Contrasting physical mechanisms of yellowfin tuna fluctuations between the western and eastern Indian Ocean

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.

Impacts of central-Pacific El Niño and physical drivers on eastern Pacific bigeye tuna

Bigeye tuna Thunnus obesus is an important migratory species that forages deeply,and El Niño events highly influence its distribution in the eastern Pacific Ocean.While sea surface temperature is widely recognized as the main factor affecting bigeye tuna(BET)distribution during El Niño events,the roles of different types of El Niño and subsurface oceanic signals,such as ocean heat content and mixed layer depth,remain unclear.We conducted A spatial-temporal analysis to investigate the relationship among BET distribution,El Niño events,and the underlying oceanic signals to address this knowledge gap.We used monthly purse seine fisheries data of BET in the eastern tropical Pacific Ocean(ETPO)from 1994 to 2012 and extracted the central-Pacific El Niño(CPEN)indices based on Niño 3 and Niño 4indexes.Furthermore,we employed Explainable Artificial Intelligence(XAI)models to identify the main patterns and feature importance of the six environmental variables and used information flow analysis to determine the causality between the selected factors and BET distribution.Finally,we analyzed Argo datasets to calculate the vertical,horizontal,and zonal mean temperature differences during CPEN and normal years to clarify the oceanic thermodynamic structure differences between the two types of years.Our findings reveal that BET distribution during the CPEN years is mainly driven by advection feedback of subsurface warmer thermal signals and vertically warmer habitats in the CPEN domain area,especially in high-yield fishing areas.The high frequency of CPEN events will likely lead to the westward shift of fisheries centers.

Numerical Study of Propulsion Mechanism for Oscillating Rigid and Flexible Tuna-Tails

Numerical study on the unsteady hydrodynamic characteristics of oscillating rigid and flexible tuna-tails in viscous flow-field is performed. Investigations are conducted using Reynolds-Averaged Navier-Stokes （RANS） equations with a moving adaptive mesh. The effect of swimming speed, flapping amplitude, frequency and flexure amplitude on the propulsion performance of the rigid and flexible tuna-tails are investigated. Computational results reveal that a pair of leading edge vortices develop along the tail surface as it undergoes an oscillating motion. The propulsive efficiency has a strong correlation with various locomotive parameters. Peak propulsive efficiency can be obtained by adjusting these parameters. Particularly, when input power coeffcient is less than 2.8, the rigid tail generates larger thrust force and higher propulsive efficiency than flexible tail. However, when input power coefficient is larger than 2.8, flexible tail is superior to rigid tail.

Comparison of nominal and standardized catch per unit effort data in quantifying habitat suitability of skipjack tuna in the equatorial Pacific Ocean

In the western and central Pacific Ocean,upper strata waters exhibit highly dynamic oceanographic features under ENSO variability.This has been proved to be responsible for the dynamic change of both abundance and zonal distribution of skipjack tuna(Katsuwonus pelamis).Although causality has been suggested by researchers using physical-biological interaction models,cumulative evidence needs to be obtained and the tenability of assertion needs to be tested from an ecological habitat perspective,based on fisheries data.For purse seine fishery,the use of catch per unit effort(CPUE)as an indication of the abundance is confusing because of technical improvements over the whole exploitation history and unbalanced individual fishing characteristic of vessels.It is particularly interesting to discriminate between habitat characteristics in comparative scenarios of CPUE application.This study identified habitat traits based on a series of oceanographic factors from a global ocean reanalysis model.A comparison was conducted between two habitat models based on unprocessed purse seine CPUE and standardized CPUE considering fishing characteristics.The results suggest that standardized CPUE could model the regular zonal shift of habitat compatible with the observed fishing efforts transfer,and achieved better prediction capacity than unprocessed CPUE.Furthermore,the habitat of skipjack tuna was also characterized and linked with surface and subsurface thermal environment,ocean current,dissolved oxygen,biotic environment,and ENSO variability.The monthly-averaged habitat suitable index,derived from the optimal habitat model prediction,showed a significant linear relationship with the southern oscillation index,which suggested that El Ni?o episodes eventually provide more preferable habitat for skipjack tuna under ENSO variability.

