate (SGR) and protein efficiency ratio (PER) among the dietary groups. However, the pairwise linear regression of WG showed that the dietary lysine requirement of greater amberjack juvenile is 2.11% of the diet. The activity of catalase enzyme among the dietary treatments differed significantly (p <.05) in both the liver and intestine. Similar results were found for the heat shock proteins (HSP70 and HSP90) with a tissue‐specific response. Based on the results obtained, the dietary lysine requirements that can support maximum WG and PER of greater amberjack juvenile were found to be between 2.03% and 2.11% of the diet (4.55%–4.73% of dietary protein). [ABSTRACT FROM AUTHOR]

The histological process of gonadal differentiation, together with the endocrine changes of sex steroid hormones and some of their precursors, was studied in hatchery-produced greater amberjack Seriola dumerili from 101 until 408 days post-hatching (dph), with samplings conducted every 50 days. Histological processing showed that sex differentiation began at 101 dph with the formation of the ovarian cavity in females, while the presumptive males did not yet contain any germ cells in their gonad. At 150 dph, we observed the first germ cells in the developing testes. Sex differentiation in almost all sampled individuals was complete at 408 dph. No size dimorphism was observed between the sexes, and the sex ratio was 1:1, suggesting that there was no influence of early rearing in captivity on sex differentiation. Plasma concentrations of adrenosterone (Ad), androstenedione (Δ4), 11-ketotestosterone (11ΚΤ), testosterone (Τ), estradiol (Ε2), progesterone (P4) and 17,20β-dihydroxy-4-pregnen-3-one (17,20βP) were measured in males and females with the use of liquid chromatography tandem mass spectrometry (LC–MS/MS) to examine their role in the sex differentiation process. From the seven hormones, the only one that exhibited differences between the sexes was 11-KT and the plasma 11-KT concentration was found to be a useful indication of greater amberjack sex. Variations were observed in the mean values of Ad, Δ4, 11-KT, T, P4 and 17,20βP over time in one or both sexes, indicating their involvement in the sex differentiation process. [ABSTRACT FROM AUTHOR]

Optimizing the growth and survival of marine fish larvae, while reducing the cost of production, is important for the development of viable hatcheries on an industrial scale. This study was aimed to determine whether Artemia sp. use could be minimized while maintaining high growth and survival, and low skeleton anomalies occurrence in greater amberjack (Seriola dumerili) during the weaning period. Five co‐feeding protocols, named as 1% A, 25% A, 50% A, 75% A and 100% A, according to different initial Artemia sp. densities provided (0.02, 0.5, 1, 1.5 and 2 Artemia sp. ml−1 day−1, respectively) were tested from 32 to 48 days post‐hatching (dph). Growth of larvae fed with protocols 1% A, 25% A and 50% A were significantly higher than larvae fed with protocols 75% A and 100% A. Survival increased as the effect of Artemia sp. increased. The incidence of total skeletal severe anomalies was high in larvae fed protocols 1% A and 25% A. Besides, the expression of growth and stress‐related genes were higher at 40 dph and then decreased significantly at 48 dph in all the co‐feeding protocols. The results obtained from this study suggest that the amount of Artemia sp. utilized can be significantly reduced during the weaning phase for this species. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the efficacy of dietary praziquantel (PZQ), a promising fish anthelminthic, against Zeuxapta seriolae, a lethal ectoparasite of greater amberjack (Seriola dumerili Risso) farmed in the Mediterranean and elsewhere. The trial was carried out in small cages (3 m3) in situ, harbouring fish (125 ± 14 g) naturally infected with Z. seriolae, at 25 ± 1 °C water temperature. Praziquantel-medicated diet (150 mg PZQ/kg fish) was delivered for three days against a control group. Measurement of both adults and oncomiracidia of Z. seriolae in sampled gill arches revealed significant differences between the tested groups (PZQ: 19.3 ± 9.8 vs. Control: 3.8 ± 6.3). Considering an estimated efficacy of 80.4% in the medicated fish, the present study indicates that oral PZQ treatments can confront Z. seriolae infections considerably in farmed greater amberjack and, perhaps, replace the commonly used hydrogen peroxidase baths. [ABSTRACT FROM AUTHOR]

