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Copyright of South China Fisheries Science is the property of South China Fisheries Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

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]

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]

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]

Carbon stable isotopes (δ13C) are widely used in ecological studies to understand diet, food web dynamics, and movements of marine fishes. Still, δ13C is influenced by lipid content and often requires chemical extraction or mathematical correction. Here, we developed a species-specific mathematical lipid correction for white muscle tissue of yellowfin tuna (Thunnus albacares), a highly migratory finfish of considerable economic and ecological value. Lipid extraction was conducted on yellowfin tuna white muscle tissue (C:N range: 2.96–6.49), and both linear and non-linear lipid correction models for δ13C were fitted and assessed. Lipid extraction increased δ13C, and to a lesser extent, δ15N values in yellowfin tuna white muscle tissue, but had no effect on δ34S. Both non-linear models provided better fits to the data than the linear model, suggesting an asymptotic relationship between C:N and ∆δ13C. Results support the growing body of evidence that C:N ratios can be used to predict lipid corrected δ13C and highlight the value of mathematical correction approaches. We provide species-specific parameter estimates that can be used for lipid correction of white muscle tissue for δ13C analysis in yellowfin tuna and similar species for which species-specific models have yet to be developed. [ABSTRACT FROM AUTHOR]

Copyright of South China Fisheries Science is the property of South China Fisheries Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of South China Fisheries Science is the property of South China Fisheries Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study analyses the mercury (Hg) concentration in the meat of Thunnus albacares and Thunnus obesus caught from the western equatorial Atlantic Ocean. The objective was to estimate the Hg intake via tuna ingestion and presents the possible health risk assessment. For T. albacares and T. obesus, the median concentration was 212 ng·g-1 and 475.1 ng·g-1 wet weight, respectively. The Hg concentrations were below the maximum tolerable limit established by international and Brazilian regulations for fishery products. The consumption would pose a risk for human populations that ingest more than 80 g·day-1. Regular monitoring of both human consumption rates and Hg levels in fish are recommended. [ABSTRACT FROM AUTHOR]

A total of 756 yellowfin tuna (Thunnus albacares) caught by a Chinese drifting longliner in the tropical western and central Pacific Ocean (WCPO) from May 2018 to March 2019 were investigated to describe the reproductive biology of the species. Generalized linear model and polytomous logistic regression for the ordinal response model were employed to assess the effects of biometric and spatiotemporal factors (such as individual fork length (FL), fishing depth, dissolved oxygen, and month) on the reproductive traits of yellowfin tuna. The results showed that FLs ranged from 87 to 163 cm, averaging 115.8 cm (SD = ±14.2) for females and 121.8 cm (SD = ±16.8) for males. The proportion of males in the sampled fish was 0.61 (SD = ±0.29), and larger males (>130 cm) were proportionally predominant. Analyses based on the monthly variation of the gonadosomatic index and monthly proportion of sexual maturity stages of the gonads showed that the main spawning period of yellowfin tuna lasts from September to December. In addition, the 50% first maturity FLs of males and females were 111.96 cm (SD = ±1.04) and 119.64 cm (SD = ±1.30), respectively. This study provides new information on the reproductive development of T. albacares in the tropical WCPO region. These reproductive parameters reduce uncertainty in current stock assessment models, which will ultimately assist the fishery in becoming sustainable for future generations. [ABSTRACT FROM AUTHOR]

In the study, the parasite from the yellowfin tuna (Thunnus albacares) was separated, and morphological observation and molecular identification were carried out. Our results showed that the parasite was similar to Pennella sp. Its cephalothorax was covered by spherical to spherical non-branched nipples of almost the same size, which were very similar in shape and arrangement. A pair of slightly larger, the unbranched antenna was present on the outer margin of the small papillae-covered area. The gene sequence of COX1 with a length of 1,558 bp in the mitochondria of the parasite was 100% similar to Pennella sp. (MZ934363). The mitochondrial genome had a total length of 14,620 bp. It consisted of 36 genes (12 protein-coding, 22 transfer RNAs and 2 ribosomal RNAs) and a dummy control region, but the mitochondrial genome had no ATP8 gene. Morphological observation showed that Pennella sp. was dark red, with a convex cephalothorax, with a total length of 8.42 cm, parasitic on the dorsal side of yellowfin tuna. Pennella sp. included the cephalothorax, neck, trunk, abdomen and egg belt. This study was the first report on the mitochondrial genome of Pennella sp. The results provide basic data for further identifying the parasites of Pennella genus. [ABSTRACT FROM AUTHOR]

Copyright of South China Fisheries Science is the property of South China Fisheries Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of South China Fisheries Science is the property of South China Fisheries Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Recent anecdotal reports from seafood processors in eastern Australia have described an increased occurrence of post-mortem myoliquefaction ('jellymeat') in broadbill swordfish Xiphias gladius, and macroscopic cysts throughout the musculature of yellowfin tuna Thunnus albacares. A genus of parasitic cnidarians, Kudoa (Myxosporea, Multivalvulida), species of which are known to occur in economically important wild-caught fish species globally, can cause similar quality-deterioration issues. However, Kudoa sp. epizootiology within commercially harvested, high-value fish caught within Australia is poorly understood, despite the parasite's economic importance. To determine the causative agent responsible for the observed quality deterioration in swordfish and yellowfin tuna, muscle-tissue samples from seafood processors in Mooloolaba, Australia, collected from October 2019–February 2020, were examined for parasitic infection. Kudoid myxospores were identified from both hosts and were subquadrate in shape, with four equal-sized polar capsules. The SSU rDNA sequences from both fish shared > 99% identity to Kudoa species. Kudoa musculoliquefaciens was isolated from 87.1% of swordfish sampled, suggesting that it is a widespread parasite in swordfish from the southwest Pacific Ocean. This study provides the first molecular and morphological characterisation of Kudoa thunni in yellowfin tuna and K. musculoliquefaciens in swordfish harvested from the waters of eastern Australia, expanding the geographical distribution of K. thunni and K. musculoliquefaciens to include the Coral and Tasman Seas. We demonstrate that not all infected swordfish progress to jellymeat, show the usefulness of molecular tools for reliably identifying infection by Kudoa spp., and add to the overall knowledge of kudoid epizootiology in wild-caught fish. [ABSTRACT FROM AUTHOR]