Stock assessment for Atlantic yellowfin tuna based on extended surplus production model considering life history

The modern fishery stock assessment could be conducted by various models,such as Stock Synthesis model with high data requirement and complicated model structure,and the basic surplus production model,which fails to incorporate individual growth,maturity,and fishery selectivity,etc.In this study,the Just Another Bayesian Biomass Assessment(JABBA)Select which is relatively balanced between complex and simple models,was used to conduct stock assessment for yellowfin tuna(Thunnus albacares)in the Atlantic Ocean.Its population dynamics was evaluated,considering the influence of selectivity patterns and different catch per unit effort(CPUE)indices on the stock assessment results.The model with three joint longline standardized CPUE indices and logistic selectivity pattern performed well,without significant retrospective pattern.The results indicated that the stock is not overfished and not subject to overfishing in 2018.Sensitivity analyses indicated that stock assessment results are robust to natural mortality but sensitive to steepness of the stock-recruitment relationship and fishing selectivity.High steepness was revealed to be more appropriate for this stock,while the fishing selectivity has greater influence to the assessment results than life history parameters.Overall,JABBA-Select is suitable for the stock assessment of Atlantic yellowfin tuna with different selectivity patterns,and the assumptions of natural mortality and selectivity pattern should be improved to reduce uncertainties.

Preparation of DHA-and EPA-enriched Glycerides by Enzymatic Interesterification Using Tuna Oil and Capric Acid

This study focused on the preparation of docosahexaenoic acid(DHA) and eicosapentaenoic acid(EPA)enriched-triacylglycerols by enzymatic interesterification using tuna oil and capric acid. The content of DHA+EPA is 26.86% in the tuna oil used in this study. A response surface methodology(RSM) was used to optimize the reaction parameters(reaction temperature, substrate molar ratio, enzyme amount and reaction time), and the optimized conditions were determined to be: reaction temperature 58℃, substrate molar ratio(capric acid : tuna oil) 4:1, enzyme amount 4%, and reaction time 7.5 h. Under the optimized conditions, the content of DHA+EPA in the glycerides was 40.03%, which is 13.17% higher than that in raw tuna oil. In addition,the MLM-type structured lipids containing medium chain fatty acids(capric acid) at positions sn-1,3 and a long chain fatty acid(DHA/EPA) at the position sn-2 may have many health benefits for humans.

Quality Characteristics of Dark Muscle from Yellowfin Tuna Thunnus albacares to Its Potential Application in the Food Industry

Dark muscle from yellowfin tuna is an important edible fish by-product. However, it has a low commercial value, and it is underutilized. The present study was conducted to establish the characteristic of this by-product. Myoglobin concen- tration in tuna dark muscle is high (9650.12 mg/kg). Total iron in tuna muscle was 32.11 mg/kg, higher than other animal foods like veal or pork, and heme iron concentration was 23.56 mg/kg (73.38% of the total iron), indicating a high bioavailability of heme iron in dark muscle from yellowfin tuna, which is a nutritional advantage. As for the techno- logical properties, yellowfin tuna dark muscle had a water holding capacity of 8.37 g water/g and oil holding capacity of 8.11 g oil/g. This indicates that tuna dark muscle has possible applications to elaborate products, such as emulsion- ated foods or cooked products, so its industrialization is possible.

Numerical model and hydrodynamic performance of tuna finlets

Finlets, a series of small individual triangular fins located along the dorsal and ventral midlines of the body, are remarkable specializations of tuna and other scombrid fishes capable of high-speed swimming. In this study, a symmetric model containing nine finlets of tuna is proposed to overcome the limitation of measurement without losing authenticity. Hydrodynamic performance along with three-dimensional flow structures obtained by direct numerical simulation are demonstrated to disclose the underlying hydrodynamics mechanism of finlets. Complex interactions of leading-edge vortices(LEVs), trialing-edge vortices(TEVs), tip vortices(TVs) and root vortices(RVs) are observed from the three-dimensional vortical structures around the finlets. Two more cases consisting of the 3rd to 9th(without the first two) and the 3rd to 7th(without the first two and the last two) finlets are also simulated to examine the effects of the first two and the last two finlets.

