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ABSTRACT This study monitored 37 longliners fishing in waters near the Marshall Islands from 2020 to 2022 by Liancheng Overseas Fishery (Shenzhen) Co., Ltd.'s operation management system. This study developed nine predictive models on the relationship between catch per unit effort (CPUE) data for yellowfin tuna (Thunnus albacares) and the environmental data. The environmental data integrate 48 variables, including eddy kinetic energy, chlorophyll a concentration, sea surface height, and additional measures of vertical oceanic conditions, alongside spatiotemporal parameters (year, month, day, longitude, and latitude). This study employed four spatial resolutions (0.25° × 0.25°, 0.5° × 0.5°, 1° × 1°, and 2° × 2°) to develop nine predictive models: KNN, RF, GBDT, CART, LightGBM, XGBoost, CatBoost, AdaBoost, and Stacking (RF, KNN, GBDT, and LR). These models, with a daily time resolution, were trained using 75% of the data and tested with the remaining 25%. The optimal spatial resolution and model were determined through a comprehensive comparison of model evaluation metrics across these spatial resolutions. The SMOTETomek algorithm was then applied to resample 75% of the data at the optimal spatial resolution, forming a new training dataset. This dataset was used to refine the model, subsequently tested with the remaining 25% of the data. Results indicated that (1) the optimal spatial resolution is 0.25° × 0.25° and the optimal model is RF; (2) the SMOTETomek algorithm enhances the model's predictive performance; and (3) the developed SMK‐RF model, exhibiting Acc and AUC values of 76.73% and 82.47%, respectively, accurately predicts the central fishing grounds for yellowfin tuna, consisting closely with actual fishing activity. [ABSTRACT FROM AUTHOR]

Ecosystems and biodiversity across the world are being altered by human activities. Habitat modification and degradation are among the most important drivers of biodiversity loss. These modifications can have an impact on species behavior, which can, in turn, impact their mortality. While several studies have investigated the impacts of habitat degradation and fragmentation on terrestrial species, the extent to which habitat modifications affect the behavior and fitness of marine species is still largely unknown, particularly for pelagic species. Since the early 1990s, industrial purse seine vessels targeting tuna have started deploying artificial floating objects—Drifting Fish Aggregating Devices (DFADs)—in all oceans to increase tuna catchability. Since then, the massive deployment of DFADs has modified tuna surface habitat, by increasing the density of floating objects, with potential impacts on tuna associative behavior and mortality. In this study, we investigate these impacts for yellowfin tuna in the Indian Ocean. Using an individual‐based model based on a correlated random walk and newly available data on DFAD densities, we quantify for the first time how the increase in floating object density, due to DFAD use, affects the percentage of time that yellowfin tuna spend associated, which, in turn, directly impacts their availability to fishers and fishing mortality. This modification of tuna associative behavior could also have indirect impacts on their fitness, by retaining tuna in areas detrimental to them or disrupting schooling behavior. Hence, there is an urgent need to further investigate DFAD impacts on tuna behavior, in particular, taking social behavior into account, and to continue regulation efforts on DFAD use and monitoring. [ABSTRACT FROM AUTHOR]

The quality of the yellowfin tuna caught by small-scale fishers is heavily influenced by how the catches are handled and stored on board. One effective method that small-scale fishers can use to maintain the quality of their catch is by cooling it with ice. This helps prevent the growth of bacteria in the fish, which can cause sensory, physical, microbiological, and chemical damage. Such damage can result in poor catch quality and lower market value. Therefore, this study aimed to assess the quality of the yellowfin tuna catches by small-scale fishermen in Bone Bay, specifically at the Lonrae fish landing site. This assessment involved conducting sensory, physical, microbiological, and chemical tests on the catch. The results indicated that the catch had high quality, as evidenced by a sensory score of 8. The fish had a pH ranging from 5.7 to 5.8 and a temperature close to 0°C. The average total bacteria count was 1.1 x 104 colonies/g, and there were no traces of Salmonella or Escherichia coli (<3 MPN/g). The histamine values ranged from 6.99 to 7.31. Heavy metals, specifically mercury, lead, and cadmium, were measured at 0.05, 0.0166, and 0.0049mg/ k, respectively. [ABSTRACT FROM AUTHOR]

Tuna has a significant economic value in the world and is the third largest fishery commodity in Indonesia after shrimp and demersal fish. Tuna has a relatively high price compared to other fish commodities, and its demand continues to increase. Fishing gear suitable for catching large pelagic fish, such as tuna includes the handline fishing gear. Fishermen commonly use tuna handlines for this purpose, and Maluku fishermen specifically use them to catch the yellowfin tuna. However, tuna caught with handlines often face predation from other fish, and their quality diminishes as they struggle to escape. To improve the quality of the caught fish, a device known as the "tuna jacket" has been introduced. This handling device serves as a protective cover for fish under attack or being eaten by other fish. Additionally, the tuna jacket restricts the movement of captured fish, leading to their quicker death. This research aimed to analyze the effectiveness of using tuna jackets in handline fisheries in Maluku waters, Indonesia. The study's results indicate that tuna jackets are more effective compared to the control methods. However, fishermen have a negative perception of the tuna jacket since its use can reduce their income. [ABSTRACT FROM AUTHOR]

Taiwan Bank (TB) is located in the southern Taiwan Strait (TS). The uplifted continental slope and bottom currents in this area result in the formation of upwelling areas, which serve as crucial fishing grounds. Climate-induced fluctuations in fish populations occur in the TS. However, how predation and competition affect the interspecies relationships in the TB ecosystem warrants clarification. In this study, we collected high-grid-resolution data on fishery activity (2013–2019) and constructed ecosystem models using Ecopath with Ecosim (EwE). Three mass-balanced models for determining the influence of El Niño–Southern Oscillation (ENSO) events on the TB ecosystem were constructed using EwE. A range of groups, including representative pelagic, benthic, and reef species, were collected for analyzing the relationship between migratory and sedentary species in terms of ecosystem structure variation due to climate change. The results demonstrated that the total system throughput (TST) was 10,556–11,122 t km−2 year−1, with an average transfer efficiency of 12.26%. According to the keystoneness index, calculated through mixed trophic impact analysis, Polydactylus sextarius and Scomber japonicus were the key species with top–down control and relatively high impact on the ecosystem in normal years. The keystone species also shifted to the predator fish Thunnus albacares and Katsuwonus pelamis during El Niño and La Niña events, respectively. Moreover, total biomass, TST, consumption, and respiration were noted to increase during ENSO events. However, during La Niña events, the diversity and connectance indexes were relatively low but pelagic species' biomass was relatively high, whereas the biomass of most benthic and reef species was relatively high during El Niño events. [ABSTRACT FROM AUTHOR]

Managing populations of wild harvested species requires the ability to regularly provide accurate abundance assessments. For most marine species, changes in abundance can only be monitored indirectly, using methods reliant on harvest-based indices, with significant inherent limitations surrounding the estimation and standardization of harvest effort. Tropical tunas are some of the most exploited marine species in the world and are among several species in critical need of alternative methods for estimating abundance. Addressing this concern, we developed the Associative Behaviour-Based abundance Index (ABBI), designed to provide direct abundance estimates for animals, which exhibit an associative behaviour with aggregation sites. Its implementation in the western Indian Ocean on skipjack tuna (Katsuwonus pelamis), yellowfin tuna (Thunnus albacares) and bigeye tuna (Thunnus obesus), revealed similar trajectories in their relative abundance. The ABBI stands as a potentially promising alternative to enhance traditional tropical tuna stock assessments methods, as well as a new opportunity to assess the abundance of other wild species that display an associative behaviour with physical structures found in their natural environment. [ABSTRACT FROM AUTHOR]