Assessing fishing capacity and biological reference points are basic parameters for the conservation of fishery resources. The catch-based Monte Carlo maximum sustainable yield (CMSY) and Bayesian state-space Schaefer production model (BSM) were applied to assess the fishing capacity of Yellowfin tuna (YFT) (Thunnus albacares) and Longtail tuna (LTT) (Thunnus tonggol) fishery from Pakistan. Long-term and short-term data series was used to evaluate the robust information to avoid the change in data series error. Twenty-two years and fifteen years catch and catch per unit efforts (CPUE) data were used to evaluate the stock status. The estimated values of YFT from twenty-four years of BSM and CMSY model at r = 0.034, k = 1015, and MSY = 8.86, r = 0.47, k = 718 and MSY = 8.82 respectively. Biomass and exploitation rate were at B/B MSY = 0.515 and F/F MSY = 1.83 respectively. The biological reference points from BSM and CMSY model of YFT using 2007–2021 data were r = 0.034, k = 966 and MSY = 8.57, r = 0.077, k = 340 and MSY = 5.77 respectively. B 2021 /B MSY and F/F MSY were at 0.54 and 1.83 respectively indicating higher values than the fishing capacity. While, the CMSY estimated values for LTT using long- and short-term data were r = 0.04, 0.05; k = 603, 567; MSY = 7.45; 7.33 respectively. Whereas, BSM values r = 0.33; 0.31, k = 922; 923, MSY = 7.73; 7.34 respectively. The estimated BSM B 2021 /B MSY (<1.0) and F 2021 /F MSY (>1.0) for both species were higher than the fishing capacity limits. The results from both models using two different time series data indicates that the stock of this important fishery is in overexploited state. Present findings provide the fishing capacity to set the harvest control point for tuna fishery. It is advised to monitor illegal, unreported and unregulated fishing activities. The fishery managers should adopt management steps to maintain the stock of tuna fishery from Pakistan, northern Arabian Sea. • First time study on stock assessment of important fish species of Tuna fishery were conducted from northern Arabian Sea Pakistan. • Now a days CMSY and BSM models are frequently used to assess the fish stock assessment for better fishery management. • The estimated BSM B 2021 /B MSY (<1.0) and F 2021 /F MSY (>1.0) for both species were higher than the fishing capacity limits. • The results from models using different time series data indicates that the stock of fishery is overexploited. • Present findings provide the fishing capacity to set the harvest control point for tuna fishery. [ABSTRACT FROM AUTHOR]

Yellowfin tuna are the mainstay of the traditional tuna fisheries in St Helena waters, but there is limited knowledge of their ecology and feeding behaviour in the area. In this study yellowfin tuna stomach contents were used to assess spatio‐temporal changes in feeding strategy and consider the role of tuna in the local ecosystem. Comparisons of the feeding spectra of yellowfin tuna between inshore regions of St Helena and oceanic seamounts demonstrated that in both areas the species was largely piscivorous. In inshore waters yellowfin consumed more neritic fauna, including significant numbers of crab megalopa, whereas around seamounts the diet included a greater diversity of epi‐ and mesopelagic fish and squids. The most important fish prey species in inshore waters was the St Helena butterflyfish Chaetodon sanctahelenae, and around seamounts was the pufferfish Lagocephalus lagocephalus. Results indicate that the diet spectrum of yellowfin tuna in St Helena waters is relatively similar to those of conspecifics living in waters with relatively low productivity, with strategies indicative of food‐poor ecosystems. The availability of coastal fauna may make areas around islands and seamounts more attractive for feeding aggregations of yellowfin tuna, compared to the open ocean. The relatively unselective feeding of yellowfin tuna means that stomachs can provide valuable data on the species diversity, particularly in remote areas with limited opportunities for dedicated research expeditions. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the influence of the fishing location on yellowfin tuna’s (YFT; Thunnus albacares) white muscle total lipid (TL) content and fatty acid profile. The comparison included 45 YFT loins, equally divided between the Atlantic, Indian and Pacific Oceans. The ocean had no significant influence on YFT TL content, total PUFA and total n-3 PUFA (p > 0.05), averaging 1.09 g/100 g of muscle, 229.2 and 192.8 mg/100 g of muscle, respectively. On the other hand, the YFT harvested on the Indian Ocean displayed significantly higher contents of both SFA and MUFA totals than the Atlantic Ocean counterparts (p < 0.05), while the YFT harvested in the Pacific Ocean presented intermediate values, not differing significantly from the other two origins. The YFT from the Indian and Pacific oceans held twice the n-6 PUFA content recorded in the Atlantic YFT (44.1 versus 21.1 mg/100 g of muscle). Considering the recommended daily intake of EPA plus DHA is 250 mg, the consumption of 100 g of YFT from the Atlantic, Indian and Pacific Oceans would provide 149.2 mg, 191.8 mg or 229.6 mg of EPA plus DHA, representing 59.7%, 76.7% or 91.8% of the recommended daily intake, respectively.