Influence of Climatic Conditions on the Time Series Fluctuation of Yellowfin Tuna <i>Thunnus albacares</i>in the South Pacific Ocean

Yellowfin tuna (Thunnus albacares) is one of the most commercially important fish species for South Pacific island nations and territories and for effective conservation efforts it is important to understand the factors which affect its time series pattern. Our research was aimed at elucidating the climatic factors which affected the trajectory of the yellowfin tuna stock in the Eastern and Western South Pacific Ocean. We utilized various climatic factors for the years t - n with n = 0, 1, ..., 8 and investigated their statistical relationship with the catch per unit effort (CPUE) of yellowfin tuna stock from 1957-2008 for three South Pacific zones ranging from the East to the West Pacific Ocean within the coverage area of the Western and Central Pacific Convention Area. Results showed that the climatic conditions of: (i) the global mean land and ocean temperature index (LOTI), (ii) the Pacific warm pool index (PWI) and (iii) Southern Oscillation Index (SOI) had significant relationship with the CPUE of yellowfin tuna in all three zones. LOTI, PWI and SOI were used as independent variables and fitted through modeling to replicate the CPUE trajectory of the yellowfin tuna in Zone 1, Zone 2 and Zone 3. Model selection was based on significant parameter estimates (p < 0.05), Akaikes Information Criterion (AIC) and R2 values. Models selected for all three zones had LOTI, PWI and SOI as the independent variables. This study shows that LOTI, PWI and SOI are climatic conditions which have significant impact on the fluctuation pattern of the yellowfin tuna CPUE in the Eastern and Western South Pacific Ocean. From the findings of this study it can be recommended that when management decisions are made for yellowfin tuna fishery conservation and sustainability in the Eastern and Western South Pacific, it is imperative to take the effect of climatic factors into account.

Levels of Mercury and Polychlorobiphenyls in Bluefin Tuna from the Western Mediterranean Sea: A Food Safety Issue?

In this paper, the presence and amount of mercury and polychlorobiphenyls (PCBs) were determined in 23 bluefin tuna samples collected in the spring of 2012 in Porto Scuso (South West Sardinia, Italy) and Villa Putzu (South East Sardinia, Italy) in order to assess the current levels of these two contaminants in fish muscle and the consequent risk to humans consuming said fish. Values of polychlorobiphenyls in bluefin tuna muscle vary between 0.155 and 1.403 mg/kg f.w.;the average of PCBs in tuna muscle is 0.732 mg/kg f.w. With regard to PCBs the presence of more elevated concentrations is confirmed in larger fish. The results regarding mercury in muscle show an average of 0.660 mg/kg f.w. and mercury values vary between 0.140 f.w. and 2.211 mg/kg f.w.;for mercury as well, the highest concentrations were found in the largest bluefin tuna. Six samples, 26% of total, contained more than 1 mg/kg f.w., which is the maximum level set by the European Commission (EC, Regulation n. 1881/2006) for this species. Mercury, in particular methylmercury, poses a risk to public health, therefore, taking into account the important nutritional contribution that tuna fish makes to the diet, it is advisable that women of childbearing age, pregnant and breastfeeding women as well as young children strictly limit their consumption of tuna from this area of the Mediterranean.