Age-reading protocols for tuna species using annual growth zones in thin-cut transverse otolith sections have produced greater age estimates than previous methods. Lifespan estimates for yellowfin (YFT) and bigeye (BET) tuna (Thunnus albacares and T. obesus) were validated up to 16–18 years in the western North Atlantic Ocean using bomb 14C dating and the current study extends the approach to YFT and BET of the western and central Pacific Ocean (WCPO). Archived otoliths from young-of-the-year (YOY) tuna caught in the WCPO were analysed for 14C to establish a reference chronology covering 30 years (1989–2019). This YOY 14C time series exhibited strong concordance with existing coral-otolith 14C references for the tropical-subtropical Pacific Ocean and was combined as a single chronology. Otolith cores from YFT aged 1–14 years and BET aged 1–13 years from presumed annual counts were analysed for 14C. These measurements aligned with the reference chronology for the calculated hatch years for both species. These findings provide strong evidence that growth zones in thin-sectioned otoliths are deposited annually for YFT and BET of the WCPO and that age interpretation is correct using the current age reading protocol with little to no bias. [ABSTRACT FROM AUTHOR]

Summary: Brown stain is a major problem for tuna during storage. This study aimed to investigate the impact of antioxidants on myoglobin oxidation and the promotion of metmyoglobin (MetMb) reduction in tuna slices. Response surface methodology (RSM) was used to optimise the formula of the compound antioxidant in yellowfin tuna (YFT) slices, with the percentage of MetMb as the response value. The ratios of ε‐polylysine, sodium lactate and D‐sodium ascorbate were 0.43%, 2.21% and 2.71%, respectively. The interactions between sodium lactate and D‐sodium ascorbate had a greater impact on the percentage of MetMb. Then, verification experiments were conducted, and the results revealed that the samples treated with compound antioxidants had higher a* values, total sulfhydryl content, Ca2+‐ATPase activity, total reducing activity (TRA) and MetMb‐reducing activity (MRA) and lower percentages of MetMb and carbonyl contents than did the control samples. It also helps to maintain the stability of the NADH/NAD+ ratio, which contributes to facilitating MetMb reduction. The results showed that the compound antioxidant significantly inhibited myoglobin oxidation, promoted the reduction of MetMb in tuna slices and significantly enhanced the myoglobin stability of refrigerated YFT slices. [ABSTRACT FROM AUTHOR]

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Complementary approaches (stomach contents, DNA barcoding, and stable isotopes) were used to examine seasonal shifts in the feeding ecology of an oceanic predator, yellowfin tuna (Thunnus albacares, n = 577), in the northern Gulf of Mexico. DNA barcoding greatly enhanced dietary resolution and seasonally distinct prey assemblages were observed for both sub-adults and adults. In general, diet was characterized by ommastrephid squids and exocoetids in spring, juvenile fishes (i.e., carangids and scombrids) in summer, migratory coastal fishes during fall, and an increased consumption of planktonic prey (e.g., amphipods) in winter. Seasonal variability in bulk stable isotope values (δ13C, δ15N, and δ34S) was also observed, with low δ15N values and high δ34S values during late summer/early fall and high δ15N values (low δ34S) during late winter/early spring. Bayesian stable isotope mixing models corroborated seasonal diet shifts, highlighting the importance of oceanic nekton in spring/summer, coastal nekton during fall, and oceanic plankton during winter. Seasonal shifts in diet appeared to be influenced by prey reproductive cycles, habitat associations, and environmental conditions. Findings highlight the complex food web dynamics supporting an opportunistic oceanic predator and the importance of seasonal cycles in prey availability to predator resource utilization in open-ocean ecosystems. [ABSTRACT FROM AUTHOR]

Tropical tuna fisheries support some of the largest artisanal and industrial fisheries worldwide. Approximately 37% of the tropical tuna catch by industrial purse seiners is obtained from tuna associated with drifting fish aggregating devices (DFADs), where three tuna species coexist: skipjack (Katsuwonus pelamis) , bigeye (Thunnus obesus), and yellowfin tuna (Thunnus albacares) , with stocks subject to different health status. Purse seine fishers heavily rely on acoustic technology to detect and assess the quantity of tuna at DFADs. Yet, accurately distinguishing between species using solely acoustic methods is limited by insufficient knowledge about each species' acoustic response across frequencies. This study was carried out on six swimbladdered individuals belonging to two sets with mean lengths of 51.9 ± 9.5 and 52.9 ± 2 cm. It focuses on the frequency response obtained from ex situ measurements of yellowfin tuna recorded at 38, 70, 120, and 200 kHz, which revealed a flat response across frequencies, with b20 values of −72.4 ± 9, −73.2 ± 8, -72.3 ± 8, and −72.3 ± 9 dB, respectively. These results, contrast with previous findings on bigeye and skipjack, demonstrating the discrimination potential of acoustics in these three species. To harness this potential, a discrimination algorithm was developed. [ABSTRACT FROM AUTHOR]

Flores Sea has a very huge potential for large pelagic fish which is dominated by tuna. However, efforts to predict potential fishing areas are still very limited, especially by using Satellite Remote Sensing Data. The methods generally used are conventional methods which have limitations in terms of data accuracy, area coverage, and efficiency. This study aimed to map the oceanographic conditions of potential fishing zones through the interpretation of Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) satellite imagery and to determine the oceanographic conditions favored by the yellowfin tuna (Thunnus albacares) in the Southern Flores sea. The data collection was conducted directly in the field using longline fishing gear, where the fishing position and catch per trip were categorized as primary data. To analyze the data, the Generalized Additive Model (GAM) using oceanographic parameters (chlorophyll-a, depth, temperature, and salinity) was used. Using the Generalized Additive Model (GAM) with a CED value of 60.40% and an AIC value of 770.8742, the results showed that the sea surface temperature (SST), chlorophyll-a concentration, salinity, and depth are variables that affect fish catch. Oceanographic parameters in the yellowfin tuna fishing potential zone include a temperature range from 28.5 to 29°C, chlorophyll-a concentration of 0.10- 0.14mg/ m2, salinity of 33.7-34ppt, and depth of 3500-1500m, with the largest Zone of Potential Fishing (ZPPI) in September 2023 covering 31,808 km2, with the largest fish catch amounting to 1038kg. [ABSTRACT FROM AUTHOR]

This study investigates the valorization potential of yellowfin tuna (Thunnus albacares) tails to produce high-value commercial products. Firstly, the tuna tails were placed in a perforated stainless-steel cylinder, and hydraulic pressure was applied to separate the skin from the muscle in the tails. The extracted muscle was then utilized as a nitrogen source for the growth of the proteolytic enzyme producer Bacillus subtilis, while the skins were employed for gelatin extraction. The proteases from B. subtilis were partially purified and used to produce antioxidant peptides from the obtained gelatin. The gelatin formed a gel upon cooling, with gelling and melting temperatures of 16 °C and 22 °C, respectively, and a Bloom strength of approximately 160. Response Surface Methodology (RSM) was employed to determine the optimal hydrolysis conditions to achieve the highest antioxidant activity (35.96% measured as DPPH radical scavenging activity), which were 50 °C and 6.5 IU of enzyme. The findings emphasize the importance of an integrated approach to maximize the value of tuna by-products, promoting sustainability within the framework of a circular bioeconomy. Overall, these results contribute to the efficient utilization of tuna by-products, waste reduction, and enhanced economic viability of the tuna industry. [ABSTRACT FROM AUTHOR]