Gelatin, which is thermally converted from collagen, is widely utilized in the pharmaceutical industry as a raw material for hard and soft capsules. The aim of this study was to produce gelatin from yellowfin tuna skin, the by-product of tuna processing, and determine the optimal concentration for hard capsule production. Capsules were prepared from the skin gelatin. The tuna skin gelatin was characterized as follows: pH 6.0, gel strength 191 g Bloom, water content 7.01%, ash content 0.92, setting temperature 22.3 °C, and viscosity 12,700 cP. A 20% gelatin solution was found to be the best concentration among the concentrations examined for hard capsule production, and gave a body capsule height of 19.4 mm, cap capsule height of 12.8 mm, weight of 0.07 g, disintegration time of 4.09 min, pH of 5.92, and moisture content of 12.0%. The results suggest that tuna skin gelatin can be an excellent source of hard capsule material. [ABSTRACT FROM AUTHOR]

The fishery and stock structure of Thunnus albacares off Andhra waters along western Bay of Bengal was studied from 2012 to 2015. The average annual landing of the species during the study period was 5,952 t contributing 32.9 % of the total tuna landings. Gill nets contributed 59 % of the catches, followed by hook and lines (34 %). Von Bertalanffy growth equation was Lt = 196.35 [1 – e –0.23 (t+0.0546)] and natural mortality, fishing mortality and total mortality was 0.4, 0.71 and 1.11 with exploitation ratio of 0.64 and exploitation rate of 0.43. Annual average stock, standing stock biomass and maximum sustainable yield were 13,879 t, 8,383 t and 4,653 t, respectively. Yield per recruit and biomass per recruit estimated were 2584.7 g and 3640.4 g. The exploitation rate, yield and yield per recruit indicate the stock of T. albacares to be overexploited. To sustainably and optimally harvest the species, reduction in the present fishing effort by 60 % is necessary, thereby increasing the yield by 35.31 %. With overcapacity in the number of gillnetters and hook and line units operating in the waters off Andhra Pradesh, implementation of the recommended fleet size proposed by Central Marine Fisheries Research Institute by means of buy-back measures and strict adherence to Minimum Legal Size at harvest would ensure sustainable and optimum exploitation of the resource. [ABSTRACT FROM AUTHOR]

Hyaluronic acid (HA) is commonly extracted from terrestrial and bacterial sources. However, due to the risk associated with animal and bacterial derived contaminants and the laborious production that tend to compromise the quality of HA, research studies have recently shifted to the exploration of HA in marine resources and the enhancement of the protocols for its production. In this study, isolation of HA from yellowfin tuna Thunnus albacares (Bonnaterre, 1788) eyeball was carried out through standardisation of the different steps in HA isolation, including tissue extraction, enzymatic hydrolysis, precipitation with cetylpiridinium chloride (CPC) - sodium chloride (NaCl) solution, filtration and diafiltration, precipitation in alkaline hydroalcoholic solution, and lyophilisation. Results revealed that the highest HA yield and purity were observed in the indirect treatment wherein the raw material was pre-treated with acetone, formaldehyde, and sodium acetate solution prior to water extraction and incubation of the mixture for 24 h. Enzymatic hydrolysis revealed that 6 h was the maximum tissue hydrolysis period. Results further showed that the optimum conditions for HA isolation were through the use of 3% CPC:3M NaCl concentration for recovery and fractionation and a 1:3 mL.mL-1 supernatant:ethanol ratio for alcoholic precipitation. The data gathered from this study could help maximise the benefits of the tuna processing waste in the country and may open a new opportunity for more cost-effective production of a valuable bioactive compound from a natural source. [ABSTRACT FROM AUTHOR]

This dissertation addressed questions related to the selective advantages of regional endothermy and its independent evolution among several fish groups. The chapters integrate laboratory and field physiological measurements to provide a better understanding ofthe evolution of regional endothermy and its importance as an adaptation to the pelagic environment. Studies on the swimming energetics of the eastern Pacific bonito (Sarda chiliensis) revealed that the bonito had a similar cost of transport to that of similar sized yellowfin tuna (Thunnus albacares) and that the bonito had a significantly lower standard metabolic rate than tuna. Thermal studies on live slender tuna, Allothunnus fallai, were the first to document both red muscle (RM) and eye and brain endothermy for this species and establish regional endothermy as a synapomorphy of the Tribe Thunnini. Additional findings for A.fallai revealed this species to possess a brain heater, a thermogenic organ composed of portions of all four of the rectus muscles. These findings demonstrate that the use of a heater tissue to elevate cranial temperatures has evolved independently in at least three fish groups.Movement studies on the mako shark (Isurus oxyrinchus) used acoustic telemetry to record the in-vivo stomach temperatures and depth distribution off the coast of Southern California. This work showed that the tracked makos remained in the upper 12 m of the water column during up to 80% of the track period and that larger makos dove to greater depths. Stomach temperature data were recorded for all tracked makos (including young of the year), and these data were used to document feeding events in five of the seven tracking sessions.A study on the muscle morphology of three thresher shark species (common thresher, Alopias vulpinus, pelagic thresher, A. pelagicus, and bigeye thresher, A. superciliosus) revealed interspecific differences in the RM transverse position and distribution along the body. The common thresher is the only alopiid to possess a RM arrangement similar to that of the endothermic lamnid sharks, suggesting that this species is likely the only thresher to be capable of RM endothermy.