• No sexual size dimorphism was observed in up to 5-year-old greater amberjack. • Puberty occurred in 3-year-old hatchery-produced male greater amberjack. • Puberty occurred in 5-year-old hatchery-produced female greater amberjack. • Gonadal size was significantly smaller than mature, reproductively active fish in the wild. • Spawning induction with GnRHa was not effective, suggesting a dysfunction in females. We evaluated the onset of puberty of first-generation (F1) hatchery-produced greater amberjack (Seriola dumerili) reared in sea cages for 5 years. Fish were sampled every year in June, at the expected peak of the spawning period in the Mediterranean Sea. No sexual dimorphism in body weight was observed in the study. The ovaries of 1 and 2-year-old (yo) females consisted of primary oocytes only, while at the age of 3-yo early vitellogenic (Vg) oocytes were also identified, but with extensive follicular atresia. At the age of 4-yo, late Vg oocytes were observed, but again extensive follicular atresia characterized the ovaries of 50 % of females. At the age of 5-yo, follicular atresia of Vg oocytes was very limited. In males, gametogenesis was evident already in 1- and 2-yo fish, and 100 % of sampled 3-yo males produced collectable viable sperm. Plasma testosterone (T), 17β-estradiol (E2), and 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) remained similar in 3 – 5-yo females, with T and E2 levels being highest in females in advanced vitellogenesis or with significant follicular atresia, compared to immature females. In males, plasma T declined over the years, while 11-ketotestosterone (11-KT) and 17,20β-P were highest in 4 and 5-yo males, with spermatozoa motility characteristics being improved from the 4th year onwards. The administration of GnRHa implants to 5-yo fish induced only two spawns, albeit no fertilized eggs were obtained. The results indicate that hatchery-produced greater amberjack males mature well and within the same age observed in the wild, however with smaller gonad size. On the contrary, females mature later than in the wild, also with a smaller gonad size. Spawning in response to GnRHa treatment was not effective, suggesting that Mediterranean hatchery-produced broodstocks may be dysfunctional, and further research is needed to document any improvement as the fish get older, or to determine if the results may be related to the specific stock of fish. [ABSTRACT FROM AUTHOR]

The environmental characteristics of the Taiwan Strait (TS) have been linked to variations in the abundance and distribution of greater amberjack (Seriola dumerili) populations. Greater amberjack is a commercially and ecologically valuable species in ecosystems, and its spatial distribution patterns are pivotal to fisheries management and conservation. However, the relationship between the catch rates of S. dumerili and the environmental changes and their impact on fish communities remains undetermined in the TS. The goal of this study was to determine the spatiotemporal distribution pattern of S. dumerili with environmental characteristics in the TS from south to north (20°N–29°N and 115°E–127°E), applying generalized additive models (GAMs) and spatiotemporal fisheries data from logbooks and voyage data recorders from Taiwanese fishing vessels (2014–2017) as well as satellite-derived remote sensing environmental data. We used the generalized linear model (GLM) and GAM to analyze the effect of environmental factors and catch rates. The predictive performance of the two statistical models was quantitatively assessed by using the root mean square difference. Results reveal that the GAM outperforms the GLM model in terms of the functional relationship of the GAM for generating a reliable predictive tool. The model selection process was based on the significance of model terms, increase in deviance explained, decrease in residual factor, and reduction in Akaike’s information criterion. We then developed a species distribution model based on the best GAMs. The deviance explained indicated that sea surface temperature, linked to high catch rates, was the key factor influencing S. dumerili distributions, whereas mixed layer depth was the least relevant factor. The model predicted a relatively high S. dumerili catch rate in the northwestern region of the TS in summer, with the area extending to the East China Sea. The target species is strongly influenced by biophysical environmental conditions, and potential fishing areas are located throughout the waters of the TS. The findings of this study showed how S. dumerili populations respond to environmental variables and predict species distributions. Data on the habitat preferences and distribution patterns of S. dumerili are essential for understanding the environmental conditions of the TS, which can inform future priorities for conservation planning and management.