To accurately identify the key features influencing the fisheries distribution of Pacific yellowfin tuna, this study analyzed data from 43 longline fishing vessels operated from 2008 to 2019. These vessels operated in the Pacific Ocean region (0° to 30° S; 110° E to 170° W), with a specific focus on 25 features of yellowfin tuna derived from marine environment data. For this purpose, this study opted for the Lasso regression analysis method to select features to predict Pacific yellowfin tuna fishing grounds, exploring the relationship between the catch per unit effort (CPUE) of yellowfin tuna and multiple features. This study reveals that latitude and water temperature at various depths, particularly the sea surface temperature of the preceding and subsequent months and the temperature at depths between 300 and 450 m, are the most significant features influencing CPUE. Additionally, chlorophyll concentration and large-scale climate indices (ONI and NPGIO) also have a notable impact on the distribution of CPUE for yellowfin tuna. Lasso regression effectively identifies features that are significantly correlated with the CPUE of yellowfin tuna, thereby demonstrating superior fit and predictive accuracy in comparison with other models. It provides a suitable methodological approach for selecting fishing ground features of yellowfin tuna in the Pacific Ocean. [ABSTRACT FROM AUTHOR]

Machine learning occupies a central position in the modeling of fish distribution patterns. The augmentation of explanatory variables in fish habitat through many kinds of observational methodologies necessitates the discernment of an optimal combination of these variables for fish distribution modeling. We proposed a feature selection technique, recursive feature elimination with cross-validation (RFECV), to determine optimal variables combinations for yellowfin tuna distribution in the Pacific Ocean. Four tree-based models, random forest, eXtreme Gradient Boosting, Light Gradient Boosting Machine, and categorical boosting driven by RFECV, were developed using comprehensive fisheries and biotic/abiotic data. Habitat variables including sea temperature, dissolved oxygen concentration, chlorophyll-a concentration, sea salinity, and sea surface height were identified as significant features by all models. The models were trained using the corresponding selected variables, and these trained models were employed to predict the spatiotemporal distribution of yellowfin tuna from 1995 to 2019. The results obtained could inform useful knowledge for the sustainable exploitation of yellowfin tuna in the Pacific Ocean and furnish a benchmark of feature selection for machine-learning-based distribution modeling of other pelagic species. [ABSTRACT FROM AUTHOR]

This study investigated the effects of acute ammonia nitrogen (NH3-N) exposure on kidney antioxidant ability and phosphatases and related gene expression in juvenile yellowfin tuna (Thunnus albacares). The 180 juvenile yellowfin tuna (260.39 ± 55.99 g, 22.33 ± 2.28 cm) were exposed to ammonia for 6, 24, and 36 h using natural seawater (0 mg/L) as a control and NH3-N at 5 and 10 mg/L. The lipid peroxidation byproduct malondialdehyde (MDA) and the levels of antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-PX), alkaline phosphatase (AKP), and acid phosphatase (ACP), were measured using the colorimetric method in the trunk kidney to determine changes in antioxidant ability and phosphatase activity of juvenile yellowfin tuna exposed to NH3-N. Results indicated that, at 36 h, MDA, SOD, CAT, and GSH-PX levels rose in the 5 mg/L group versus the control. In the 10 mg/L group, MDA and SOD, CAT, and GSH-PX activities significantly increased after 24 and 36 h exposure compared to the control. Phosphatases play a pivotal role in the immune system. AKP activity significantly increased at 6 h, and ACP activity markedly rose at 36 h in the 5 mg/L group versus the control. Real-time fluorescence quantitative PCR was applied to detect alterations in the antioxidant genes SOD2, CAT, and glutathione peroxidase 1b (GPX1b) and immune cytokines-related genes Interleukin 10 (IL-10) and Interleukin 6 receptor (IL-6r) expression in the head kidney in juvenile tuna. Relative to the control, antioxidant gene expression in the 5 mg/L group significantly rose at 6 and 36 h, and in the 10 mg/L group, SOD2 and GPX1b were significantly elevated at 36 h. Compared to the control group, IL-10 expression in the 5 mg/L group significantly increased at 6 h, whereas IL-6r expression decreased. In the 10 mg/L group, both IL-10 and IL-6r levels were observed to be lower. Low ammonia nitrogen concentrations boost antioxidant defenses, phosphatase activities, and gene expression levels, whereas higher levels may induce suppressive effects. In yellowfin tuna juvenile farming, NH3-N concentration significantly affects the health of the juveniles. When the NH3-N concentration is between 5–10 mg/L, the stress duration should be limited to 24 h; if the concentration is below 5 mg/L, the stress duration can be extended to 36 h. [ABSTRACT FROM AUTHOR]

The yellowfin tuna represents a significant fishery resource in the Pacific Ocean. Its resource endowment status and spatial variation mechanisms are intricately influenced by marine environments, particularly under varying climate events. Consequently, investigating the spatial variation patterns of dominant environmental factors under diverse climate conditions, and understanding the response of yellowfin tuna catch volume based on the spatial heterogeneity among these environmental factors, presents a formidable challenge. This paper utilizes comprehensive 5°×5° yellowfin tuna longline fishing data and environmental data, including seawater temperature and salinity, published by the Western and Central Pacific Fisheries Commission (WCPFC) and the Inter-American Tropical Tuna Commission (IATTC) for the period 2000–2021 in the Pacific Ocean. In conjunction with the Niño index, a multiscale geographically weighted regression model based on geographically weighted principal component analysis (GWPCA-MGWR) and spatial association between zones (SABZ) is employed for this study. The results indicate the following: (1) The spatial distribution of dominant environmental factors affecting the catch of Pacific yellowfin tuna is primarily divided into two types: seawater temperature dominates in the western Pacific Ocean, while salinity dominates in the eastern Pacific Ocean. When El Niño occurs, the area with seawater temperature as the dominant environmental factor in the western Pacific Ocean further extends eastward, and the water layers where the dominant environmental factors are located develop to deeper depths; when La Niña occurs, there is a clear westward expansion in the area with seawater salinity as the dominant factor in the eastern Pacific Ocean. This change in the spatial distribution pattern of dominant factors is closely related to the movement of the position of the warm pool and cold tongue under ENSO events. (2) The areas with a higher catch of Pacific yellowfin tuna are spatially associated with the dominant environmental factor of mid-deep seawater temperature (105–155 m temperature) to a greater extent than other factors, the highest correlation exceeds 70%, and remain relatively stable under different ENSO events. The formation of this spatial association pattern is related to the vertical movement of yellowfin tuna as affected by subsurface seawater temperature. (3) The GWPCA-MGWR model can fully capture the differences in environmental variability among subregions in the Pacific Ocean under different climatic backgrounds, intuitively reflect the changing areas and influencing boundaries from a macro perspective, and has a relatively accurate prediction on the trend of yellowfin tuna catch in the Pacific Ocean. [ABSTRACT FROM AUTHOR]

This study aimed to explore the impact of acute acidification on the antioxidant, metabolic performance, and liver histology of juvenile yellowfin tuna. The experiment subjected juvenile yellowfin tuna to a pH gradient environment of 8.1, 7.6, 7.1, and 6.6 for 48 h. The findings indicate that a seawater pH of 7.1 significantly impacts the antioxidant and metabolic systems of the juvenile yellowfin tuna in comparison to the control group. At pH 7.1, there were observed increases in glutathione reductase (GR), total antioxidant capacity (T-AOC), lactate dehydrogenase (LDH), hexokinase (HK), pyruvate kinase (PK), sodium-potassium ATPase (Na+K+-ATP), and calcium-magnesium ATPase (Ca2+Mg2+-ATP). Conversely, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides (TGs) were not significantly different across the treatment groups. However, an increase in transaminases at pH 7.1 suggested potential liver damage, which was further supported by observed structural liver tissue degeneration and hepatocyte vacuolation. In conclusion, under conditions of acute acidification stress, there is a decrease in antioxidant capacity and a suppression of metabolic levels in juvenile yellowfin tuna, leading to oxidative damage. This study lays the foundation for an in-depth understanding of the response mechanisms of juvenile yellowfin tuna in response to seawater acidification as well as healthy tuna farming in the broader context of seawater acidification. [ABSTRACT FROM AUTHOR]

