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Understanding the spatial ecology of commercially exploited species is vital for their conservation. Atlantic bluefin tuna (Thunnus thynnus, ABT) are increasingly observed in northeast Atlantic waters, yet knowledge of these individuals' spatial ecology remains limited. We investigate the horizontal and vertical habitat use of ABT (158 to 241 cm curved fork length; CFL) tracked from waters off the United Kingdom (UK) using pop-up satellite archival tags (n = 63). Analyses reveal distinctive movements from the UK to the Bay of Biscay (BoB) and Central North Atlantic between September and December, and size-specific habitat preferences in May and July—all ABT < 175 cm CFL inhabiting the BoB and 73% of ABT ≥ 175 the Mediterranean Sea. All ABT tracked for more than 300 days (n = 25) returned to waters off the UK the following year, where most stayed (n = 22; 88%) and three continuing north with deployments ending off northwest Ireland. ABT mostly occupied waters between 0 and 20 m (daytime 49 ± 6% of time; nighttime 71 ± 6%). Vertical habitat use was coupled with illumination, mean depth occupied, maximum depth reached, and vertical movement rate increased during the daytime and when moons were brightest. These data provide valuable insights into the spatial ecology of ABT reoccupying northerly foraging areas following decades of absence. [ABSTRACT FROM AUTHOR]

Thunnus thynnus (Atlantic Bluefin Tuna) is an opportunistic generalist predator in the pelagic zone of the Atlantic Ocean. In the northwest Atlantic Ocean, Atlantic Bluefin Tuna diets are primarily based on small pelagic prey. Seabirds often prey on the same pelagic forage fish as tuna, leading to an overlap in the timing and location of both seabird and Atlantic Bluefin Tuna foraging activity and the potential for tuna–seabird interactions. Here, we present the first documented evidence of Atlantic Bluefin Tuna consuming a seabird in the Northwest Atlantic Ocean. This is the second report of Atlantic Bluefin Tuna consuming a seabird in the entire species' range. The evidence for this interaction comes from the stomach contents of a commercially harvested Atlantic Bluefin Tuna caught ∼1.6 km offshore of Newfoundland in October 2022. The unknown bird in the Atlantic Bluefin Tuna stomach was identified through DNA metabarcoding as Fratercula arctica (Atlantic Puffin), a diving seabird for which an overlap with pelagic predatory fish is credible. While rarely observed, it is important to identify such interactions between seabirds and predatory fish to gain a more complete understanding of food-web interactions in marine pelagic ecosystems. [ABSTRACT FROM AUTHOR]

In this study, to investigate the quality of wild and farmed frozen southern bluefin tuna, physicochemical analyses and sensory evaluations were conducted. Principal component analysis was then performed using the results obtained to examine the correlation between the bluefin tuna's taste characteristics and physicochemical properties. The sensory evaluation suggested differences in texture and acidity between wild and farmed fish, whereas the principal component analysis indicated differences in fatty acid and amino acid composition. Wild fish contained higher levels of docosahexaenoic acid and monounsaturated fatty acids, while farmed fish had higher levels of saturated fatty acids. Regarding free amino acids and dipeptides, wild fish had higher levels of anserine and alanine, whereas farmed fish showed higher levels of glutamine and histidine, and acidity was observed in farmed fish. Furthermore, based on the results of the principal component analysis, it was inferred that the content of inosinic acid, which is considered an umami component in fish, may have a low impact on palatability. These factors were suggested to influence the differences between wild and farmed tuna. [ABSTRACT FROM AUTHOR]

While bionic designs show significant promise in improving the hydraulic performance of fluid machinery, achieving these benefits in engineering applications requires meticulous design and optimization. Inspired by the biomimetic features of humpback whale and Atlantic bluefin tuna, we proposed a bio-inspired design approach to collaboratively optimize both the impeller and diffuser of slanted axial-flow pumps, incorporating leading-edge (LE) tubercles and trailing-edge (TE) serrations. To improve the overall hydraulic performance, several geometric design variables of LE tubercles and TE serrations were considered using a surrogate model for multi-objective optimization. In contrast with the baseline case without bionic design, LE tubercles and TE serrations significantly improved the hydraulic performance under overload conditions, increasing the head and efficiency by up to 7.59% and 3.47%, respectively. In particular, we found that the wavy shape of the LE tubercles promoted a more gradual pressure distribution around the impeller, reducing the formation of low-pressure regions near the suction side that lead to cavitation and decreasing the cavitation bubble volume by up to 19.40%. TE serrations were shown to minimize flow separations and vortex shedding, thereby stabilizing vortex patterns and reducing transverse flow between the serrations. Optimizing the TE serrations resulted in a 16.38% decrease in discharge passage loss compared to the baseline. Extending the TE serration section helped to reduce flow deviation in the outlet passage, decreasing the deviation coefficient by up to 17.46% under rated condition. An experimental comparison validated the advantage of the bio-inspired design approach. [ABSTRACT FROM AUTHOR]

Abstract This study elucidated the role of DHA-modulated genes in the development and growth of Atlantic bluefin tuna (Thunnus thynnus) larvae ingesting increasing levels of DHA in their rotifer prey. The effect of feeding low, medium, and high rotifer (Brachionus rotundiformis) DHA levels (2.0, 3.6 and 10.9 mg DHA g−1 DW, respectively) was tested on 2–15 days post hatching (dph) bluefin tuna larvae. Larval DHA content markedly (P