Greater amberjack (Seriola dumerili) is a very promising candidate for the diversification of the Mediterranean aquaculture due to its high demand, excellent flesh quality and high market prices. Its production expansion has, however, failed so far, due to several bottlenecks mainly related to pathology. This review addresses the major pathogens, which hinder the culture of greater amberjack with special focus in the Mediterranean region, and highlights possible treatment solutions. Among the important recorded pathogens of caged greater amberjack in the Mediterranean, the gill monogenean Zeuxapta seriolae seems to be the most problematic, causing significant losses. While formalin immersions are inefficient to combat this parasite, baths with hydrogen peroxide are extremely effective and praziquantel administration could be a more practical in‐feed treatment solution. The digenean blood flukes, Paradeontacylix spp., also account for important losses in greater amberjack farms in the same region. Dietary administration of praziquantel constitutes an effective therapeutic measure against those infections. Vibrio harveyi is also a bacterial pathogen severely affecting fish maintained both in land‐based facilities and in cages, whereas Epitheliocystis is a disease reported frequently that can be fatal when it occurs at early stages. Skin flukes such as Benedenia seriolae and Neobenedenia girellae as well as other parasites bacteria and viruses mentioned herein, which have caused substantial losses in Asian enterprises, but have not been identified yet in greater amberjack farmed in the Mediterranean, should be considered as potential threats. [ABSTRACT FROM AUTHOR]

Jaw malformations are a serious problem in fingerlings of the greater amberjack, Seriola dumerili. To establish a countermeasure against these malformations, we conducted a larval behavioural test to identify their root cause, and we investigated the ability of low‐brightness rearing tank walls to control their occurrence. Larval distribution was examined in a horizontally illuminated rectangular transparent aquarium (20 cm × 100 cm × 25 cm), and their distribution was biased towards the light source after this lighting was provided from 3 to 13 days post hatching (dph), indicating positive phototaxis; this response disappeared on 22 dph (there are no data between 13 and 22 dph). Larvae were observed to swim phototactically towards the light source and repeatedly collided with the tank wall (walling behaviour). To investigate the ability of wall brightness to control the incidence of jaw malformations, we compared their incidence in a rearing trial with different Munsell colour values for the tank walls: 2.11 (black), 5.85 (grey) and 9.52 (white). The incidence rate of jaw malformations at 25 dph was significantly lower in the tanks with lower‐brightness walls, that is, 5.8%, 22.5% and 26.8% for black, grey and white respectively. Larval walling behaviour was most intense for white, followed in order by grey and black. These results indicate that positive phototaxis elicits larval walling behaviour, causing jaw malformations, and that low‐brightness tank walls control this process. [ABSTRACT FROM AUTHOR]

Potato protein concentrate (PPC) is a promising candidate as a fish meal (FM) substitute because it has high protein and essential amino acid content. In the present study, we replaced FM in greater amberjack diets with PPC to investigate the effect on growth and feed utilization. Four isonitrogenous, isolipidic and isocaloric experimental diets were prepared by substituting 0, 20, 40 and 60% of FM protein with PPC (Control, P20, P40 and P60 respectively). The in vitro protein digestibility of protein in PPC was 88.8%, relative to 100% protein in the FM. The in vitro protein digestibility of protein in the experimental diets also decreased with increasing PPC and was lowest at 84.2% in P60. After the 7‐week feeding trial, final body weight, weight gain and thermal growth coefficient tended to decrease with increasing PPC and were significantly lower in P60 than in the control (p <.05). Further, fish fed with diets P40 and P60 showed significantly lower feed conversion and protein efficiency ratios than the control group (p <.05). In conclusion, the results suggest that PPC can replace up to 20% of FM in the diet of greater amberjack without compromising the growth performance or feed efficiency. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the efficacy of dietary praziquantel (PZQ), a promising fish anthelminthic, against Zeuxapta seriolae, a lethal ectoparasite of greater amberjack (Seriola dumerili Risso) farmed in the Mediterranean and elsewhere. The trial was carried out in small cages (3 m3) in situ, harbouring fish (125 ± 14 g) naturally infected with Z. seriolae, at 25 ± 1 °C water temperature. Praziquantel-medicated diet (150 mg PZQ/kg fish) was delivered for three days against a control group. Measurement of both adults and oncomiracidia of Z. seriolae in sampled gill arches revealed significant differences between the tested groups (PZQ: 19.3 ± 9.8 vs. Control: 3.8 ± 6.3). Considering an estimated efficacy of 80.4% in the medicated fish, the present study indicates that oral PZQ treatments can confront Z. seriolae infections considerably in farmed greater amberjack and, perhaps, replace the commonly used hydrogen peroxidase baths.