Yellowfin tuna (Thunnus albacares) is a valuable pelagic migratory fish with potential for aquaculture. Despite this, there is limited understanding of the biological and physiological characteristics of this species, particularly regarding sex differences in growth performance. The liver, a crucial organ for digestion and metabolism, plays a significant role in regulating fish growth. This study aimed to compare liver enzyme activities and transcriptome profiles between female and male yellowfin tuna to uncover the molecular mechanisms underlying difference between the sexes. The results revealed that female yellowfin tuna exhibited higher amylase and lipid metabolism enzyme activities, while male yellowfin tuna showed higher glucose-6-phosphate dehydrogenase and antioxidant enzyme activities. Additionally, through Illumina sequencing technology, the study generated 37.74 Gb of clean data and identified 36,482 unique genes (UniGenes) in the liver transcriptome. A total of 2542 differentially expressed genes were found, with enriched Gene Ontology terms and pathways related to metabolic processes, particularly lipid metabolism and transport. These findings suggest that female yellowfin tuna have superior digestive enzyme activities and lipid metabolism, while male yellowfin tuna excel in sugar metabolism, ATP production, and antioxidant defense. This study provides valuable insights into sex differences in yellowfin tuna and could aid in advancing full-cycle aquaculture practices for this species. [ABSTRACT FROM AUTHOR]

This study delves into the foraging ecology of the cookiecutter shark (Isistius brasiliensis) in the Saint Peter and Saint Paul Archipelago (SPSPA), assessing bite marks on pelagic fishes collected between March and September 2018. Examination of 200 individuals from five species revealed the shark's predilection for targeting adult fish, ensuring efficient removal of energy‐rich tissue layers. However, a notable exception is Thunnus albacares, preyed on predominantly during its juvenile stage, possibly due to vertical spatial segregation. Recent bites were pervasive across species, with wahoo displaying a distinctive pattern. Cookiecutter shark bites predominantly targeted the lateral body portion (>55%) except for yellowfin tuna, which exhibited a preference for the ventral region (95%). The estimated length distribution suggests the SPSPA as a potential nursery area for cookiecutter sharks. Bite mark positions and frequencies may be linked to fish behavior, swimming velocity, and fishing gear strategy, highlighting the complex interplay in pelagic ecosystems. [ABSTRACT FROM AUTHOR]

Spatial models enable understanding potential redistribution of marine resources associated with ecosystem drivers and climate change. Stock assessment platforms can incorporate spatial processes, but have not been widely implemented or simulation tested. To address this research gap, an international simulation experiment was organized. The study design was blinded to replicate uncertainty similar to a real‐world stock assessment process, and a data‐conditioned, high‐resolution operating model (OM) was used to emulate the spatial dynamics and data for Indian Ocean yellowfin tuna (Thunnus albacares). Six analyst groups developed both single‐region and spatial stock assessment models using an assessment platform of their choice, and then applied each model to the simulated data. Results indicated that across all spatial structures and platforms, assessments were able to adequately recreate the population trends from the OM. Additionally, spatial models were able to estimate regional population trends that generally reflected the true dynamics from the OM, particularly for the regions with higher biomass and fishing pressure. However, a consistent population biomass scaling pattern emerged, where spatial models estimated higher population scale than single‐region models within a given assessment platform. Balancing parsimony and complexity trade‐offs were difficult, but adequate complexity in spatial parametrizations (e.g., allowing time‐ and age‐variation in movement and appropriate tag mixing periods) was critical to model performance. We recommend expanded use of high‐resolution OMs and blinded studies, given their ability to portray realistic performance of assessment models. Moreover, increased support for international simulation experiments is warranted to facilitate dissemination of methodology across organizations. [ABSTRACT FROM AUTHOR]

Summary: There is a debate on the optimal tempering rate for preserving the quality of aquatic muscle products. An adjustable and uniform tempering method is required to address this. Radio frequency (RF) heating, with its rapid and volumetric heating characteristics and adjustable tempering rate, has shown great potential in frozen food tempering. In this study, we utilised a developed improved RF heating method with controlled heating rates and uniformity to investigate the quality attributes of yellowfin tuna flesh samples subjected to two freezing rates (0.35 and 0.47 cm h−1) and three tempering rates (0.5, 1.0, and 1.5 °C min−1), respectively, to reveal the influence of freezing and tempering rates influence on tuna quality attributes. In the majority of treatment groups, the differences in drip loss, TBARS, TVB‐N, MetMb, colour, and protein solubility between the high‐speed freezing and slow‐thawing groups were minimal. It was found that fast freezing allows smaller‐scale ice crystal generation, which has the least influence on muscle fibre, and a low tempering rate could gently regulate the influence of ice crystal size on muscle structures. [ABSTRACT FROM AUTHOR]

As an economically critical pelagic migratory species, yellowfin tuna (Thunnus albacores, YFT) is very sensible to physical and environmental conditions, such as sea surface temperature (SST), ocean heat content (OHC), and the mixed layer depth (MLD). We investigated the impact of SST, OHC, and MLD on fluctuations of YFT catch in the western/eastern Indian Ocean using the long time series of 63-year environmental and YFT datasets. We found that the impact of SST on YFT was heavily overestimated in the past, and MLD plays a more critical role in the YFT catch fluctuation. When the MLD deepens (>34.8 m), SST was more influential in predicting the catches of YFT than OHC in the western Indian Ocean, and OHC was more critical to YFT than SST in the eastern Indian Ocean. However, when the MLD shallows (<34.8 m), MLD was more vital to predict the catch per unit effort (CPUE) of YFT than SST/OHC in the western. After 2000, there was an asynchronous pattern of YFT CPUE induced by higher frequency variations and ocean hiatus of SST/OHC signals in the western and eastern Indian Oceans basins. The impact of the subsurface hiatus may induce the decrease of YFT in the eastern Indian Ocean. The above findings clarified a non-stationary relationship between the environmental factors and catches of YFT and provided new insights into variations in YFT abundance. [ABSTRACT FROM AUTHOR]

The yellowfin tuna is a very abundant tropical tuna species in the western equatorial Atlantic Ocean and an important fishery resource for the Brazilian tuna fleet. In this study we performed stable isotope analysis to better understand the spatial trophodynamics and dietary changes in yellowfin tuna around two insular marine protected areas in Brazil. A total of 65 yellowfin tuna specimens measuring between 47 and 138 cm LT (total length) were sampled around the archipelagos of Fernando de Noronha (FNA; n = 34) and Saint Peter and Saint Paul (SPSPA; n = 31) between July 2018 and September 2019. Bayesian mixing models and generalized additive models were used to investigate the contributions of four different prey items (zooplankton, cephalopods, fish larvae, and flying fish) to yellowfin tuna diet in each area and their potential changes in relation to predator growth. The four prey items were found to have different overall contributions between the two studied areas, with zooplankton being the most important prey in FNA, whereas flying fish was the most relevant prey to the species' diet in SPSPA. Significant changes in the species diet by size were also found, with fish smaller than 90 cm (TL) having a more generalist diet and larger animals relying more on consuming larger and more nutritious prey (i.e., flying fish). Our results suggest that these two marine protected areas play an important role in ocean dynamics, providing important and different foraging grounds for the development of this predator species. [ABSTRACT FROM AUTHOR]