Constructing Genetic Linkage Maps Using the Whole Genome Sequence of Pacific Bluefin Tuna (Thunnus orientalis) and a Comparison of Chromosome Structure among Teleost Species

Pacific bluefin tuna (Thunnus orientalis) is one of the most economically important species in the Percomorpha group of teleost fishes. Their migrations are extensive and depend upon continuous swimming at a high rate of speed throughout their life. The draft genome sequence of this species has been reported but remains highly fragmented. We constructed a Pacific bluefin tuna genetic linkage map using microsatellite markers developed on each of the scaffolds from the draft genome sequence to link these genome fragments and understand the genomic structure of species in Percomorpha. Of the 606 polymerase chain reaction microsatellite primer pairs tested, 473 were polymorphic in the mapping populations for the linkage analysis. We constructed sex-specific maps for 24 linkage groups consisting of 470 markers, which allowed us to place scaffolds that cumulatively represented 20.8% (153.8 Mb) of the sequenced genome onto the linkage groups. The distribution of orthologous genes on the chromosomes of tuna and four other teleost fish species suggested that the constitution of tuna chromosomes is closest to that of medaka. Both species have the 24 chromosomes of the ancestral teleost, including several chromosomal inversions. The integrated map developed in this study will be useful to construct a complete physical map to conduct comparative teleost genomics and genetic studies on economically useful traits in Pacific bluefin tuna.

Case Study: A Simulation Model of the Spawning Stock Biomass of Pacific Bluefin Tuna and Evaluation of Fisheries Regulations

This study proposes a simulation model that well reproduces the spawning stock biomass of Pacific bluefin tuna. Environmental factors were chosen to estimate the recruitment per spawning stock biomass, and a simulation model that well reproduced the spawning stock biomass was developed. Then, effects of various fisheries regulations were evaluated using the simulation study. The results were as follows: 1) arctic oscillations, Pacific decadal oscillations and the recruitment number of the Pacific stock of Japanese sardine were chosen as the environmental factors that determined the recruitment per spawning stock biomass;2) spawning stock biomass could be well reproduced using a model that reproduced the recruitment per spawning stock biomass and the survival process of the population that included the effect of fishing;and 3) the effects of various fisheries regulation could be evaluated using the simulation model mentioned above. The effective regulation in the simulations conducted in this paper was a prohibition of fishing for 0- and 1-year-old fish in terms of recovering the spawning stock biomass. The reduction of fishing mortality coefficients for all age fish to 50% of actual values also showed a good performance. The recent reductions of the recruitment and spawning stock biomass were likely caused by heavy harvesting, especially of immature fish, since 2004.

Tuna A150减摇水舱设计优化研究

针对上海船舶研究设计院全新AHTS系列船型之一的Tuna A150,基于数值计算开展了平面被动式减摇水舱的设计优化工作。计算采用势流理论和粘流理论相结合的时域耦合计算方法,主要就减摇水舱的不同阻尼格栅形式进行计算对比,分析了不同格栅形式的不规则波中减摇率,以此作为评价减摇水舱性能的主要技术指标。结果表明,阻尼格栅形式、透空率和横向间距对减摇率均有重要影响。

Discovery of the strong antioxidant selenoneine in tuna and selenium redox metabolism

A novel selenium-containing compound,selenoneine,has been isolated as the major form of organic selenium in the blood and tissues of tuna.Selenoneine harbors a selenium atom in the imidazole ring,2-selenylNα,Nα,Nα-trimethyl-L-histidine,and is a selenium analog of ergothioneine.This selenium compound has strong antioxidant capacity and binds to heme proteins,such as hemoglobin and myoglobin,to protect them from iron auto-oxidation,and it reacts with radicals and methylmercury(MeHg) .The organic cations/carnitine transporter OCTN1 transports selenoneine and MeHg,regulates Se-enhanced antioxidant activity,and decreases MeHg toxicity.Thus,the dietary intake of selenoneine,by consuming fish,might decrease the formation of reactive oxygen radicals that could oxidize nucleotides in DNA,and thereby inhibit carcinogenesis,chronic diseases,and aging.