Tuna are economically important as food resources in food markets. However, because tuna is often processed into steaks or fillets, the meat can be difficult to identify through morphological features. For effective fishery management and to protect the rights of consumers, it is necessary to develop a molecular method to accurately identify the species used in tuna products. Herein, we discovered five single-nucleotide polymorphism (SNP) sites via 2b-RAD sequencing and developed five SNP-based real-time polymerase chain reaction assays for the rapid identification of five highly priced tuna species. Three species-specific TaqMan systems were designed to identify albacore tuna (Thunnus alalunga), bigeye tuna (T. obesus), and southern bluefin tuna (T. maccoyii) and two cycling systems were designed to identify yellowfin tuna (T. albacares) and Atlantic bluefin tuna (T. thynnus). The systems showed good specificity and sensitivity (sensitivity of 0.0002 ng μL−1 for albacore tuna, bigeye tuna, and southern bluefin tuna and 0.002 ng μL−1 for yellowfin tuna and Atlantic bluefin tuna). Both systems were able to distinguish the target species from other species in a specific, sensitive, and accurate manner. Thus, these methods can be employed for the identification of species used in tuna products, protecting consumers and producers from economic fraud. [ABSTRACT FROM AUTHOR]

Background Mercury intake is caused by eating seafood, such as tuna and other predatory fish species. To reduce the health risks of mercury intake, it is necessary to continuously measure and monitor mercury concentrations at fish farms and markets. We have developed a compact system that can detect multiple heavy metals by liquid asymmetric-electrode plasma optical emission spectroscopy (LAEP-OES). Objective The validity of the LAEP-OES method for total mercury levels was evaluated using standard solutions, certified substances, and specimens of bluefin tuna and other fish species. Methods All specimens were dissolved in 4 M lithium hydroxide solution and then dispensed into a sample reservoir well of the single-use measurement reagent pack. Total mercury levels were automatically measured within 15 min of placement into the dedicated equipment. A total of 102 fish specimens, classified into 10 fish species, were evaluated using the new method and the results were compared to those obtained from validated analytical methods. Results LOD (0.02 mg/kg), LOQ (0.07 mg/kg), repeatability (4.0%), intermediate precision (9.8%), and trueness (recoveries 107%) of the proposed method were within satisfactory limits for total mercury levels in fish. Additionally, when using various fish species, the method had a strong positive correlation with the results of cold-vapor atomic absorption spectrometry (CV-AAS, the official method) with Spearman rs  = 0.984. Conclusion The LAEP-OES method can be used for measuring total mercury levels in bluefin tuna. Total mercury measurement using this new method has the potential to be applied to other fish species. Highlights Total mercury levels in fish were measured using our unique analysis system. Pacific bluefin tuna, southern bluefin tuna, and Atlantic bluefin tuna distributed in the Japanese market were analyzed for total mercury in their wild and farmed fish varieties. [ABSTRACT FROM AUTHOR]

There is an increased demand for tuna meat to supply the growing global sushi and sashimi market. Current methods to farm tunas, especially Atlantic bluefin tunas (ABFTs; Thunnus thynnus), are unsustainable. This is driving a movement towards closed-cycle ABFT aquaculture, i.e., farming tuna from spawning and hatching to slaughter on land, to try and meet the demand for these fish. Tunas are not domesticated species and thus face different challenges in terms of closed-cycle aquaculture when compared to other farmed fish species. Tunas also possess unique physiological traits such as regional endothermy and ram ventilation which affect their needs and how they are farmed. No current global standards exist to measure or monitor ABFT welfare in captivity, because there are many unknown factors surrounding ABFT welfare in aquaculture settings. There is a need to conduct studies that measure the baseline physiological parameters of ABFT in closed-cycle systems. Issues such as manipulation of breeding cycles, tank design, and slaughter procedures need attention and further research is required before such welfare indicators can be established. Stress is an overarching concern for animal welfare. In particular, pre-slaughter crowding and stress negatively affect the quality of the meat produced due to lactic acid buildup in the red muscle. Further research needs to be conducted throughout all life stages in terms of both animal welfare implications and the commercial viability of farmed ABFTs. [ABSTRACT FROM AUTHOR]

The swimbladder, when present, is the main contributor to the acoustical target strength (TS) of fish. Numerical modeling of target strength must include swimbladder dimensions, orientation, and shape for the proper estimation of target strength and its directivity. Several Atlantic Bluefin tuna (Thunnus thynnus, ABFT) specimens between 90 and 100 cm of fork length were studied by performing computed tomographic (CT) post-mortems in both fresh and frozen states. ABFT swimbladder 3D models were derived for the first time to be compared with experimental TS measurements through numerical simulation methods, using the Method of Fundamental Solutions (MFS). The numerical estimation (−23.3 dB) agreed with the experimental measurement of TS (−22.1 dB) performed in a tank with tuna with a mean fork length of 100 cm, showing the importance of considering realistic swimbladder shapes and swimming behavior in the numerical simulation of TS. [ABSTRACT FROM AUTHOR]

Atlantic bluefin tuna (ABFT; Thunnus thynnus) is a highly migratory species. To investigate the migrations and vertical behaviours of ABFT migrating to Nordic waters, we deployed pop-up satellite archival transmitting tags on 25 ABFT off Norway (curved fork length: 228–292 cm). We obtained 16 full-year migrations, which differed between individuals, and physically recovered 13 tags, which provided 4699 days of archival depth and temperature data. ABFT occupied waters from the Arctic Circle to as far south as Cabo Verde, Africa, and occupied depths down to 1190 m and temperatures from 0.5 to 27.8°C. During their annual migrations, ABFT spent, on average, 68 days in Norwegian waters, 65 days in the Newfoundland Basin, 35 days around the Canary Islands and 33 days in the West European Basin. Most ABFT entered the Mediterranean Sea with a mean entry date of 13 May and visited known spawning grounds, staying, on average, 44 days. All ABFT with full-year deployments returned to Norwegian waters. ABFT displayed high site-fidelity and dynamic vertical diving behaviours that varied between hotspots and seasons. These spatiotemporal data provide important ecological knowledge for sustainable management and the conservation of the recently recovered eastern ABFT stock. [ABSTRACT FROM AUTHOR]