The article provides description of spontaneous granulomatous aerocystitis by Phoma herbarum in a wild greater amberjack. Topics discussed include information on the Phoma herbarum Westend as a saprophytic fungus mostly recognized as a plant pathogen; discussions on the pathogen causing a chronic progressive and lethal visceral mycosis; and the infections by P. hebrarum in fish characterized by lethargy and erratic swimming.

• GnRHa implants were more effective than injections in inducing spawning. • High fecundity and good egg quality was produced by both hormonal treatments. • GnRHa implants also supported vitellogenesis. The greater amberjack (Seriola dumerili) is one of the most promising finfish species for aquaculture, due to its cosmopolitan distribution and acceptability, high growth rates and large size. However, lack of reproduction control has been one of the main bottlenecks for its commercialization. The study examined two endocrine methods for the induction of oocyte maturation/ovulation and spawning, which are based on the induction of endogenous Luteinizing Hormone (LH) release from the pituitary, through the use of Gonadotropin Releasing Hormone agonist (GnRHa) either in the form of sustained-release delivery systems (implants) or injections (acute release). The stock (n = 28) consisted of wild fish captured in 2011 and each GnRHa administration method was conducted in two replicates, with 6 and 8 fish per tank, respectively, at a 1:1 sex ratio. Fish were given a GnRHa injection once a week (three administrations), or a GnRHa implant every 2 weeks (two administrations). Mean daily relative fecundity was significantly higher (t 1.3 = −5.24, P = 0.012) in the implanted fish (15,170 ± 2,738 eggs kg−1 female day−1) compared to the injected fish (6,119 ± 2,790 eggs kg−1 female day−1). Total relative fecundity was also significantly higher (t 1.3 = −9.93, P = 0.003) in the implanted fish (102,402 ± 20,337 eggs kg−1 female) compared to the injected ones (26,517 ± 9,938 eggs kg−1 female), but there were no differences in the quality of eggs in terms of fertilization, 24-h embryo survival, hatching and 5-d larval survival. The number of females with fully vitellogenic oocytes eligible for induction of spawning decreased from the initial to the final sampling, from 7 to 6 females for the GnRHa implant treatment and from 7 to 3 females for the GnRHa injection treatment. In addition to apparently promoting the proper endocrine changes leading to multiple cycles of oocyte maturation, ovulation and spawning, and thus producing larger numbers of eggs; the use of GnRHa implants may be more appropriate in greater amberjack than multiple injections because (a) it also stimulates vitellogenesis and (b) involves less handling of the fish. [ABSTRACT FROM AUTHOR]