The waters around the Galápagos Marine Reserve (GMR) are important fishing grounds for authorized artisanal vessels fishing within the reserve as well as for national and foreign industrial fleets operating in the wider Ecuadorian Insular Exclusive Economic Zone (IEEZ). Although it was not originally designed for fisheries management, Automatic Identification System (AIS) data provides useful, open access, near real-time and high-resolution information that allows for increased monitoring, particularly around Marine Protected Areas (MPAs) and in Areas Beyond National Jurisdiction. This study uses AIS data provided by Global Fishing Watch to assess the spatial distribution and seasonal dynamics of fishing effort by vessel flag within the GMR and the IEEZ from 2012 to 2021. Based on kernel density estimation analysis, we determinate the core-use areas (50%) and spatial extent (95%) of fishing activities by fleets (Ecuadorian and foreign), gear types and seasons (warm, from December to May; and cold, from June to November). Our results show that the Ecuadorian fleet recorded the most observed fishing hours in the study area, with 32,829 hours in the IEEZ and 20,816 hours within the GMR. The foreign flags with the most observed fishing hours in the IEEZ were Panama (3,245 hours) and Nicaragua (2,468.5 hours), while in the GMR were the 'Unknown flag' (4,991.4 hours) and Panama (133.7 hours). Vessels fished employing different fishing gears, but the waters of the GMR and IEEZ were mostly targeted by tuna purse-seiners and drifting longlines. The spatial distribution of the fishing effort exhibits marked seasonal variability, likely influenced by seasonal migrations of target species such as tunas (e.g., Thunnus albacares, T. obesus and Katsuwonus pelamis), marlins (e.g., Makaira nigricans) and sharks (e.g., Alopias pelagicus). The collection and use of this type of spatial and seasonal information is an essential step to understand the dynamics of fishing activities in national waters and improve fisheries management, particularly in less studied areas and fisheries. [ABSTRACT FROM AUTHOR]

The enzymatic extraction of proteins from fish biomasses is being widely investigated. However, little or almost no research has paid attention to the exploitation of unsorted fishery biomasses. This work is part of a larger study, Part I of which has already been published, and focuses on an extensive characterization of two collagenous samples, namely gelatin (G) and hydrolyzed gelatin peptides (HGPs), extracted from a dehydrated fish biomass coming from unsorted canned yellowfin tuna side streams. The results indicate crude protein fractions of 90–93%, pH values between 3 and 5, white–yellow colors, collagen-like FTIR spectra, and 17% in terms of total amino acid content. Viscosity and the study of dynamic viscous–elastic behavior were analyzed. Thermo-gravimetric analysis was performed to assess the residual ashes. Both samples were investigated to determine their molecular weight distribution via size-exclusion chromatography, with a higher total average molecular weight for G compared to HGPs, with values of 17,265.5 Da and 2637.5 Da, respectively. G demonstrated technological properties similar to analogous marine gelatins. HGPs demonstrated antioxidant activity as per FRAP assay. All the results open up new perspectives for the potential use of these substances in biodegradable packaging, dietary supplements, and skin care cosmetics. [ABSTRACT FROM AUTHOR]

Several odontocete species depredate catch and bait from fishing gear, resulting in their bycatch and causing substantial economic costs. There are no known mitigation methods for odontocete depredation in pelagic longline fisheries that are effective, do not harm odontocetes and are commercially viable. Understanding odontocetes' depredation strategies can contribute to mitigating this human-wildlife conflict. Using observer data from the Hawaii-based tuna longline fishery, this study summarized teleost and elasmobranch species-specific mean posterior odontocete depredation rates using a simple Bayesian binomial likelihood estimator with a Bayes-Laplace prior. Depredation rates of species with sufficient sample sizes ranged from a high of 1.2% (1.1 to 1.3 95% highest posterior density interval or HDI) for shortbill spearfish to a low of 0.002% (0.001 to 0.003 95% HDI) for blue shark. Depredation of catch is a rare event in this fishery, occurring in about 6% of sets. When depredation did occur, most frequently odontocetes depredated a small proportion of the catch, however, there was large variability in depredation rates between teleost species. For example, bigeye tuna was two times more likely to be depredated than yellowfin tuna (odds ratio = 2.03, 95% CI: 1.8–2.3, P<0.0001). For sets with depredation, 10% and 2% of sets had depredation of over half of the captured bigeye tuna and combined teleosts, respectively. All elasmobranch species had relatively low depredation rates, where only 7 of almost 0.5M captured elasmobranchs were depredated. Odontocetes selectively depredate a subset of the teleost species captured within sets, possibly based on net energy value, chemical, visual, acoustic and textural characteristics and body size, but not median length, which was found to be unrelated to depredation rate (Pearson's r = 0.14, 95% CI: -0.26 to 0.50, p = 0.49). Study findings provide evidence to support the identification and innovation of effective and commercially viable methods to mitigate odontocete depredation and bycatch. [ABSTRACT FROM AUTHOR]

The tuna fishery resources, particularly yellowfin tuna (YFT), in Ternate waters, North Maluku, Indonesia (fishery management area 715), are currently classified as fully exploited at 0.97% utilization rate of the available potentials, i.e., 31.659 ton/year. This calls for an attempt to manage the yellowfin tuna in such a way that its existence in the waters can be maintained. Studies on fish population parameters are an effort to obtain scientific information as a recommendation for sustainable fisheries management. This research used experimental fishing by measuring the fish's length. Then, its population was estimated using FISAT II program, and its spawning potential ratio (SPR) was analyzed using length based-spawning potential ratio (LB-SPR) software. It was expected that this would be able to give the yellowfin tuna current status and condition in Ternate waters. Conducted from May through August 2023, and analyzing 4,904 fish, the research managed to determine the population parameters of yellowfin tuna in Ternate waters. Its asymptotic length (L8), growth coefficient (K) and t0 were 117.60 cm, 1.4 per year, and 0.17 year, respectively. These were then plotted to obtain a von Bertalanffy growth curve using the formula Lt = 117,60*(1-Exp-1,4(t-0,17). From the analysis, it was found that the fish total mortality, natural mortality and captive mortality rates were 3.89, 1.55, and 2.34, respectively. Furthermore, it was found that recruitment occurred twice a year, i.e., on March and August at 6.72 and 25.18%, with the Y/R value being 0.039 and B/R value of 0.482. Meanwhile, the spawning potential ratio (SPR) value was 19%, indicating that the utilization rate had been over exploited (SPR< 20%) and it was supported by the fact that the exploitation rate value had been over 0.60 (over fishing) from the Emax value (0.421). Therefore, management is needed to ensure the sustainability of yellowfin tuna stocks. [ABSTRACT FROM AUTHOR]