Decades of study have attempted to describe the population genetic structure of tuna species, including a significant number of studies focused on yellowfin (Thunnus albacares). Very often, analyses do not agree on how many stocks exist per species, and where their boundaries lie. This is possibly because studies vary so much across numerous variables, such as the geographic range covered in a study, the number and type of genetic markers used, and the number of sites sampled. This meta-analysis of 22 yellowfin studies attempts to standardize and isolate the key variables to assessing the strength of correlation with the resulting number of populations a study observes. Overall trends across the studies suggest that genetic markers with a high probability of being under selective constraints, or are located in coding regions, are more or less likely to sense population structure depending on geographic range coverage. Alternatively, when assessing neutral or non-coding genomic regions, studies also benefit from (i) more polymorphic and numerous loci, and (ii) increasing the number of sampling locations analyzed, both of which increase the statistical power of an analysis. Finally, trends were clearest when groups of accurately identified coding and non-coding, or neutral and non-neutral, studies were further subdivided by whether they used mitochondrial or nuclear DNA, confirming that analyses of the two genomes should not be compared directly. Our meta-analysis provides concrete support for long held assumptions about the relationships between population genetics study parameters and outcomes, and provides guidance for future studies on how to maximize the likelihood of identifying population structure where it exists. [ABSTRACT FROM AUTHOR]

The most common methods that can be used for species identification of tuna include methods based on detection of species-specific DNA via the polymerase chain reaction (PCR) method. The problem with DNA detection in processed products is the possibility of DNA fragmentation during the technological process. The quantity and quality of extracted DNA is a crucial step for species identification based on the DNA analysis. In this study, two DNA extraction methods (DNeasy Blood & Tissue Kit and DNeasy mericon Food Kit) for tuna DNA isolation were compared. Eight food products of canned tuna (three of them were declared as Thunnus albacares and five products were declared as Katsuwonus pelamis) with a different addition of various ingredients were tested. Furthermore, three different times of proteolysis (30 min, 60 min, overnight) for each sample and each extraction kit were evaluated. The DNA concentration was determined by a Qubit dsDNA HS Assay Kit fluorescence method and quantified using a Qubit fluorometer. The DNA purity was evaluated using the A260/A280 ratio of absorbances measured on a spectrophotometer. The main indicator of DNA quality and quantity was its amplifiability in the subsequent real-time PCR for Thunnus species, Thunnus albacares and Katsuwonus pelamis. Based on the results, both kits can be used for tuna species determination in highly heat-treated products with different composition, nevertheless, the DNeasy mericon Food Kit provided better statistical values in some parameters. The effect of different times of proteolysis was significant in most of the samples with regard to the crossing point values determined by real-time PCR. [ABSTRACT FROM AUTHOR]

This research project was undertaken on two species of tropical tuna: the yellowfin Thunnus albacares and the skipjack Katsuwonus pelamis, to explore the dynamic physiological design features of tunas which underly the highly-developed thunniform propulsion mechanism. To achieve an integrated understanding of tuna swimming mechanics, a combination of electromyography, kinematics, and direct force measurements was used to probe the dynamic function of the myotomal red muscle as fish swam over a range of sustained, aerobic swimming speeds in a large water tunnel.In both species, onset of red muscle activation proceeds sequentially in a rostra-caudal direction, while deactivation is nearly simultaneous at all sites, coincident with peak force in the caudal tendons. In yellowfin, there is complete segregation of contralateral activity, while in skipjack there is slight overlap. In both species, all red muscle on one side is active simultaneously for part of each cycle. Comparison with other fish species shows that the tuna EMG patterns culminate a spectrum of activation patterns underlying swimming modes from anguilliform to thunniform.Coupling kinematics with EMG data revealed that muscle activation occurs after the midline has reached its maximum convexity at any given axial location; therefore, it was concluded that midline curvature is not an accurate indicator of local strain in the myotomal cone muscle. Activation and curvature waves travel down the body at the same rate, so muscle function is predicted not to vary by axial location. In yellowfin, peak force occurs in the caudal tendons as the tail tip crosses the midpoint of its sweep; in skipjack, when the tip is about three-quarters through its sweep.Internal force measurements were made for the first time in any fish species by fitting a stainless steel buckle force transducer around the pair of deep caudal tendons on one side. At cruising speeds, mean forces were 1.3-3.8 N in yellowfin and 1.6-4.1 N in skipjack. At restrained burst speeds, forces were approximately 10 times higher. The biomaterial properties of the tendons show that they function as inextensible linkages, rather than biological springs, in transferring muscle force to the tail.

Oxygen transport and cardiovascular responses to exercise and environmental changes were studied in swimming yellowfin tuna (Thunnus albacares). a high­ performance teleost. Use of a large water tunnel permitted measurements of heart rate (fH), relative stroke volume (SV), and arterial and venous blood-gas variables during increases in swimming velocity or rapid changes in ambient temperature and oxygen content that simulated vertical migrations through the thermocline.In addition. a model of aerobic swimming performance for a 50 cm yellowfin was developed, based on the oxygen delivery potential of the cardiovascular system, and oxygen demand during swimming. This model predicts a lower maximal sustained (aerobic) velocity (~3-4 fork lengths [FL]/s) compared to previous estimates. This model also predicts that the rate of total oxygen consumption is not maximal at the maximal sustained velocity, suggesting that additional aerobic scope is available for other high­ oxygen demand metabolic functions (e.g., digestion. oxygen debt recovery, and growth).Measured FHs, although highly variable among individuals, were generally lower than previously reported, averaging from 68 to 102 bpm with a velocity increase from 1.0 to 2.9 FL/s. These FHs are comparable to other active teleosts at similar velocities. A significant bradycardia developed at an oxygen tension of 16.1 kPa O2, and fH was very sensitive to changes in temperature (Q10 = 2.37, 28°C to l8°C).Relative SV measurements revealed a slight decrease with exercise (mean 3.9%), indicating that, unlike most other fishes, cardiac output in the yellowfin is regulated primarily through changes in fH. However, SV increased with a drop in temperature, moderating the effect of fH on cardiac output (Q10 = 1.52).Yellowfin blood has a high-oxygen carrying capacity (16 to 18 ml O2/dl) and a low in vivo oxygen affinity (P50 = 5.3 kPa). Exercise caused in rise in arterial (74 to 88%) and a decline in venous oxygen saturation (48 to 44%), increasing the arterial-venous oxygen content difference [(a-v)O2], but leaving a large venous oxygen reserve. It is estimated that cardiac output and (a-v)O2 contributed equally to the increased oxygen uptake.xviii