Greater amberjack is a popular aquaculture species, but its nutritional requirements remain poorly understood. The present study aimed to identify feeding stimulants for greater amberjack from a synthetic extract (SE) of jack mackerel muscle. A bioassay involving a semi-purified casein diet supplemented with feeding stimulant candidates was performed. The SE was composed of amino acids, nucleotides, and other compounds. Relative feed intake (RFI) in the SE treatment was similar to that in the natural extract treatment. The all-nucleotide treatment [inosine monophosphate (IMP), inosine, adenosine monophosphate (AMP), adenosine diphosphate (ADP), and adenosine triphosphate (ATP)] showed a comparable RFI to that of the SE treatment. Furthermore, the RFI did not decrease when amino acids and other compounds were omitted from the SE, but significantly decreased when nucleotides were removed from the SE. Exclusion of inosine, AMP, ADP, and ATP had no effect on the RFI. Among nucleotides, only IMP supplementation showed a comparable RFI to that in the SE and all-nucleotide treatments. Even without IMP, RFI increased with increasing concentrations of nucleotides and their combined application (especially inosine + ADP). These results indicate that the feeding stimulatory effect of jack mackerel muscle extract on greater amberjack depended mainly on IMP. [ABSTRACT FROM AUTHOR]

Abstract Elevated mortality during early stages and high occurrence of skeletal anomalies are major concerns in Greater amberjack (Seriola dumerili) juvenile's production. Identification of nutritional requirements during live prey feeding stages, particularly those related with n-3 HUFA would help to formulate specific diets for this species improving larval survival and reducing skeleton anomalies. In this study S. dumerili larvae were reared from 17 to 35 days post hatching (dph). Larvae were fed Artemia sp. containing five different n-3 HUFA levels from 2.7 to 20.5% TFA. Growth, survival, skeletal anomalies occurrence and larval biochemical composition were determined. Best growth, final survival and survival after air stress test were achieved in the range of dietary n-3 HUFA concentrations, between 5 and 20%TFA. The lowest occurrence of skeletal anomalies was achieved in fish fed 12% n-3 HUFA content in Artemia , and the occurrence of cranial anomalies was correlated to increased dietary n-3 HUFA levels. Besides, whole body larval fatty acid profiles showed a positive correlation with dietary n-3 HUFA. Based on the overall results the recommended n-3 HUFA dietary level during Artemia feeding for larval S. dumerili was suggested between 12 and 17%TFA. Highlights • Increased Artemia n-3 HUFA content over 5% using rich DHA emulsions improves larval growth and survival. • Maximum growth and survival after stress test were achieved with dietary n-3 HUFA in a range of 5–20%TFA. • Based on growth and survival results n-3 HUFA dietary level during Artemia feeding stage from 12–17%TFA is reommended. • A linear correlation between increase in dietary DHA and increase in cranial anomalies was identified. [ABSTRACT FROM AUTHOR]

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

A key aspect of the sustainable management of commercially important coastal pelagic fish stocks is the identification of the spatio-temporal dynamics of aggregation behaviour. An exemplary case species is the greater amberjack, Seriola dumerili. This top-predator is an important commercial resource exploited by recreational and commercial fisheries worldwide. Greater amberjack is known to form aggregations during important stages of its life-history, making it highly vulnerable to overfishing with potential consequences to its conservation. To improve the limited knowledge on the spatio-temporal aggregation areas of this important resource, this study combined fishing fleet dynamics (Vessel Monitoring System records), environmental and landing data into a species distribution model to predict such vulnerable events in space and time around the Balearic Islands. Our results indicated that S. dumerili aggregations were generally encountered in coastal areas at shallow depths (<100 m), low salinities, low chlorophyll concentrations, and weak meridional and zonal current velocities around the Balearic Islands. The preference for these environmental variables and processes is probably related to searching for an optimal scenario that maximises the success of larval development and survival of its offspring. Moreover, the distribution model suggested the possibility of a longer spawning period than previously predicted. This research demonstrates the use of a perceptive statistical tool that efficiently combines fisheries-dependent data and environmental data to highlight essential factors that influence the aggregation behaviour of S. dumerili and thus provides essential information for the conservation and sustainable exploitation not only of the greater amberjack, but also for other gregarious species highly-vulnerable to fishing by their aggregation behaviour. • Fleet dynamics (VMS), landing, and environmental data combined in a distribution model. • Greater amberjack could have a longer spawning period than previously predicted. • Aggregations of this species mainly occur at shallow depths (<100 m). • Identification of aggregation areas is key for sustainable management. [ABSTRACT FROM AUTHOR]