This study elucidated the role of DHA-modulated genes in the development and growth of Atlantic bluefin tuna (Thunnus thynnus) larvae ingesting increasing levels of DHA in their rotifer prey. The effect of feeding low, medium, and high rotifer (Brachionus rotundiformis) DHA levels (2.0, 3.6 and 10.9 mg DHA g−1 DW, respectively) was tested on 2–15 days post hatching (dph) bluefin tuna larvae. Larval DHA content markedly (P < 0.05) increased in a DHA dose-dependent manner (1.5, 3.9, 6.1 mg DHA g−1 DW larva, respectively), that was positively correlated with larval prey consumption and growth (P < 0.05). Gene ontology enrichment analyses of differentially expressed genes (DEGs) demonstrated dietary DHA significantly (P < 0.05) affected different genes and biological processes at different developmental ages. The number of DHA up-regulated DEGs was highest in 10 dph larvae (491), compared to 5 (12) and 15 dph fish (34), and were mainly involved in neural and synaptic development in the brain and spinal cord. In contrast, DHA in older 15 dph larvae elicited fewer DEGs but played critical roles over a wider range of developing organs. The emerging picture underscores the importance of DHA-modulated gene expression as a driving force in bluefin tuna larval development and growth. [ABSTRACT FROM AUTHOR]

Pacific bluefin tuna (Thunnus orientalis) remains heavily depleted due to overexploitation. Aquaculture and stock enhancement based on artificial seedlings could be effective solutions to this problem. However, widespread adoption of seedling production is limited because spawning in captivity of bluefin tuna, a large pelagic top predator, requires much space, time, cost, and labour. To downsize and shorten their generation time, here, we show that xenogeneic germ cell transplantation enables a surrogate production of functional bluefin tuna sperm in hybrid little tuna (genus: Euthynnus), which attain sexual maturity at a smaller body size and shorter time. Intraperitonially transplanted bluefin tuna germ cells migrate towards and are incorporated into the gonads of little tuna larvae. These recipients produce functional donor-derived bluefin tuna sperm at a mere 8 months of age and 1 kg of body size. This result represents an advance toward compact, low-cost, and time-efficient seedling production that will improve the efficiency of bluefin tuna aquaculture. Here, the authors show that germ cell transplantation and surrogate production of bluefin tuna sperm in small-bodied fish species shortens the period in which sperm is produced. This study opens the possibility of highly efficient seed production in bluefin tuna. [ABSTRACT FROM AUTHOR]

Introduction: Considering the need to feed the increasing world population, it is essential to ensure that food production systems are sustainable. Aquaculture has been identified as a potential crucial source of sustainable food with its significant potential for future growth, notably by the recent EU regulations aiming at boosting food security and sustainable food systems. In this context, it is important to reflect on how the aquaculture of carnivorous species, which are exhibiting the highest growth rates, stands in respect of environmental impacts and contribution to the overall food supply. In particular, tuna aquaculture has been largely criticized for its high environmental impacts and general low sustainability. Methods: Here, we present a methodology to assess the sustainability of seafood production systems, with a first analysis applied to Atlantic bluefin tuna (BFT) aquaculture, detailed for both BFT fattening and farming. Results: Results suggest that the limited economic and social contributions of BFT aquaculture do not currently compensate its environmental impacts with an estimate of a 3.4-fold higher long-term social cost than the short-term economic gain. Discussion: However, it is also a species where the production cycle is not closed in commercial operation, and with a significant potential for further improvement as the control of the production process increases. [ABSTRACT FROM AUTHOR]

Knowledge about sex‐specific difference in life‐history traits—like growth, mortality, or behavior—is of key importance for management and conservation as these parameters are essential for predictive modeling of population sustainability. We applied a newly developed molecular sex identification method, in combination with a SNP (single nucleotide polymorphism) panel for inferring the population of origin, for more than 300 large Atlantic bluefin tuna (ABFT) collected over several years from newly reclaimed feeding grounds in the Northeast Atlantic. The vast majority (95%) of individuals were genetically assigned to the eastern Atlantic population, which migrates between spawning grounds in the Mediterranean and feeding grounds in the Northeast Atlantic. We found a consistent pattern of a male bias among the eastern Atlantic individuals, with a 4‐year mean of 63% males (59%–65%). Males were most prominent within the smallest (< 230 cm) and largest (> 250 cm) length classes, while the sex ratio was close to 1:1 for intermediate sizes (230–250 cm). The results from this new, widely applicable, and noninvasive approach suggests differential occupancy or migration timing of ABFT males and females, which cannot be explained alone by sex‐specific differences in growth. Our findings are corroborated by previous traditional studies of sex ratios in dead ABFT from the Atlantic, the Mediterranean, and the Gulf of Mexico. In concert with observed differences in growth and mortality rates between the sexes, these findings should be recognized in order to sustainably manage the resource, maintain productivity, and conserve diversity within the species. [ABSTRACT FROM AUTHOR]

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The use of Pop‐up Satellite Archival Tags (PSATs) has provided considerable new information about the behaviour of migrating (silver) eels (Anguilla spp.) at sea, with 9 of 19 recognised species or subspecies tagged to date. However, such studies often reported premature tag detachment and relatively high rates of predation. Since 2000, several PSAT‐tagged New Zealand longfin eels, Anguilla dieffenbachii, were released to understand migratory behaviour and location of potential spawning grounds. Of 20 PSAT‐tagged eels released in 2019, all tags detached prematurely, but 7 (58%) were likely eaten or injured by predators 1–81 days after release. Two eels were probably eaten by sperm whales, whereas other tagged eels were likely eaten by lamniform and non‐lamniform sharks, and southern bluefin tuna. Because of the high rate of predation, we recommend that future releases should be from smaller catchments or offshore. [ABSTRACT FROM AUTHOR]