A combination of a RADseq method (ddRAD) with long read high throughput sequencing (Roche 454) was tuned up in order to identify and validate a set of SNPs useful for gene diversity analysis in two important South American commercial tuna ( Thunnus albacares and Scomberomorus brasiliensis ). A total of 11 and 21 individuals of T. albacares and S. brasiliensis, respectively, were used for SNP identification. DNA was individually digested with two restriction enzymes ( Sbf I and Sph I) and fragments between 300 and 600 bp selected. Combinatorial barcoding was used to identify individuals by including short sequences (5–7 bp) in the adaptors of each restriction site (P1 and P2). After adaptor ligation, samples were pooled and size-selected, amplified by PCR, and sequenced on a 454 GS-Junior sequencer. A total of 180,779 reads were produced with an average length and coverage of 287 bp and 26x, respectively. Sets of 60 and 79 SNPs were in silico selected for T. albacares and S. brasiliensis , respectively, and were tested and validated in 74 and 66 individuals, respectively, on a MassARRAY platform. A total of 36 and 47 SNPs were polymorphic and useful for population analysis. A preliminary study on two distant Brazilian populations of both species (∼3000 km) with these SNPs suggested the absence of significant structure among local populations of both species. Our results demonstrate the possibility of combining ddRAD with long read high throughput sequencing for marker development in species with scarce genomic resources. [ABSTRACT FROM AUTHOR]

The most common techniques used to identify tuna species include methods based on the detection of specific DNA. The quality of species-specific DNA crucially affects the efficiency of amplification during the subsequent polymerase chain reaction (PCR). Detection of DNA in processed products can be adversely affected by DNA fragmentation during the processing steps and the use of ingredients that may inhibit the PCR reaction. In this study, several processing treatments applied to the muscle tissue of yellowfin tuna (Thunnus albacares) were evaluated. For DNA isolation three DNA extraction methods were compared. The concentration, purity, and amplificability of DNA were tested. The results revealed the variability among extraction procedures in terms of DNA quality and quantity in tuna muscle tissue processed under different processing technologies. [ABSTRACT FROM AUTHOR]

Overfishing has been drastically changing food webs in marine ecosystems, and it is pivotal to quantify these changes at the ecosystem level. This is especially important for ecosystems with a high diversity of top predators such as the Eastern Atlantic marine region. In this work we used high-throughput sequencing methods to describe the diet of the two most abundant tuna species, the Skipjack tuna (Katsuwonus pelamis) and the Yellowfin tuna (Thunnus albacares), highly targeted by fisheries off west Africa. We also explored prey diversity overlap between these tuna species and the seabird species breeding in Cabo Verde that are most likely to share prey preferences and suffer from bycatch, the Brown booby (Sula leucogaster) and Cape Verde shearwater (Calonectris edwardsii). Overall, the diet of both tuna species was more diverse than that of seabirds. Skipjack tuna diet was dominated by prey from lower trophic levels, such as krill, anchovies, and siphonophores, while the Yellowfin tuna diet was mainly based on epipelagic fish such as flying and halfbeak fishes. Some of the most abundant prey families detected in the Yellowfin tuna diet were shared with both seabird species, resulting in a high prey diversity overlap between this tuna species and seabirds These results have implications for the management of tuna fisheries in the Eastern Tropical Atlantic, because a large decrease of both tuna species might have cascading effects on both primary and secondary consumer levels, and the decrease of these underwater predators may have implications on the viability of tropical seabird populations. • DNA metabarcoding assess diet of tuna and seabirds of Eastern Atlantic Ocean. • Skipjack tuna diet was dominated by prey from lower trophic levels. • Significant diet overlap between Brown booby and Yellowfin tuna. • Results have implications for the management of fisheries in this region. [ABSTRACT FROM AUTHOR]