The present study evaluated the effects of wash-out on the fatty acid (FA) composition in the muscles of Mediterranean yellowtail. After 109 days during which fish were fed either a fish oil (FO)-based diet (FO 100) or a diet (FO 0) in which FO was completely substituted by vegetable oils, all fish were subjected to a wash-out with FO 100 diet for 90 days. The FA profile of muscles in fish fed FO 0 diet at the beginning of the experiment reflected that of dietary vegetable oils, rich in linoleic acid (LA), and α-linolenic acid (ALA), and was deficient in AA (arachidonic acid), EPA (eicosapentaenoic acid), and DHA (docosahexaenoic acid). No essential FA were fully restored in fish previously fed FO 0 diet on 45th or 90th day of wash-out. At the end of wash-out, the FA composition showed that AA, EPA, and DHA in the white muscles increased by +33%, +16%, and +43% (p < 0.001), respectively. Similarly, AA and DHA in the red muscles increased by +33% and +41% respectively, while EPA remained similar to fish fed FO 0 diet exclusively. Therefore, a 90-d wash-out can partially improve the FA profile in muscles of Mediterranean yellowtail previously fed vegetable oil-based diets.

The study aimed to evaluate how replacing different proportions of fish oil (FO) with vegetable oils (VO) in the diet of Mediterranean yellowtail, Seriola dumerili (Risso, 1810), affects the fatty acids (FA) signature, i.e.; overall FA profile, in different tissues. A total of 225 Mediterranean yellowtail juveniles (initial live weight: 176 ± 3.62 g) were fed for 109 days with one of three diets: A control diet (FO 100), with FO as the only lipid source, or diets with 75% and 100% of FO replaced with a VO mixture. At the end of the feeding trial, the brains, muscles, livers, and visceral fat were sampled in four fish per tank (12 per treatment), and their fat were extracted and used for FA analysis. The FA signatures of red and white muscle, liver, and visceral fat tissues changed when the dietary FA source changed, whereas FA signatures in the brain were rather robust to such dietary changes. These new insights might help evaluate whether key physiological functions are preserved when fish are fed diets with low FO levels, as well as define the dietary FA requirements of Mediterranean yellowtail to improve the sustainability of the production and welfare of the fish.

The greater amberjack (Seriola dumerili) is a commercially and recreationally important marine fish species in the southeastern United States, where it has been historically managed as two non-mixing stocks (Gulf of Mexico and Atlantic). Mark-recapture studies and analysis of mitochondrial DNA have suggested the two stocks are demographically independent; however, little is currently known about when and where spawning occurs in Gulf of Mexico amberjack, and whether stock mixture occurs on breeding grounds. The primary objective of this study was to quantify stock mixture among breeding populations of amberjack collected from the Atlantic and Gulf of Mexico. Genetic data based on 11 loci identified very low, though statistically significant differentiation among Gulf of Mexico samples (GST = 0.007, GST′ = 0.009; all P = 0.001) and between reproductive adults collected from two spawning areas (GST = 0.007, GST′ = 0.014; all P = 0.001). Naïve Bayesian mixture analysis supported a single genetic cluster [p(S|data) = 0.734] whereas trained clustering (using Atlantic and Gulf spawning fish) gave the highest support to a two-cluster model (p(S|data) = 1.0). Our results support the argument that the genetic structuring of greater amberjack is more complex than the previously assumed two, non-mixing stock model. Although our data provide evidence of limited population structure, we argue in favour of non-panmixia among reproductive fish collected from the Gulf of Mexico and Florida Keys. [ABSTRACT FROM AUTHOR]