Aim: Predicting spatial and temporal changes in species distributions is difficult for highly mobile species, making effective management challenging. We aim to understand the seasonal variability in habitat suitability for Atlantic bluefin tuna (Thunnus thynnus; ABFT) by using tracking data to create species distribution models. Location: North‐east Atlantic Ocean. Methods: Forty‐nine ABFT were tagged with pop‐up archival satellite tags along the west coast of Ireland during successive autumns from 2016 to 2021. Four thousand two hundred and sixteen daily locations were used to build a habitat model to describe ABFT environmental preferences and habitat suitability. For each location, 100 'pseudoabsence' locations were simulated using correlated random walks. Results: Tags had a mean retention rate of 237 ± 107 days, resulting in 11,602 cumulative days at liberty, and a mean daily distance travelled of 51 ± 143 km. ABFT showed two primary migration routes from Ireland, travelling to the Bay of Biscay or across the Mid‐Atlantic ridge in the winter. However, in 2019 six individuals travelled northwards towards Iceland, likely in response to a marine heatwave. Eight ABFT entered the Mediterranean in May/June for putative spawning, with six returning to Irish waters a year later. Five environmental covariates best described ABFT habitat, with habitat suitability highest at sea surface temperatures (SST) of 15–18°C, a mixed layer depth between ~200 and 300 m, high relief bathymetric features (i.e. shelf breaks and seamounts) and frontal regions as revealed by non‐linear preferences of eddy kinetic energy and SST standard deviation. Main Conclusions: In the last decade, ABFT have been re‐establishing historic foraging grounds in higher latitudes, for example, Irish and Nordic waters. Our model shows the extent of suitable habitat in these regions and how recent ocean warming may have contributed to northern expansions. Understanding the drivers behind these reappearances is fundamental to successful future management. Achoimre: Aidhm: Tá sé deacair athraithe i ndáileadh ama agus spásdháileadh speiceas atá an‐soghluaiste a thuar, rud a chiallaíonn go bhfuil sé dúshlánach bainistiú éifeachtach a dhéanamh. Tá muid ag iarraidh inathraitheacht shéasúrach in oiriúnacht ghnáthóg an Tuinnín Gorm Atlantach (Thunnus thynnus; TGA) a thuiscint tríd sonraí rianaithe a úsáid chun samhail dháileadh speiceas a chruthú. Suíomh: Oirthuaisceart an Atlantaigh. Modh: Rinneadh clibeadh ar 49 TGA le clibeanna cartlainne a thagann go barr uisce ar chósta iarthar na hÉireann le linn ceithre fhómhair i ndiaidh a chéile ó 2016–2021. Úsáideadh 4216 suíomhanna laethúil chun samhail ghnáthóg a chruthú a rinne cur síos ar roghanna timpeallachta agus oiriúnacht ghnáthóg an TGA. I gcomhair gach suíomh, ionsamhlaíodh 100 suíomhanna bréag‐neamhláithreacht ag úsáid siúlóidí randamacha comhghaolaithe. Torthaí: Bhí meán ráta coinneála de 237 ± 107 lá ag na clibeanna, rud a thug 11,602 lá taifeadta i ndiaidh a chéile agus meán fhad laethúil taistealta de 51 ± 143 km dá bharr. Léirigh TGA dhá phríomhbhealaí imirce ó hÉirinn, ag taisteal go Bá na Bioscáine nó thar Droim an Atlantaigh Láir i rith an gheimhridh. Ach i 2019 thaisteal sé iasc ó thuaidh i dtreo an Íoslainn, is dócha mar gheall ar thonn teasa mara. Chuaigh ocht TGA isteach sa Mheánmhuir i rith mí Bealtaine/mí an Mheitheamh chun uibheacha a sceitheadh de réir dealraimh. Tháinig sé dóibh ar ais go huiscí na hÉireann an bhliain dar gcionn. Déanann cúig athróg timpeallachta an cur síos is fearr ar ghnáthóg an TGA, tá oiriúnacht ghnáthóg is airde ag teocht barr uisce (TBA) de 15–18°C, nuair atá doimhneacht an chisil mheasctha idir ~200 agus 300 m, ag gnéithe bataiméadrach ard‐rilíf (i.e. scoilteanna scairbhe agus tuláin grinnill), agus ag réigiúin frontacha léirithe ag roghanna neamh‐líneacha fuinneamh cinéatach guairneánach agus diall caighdeánach TBA. Príomhchonclúidí: Le leathscór bliain anuas tá TGA tar éis réigiúin sealgaireachta stairiúil a athbhunú in áiteanna le hard‐domhanleithead, ar nós uiscí na hÉireann agus uiscí Nordacha. Taispeánann ár samhail achar an ghnáthóg oiriúnach sna réigiúin seo agus an bhaint féideartha a bhí ag téámh aigéanach le gairid ar leathadh ó thuaidh. Tá sé buntábhachtach na cúiseanna don athfhilleadh seo a thuiscint i gcomhair bainistiú rathúil amach anseo. [ABSTRACT FROM AUTHOR]

This study explores consumer evaluations of Pacific and Southern Bluefin Tuna parts in Japan, using text mining on Rakuten Ichiba reviews from January 2015 to December 2019. Our analysis identified distinct preferences and concerns regarding texture, fat content, and culinary applications, emphasizing species differences. Texture issues, notably sinews in Southern Bluefin Tuna's Akami and unexpected bone in its Chu-toro, highlight the need for improved product descriptions and customer education. Findings imply implications for seafood industry strategies, emphasizing accurate product information for enhanced customer satisfaction. Future research should gather demographic data for tailored strategies. This study demonstrates text mining's role in guiding targeted marketing and refining product in the seafood sector. [ABSTRACT FROM AUTHOR]

Summary: Fish is well known for its perishable nature. Essential oils in food packaging seem to be safe and reliable both in terms of safety for the consumer and in terms of improving the shelf life of the product. This study aimed to evaluate the effects of two different essential oil vapours (one with rosemary and the other one with lemon extract) on three different types of fishery products (swordfish steaks, bluefin tuna steaks and Argentinian prawns) stored in a protective atmosphere packaging, monitoring the shelf life up to 8 days through microbiological, chemical and sensorial analyses. The results showed that the products preserved with the inclusion of essential oils have reached the end of the shelf‐life period respecting the process hygiene and food safety criteria, receiving a greater appreciation rating from the consumer panel at the end of shelf life for the prawns and swordfish samples with the addition of rosemary essential oils vapours, which instead highlighted the worst result at the end of shelf life for tuna. [ABSTRACT FROM AUTHOR]