A variety of tunas of the genus Thunnus are consumed daily in Japan as sliced raw fish (sashimi and sushi). The consumption of fresh sliced raw fish, i.e., unfrozen or uncooked, can sometimes cause food poisoning that is manifested by transient diarrhea and vomiting for a single day. One of the causes of this type of food poisoning has been identified as live Kudoa septempunctata (Myxosporea: Multivalvulida) in the olive flounder ( Paralichthys olivaceus). Furthermore, raw slices of fresh tunas are highly suspected to be a possible causative fish of similar food poisoning in Japan. In the present study, we conducted a survey of kudoid infections in tunas (the yellowfin tuna Thunnus albacares, the Pacific bluefin tuna Thunnus orientalis, and the longtail tuna Thunnus tonggol) fished in the western Pacific Ocean off Japan and several East Asian countries and characterized morphologically and genetically the kudoid myxospores in pseudocysts or cysts dispersed in the trunk muscles. Pseudocysts of solely Kudoa hexapunctata were identified in the Pacific bluefin tuna (four isolates), whereas in the yellowfin tuna (21 isolates) pseudocysts of Kudoa neothunni and K. hexapunctata were detected at a ratio of 15:6, respectively, in addition to cyst-forming Kudoa thunni in five yellowfin tunas. In the trunk muscles of six longtail tunas examined, pseudocysts of K. neothunni (all six fish) and K. hexapunctata (two fish) were densely dispersed. The myxospores of K. neothunni found in these longtail tunas had seven shell valves and polar capsules (SV/PC) instead of the more common six SV/PC arranged symmetrically. Nucleotide sequences of the 18S and 28S ribosomal RNA gene (rDNA), some with the internal transcribed spacer regions as well, of K. hexapunctata and K. neothunni from the three Thunnus spp., including the seven-SV/PC morphotype, were very similar to previously characterized nucleotide sequences of each species, whereas the 18S and 28S rDNA of four isolates of K. thunni from yellowfin tunas showed a range of nucleotide variations of 99.0-99.9% identity over 1752-1763-bp long partial 18S rDNA and 97.4-99.9% identity over 797-802-bp long partial 28S rDNA. Therefore, this rather high variation of the rDNA nucleotide sequences of K. thunni proved to be contrary to the few variations of K. neothunni and K. hexapunctata rDNA nucleotide sequences. The present study provides a new host record of the longtail tuna for K. neothunni and K. hexapunctata and reveals a high prevalence of the seven-SV/PC myxospore morphotype of K. neothunni in this tuna host. [ABSTRACT FROM AUTHOR]

The squid Hyaloteuthis pelagica (Bosc, 1802) and the octopus, Ocythoe tuberculata Rafinesque, 1814 have been recorded from Ascension Island for the first time. Both species were found in yellowfin tuna stomachs caught from inshore coastal waters (within 5 km). The specimens were in good condition with distinguishing features still apparent, signifying very recent ingestion. Morphological features were examined, photographs taken and specimens stored for use as part of an on-going study investigating dietary habits of yellowfin tuna. [ABSTRACT FROM AUTHOR]

Specific dynamic action (SDA), the increase in metabolic expenditure associated with consumption of a meal, represents a substantial portion of fish energy budgets and is highly influenced by ambient temperature. The effect of temperature on SDA has not been studied in yellowfin tuna ( Thunnus albacares , Bonnaterre 1788), an active pelagic predator that occupies temperate and subtropical waters. The energetic cost and duration of SDA were calculated by comparing routine and post-prandial oxygen consumption rates. Mean routine metabolic rates in yellowfin tuna increased with temperature, from 136 mg O 2 kg − 1 h − 1 at 20 °C to 211 mg O 2 kg − 1 h at 24 °C. The mean duration of SDA decreased from 40.2 h at 20 °C to 33.1 h at 24 °C, while mean SDA coefficient, the percentage of energy in a meal that is consumed during digestion, increased from 5.9% at 20 °C to 12.7% at 24 °C. Digestion in yellowfin tuna is faster at a higher temperature but requires additional oxidative energy. Enhanced characterization of the role of temperature in SDA of yellowfin tuna deepens our understanding of tuna physiology and can help improve management of aquaculture and fisheries. [ABSTRACT FROM AUTHOR]

Isla del Coco National Park (ICNP), Costa Rica, is renowned for its large aggregations of pelagic species, especially sharks (Carcharhinidae and Sphyrnidae), billfish (Istiophoridae) and tuna (Scombridae). The high abundance of these sought after species, attracts commercial fishing vessels that enter the protected waters of the Park. Illegal fisheries thus represent one of the biggest threats to the ecological integrity of this World Heritage Site. The ICNP dedicates important resources to protection and control via regular surveillance patrols, along the 12 nautical miles that have Marine Protected Area (MPA) status. During 2012, 2013 and between January and August 2014, 405 surveillance patrols within the MPA found 108 fishing lines, more than 13 000 hooks, seized more than 500 km of fishing line and 257 pelagic individuals. The yellowfin tuna (Thunnus albacares) was the most abundant species, representing more than 72.3 % of the total catch; seized individuals had a mean total length of 153.35±23.19 cm (Min=90 cm; Max=190 cm); which indicates that most individuals were adults. Analysis of monthly CPUE showed that the highest relative abundance of illegally caught T. albacores was between May and August of each year, with a mean relative abundance of 26.13±54.71, 11.63±23.79, 13.71±24.52 tunas per 1 000 hooks in 2012, 2013, 2014, respectively. This species had a high survival rate (nearly 80 % of the individuals found on the lines were still alive), probably due to the short fishing lines used by illegal fishermen, combined with the swift intervention of rangers. The CPUE of T. albacares found in this study is greater than records in Costa Rica's Exclusive Economic Zone (0.74 and 0.44 per 1 000 hooks respectively). These results highlight the importance of ICNP as an aggregation site for T. albacares and the need for its effective protection. It is important that ranger intervention continue to be as rapid and effective as possible, in order to decrease the impact of illegal fishing on the marine biodiversity of the ICNP. [ABSTRACT FROM AUTHOR]