Predicting antigens that would be protective is crucial for the development of recombinant vaccine using genome based vaccine development, also known as reverse vaccinology. High-throughput antigen screening is effective for identifying vaccine target genes, particularly for pathogens for which minimal antigenicity data exist. Using red sea bream iridovirus (RSIV) as a research model, we developed enzyme - linked immune sorbent assay (ELISA) based RSIV-derived 72 recombinant antigen array to profile antiviral antibody responses in convalescent Japanese amberjack ( Seriola quinqueradiata ). Two and three genes for which the products were unrecognized and recognized, respectively, by antibodies in convalescent serum were selected for recombinant vaccine preparation, and the protective effect was examined in infection tests using Japanese amberjack and greater amberjack ( S. dumerili ). No protection was provided by vaccines prepared from gene products unrecognized by convalescent serum antibodies. By contrast, two vaccines prepared from gene products recognized by serum antibodies induced protective immunity in both fish species. These results indicate that ELISA array screening is effective for identifying antigens that induce protective immune responses. As this method does not require culturing of pathogens, it is also suitable for identifying protective antigens to un-culturable etiologic agents. [ABSTRACT FROM AUTHOR]

Abstract: In order to successfully diversify Mediterranean aquaculture, it is necessary to determine optimum culture conditions of potential candidate species such as greater amberjack (Seriola dumerili). Among culture conditions, rearing temperature is a key factor for achieving optimum growth and maintaining fish welfare. However, little is known about the optimum culture conditions of greater amberjack (Seriola dumerili). Thus, the aim of this study was to determine the effect of three different rearing temperatures (17, 22 and 26°C) during 120 days on growth performance, body morphometry, biochemical composition, gut transit and liver morphology of greater amberjack (Seriola dumerili) juveniles. After 120 days of rearing, fish raised at 26°C showed higher (p < .05) body weight and specific growth rate than fish held at lower temperatures, as well as improved feed utilization, protein efficiency and nutrient retention percentages. Fish stomach emptying was faster (p < .05) in fish raised at 26°C than in fish held at 22°C and 17°C. Similar results were obtained for gut transit time, being gut emptying faster (p < .05) in fish reared at 26°C than in fish cultured at lower temperatures. Rearing temperature also induced changes in fish morphology which resulted in a higher (p < .05) caudal propulsion efficiency index for fish reared at 26°C. Based on these results, we conclude that greater amberjack fingerlings perform better at 26°C than at 22°C or 17°C. [ABSTRACT FROM AUTHOR]

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

The greater amberjack Seriola dumerili is an excellent candidate for the Mediterranean aquaculture, due to its large body size and high growth rate, as well as its high flesh quality and commercial value worldwide. For its successful incorporation in the aquaculture industry, an in-depth understanding of the reproductive function of the species under rearing conditions is necessary, since completion of oogenesis in captivity is currently a bottleneck for the commercial production of the species. Liver and ovary samples from wild and captive-reared greater amberjack females were collected at three different phases of the reproductive cycle: early gametogenesis (EARLY, late April-early May), advanced gametogenesis (ADVANCED, late May-early June) and spawning (SPAWNING, late June-July). The cDNAs of three vitellogenins (VtgA, VtgB and VtgC) were partially sequenced and a qRT-PCR for their expression was used to compare ovarian maturity stage and liver vitellogenin transcript levels between wild and captive-reared individuals. An extensive atresia of late vitellogenic follicles, which prevented any further oocyte development and spawning was observed in captive-reared individuals during the ADVANCED phase. The expression levels of the three vitellogenins, as well as the amount of yolk globules in vitellogenic oocytes, did not differ significantly between captive-reared and wild females, indicating that the observed oogenesis impairment in greater amberjack reared in captivity was not related to an insufficient liver synthesis or a reduced oocyte uptake of vitellogenin. [ABSTRACT FROM AUTHOR]