Salting pretreatment is an effective method to improve the quality of frozen fish. This study investigated the quality changes and proteomic profile differences of frozen yellowfin tuna fillets pretreated with ultrasound-assisted salting (UAS) and static salting (SS). This study was centered on three aspects: physicochemical indicators' determination, histological observation, and proteomic analysis. The results showed that UAS significantly increased yield, salt content, and water-holding capacity (WHC), decreased total volatile base nitrogen (TVBN) compared to SS (p < 0.05), and significantly increased water in the protein matrix within myofibrils. Histological observations showed that the tissue cells in the UAS group were less affected by frozen damage, with a more swollen structure and rougher surface of myofibrils observed. Furthermore, 4D label-free proteomics revealed 56 differentially abundant proteins (DAPs) in UAS vs. NT comparison, mainly structural proteins, metabolic enzymes, proteasomes, and their subunits, which are associated with metabolic pathways such as calcium signaling pathway, gap junction, actin cytoskeletal regulation, and necroptosis, which are intimately associated with quality changes in freeze-stored tuna fillets. In brief, UAS enhances the potential for the application of salting pretreatment to improve frozen meat quality, and 4D label-free proteomics provides knowledge to reveal the potential links between quality and molecular changes in processed frozen meat to optimize future UAS meat processing. [ABSTRACT FROM AUTHOR]

Oxygen minimum zones in the open ocean are predicted to significantly increase in volume over the coming decades as a result of anthropogenic climatic warming. The resulting reduction in dissolved oxygen (DO) in the pelagic realm is likely to have detrimental impacts on water-breathing organisms, particularly those with higher metabolic rates, such as billfish, tunas, and sharks. However, little is known about how free-living fish respond to low DO environments, and therefore, the effect increasing OMZs will have cannot be predicted reliably. Here, we compare the responses of two active predators (bigeye tuna Thunnus obesus and yellowfin tuna Thunnus albacares) to DO at depth throughout the eastern Pacific Ocean. Using time-series data from 267 tagged tunas (59,910 days) and 3D maps of modelled DO, we find that yellowfin tuna respond to low DO at depth by spending more time in shallower, more oxygenated waters. By contrast, bigeye tuna, which forage at deeper depths well below the thermocline, show fewer changes in their use of the water column. However, we find that bigeye tuna increased the frequency of brief upward vertical excursions they performed by four times when DO at depth was lower, but with no concomitant significant difference in temperature, suggesting that this behaviour is driven in part by the need to re-oxygenate following time spent in hypoxic waters. These findings suggest that increasing OMZs will impact the behaviour of these commercially important species, and it is therefore likely that other water-breathing predators with higher metabolic rates will face similar pressures. A more comprehensive understanding of the effect of shoaling OMZs on pelagic fish vertical habitat use, which may increase their vulnerability to surface fisheries, will be important to obtain if these effects are to be mitigated by future management actions. [ABSTRACT FROM AUTHOR]

Alcalase enzyme (1 mg) and ultrasound (400 W) at 0–20 min were applied to obtain sulfated polysaccharides from yellowfin skin. Applying 15 min ultrasound resulted in a 0.12% increase in the rate of recovery yield. The intact structure of polysaccharides was determined by Fourier transform infrared spectroscopy, X-ray diffractometry, and scanning electron microscope. Ultrasound improved the thermal behavior of sulfated polysaccharides by affecting their microstructure, as analyzed by DSC. The color characterization (L*, a*, and b*) of ultrasound-treated samples was found to be superior compared to the control. Applying 15 min led to 16% and 9% enhancing DPPH and ABTS radical scavenging activities along with improving ferric-reducing antioxidant power of the polysaccharide. [ABSTRACT FROM AUTHOR]

The highest yield (34%) and imino acid (18.7%) of collagen were obtained from yellowfin tuna (Thunnus albacares) skin using 20 min ultrasound. The collagen was identified as type I collagen according to the results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and its structure remained intact, proved by ultraviolet spectroscopy (UV) and fourier transform infrared spectroscopy (FTIR). Collagen solubility was superior in acidic and low salt environments. Ultrasound cavitation for 20 min improved collagens' emulsifying (EAI: 78.8 m2/g and ESI: 110.3 min) and foam properties (FA: 151.8% and FS: 133.3%) and water holding capacity (51.9%) by enhancing internal hydrophobic interactions and surface hydrophobicity. 20 min ultrasound resulted in desirable DPPH (61.1%) and ABTS (53.1%) radical scavenging and ferric-reducing antioxidant power (0.078 ABS). [ABSTRACT FROM AUTHOR]

The last decade has witnessed a steady transition from the linear economic model to a restorative system that drives substantial and lasting improvements of the global resource productivity. In this scenario, the blue economy encompasses all industries and sectors related to oceans, seas and coasts. The blue economy model promotes a series of actions towards sustainability, which include minimization of food waste production through the re-utilization of the marine by-products. Within the food chain, the large amount of waste generated by the tuna fishery industry represents a rich pool of bioactive molecules, including polyunsaturated fatty acids, vitamins, amino acids (AAs) and peptides. Specifically, small- and medium-size peptides are emerging as a more convenient alternative to conventional antibiotic agents, against a variety of bacteria, fungi and viruses. This study focused on the retrieval of the protein fractions contained in the discards from the yellowfin tuna (Thunnus albacares) cannery industry. Protein hydrolysates obtained by enzymatic digestion were characterized by a peptidomic strategy based on reversed-phase ultra-high–pressure liquid chromatography followed by quadrupole-time-of-flight tandem mass spectrometry detection (data dependent analysis). A total of 196 AAs sequences were identified by matching MASCOT database, and their activity was predicted by support vector machine–based computational tools. As a result, significant antimicrobial scores were obtained for 22% of the identified peptides. Specifically, antibacterial, antifungal and antiviral properties were predicted based on compositional features (pseudo AA compositions and normalized AA compositions) and physicochemical properties (isoelectric point, hydrophobicity and net-charge). [ABSTRACT FROM AUTHOR]

In a balanced diet, regular fish consumption provides positive outcomes for human health. On the other hand, the seafood supply chain faces a significant food safety risk due to the presence of potentially toxic elements (PTEs). In the present study, to assess the risk for Italian consumers, the concentrations of five PTEs, namely lead, chromium, cadmium, mercury, nickel, and aluminum, were determined in the three most consumed preserved fish in Italy: tuna (Thunnus albacares, Katsuwonus pelamis), mackerel (Scomber scombrus) and anchovy (Engraulis encrasicolus). Samples were collected from the national market, and the instrumental analysis was performed by inductively coupled plasma mass spectrometry (ICP-MS). The analyzed PTEs were found in all the species that were investigated. However, after considering the target hazard quotient (THQ) and the hazard index (HI), it was observed that the three fish preserves did not pose any risk of chronic toxicity for the average consumer, even at the highest concentrations detected. However, for significant consumers, mercury detected in tuna samples represented almost 90% of the tolerable weekly intake (TWI) reported by the European Food Safety Authority (EFSA), representing a matter of concern for consumers, particularly regarding developmental neurotoxicity, whose HI exceeded 111%. The acute toxicity of nickel was also considered for significant consumers at the highest concentration detected, and the margin of exposure (MOE) calculated was above 7000, much higher than the value of 30 indicated by EFSA. Due to the lack of data on non-professional carcinogenicity or human intake through foods with low cancer risk, this toxicity was not considered in the analysis of PTEs. [ABSTRACT FROM AUTHOR]