Thunnus albacares is an important fishery species throughout the world. Polymorphisms of sequence variations in mtDNA COI genes were assessed to explore the genetic differentiations among 11 populations of T. albacares sampled from the central Pacific Ocean. Sixty-one mtDNA haplotypes and 38 variable sites were detected. Analysis of mtDNA COI sequences revealed that tuna from the 11 localities were characterized by moderately high haplotype diversity ( h = 0.650 ± 0.040), while sequence divergence between haplotypes was relatively low ( π = 0.00364 ± 0.00044). Analyses of molecular variance and F analysis supported that significant genetic differentiations existed between some of the sampled populations. Tests of neutral evolution and mismatch distribution analysis suggested that T. albacares might have experienced a population expansion, which possibly occurred within the last 0.82 million years. Our study unraveled the genetic structure of the extant population of T. albacares and addressed the related fishery management issues including fishery stock identification and management. [ABSTRACT FROM AUTHOR]

Effect of different filling medium on cooking time and quality of yellowfin tuna during canning was assessed. Lag phase for heating was lowest for tuna processed in sunflower oil whereas lag factor for cooling was lowest for tuna in groundnut oil. Reduction in total process time was noticed in tuna processed in sunflower oil owing to faster heating rate as compared to processing in coconut oil and groundnut oil. Histamine content increased significantly ( P < 0.05) after heat treatment irrespective of medium. Increase in lightness ( L ∗ ) and textural parameters, chewiness and springiness was observed for tuna after heat processing. Heat processing in sunflower oil medium also showed reduced rate of lipid oxidation probably due to its protective antioxidant activity. Energy value of yellowfin tuna processed in sunflower oil was 177 kcal 100 g −1 which is slightly higher than samples processed in coconut oil and groundnut oil. [ABSTRACT FROM AUTHOR]

Assessment of isotopic compositions at the base of food webs is a prerequisite for using stable isotope analysis to assess foraging locations and trophic positions of marine organisms. Our study represents a unique application of stable-isotope analyses across multiple trophic levels (primary producer, primary consumer and tertiary consumer) and over a large spatial scale in two pelagic marine ecosystems. We found that δ 15 N values of particulate organic matter (POM), barnacles and phenylalanine from the muscle tissue of yellowfin tuna all showed similar spatial patterns. This consistency suggests that isotopic analysis of any of these can provide a reasonable proxy for isotopic variability at the base of the food web. Secondly, variations in the δ 15 N values of yellowfin tuna bulk-muscle tissues paralleled the spatial trends observed in all of these isotopic baseline proxies. Variation in isotopic composition at the base of the food web, rather than differences in tuna diet, explained the 11‰ variability observed in the bulk-tissue δ 15 N values of yellowfin tuna. Evaluating the trophic position of yellowfin tuna using amino-acid isotopic compositions across the western Indian and equatorial Pacific Oceans strongly suggests these tuna occupy similar trophic positions, albeit absolute trophic positions estimated by this method were lower than expected. This study reinforces the importance of considering isotopic baseline variability for diet studies, and provides new insights into methods that can be applied to generate nitrogen isoscapes for worldwide comparisons of top predators in marine ecosystems. [ABSTRACT FROM AUTHOR]

Climate change will expose many marine ecosystems to temperature, oxygen and CO 2 conditions that have not been experienced for millennia. Predicting the impact of these changes on marine fishes is difficult due to the complexity of these disparate stressors and the inherent non-linearity of physiological systems. Aerobic scope (the difference between maximum and minimum aerobic metabolic rates) is a coherent, unifying physiological framework that can be used to examine all of the major environmental changes expected to occur in the oceans during this century. Using this framework, we develop a physiology-based habitat suitability model to forecast the response of marine fishes to simultaneous ocean acidification, warming and deoxygenation, including interactions between all three stressors. We present an example of the model parameterized for Thunnus albacares (yellowfin tuna), an important fisheries species that is likely to be affected by climate change. We anticipate that if embedded into multispecies ecosystem models, our model could help to more precisely forecast climate change impacts on the distribution and abundance of other high value species. Finally, we show how our model may indicate the potential for, and limits of, adaptation to chronic stressors. [ABSTRACT FROM AUTHOR]

The genetic population structure of the Pacific bluefin tuna (PBF) Thunnus orientalis and the yellowfin tuna (YFT) T. albacares in the North Pacific Ocean was investigated. The polymorphism of microsatellite (SSR) loci and sequences of mitochondrial DNA control region (mtCR) were analyzed for 71 samples of PBF from Japan and Mexico and 45 samples of YFT from Japan and Panama. In the SSR analyses, both single-locus (−0.010 to 0.008 in PBF and −0.023 to 0.020 in YFT) and global multilocus (0.003 in PBF and −0.002 in YFT) F values among the geographic populations were low and not significant in these species. In the mtCR analyses, neither the neighbor-joining tree nor the minimum spanning network showed genetic differentiation among the geographic populations in each species. The pairwise F values among the geographic populations of them (−0.005 in PBF and −0.020 to −0.014 in YFT) were low and not significant. Our SSR and mtCR data suggested that genetic differentiations were not evident among the eastern and western populations in the North Pacific Ocean either in PBF or in YFT. Mismatch distributions, demographic parameters, and neutrality tests suggested that sudden population expansion of PBF and YFT in the North Pacific Ocean occurred 628,000-731,000 and 450,000-525,000 years ago, respectively. [ABSTRACT FROM AUTHOR]