Using data-limited approaches to assess data-rich Indian Ocean bigeye tuna:Data quantity evaluation and critical information for management implications

The majority of fishery stocks in the world are data limited,which limits formal stock assessments.Identifying the impacts of input data on stock assessment is critical for improving stock assessment and developing precautionary management strategies.We compare catch advice obtained from applications of various datalimited methods(DLMs)with forecasted catch advice from existing data-rich stock assessment models for the Indian Ocean bigeye tuna(Thunnus obesus).Our goal was to evaluate the consistency of catch advice derived from data-rich methods and data-limited approaches when only a subset of data is available.The Stock Synthesis(SS)results were treated as benchmarks for comparison because they reflect the most comprehensive and best possible scientific information of the stock.This study indicated that although the DLMs examined appeared robust for the Indian Ocean bigeye tuna,the implied catch advice differed between data-limited approaches and the current assessment,due to different data inputs and model assumptions.Most DLMs tended to provide more optimistic catch advice compared with the SS,which was mostly influenced by historical catches,current abundance and depletion estimates,and natural mortality,but was less sensitive to life-history parameters(particularly those related to growth).This study highlights the utility of DLMs and their implications on catch advice for the management of tuna stocks.

An Examination of Sustainable Management of Pacific Bluefin Tuna Stock

This paper addresses a fundamental question in conservation ecology, which is the balance between rebuilding of a species’ population and exploiting them, by examining an appropriate sustainable management regulation for Pacific Bluefin tuna. The population of Pacific Bluefin tuna has been heavily depleted to just 2.6% of its historic unfished size by many years of overfishing. In order to rebuild the population, an immediate implementation of a moratorium on all commercial fishing was proposed by NGOs such as the Pew Charitable Trusts and Greenpeace. The primary objective of this paper is to examine the necessity of the moratorium as a sustainable stock management regulation. The paper concludes that an additional 10% reduction in catch limit of fish less than 30 kg could be a better alternative management regulation than a total ban on all fishing. This option can increase the probability of the stock recovery, while allowing to catch as many large fishes as under the current management regulation. Through the examination of sustainable stock management for Pacific Bluefin tuna, it can be said that it is important to consider the balance between the recovery of the population and utilization of them. Since millions of people rely on the consumption of the species, it is more realistic to gradually rebuild the population with an intermediate target and an efficient additional catch limit. This consideration can be applied to conservation of other species such as whales and eels.

An Assessment to Relationships between the Yellowfin Tuna and the Spotted Dolphin in Eastern Pacific Ocean (EPO) from 1998 to 2006

Database belong to the Programa Nacional de Aprovechamiento del Atún y Protección de los Delfines (PNAAPD) from México. The area covers from latitude 5 to 20 N and longitude 90 to 125 W, Eastern Pacific Ocean (EPO), for 1998, 2001, 2002, 2005 and 2006 includes date, geographical position, sea surface temperature, tuna’s catch, yellowfin tuna’s size and dolphin’s number. 5 degress squares of latitude and longitude, each year were made. Yellowfin tuna number was normally distributed (KSd = 0.02, P > 0.20). The problem to solve is the relationship of the spotted dolphin and yellowfin tuna, that may analyze in the background of a non linear generalized model. Considering the array of latitude and longitude over the years that the abundance of yellowfin tuna is a dependent variable and the spotted dolphin abundance is the covariance continuous variable, the interaction and covariance, indicates a significant contribution to variability. The tuna abundance index does produce significative differences in latitude and longitude. Considering the dolphin as a dependent variable and the yellowfin tuna as a covariance continuous variable, the dolphin abundance index produced significative differences in latitude and longitude.