Yellowfin tuna (Thunnus albacares) is the world's second-largest commodity with good nutrition. After processing, some wastes / residues / by-products can be used to produce surimi which still retains the tuna meat properties. The manufacturing of surimi requires safe preservatives, such as the natural preservative, atung (Parinarium glaberimum Hassk), which contains antibacterial substances. Therefore, the present work aimed to determine the effectiveness of 4% (w/v) atung solution on the quantity and quality of yellowfin tuna surimi produced from tuna by-products. The fish meat was treated with a washing agent of ice water and 4% atung solution with several washing frequencies. The parameters assessed were the yield and quality of surimi by analysing the protein content, myofibrillar protein content (salt soluble), water-holding capacity, Salmonella spp., and E. coli. In addition, the parameters included teeth-cutting, ashi strength, and folding. The 4% (w/v) atung solution effectively produced tuna fish surimi with 68.50% yield, 20.62% protein, 8.87% myofibrillar protein, and free from Salmonella spp. and E. coli. The waterholding capacity of the surimi was recorded at 68.9% and increased to 73.3% after three washes. The use of 4% (b/v) atung solution effectively produced surimi with a teethcutting value of 7.80 - 7.92, and an ashi strength of 7.97 - 8.08, whereas the folding test was B to A (3.80) after four washes. [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 Yellowfin tuna (Thunnus albacares) is a large tuna exploited by major fisheries in tropical and subtropical waters of all oceans except the Mediterranean Sea. Genomic studies of population structure, adaptive variation or of the genetic basis of phenotypic traits are needed to inform fisheries management but are currently limited by the lack of a reference genome for this species. Here we report a draft genome assembly and a linkage map for use in genomic studies of T. albacares. Methods and results: Illumina and PacBio SMRT sequencing were used in combination to generate a hybrid assembly that comprises 743,073,847 base pairs contained in 2,661 scaffolds. The assembly has a N50 of 351,587 and complete and partial BUSCO scores of 86.47% and 3.63%, respectively. Double-digest restriction associated DNA (ddRAD) was used to genotype the 2 parents and 164 of their F1 offspring resulting from a controlled breeding cross, retaining 19,469 biallelic single nucleotide polymorphism (SNP) loci. The SNP loci were used to construct a linkage map that features 24 linkage groups that represent the 24 chromosomes of yellowfin tuna. The male and female maps span 1,243.8 cM and 1,222.9 cM, respectively. The map was used to anchor the assembly in 24 super-scaffolds that contain 79% of the yellowfin tuna genome. Gene prediction identified 46,992 putative genes 20,203 of which could be annotated via gene ontology. Conclusions: The draft reference will be valuable to interpret studies of genome wide variation in T. albacares and other Scombroid species. [ABSTRACT FROM AUTHOR]

Introduction: Tuna has a cost-effective energy supply to support the regional endothermic and high-speed swimming performance. The gut symbiotic microbiotas and their metabolites play essential roles in tuna's diet digestion, absorption, and energy acquirement, which are often highly related to the ontogenetic development of tuna. Methods: We compared gut microbial compositions and metabolites, as well as mRNA expression of the intestine between juvenile and adult yellowfin tuna using 16S rRNA sequencing, metabolomic and transcriptomic, respectively. Results and discussion: The results revealed that adults had a significantly higher microbial diversity and abundance of Acinetobacter than juveniles. Regarding the gut microbiota-derived metabolites, fatty acids, especially glycerophospholipid and sphingolipid, were significantly enriched in adults than in juveniles. Moreover, the short-chain fatty acid (butyrate and isobutyrate) contents were significantly higher in adults than in juveniles. To find the relationship between gut microbiotas and host physiology, intestinal transcriptome analysis demonstrated that the enriched pathways of differential expression genes (DEGs) in adult tuna were the lipid metabolism pathway, including "fat digestion and absorption," "cholesterol metabolism," "steroid hormone biosynthesis," "glycerolipid metabolism," and "glycerophospholipid metabolism." However, protein digestion and absorption and pancreatic secretion pathways were significantly enriched in the juveniles. The conjoint analysis indicated that the enriched pathways of both differential metabolites (DMs) and DEGs were remarkably related to the regulation of glycerophospholipids metabolism in adult tunas. This study highlights the role of gut microbiotas in fish nutrition metabolism. These findings provide new insights into the view of ontogenetic shifts of gut microbiotas and their metabolites on host health and gut function in endothermic and high-speed swimming marine fish species. [ABSTRACT FROM AUTHOR]

The management of fish aggregating devices (FAD) creates heated debates in tuna fishery management organizations striving to reduce the number of deployed floating objects. Through several econometric models and a machine learning approach, we evaluate the consequences of three management scenarios on the catch and profit of the French purse‐seine fleet operating in the Indian Ocean: (1) a half reduction in the number of authorized buoys per vessel, (2) a 72‐day closure of FAD fishing with and (3) without re‐allocation of effort on free schools. The results show a significant decrease of fleet profits by 7%, 10% and 18% respectively. We hypothesize an "economic trap" of FAD fishing caused by the far greater efficiency of this harvesting technique for larger vessels searching for economies of scale, and by the overfished status and catch limitation of yellowfin (Thunnus albacares) and bigeye (Thunnus obesus) tunas in the Indian Ocean. The results are compared with other studies looking at the impact of FAD management measures in other oceans. [ABSTRACT FROM AUTHOR]

The objective of this research was to determine the fat oxidation and lipid profile of a Yellowfin (T. albacares) sausage using Lactic Bacteria (L. plantarum). For this purpose, during the sausage production process, lactic bacteria L. plantarum was added at a concentration of 8x10² UFC/ml at a dilution of 10-1 plus a control treatment (without lactic bacteria). During the different days of storage (day 0, day 4, day 8 and day 12), fat oxidation was evaluated using the acidity index method and the lipid profile was determined on the fourth day of storage using the gas chromatography method. With respect to the results of the acidity index, the sample did not show lipid oxidation during the 12 days of storage, unlike the control, which showed lipid oxidation from day 0, suggesting that the lactic acid bacteria incorporated into the sausage could prolong storage and mitigate the effects of rancidity processes. In addition, the lipid profile of the treatment under study complies with the nutritional standards established by Codex regulations, since tuna is an excellent source of omega-3, which represents a contribution of 30% of fatty acids. [ABSTRACT FROM AUTHOR]

Recent studies argue for the presence of genetic population structure in yellowfin tuna (Thunnus albacares) in all oceans. However, the persistence of family groups has never been considered a viable mechanism of structure, nor has it been measured. We analyzed genetic similarity among 280 yellowfin tunas from seven population samples collected in the Western and Central Pacific Ocean (WCPO) using single nucleotide polymorphisms, and found population structure that was significantly explained by the presence of 96 individuals involved in 332 half or full sib dyads. We found significantly higher mean and median relatedness between individuals from the same sample groups, compared to individuals from different groups; and high relatedness between individuals caught at the same fish-aggregating device (FAD) than between those caught in the wider exclusive economic zone (EEZ). Alternatively, the EEZ of the Federated States of Micronesia may harbor exceptionally large numbers of close kin. We conclude that yellowfin directly school with related individuals through their first year, and at least demonstrate tightly overlapping regional fidelity as adults. These results may explain, to some extent, the patterns of population genetic structure recently observed in yellowfin tuna. [ABSTRACT FROM AUTHOR]

Tropical pelagic predators are exploited by fisheries and their movements are influenced by factors including prey availability, temperature, and dissolved oxygen levels. As the biophysical parameters vary greatly within the range of circumtropical species, local studies are needed to define those species' habitat preference and model possible behavioral responses under different climate change scenarios. Here, we tagged yellowfin tuna Thunnus albacares in the Galápagos Marine Reserve and tracked the horizontal and vertical movements of eight individuals for 4–97 days. The tuna traveled a mean of 13.6 km day−1 horizontally and dispersed throughout the archipelago and in offshore waters inside the Galápagos Marine Reserve and in the surrounding Ecuadorian exclusive economic zone. Vertically, they traveled a mean of 2 km day−1, although high‐resolution data from a recovered tag suggested that transmitted data underestimated their vertical movement by a factor of 5.5. The tracked yellowfin tuna spent most of their time near the surface, with an overall mean swimming depth of 24.3 ± 46.6 m, and stayed shallower at night (11.1 ± 16.3 m) than during the day (37.7 ± 60.9 m), but on occasion dived to cold, oxygen‐poor waters below 200 m. Deep dives were commonly made during the day with a mean recovery period of 51 min between exposures to modeled oxygen‐limiting conditions <1.5 mL L−1, presumably to re‐oxygenate. The depth and frequency of dives were likely limited by dissolved oxygen levels, as oxygen‐depleted conditions reach shallow depths in this region. The main habitat of tracked yellowfin tunas was in the shallow mixed layer, which may leave them vulnerable to fishing. Vertical expansion of low‐oxygen waters under future climate change scenarios may further compress their habitat, increasing their vulnerability to surface fishing gear. [ABSTRACT FROM AUTHOR]