We measured Cd and Pb in the muscle and stomach contents of Thunnus albacares and Katsuwonus pelamis to define the distribution of the elements in the tissues and their degrees of biomagnification. 210 Po was measured in the livers of both species and compared to the results of similar studies. The trophic position of the tuna species was determined by N isotope measurements. The average activity of 210 Po in the liver ranged from 119 to 157 (Bq kg −1 wet weight) in K. pelamis and T. albacares . The trophic position of T. albacares (4.60) was higher than that of K. pelamis (3.94). The Cd content of the muscle increased significantly with the trophic position of the tuna. δ 13 C in T. albacares and K. pelamis varied, with values of 3.13 and 1.88‰, respectively. The δ 15 N values in yellowfin tuna were higher than in skipjack tuna. The trophic position of T. albacares (4.60 ± 0.67) was therefore more elevated than that of K. pelamis (3.94 ± 1.06). Pb was biomagnified in T. albacares (transfer factor = 1.46) . [ABSTRACT FROM AUTHOR]

Abstract: Since Kudoa septempunctata in olive flounder (Paralichthys olivaceus) was indicated to cause food poisoning in humans, other Kudoa species are suspected to have pathogenic potential. Recently, a myxosporean possibly associated with food poisoning in humans consuming raw Pacific bluefin tuna, Thunnus orientalis, was identified as Kudoa neothunni. This is a known causative myxosporean of post-harvest myoliquefaction in yellowfin tuna Thunnus albacares. Regardless of the significant differences in the 28S rDNA sequence and the pathological character (with/without myoliquefaction) between the two T. orientalis and T. albacares isolates, they were considered intraspecific variants of K. neothunni. However, the light and low-vacuum electron microscopic observations in the present study revealed that there were two morphotypes; pointed- and round-type spores, which were significantly differentiated by the ratio of suture width to spore width. Furthermore, the two morphotypes were genetically distinguishable by the 28S rDNA sequence analysis. This morphological and molecular evidence validates that the two Kudoa types are separate species, and thus the pointed- and round-types are referred to as K. neothunni and Kudoa hexapunctata n. sp., respectively. K. neothunni was detected solely from T. albacares, whereas K. hexapunctata n. sp. was found not only from T. orientalis but also from T. albacares. [Copyright &y& Elsevier]

In this study, the effect of different vegetables baby corn, green pea, broccoli as filling ingredients along with yellowfin tuna ( Thunnus albacares) on the heat penetration characteristics and quality changes were assessed. Heating and cooling lag factors ( Jh and Jc) were least for tuna with broccoli and tuna without vegetables, respectively. Heating rate index was in the range of 13.5-19.3 min with least value for tuna with broccoli. Heat processing increased the hardness and chewiness of tuna significantly ( P < 0.05), whereas cohesiveness decreased. Thermal processing resulted in higher L*and hue ( h) value for tuna. Substantial decrease in a* value was observed for tuna with broccoli and peas where as b* value showed an increase for tuna with baby corn. Tuna packed with green pea and baby corn was rated better sensorily, whereas tuna with broccoli was rated least. [ABSTRACT FROM AUTHOR]

Four samples of yellowfin tuna, Thunnus albacares (Bonnaterre, 1788), were collected from the Andaman Sea in the Exclusive Economic Zone, Thailand in May 2010. All samples were infested by the parasitic copepod Pseudocycnus appendiculatus at their gill filaments. This report documents a new record of the Andaman Sea, Thailand for P. appendiculatus and also a new host, T. albacares, for this apparent parasite in Thailand is recorded.

Aggregations in the distribution of individuals are an almost universal phenomenon in living organisms. Groups of animals that display collective coordinated movement without forming stable social bonds such as fish schools are a special type of aggregation. In tropical tuna fisheries, aggregating behaviour is directly exploited through the use of artificial fish aggregating devices (FADs). Hence, understanding the dynamics of schooling behaviour and the potential impacts of FADs upon it may have ramifications for tuna management. As a novel way of quantifying spatiotemporal co-occurrences of animals, we applied network statistics to acoustic tracking data to identify the co-occurrences of individual yellowfin tuna, Thunnus albacares, in an array of FADs and determine the frequency and temporal dynamics of these co-occurrences. We observed large interannual variation in movement rates of tuna between FADs, and corresponding interannual variability in the mean number of spatiotemporal associates for each individual as well as the temporal stability of associations. When movement rates were high, associations within FAD aggregations decayed to randomness three times faster than when movement rates were lower. This raises the possibility that if FADs are sufficiently close for fish to perform frequent between-FAD movements, school mixing may be increased and cohesion reduced. [ABSTRACT FROM AUTHOR]

Abstract: Mercury and selenium concentrations were determined in muscle of 37 yellowfin tuna (Thunnus albacares) captured aboard of Mexican purse-seiners boats off western coast of Baja California Sur, between Punta Eugenia and Cabo Falso, from October to December 2006. Also, its prey (mainly, jumbo squid Dosidicus gigas and pelagic red crab Pleuroncodes planipes) were analyzed from the stomach contents. All the mercury values obtained were lower that mercury content recommended by standard legal limits for seafood adopted by Mexican norms (typically 0.5–1.0μgg−1). Mercury concentrations vary between 0.06 and 0.51μgg−1 in yellowfin tuna, and from 0.01 to 0.20μgg−1 in its prey, suggesting that mercury can accumulate in prey tissues and that of their predator. Biomagnification factors (BMF) between predator-prey associations were calculated. The BMFs were >1, indicating that mercury biomagnifies along the food web of yellowfin tuna. In all species studied there was a molar excess of selenium over mercury. The rank order of mean selenium/mercury molar ratios was for pufferfish (42.62)> diamond squid (15.09)>yellowfin tuna (10.29)>pelagic red crab (10.05)>panama lightfish (9.54)> jumbo squid (8.91). The selenium health benefit value (Se-HBV) was calculated to have an improved understanding of the health benefits and risk of fish consumption. [Copyright &y& Elsevier]