Fish and fish-based products are easily perishable foods due to different factors, including fragile organization, abundant endo-enzymes, psychrophilic bacteria, and impact of pre-harvest operations, that contribute to reducing its value. Therefore, a timely effective method for fish freshness and shelf-life evaluation is important. In this context, this study aimed to develop a sensory scheme based on the Quality Index Method (QIM) (sensory table and point system) for freshness monitorization and shelf-life prediction for Seriola dumerili from aquaculture in Madeira Island. Evaluation of appearance, texture, eyes, and gills was performed during 20 days of storage on ice (0 ± 1 °C). The shelf-life prediction was supported by the analysis of microorganisms (total viable colonies, TVC, counts), texture (Torrymeter), and production of trimethylamine (TMA), evaluated by HS-SPME−GC−MS and validated according to Association of Official Analytical Chemists AOAC guidelines. The result is a QIM scheme with 25 demerit points, where zero indicates total freshness. From the integration of sensory analysis, microbial growth at the time of rejection (TVC, 108 cfu/cm2 and H2S producers, 107 cfu/cm2), texture (Torrymeter value < 8), and TMA analyses (>12.5 mg/100 g), shelf-life was estimated as 12 days (±0.5 days). The obtained results show the high-throughput potential of the developed method for fish freshness assessment and shelf-life prediction. This QIM scheme is a secure way to measure quality and provide users with a reliable standardized fish freshness measure.

For farmers of new fish species, market adoption is needed in order to grow a viable business. Farmers may try to sell the new species in their firms’ domestic markets, but they might also look at other markets. However, as markets are becoming more global and competitors more international, considering internationalization may be a necessity rather than a choice. Using diffusion modelling, and based on results of an online supermarket experiment, the innovation and imitation parameters are estimated and diffusion curves for five countries predicted in an attempt to determine the best lead market for introducing fillets of farmed greater amberjack (Seriola dumerili). The production capacity consequences of implementing different internationalization strategies (i.e. “sprinkler„ and “waterfall„) were also explored. A waterfall strategy refers to the sequential introduction of a product in different markets, whereas the sprinkler strategy concerns the simultaneous introduction of a product in multiple international markets. Since a sprinkler approach requires many resources and the ability to quickly ramp up production capacity, a waterfall approach appears more suitable for farmers of greater amberjack. Italy and Spain appear to be the best lead markets for greater amberjack farmers to enter first.

The greater amberjack, Seriola dumerili (Risso, 1810), is a promising candidate for the diversification of European aquaculture production, but inconsistent reproduction in captivity prevents commercial production. Recent studies showed that greater amberjack confined in sea cages exhibited scarce gonad development and early interruption of gametogenic activity during the reproductive season. The aim of the present study was to improve our understanding of the observed impairment of spermatogenesis. Adult wild and captive-reared males were sampled during 3 different phases of the reproductive cycle: early gametogenesis (EARLY; late April to early May), advanced gametogenesis (ADVANCED; late May to early June), and spawning (SPAWNING; late June to July). Spermatogonial stem cells and proliferating germ cells were identi- fied through the immunohistochemical localization of Pou5f1 and proliferating cell nuclear antigen, respectively. Apoptotic germ cells were identified throughout the terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate nick end labeling method. Sperm quality of captive-reared fish was evaluated using computer-assisted sperm analysis. Captive-reared males exhibited seminiferous lobules of a smaller diameter, a precocious and progressive decrease of spermatogonial mitosis, and a high level of apoptosis at the beginning of the reproductive season, concomitant with a many-fold higher 17β-estradiol plasma concentration. The motile spermatozoa percentage of captive greater amberjack was lower than in other teleosts, and a drastic decrease of spermatozoa motility duration, velocity, and ATP content occurred along the reproductive season. An abnormal increase of sperm concentration as well as an increase of dead spermatozoa occurred during the SPAWNING phase, probably because of lack of sperm hydration and ejaculation and consequent sperm ageing. The present study demonstrates the extreme susceptibility of greater amberjack to rearing stress and underscores the need for improvement of the rearing and handling procedures to ameliorate gametogenesis dysfunctions in commercial aquaculture production. [ABSTRACT FROM AUTHOR]

A baited videographic survey at Pitcairn Island has significantly extended the known range for two reef-fish species: blue-lined triggerfish Xanthichthys caeruleolineatus and greater amberjack Seriola dumerili, with an additional minor extension noted for giant trevally Caranx ignobilis. This highlights the importance of further research in this remote, poorly studied island group and provides evidence supplementing the understanding of oceanographic patterns in the South Pacific. [ABSTRACT FROM AUTHOR]