This study examined the characteristics and effects of the quota transfer system implemented in the Japanese Pacific bluefin (PBF) tuna Thunnus orientalis fisheries. Social network analysis revealed that from fishing year (FY) 2018 to FY2021, the number of management units involved in quota transfer increased, the network became denser, and approximately half of the transfer pairs were maintained in the following year. The results of network structure analysis, including triad census and block modeling, showed that some management units (e.g., minister-managed purse seines, Ishikawa prefecture) play an important role in facilitating unilateral transfers and virtually mediate transfers between other units. A brief analysis using initial/final quota and catch data suggested that while the system helped with quota compliance and contributed to effective quota use, there was little evidence that quota allocation or catch was significantly concentrated after the introduction of the quota transfer system. These findings suggest that quota transfers could be further promoted by: (1) sharing up-to-date information on quota use and transfer networks; (2) providing highly accurate forecasts of sea conditions and PBF arrival; (3) semi-automating the matching and approval process; (4) encouraging multi-level quota transfers; and (5) creating more incentives for transferors. [ABSTRACT FROM AUTHOR]

The study investigated how the changes in the hours spent at home during the COVID-19 pandemic affected the Tokyo Toyosu bluefin, bigeye, and yellowfin tuna markets. Applying the nonlinear autoregressive distributed lag (NARDL) price models for the three tuna products during the four state of emergency (SOE) periods between 2020 and 2021 in Tokyo, the study reveals that an increase in the hours of stay-at-home during the first SOE had an adverse impact on all three tuna prices in the long run. The study also finds that for the bluefin tuna, an increase in the hours of stay at home had a positive impact on price in the short run when the hours of stay at home were increasing during the first SOE. This suggests that there were times when household demand for bluefin tuna increased while people spent longer in their homes during the SOE period. [ABSTRACT FROM AUTHOR]

Freezing is one of the most commonly used preservation methods for Bluefin tuna (Thunnus orientalis). However, repeated freezing and thawing would inevitably occur due to the temperature fluctuation, leading to the microstructure damage, lipid oxidation and protein integrity decline of tuna muscle without notable visual appearance change. In this study, we used a rapid evaporative ionization mass spectrometry (REIMS) technique for the real-time determination of the extent of repeated freezing and thawing cycles in tuna fillets. We found significant variance in the relative abundance of fatty acids between bluefin tuna and its fresh counterpart following freeze-thaw cycles. Meanwhile, the difference is statistically significant (p

Simple Summary: Environmental factors, maternal inheritance, and feeding success are influential factors in fish growth, especially during the larval stage, encompassing their early days of life. Growth rates play a crucial role in larval survival, particularly in species with high energy requirements such as the Atlantic bluefin tuna (ABFT). Our analyses of two patches of ABFT larvae collected in the Gulf of Mexico's spawning region during different years reveal variable larval growth, depending on prey availability. Larval growth also shows a direct relationship to maternal feeding. Estimates of larval trophic positions are primarily influenced by food web length and energy transmission efficiency, leading to differences in larval growth and underscoring the importance of considering trophic dynamics in interpreting results. These findings offer novel insights into how these factors affect ABFT larval growth, potentially informing conservation efforts and fisheries management strategies by governmental institutions. Two cohorts of Atlantic bluefin tuna (Thunnus thynnus) larvae were sampled in 2017 and 2018 during the peak of spawning in the Gulf of Mexico (GOM). We examined environmental variables, daily growth, otolith biometry and stable isotopes and found that the GOM18 cohort grew at faster rates, with larger and wider otoliths. Inter and intra-population analyses (deficient vs. optimal growth groups) were carried out for pre- and post-flexion developmental stages to determine maternal and trophodynamic influences on larval growth variability based on larval isotopic signatures, trophic niche sizes and their overlaps. For the pre-flexion stages in both years, the optimal growth groups had significantly lower δ15N, implying a direct relationship between growth potential and maternal inheritance. Optimal growth groups and stages for both years showed lower C:N ratios, reflecting a greater energy investment in growth. The results of this study illustrate the interannual transgenerational trophic plasticity of a spawning stock and its linkages to growth potential of their offsprings in the GOM. [ABSTRACT FROM AUTHOR]

Genome editing by manipulating the embryos of Pacific bluefin tuna (PBT) was recently proposed for improving the breeding and aquaculture production of PBT. However, the yield of genome-edited eggs is limited due to the narrow timing of genome editing of embryos and the labor-intensive process. Therefore, the development of a small-scale larviculture method is necessary for efficient evaluation of the phenotype and traits of genome-edited PBT larvae. The plankton-kreisel tank can form a vertical rotating flow that may prevent the sinking syndrome of PBT larvae. In this study, we applied a plankton-kreisel tank (8-L) for PBT larviculture up to 10 days post-hatch (dph). We compared the survival rate and growth of PBT larvae reared in the 8-L plankton-kreisel tank and an 8-L cylindrical tank (CT). The survival rate in the plankton-kreisel tank at 10 dph (58.9 ± 4.8%) was significantly higher than that in the CT (4.8 ± 3.6%). Larval growth was not significantly different between these tanks. We observed that the larvae that sank to the tank bottom drifted with the strong vertical rotating flow along the tank wall during the night. This flow in the plankton-kreisel tank prevents the sinking syndrome. Thus, this apparatus is proposed for small-scale larviculture experiments in PBT. [ABSTRACT FROM AUTHOR]