The aim of this study is to develop different models of aquatic forecasting and try to predict yellowfin tuna catch in the southern waters of the country with minimum possible errors. The average catch (Yi ± S. D) and logarithm of catch (LogYi ± S. D) for the years 1997 to 2021 were 35,378 ± 13,744 tons (95% confidence interval 21,634 - 49,129 tons) and 4.51 ± 0.18 tons (95% CI The confidence interval was 4.33-4.69 tons), respectively. According to the Mann-Kendall test, the average catch has increased significantly during the mentioned period (over the last two decades) (Z = 3.80, P < 0.05). Different ARIMA combined prediction models (ARIMA, (p, d, q)) were tested based on the AIC index, and the ARIMA model (1, 0, 0) had the best fit with the change trend of yellowfin tuna in the southern waters of the country (AIC=- 24). The predict of yellowfin tuna catch results in the neural network (NN) models was show that feed forward neural networks (FFNN) have better performance than other models and with less error (MAE=0.02 and RMSE=0.03). Also, according to the results of ARIMA time series and neural network models, it can be concluded that feed forward neural networks simulate catch this species fish with higher accuracy than time series models. It seems, forecasting the trend of aquatic catch can be an important tool for fisheries managers and planners for better and sustainable management of aquatic resources and should be given more attention. [ABSTRACT FROM AUTHOR]

The yellowfin tuna represents a significant fishery resource in the Pacific Ocean. Its resource endowment status and spatial variation mechanisms are intricately influenced by marine environments, particularly under varying climate events. Consequently, investigating the spatial variation patterns of dominant environmental factors under diverse climate conditions, and understanding the response of yellowfin tuna catch volume based on the spatial heterogeneity among these environmental factors, presents a formidable challenge. This paper utilizes comprehensive 5°×5° yellowfin tuna longline fishing data and environmental data, including seawater temperature and salinity, published by the Western and Central Pacific Fisheries Commission (WCPFC) and the Inter-American Tropical Tuna Commission (IATTC) for the period 2000–2021 in the Pacific Ocean. In conjunction with the Niño index, a multiscale geographically weighted regression model based on geographically weighted principal component analysis (GWPCA-MGWR) and spatial association between zones (SABZ) is employed for this study. The results indicate the following: (1) The spatial distribution of dominant environmental factors affecting the catch of Pacific yellowfin tuna is primarily divided into two types: seawater temperature dominates in the western Pacific Ocean, while salinity dominates in the eastern Pacific Ocean. When El Niño occurs, the area with seawater temperature as the dominant environmental factor in the western Pacific Ocean further extends eastward, and the water layers where the dominant environmental factors are located develop to deeper depths; when La Niña occurs, there is a clear westward expansion in the area with seawater salinity as the dominant factor in the eastern Pacific Ocean. This change in the spatial distribution pattern of dominant factors is closely related to the movement of the position of the warm pool and cold tongue under ENSO events. (2) The areas with a higher catch of Pacific yellowfin tuna are spatially associated with the dominant environmental factor of mid-deep seawater temperature (105–155 m temperature) to a greater extent than other factors, the highest correlation exceeds 70%, and remain relatively stable under different ENSO events. The formation of this spatial association pattern is related to the vertical movement of yellowfin tuna as affected by subsurface seawater temperature. (3) The GWPCA-MGWR model can fully capture the differences in environmental variability among subregions in the Pacific Ocean under different climatic backgrounds, intuitively reflect the changing areas and influencing boundaries from a macro perspective, and has a relatively accurate prediction on the trend of yellowfin tuna catch in the Pacific Ocean.

Marine pollutants bioaccumulate at high trophic levels of marine food webs and are transferred to humans through consumption of apex species. Yellowfin tuna (Thunnus albacares) are marine predators, and one of largest commercial fisheries in the world. Previous studies have shown that yellowfin tuna can accumulate high levels of persistent organic pollutants, including Transporter Interfering Chemicals (TICs), which are chemicals shown to bind to mammalian xenobiotic transporters and interfere with their function. Here, we examined the extent to which these same compounds might interfere with the activity of the yellowfin tuna (Thunnus albacares) ortholog of this transporter. To accomplish this goal we identified, expressed, and functionally assayed tuna ABCB1. The results demonstrated a common mode of vertebrate ABCB1 interaction with TICs that predicts effects across these species, based on high conservation of specific interacting residues. Importantly several TICs showed potent inhibition of Ta-ABCB1, such as the organochlorine pesticides Endrin (EC50 = 1.2 ± 0.2 μM) and Mirex (EC50 = 2.3 ± 0.9 μM). However, unlike the effects observed on mouse ABCB1, low concentrations of the organochlorine pesticide TICs p,p'-DDT and its metabolite p,p'-DDD co-stimulated verapamil-induced Ta-ABCB1 ATPase activity possibly suggesting a low transport activity for these ligands in tuna. These results provide a mechanistic basis for understanding the potential vulnerability of tuna to these ubquitous pollutants.

The lifestyle and culture of South Pacific Island countries have been long intertwined with oceanic resources. These countries are heavily dependent on tuna resources for their economies and socioeconomic livelihoods. Despite their importance, the mechanisms behind tuna stock trajectory patterns need to be better understood. With changing climatic and environmental conditions, it has become vital to understand the impact of these changes on tuna resources and if possible include them in long-term tuna harvest and management plans. A significant portion of the stock dynamics of yellowfin tuna (Thunnus albacares), albacore tuna (Th. alalunga) and bigeye tuna (Th. obesus) in the South Pacific Region may possibly be explained only by the environmental factors of sea surface temperature (SST) and Atlantic Multidecadal Oscillation AMO. The relationship of monthly SST and AMO was investigated with time series stock patterns of Th. albacares, Th. alalunga and Th. obesus in the Eastern and Western Pacific Ocean for the years 1972 to 2019. Monthly variables that exhibited significant correlation with CPUE variables were used in the Generalised Linear Model and Generalized Additive Model to reproduce the CPUE trajectory of the three tuna species from 1972 to 2019. Results showed that a significant portion of stock dynamics of Th. albacares, Th. alalunga and Th. obesus can be explained well by two environmental conditions of SST and AMO. This shows that a large portion of tuna variation in the Eastern and Southern Pacific is related to environmental conditions. Models with single variables are evidence of the significant individual effect of SST and AMO on stock time series of each tuna species. Models with two variables had a better fit in comparison to models with a single variable for all tuna stocks. Possibilities of two significantly different patterns in the trajectory of the three tuna species and environmental conditions used in the models were also observed. The trajectory patterns seemed to change around the 1990s and had significantly different means, indicating possible regime shifts. Environmental conditions play a highly significant role in structuring tuna stock trajectory in the South Pacific and need to be included in tuna management / harvest plans to ensure sustainability of this important resource. The importance of regime shifts should be recognised and further investigated for possible inclusion in tuna sustainability plans due to their influence on long-term tuna trajectory patterns.