Effect of Time and Fatty Acid Composition in Eggs of White Leghorn Hens Supplemented with Tuna Oil

The study evaluated the effect of time and fatty acid (FA) composition in eggs of laying hens supplemented with tuna oil (TO). Two hundred White Leghorn hens 30-week were divided into 5 treatments with 4 replicates of 10 birds each. Treatments were assigned randomly and consisted of 0%, 0.75%, 1.50%, 2.25% and 3% TO in commercial sorghum-soybean meal diets, in which the soybean oil was partially replaced. The experiment was conducted for 90 days. At days 28, 56 and 84 of the experiment, 10 eggs per replicate were collected for chemical analysis. Feed intake, egg production rate, egg weight, and feed conversion were not influenced by dietary treatment. FA content was significantly altered (P < 0.05) by TO, showing a progressive increase in egg n-3 FA (especially docosahexaenoic [DHA] and eicosapentaenoic [EPA] acids) when TO was added. Levels of EPA and DHA were higher (P < 0.05) in the egg lipids of TO fed hens than those in the control group. This was correlated (P < 0.05) with the concentration of TO in the diet. However, no significant differences were observed either in egg weight or percent of egg lay between groups. There was a high correlation (P < 0.05) between TO inclusion level in the diet and the incorporation of EPA (r = 0.96) or DHA (r = 0.92) into the egg yolk and an overall decrease in n-6 FA. There was a high correlation (P < 0.05) between TO inclusion level and the incorporation of linoleic acid (LA, r = -0.95) or arachidonic acid (AA, r = -0.96) into the egg yolk. The highest incorporation (P < 0.05) of total n-3 FA content in eggs was obtained with 3% TO/kg. This increase was proportional to TO inclusion levels in the diets (r = 0.95). The results indicate that the n-3 FA content in eggs can be increased by dietary supplementation with TO, and that TO can serve as a reasonable alternative feed ingredient in layer diets to produce a healthier choice of egg.

Fatty Acid Deposition on Broiler Meat in Chickens Supplemented with Tuna Oil

The aim of the present study was to evaluate the effect of feeding four levels of tuna oil on performance and fatty acid (FA) profiles of broiler chicken meat. 240 Ross broiler chickens were randomly assigned to 20 pens and divided into four treatments: 0%, 0.75%, 1%, and 1.25% of tuna oil. At 49 days, breast and legs-thighs muscles were processed for FA analysis. Concentrations of FA in legs and thighs meat were significantly higher when compared with breast meat. In both types of meats (breast and legs-thighs), the inclusion of 1.0% or 1.25% of tuna oil in the diet significantly increased (P < 0.05) the concentration of n-3 FA (especially docosahexaenoic and eicosapentaenoic acids). Fat in broiler breast contained a proportion of 29% saturated FA (SFA): 36% monosaturated FA (MFA): 35% polyunsaturated FA (PUFA);while legs and thighs meat had a proportion of 28% SFA: 38% MFA: 33% PUFA. The addition of tuna oil in the broiler diet significantly reduced the deposition of SFA, MFA, and PUFA in breast meat, while in legs and thighs these reductions were less noticeable. The significant reduction in the concentration of n-6 PUFA and the increment of n-3 PUFA were more evident in breast than in legs and thighs, and with the addition of 1% and 1.25% of tuna oil. The results of the present study suggest a difference in FA deposition attributable to supplementation with tuna oil. The addition of tuna oil could be recommendable to increase n-3 PUFA in both broiler chicken breast and legs-thighs meats, providing a healthier and functional chicken meat to consumer.

Effect of collagen and collagen peptides from bluefin tuna abdominal skin on cancer cells

In the present study, we investigated the effect of collagen and collagen peptides from bluefin tuna abdominal skin on cancer cells. Collagens were extracted from bluefin tuna (Thunnus orientails) abdominal, mackerel, and carp skin. The calf and salmon collagen were used reagent grade as a standard samples. The main protein band pattern produced by SDS-PAGE of all collagen samples consisted of two chains and one chain. For collagen peptides samples, bluefin tuna ab-dominal skin collagen and salmon skin collagen were hydrolyzed by trypsin. Among samples, salmon, mackerel, carp collagen, and their collagen peptides did not significantly reduce relative cell growth. However, the bluefin tuna abdominal skin collagen dramatically reduced HepG2 and HeLa cell growth by over 50% relative in a concentration-dependent manner when added to cells seeded 96-well plates. This suggests the collagen adding time was mightily important for effect of the collagen.