The significance of FACTS devices has been increasing as they have the ability to donate compensation for power systems, making a significant impact on power system stability and power transfer issues. However, to optimize the performance of these devices, it is important to carefully select their sizes and locations. This article aims to determine the optimal size and location of several FACTS devices to achieve two objectives: minimizing fuel costs and minimizing power losses. These objectives are solved one by one, then combined into a multi-objective function to minimize gross cost. An Enhanced Tuna Swarm Optimization is proposed to improve the performance of the original version of Tuna Swarm Optimization. The traditional Tuna swarm optimization is improved relying on "high and low-velocity ratios" included in the Marine Predator Algorithm. The main advantage of this approach is to avoid the risk of the optimal value being trapped in local minima. The IEEE 30-bus standard system is used as a case study, with SVC, TCSC, and TCPS installed as FACTS devices, and two wind turbines as renewable resources penetration. Different optimization algorithms are used, and a comparison is made to prove the superiority of the proposed algorithm compared to the other tested algorithms. [ABSTRACT FROM AUTHOR]

This paper researches the problem of Beyond Visual Range (BVR) air combat maneuver intention recognition. To achieve efficient and accurate intention recognition, an Attention enhanced Tuna Swarm Optimization-Parallel Bidirectional Gated Recurrent Unit network (A-TSO-PBiGRU) is proposed, which constructs a novel Parallel BiGRU (PBiGRU). Firstly, PBiGRU has a parallel network structure, whose proportion of forward and backward network can be adjusted by forward coefficient and backward coefficient. Secondly, to achieve object-oriented adjustment of forward and backward coefficients, the tuna swarm optimization algorithm is introduced and the negative log-likelihood estimation loss function is used as the objective function, it realizes the dynamic combination of sequence guidance and reverse correction. Finally, the attention mechanism is used to obtain more useful information to improve the recognition accuracy. Through offline recognition experiment, it is proved that A-TSO-PBiGRU can effectively improve the convergence speed and recognition accuracy compared with GRU-related networks. Compared with the other six comparison algorithms, maneuver intention recognition accuracy also has significant advantages. In the online recognition experiment, maneuver intention recognition accuracy of A-TSO-PBiGRU is 93.7%, it shows excellent maneuver intention recognition ability. [ABSTRACT FROM AUTHOR]

This study reports on diseased Chelidonichthys spinosus fish that were originally obtained from the Taiwan Strait for exhibition in an aquarium. These fish showed abnormal swimming behavior, eye damage and skin lesions. Gross examination and histopathology revealed that the C. spinosus was suffering from severe nematode infections in the pyloric caeca, liver and mesentery. Marine nematodes from internal organs were verified by partially sequencing the internal transcribed spacer (ITS) gene. Sequencing results revealed that the nematodes shared 99.75% sequence identity with Raphidascaris lophii (GenBank accession No. MW132926). Additionally, secondary Vibrio harveyi infections were also detected in some C. spinosus. This is the first report of R. lophii infection in C. spinosus. [ABSTRACT FROM AUTHOR]

The technical issues in the microgrids (MG) are predicted and the fluctuation in the MG is controlled precisely by the inclusion of distinct renewable energy sources (RESs) into the MG system. The voltage stability and distortionless harmonic are the two main factors that need to be tackled in the MG system. By solving the above‐mentioned two factors, the overall power quality (PQ) of the MG is enhanced. Multiple pieces of equipment are introduced and developed especially to resolve the issues regarding the load's nonlinearity and the source's uncertainty. Hence, a novel "hybrid tuna‐glowworm swarm optimization (HT‐GWSO)" algorithm is introduced to resolve the uncertainties in the MG and to enhance the PQ in this paperwork. The proposed algorithm is a combination of "glowworm swarm optimization (GWO) with the tuna swarm optimization (TSO)" algorithms. This algorithm is utilized in tuning the parameters of the controllers used in the MG. The reactive power is varied from the active power to enhance the PQ in this proposed scheme. The controller's parameters are optimized so that the variation in power and the error while the function is minimized in the MG system. An expensive simulation is done to prove the superiority of the suggested scheme. [ABSTRACT FROM AUTHOR]

The swimbladder, when present, is the main contributor to the acoustical target strength (TS) of fish. Numerical modeling of target strength must include swimbladder dimensions, orientation, and shape for the proper estimation of target strength and its directivity. Several Atlantic Bluefin tuna (Thunnus thynnus, ABFT) specimens between 90 and 100 cm of fork length were studied by performing computed tomographic (CT) post-mortems in both fresh and frozen states. ABFT swimbladder 3D models were derived for the first time to be compared with experimental TS measurements through numerical simulation methods, using the Method of Fundamental Solutions (MFS). The numerical estimation (−23.3 dB) agreed with the experimental measurement of TS (−22.1 dB) performed in a tank with tuna with a mean fork length of 100 cm, showing the importance of considering realistic swimbladder shapes and swimming behavior in the numerical simulation of TS.

In this article, the evolution of BFT (bluefin tuna) sizes in fattening cages is studied, for which it was necessary to perform exhaustive monitoring with stereoscopic cameras and an exhaustive analysis of the data using automatic procedures. Exploring the size evolution of BFT over a long period is an important step in inferring their growth patterns, which are essential for designing smart aquaculture and sustainable fishing, and even assessing their health status. An important objective of this work was to verify whether tuna in captivity, in addition to fattening, grow in length. To this end, our autonomous monitoring system, equipped with stereoscopic cameras, was installed from 28 July 2020 to 23 May 2021 in a fattening cage in the Mediterranean containing 724 free-swimming tuna. This system provides thousands of images that, grouped by time intervals, allow us to conduct our studies. An automatic procedure, already introduced in a previous work and capable of processing large volumes of data, is used to estimate the length and width of individuals in ventral stereoscopic images of fish, and the evolution over time is analysed for each biometric characteristic. However, verifying the evolution of length and width based only on means or medians of these measurements may be inconsistent and insufficiently accurate to support our study objectives, as individuals of different sizes and ages may grow at different rates. Therefore, a modal analysis (Bhattacharya's method) was undertaken to identify the cohorts within the population. The results showed that each modal length surpassed the length of the next cohort and that there was accelerated growth in cages compared to the wild. In addition, we proved that using a length–width–weight relationship to estimate fish weight gives more accurate results than traditional length–weight relationships for fish fattened in cages. [ABSTRACT FROM AUTHOR]

Tuna is an excellent food product, relatively low in calories, that is recommended for a balanced diet. The continuously increasing demand, especially for bluefin-tuna-based food preparations, and its relatively high market price make adulteration by intentionally mixing with other lower-priced tunas more prospective. The development of rapid methods to detect tuna adulteration is a great challenge in food analytical science. We have thus developed a simple, fast, and low-cost molecular rapid test for the visual detection of tuna adulteration. It is the first sensor developed for tuna authenticity testing. The three species studied were Thunnus thynnus (BFT), Thunnus albacares, and Katsuwonus pelamis. DNA was isolated from fresh and heat-treated cooked fish samples followed by PCR. The PCR products were hybridized (10 min) to specific probes and applied to the rapid sensing device. The signal was observed visually in 10–15 min using gold nanoparticle reporters. The method was evaluated employing binary mixtures of PCR products from fresh tissues and mixtures of DNA isolates from heat-treated tissues (canned products) at adulteration percentages of 1–100%. The results showed that the method was reproducible and specific for each tuna species. As low as 1% of tuna adulteration was detected with the naked eye. [ABSTRACT FROM AUTHOR]

Background: The use of biologging tags to answer questions in animal movement ecology has increased in recent decades. Pop-up satellite archival tags (PSATs) are often used for migratory studies on large fish taxa. For PSATs, movements are normally reconstructed from variable amounts of transmitted data (unless tags are recovered, and full data archives accessed) by coupling geolocation methods with a state-space modelling (SSM) approach. Between 2018 and 2019, we deployed Wildlife Computers PSATs (MiniPATs) from which data recovery varied considerably. This led us to examine the effect of PSAT data volume on SSM performance (i.e., variation in reconstructed locations and their uncertainty). We did this by comparing movements reconstructed using partial (< 100%) and complete (100%) geolocation data sets from PSATs and investigated the variation in Global Position Estimator 3 (GPE3; Wildlife Computers' proprietary light-based geolocation SSM) reconstructed locations and their certainty in relation to data volume and movement type (maximum dispersal distance). Results: In this analysis, PSATs (n = 29) deployed on Atlantic bluefin tuna (Thunnusthynnus) transmitted data after detaching from study animals for between 0.3 and 10.8 days (mean 4.2 ± 3 days), yielding between 2 and 82% (mean 27% ± 22%) of total geolocation data. The volume of geolocation data received was positively related to the amount of time a tag transmitted for and showed a weak negative relationship to the length of the tag deployment. For 12 recovered PSATs (i.e., 100% of geolocation data; mean ± 1 S.D. = 301 ± 90 days of data per fish), (i) if ABT travelled short-distances (< 1000 km), movements reconstructed from partial data sets were more similar to their complete data set counterpart than fish that travelled over longer distances (> 1000 km); (ii) for fish that travelled long distances, mean distance of locations from corresponding complete data set locations were inversely correlated with the volume of data received; (iii) if only 5% of data was used for geolocation, reconstructed locations for long-distance fish differed by 2213 ± 647 km from the locations derived from complete data sets; and, (iv) track reconstructions omitted migrations into the Mediterranean Sea if less than 30% of data was used for geolocation. Conclusions: For Wildlife Computers MiniPATs in our specific application, movements reconstructed with as little as 30% of the total geolocation data results in plausible outputs from the GPE3. Below this data volume, however, significant differences of more than 2000 km can occur. Whilst for a single species and manufacturer, this highlights the importance of careful study planning and the value of conducting study-specific sensitivity analysis prior to inclusion of modelled locations in research outputs. Based on our findings, we suggest general steps and refinements to maximise the value of light geolocation data from PSATs deployed on aquatic animals and highlight the importance of conducting data sensitivity analyses. [ABSTRACT FROM AUTHOR]

The commercially important Atlantic bluefin tuna (Thunnus thynnus), a large migratory fish, has experienced notable recovery aided by accurate resource assessment and effective fisheries management efforts. Traditionally, this species has been perceived as consisting of eastern and western populations, spawning respectively in the Mediterranean Sea and the Gulf of Mexico, with mixing occurring throughout the Atlantic. However, recent studies have challenged this assumption by revealing weak genetic differentiation and identifying a previously unknown spawning ground in the Slope Sea used by Atlantic bluefin tuna of uncertain origin. To further understand the current and past population structure and connectivity of Atlantic bluefin tuna, we have assembled a unique dataset including thousands of genome‐wide single‐nucleotide polymorphisms (SNPs) from 500 larvae, young of the year and spawning adult samples covering the three spawning grounds and including individuals of other Thunnus species. Our analyses support two weakly differentiated but demographically connected ancestral populations that interbreed in the Slope Sea. Moreover, we also identified signatures of introgression from albacore (Thunnus alalunga) into the Atlantic bluefin tuna genome, exhibiting varied frequencies across spawning areas, indicating strong gene flow from the Mediterranean Sea towards the Slope Sea. We hypothesize that the observed genetic differentiation may be attributed to increased gene flow caused by a recent intensification of westward migration by the eastern population, which could have implications for the genetic diversity and conservation of western populations. Future conservation efforts should consider these findings to address potential genetic homogenization in the species. [ABSTRACT FROM AUTHOR]

Rhadinorhynchus Lühe, 1911 consists of acanthocephalans parasitizing migratory fishes. Of about 50 congeners currently assigned in this genus, 10 named and six unidentified species have previously been studied in molecular phylogenetic works; the intrageneric phylogeny and molecular diversity are thus still incompletely understood. In this study, we examined the phylogenetic positions of the two species R. seriolae (Yamaguti, 1963) and R. laterospinosus Amin, Heckmann, and Ha, 2011 based on the cytochrome c oxidase subunit I and 18S rRNA genes determined from material found in the intestines of the Pacific bluefin tuna Thunnus orientalis (Temminck and Schlegel, 1844) (new host) and the frigate tuna Auxis thazard (Lacepède, 1800), respectively. This is the first record of R. laterospinosus from Japan. [ABSTRACT FROM AUTHOR]

Wildlife tourism is expanding globally, driving the need to quantify its potential impacts. Studies on the effects of marine tourism on wildlife have focused on documenting behavioural changes, but whether tourism affects the activity levels, energy budgets and ultimately the survival prospects of target animals is largely unknown. To assess the effects of cage diving on the energy expenditure of white sharks, Carcharodon carcharias , animal-borne cameras and accelerometer loggers were deployed on 18 white sharks at a cage-diving site (Neptune Islands Group Marine Park, South Australia) and recorded shark activity for ca. 490 h. A random forest machine-learning model was used to predict their behaviours based on 38 h of acceleration data with behaviours ground-truthed by animal-borne cameras. The presence of cage-diving boats using food-based attractants led to white sharks spending more time undertaking high-energy swimming and bursts of acceleration while decreasing low-energy swimming. However, raised activity during cage-diving operations was not reflected in a substantial shift in energy budgets. Calorific quantification of baits used by the cage-diving industry showed that one bait (tethered southern bluefin tuna, Thunnus maccoyii , gills and entrails) could fuel a white shark for more than a day, which could lead to temporary reduction or cessation of natural foraging, potentially impacting the health and fitness of the individual. Our study reveals new insights into the energetic effects of wildlife tourism on large marine predators. We highlight that while increases in metabolic rate are relatively small for continuously moving predators, the amount of food consumed may impact the health and fitness of individuals and should be considered when managing wildlife tourism activities. • High-energy behaviour increased during cage-diving tourism. • Behavioural changes did not translate to increases in metabolic rate. • Consuming southern bluefin tuna baits has the potential to fuel sharks for ca. 1 day. [ABSTRACT FROM AUTHOR]

Under the UNCLOS regime the practice of the ITLOS reveals some significant cases in which provisional measures are prescribed. Those prescriptions are noteworthy in two respects. First, in general, they contribute to the development of the institution of 'provisional measures' in international law. Second, and more in specific, they direct and enhance the efforts aimed at an effective marine environment protection. In the period of 1997-2009, in chronological order, the provisional measures are prescribed in "The M/V 'SAIGA' (No. 2) Case" (Case No. 2), "New Zealand v. Japan; Australia v. Japan" ("Southern Bluefin Tuna cases") (Cases Nos. 3 and 4), "Ireland v. the United Kingdom" ("The MOX Plant Case") (Case No. 10) and "Malaysia v. Singapore" (Case No. 12) cases, all of which might be considered as standard setting decisions with regard to substantial and procedural aspects of provisional measures. Furthermore, in the list of four pioneering cases, the second and third ones were significant due to the establishment of arbitral tribunals under Annex VII of the UNCLOS. Briefly, it may be concluded that the prescription of provisional measures by the ITLOS in 1997-2009, which also gave an opportunity for important literature contribution, has enlightened the path that would be followed in future provisional measures practice. [ABSTRACT FROM AUTHOR]

Most mesopelagic fish are small planktivores that migrate up at nightfall to feed in the safety of darkness and descend to depth at dawn to escape visual predators. However, the trophic roles can reverse since mesopelagic fishes also predate eggs and larvae of their predators. We use the Atlantic bluefin tuna as a model species to test the hypothesis that fishes in the open ocean synchronize spawning to moon‐lit nights (when mesopelagic fishes avoid near‐surface waters) to increase offspring fitness. Our analysis over two decades of field observations shows that tuna spawn most intensively the week before full moon. This fits predictions from a mechanistic model where spawning around full moon increases offspring fitness by two orders of magnitude due to low predation from mesopelagic fishes. Circalunar patterns of food availability can also favor fitness of offspring spawned the days before full moon. Our findings suggest that mesopelagic fishes may have an important impact on pelagic fish through predation of early life stages and cause an evolutionary drive to synchronize spawning to the lunar cycle. [ABSTRACT FROM AUTHOR]

Identifying environmental effects on the reproduction cycle and sex hormones is essential for ensuring the sustainable productivity of Pacific bluefin tuna (PBT, Thunnus orientalis) aquaculture. In the present study, 70 PBTs, commercially farmed in sea cages near Yokjido Island, South Korea, were investigated from April 2020 to March 2021. Environmental data, including water temperature and photoperiod duration, were collected. The gonadosomatic index (GSI) was calculated, and male and female maturity stages were classified monthly in proportions based on histological analysis of the gonads. Male and female gonadal developmental stages were classified into four major stages. Mature male and female PBTs were observed from May to August and June to August, respectively. Monthly changes in sex steroid hormone levels in PBT plasma were evaluated. The GSI and sex steroid hormones of males and females increased in May, peaked in June, and decreased thereafter. Our results confirmed the reproductive potential of farmed PBT and verified that reproductive maturity is reached in July. This study, to the best of our knowledge, is the first to investigate the reproductive biology of PBT in South Korea, and our results constitute a reference for future research on PBT aquaculture. [ABSTRACT FROM AUTHOR]

Pacific bluefin tuna (PBT), Thunnus orientalis, is one of the most important species for aquaculture worldwide. For the conservation of this species and sustainable development of the tuna farming industry, production based on closed‐cycle aquaculture should be promoted. In this study, to develop an efficient method for transporting PBT eggs, we simulated egg transportation to optimize stocking density and shipping duration, which are the two variables critical to the transportation procedure of PBT. Based on the findings of this study, we concluded that PBT eggs should be transported at a density of 1 × 104 eggs/L within 12 h in the field. Furthermore, we showed that collisions between eggs during transportation negatively affected the normal hatching rates of eggs, and polyethylene glycol (PEG) treatment (at 1000 μg/mL for 12 h) could reduce such damage. Our results suggest that PEG treatment is a practical approach that contributes to the stable transportation of PBT eggs, particularly in cases where the effects of physical shock damage is considerably increased. [ABSTRACT FROM AUTHOR]