Yellowfin Tuna Thunnus Albacares Research Articles

Numeric modeling of a pelagic longline based on minimum potential energy principle

Fishing parameters(such as the shooting speed of mainline,vessel speed,time interval between two hooks,numbers of hooks between two floats) can be adjusted to deploy the hooks to water layers that are preferred by target species,such as tuna.As a result,the catch rate of the target species can be increased and the catch of bycatch species(e.g.,loggerhead turtles,Caretta caretta;blue sharks,Prionace glauca;silky sharks,Car-charhinus falciformis) can be reduced.Together,these actions improve fishing efficiency and help maintain bio-logical diversity.To better understand the relationship between these factors and the fishing depth of longline gear,we developed a numeric model of the behavior of a pelagic longline.We conducted surveys on board Chinese large scale tuna longliners in the Indian Ocean between September 2008 and January 2009.During the surveys,the vessels targeted bigeye tuna(Thunnus obesus)but also caught yellowfin tuna(Thunnus albacares),swordfish(Xiphias gladius),albacore(Thunnus alalunga) and billfishes(Istiophoridae).The hook depths(188 hooks) were measured using temperature depth recorders(TDRs) and the three dimensional current was measured at a range of depths at 24 sites using an acoustic doppler current profiler(ADCP).We developed a three-dimensional numerical longline model(3DNLM) using finite element analysis and the minimum potential energy principle method.We used Matrix Laboratory(MATLAB) software to program and conduct the numerical calculations.The three di-mensional current data were assigned to seven,50 m depth intervals(e.g.,0–50,50–100,or 300–350 m).The co-ordinates of all the nodes of the longline(including the float lines,mainline,and branch lines) were calculated by inputting three-dimensional current profile data,fishing gear parameters(the diameter of the mainline and branch line,the total weight of the branch line and the bait in the water,the density of the mainline and branch line,the elastic modulus of the mainline,the length of the branch line,and the length of the float rope),operating parame-ters(vessel speed,line shooter speed,and the time interval between two hooks) into the numerical model.The model then outputs the shape of the longline under water and the depth of each hook.We verified the model output using experimental data.The model was able to accurately depict the three-dimensional shape and hook depths of the pelagic longline.There was no significant difference between the hook depth measured by TDR and the model estimate of hook depth(P=0.220.05).The average difference between two methods was 12.03 m(range: 0.02–40.36 m,S2=100.30,S=10.01,n=188).The underwater shape of the main line was represented by a wave-shaped curve.The shape was related to the force of the branch line.This load was concentrated at the re-spective node of the main line and made the depth of this node deeper.The main line between two nodes may have floated somewhat because of lift generated by sea currents,especially upwelling currents.The model estimates of the three-dimensional shape and the hook depths were influenced by the value of the drag coefficient(CN90).CN90 was defined as the drag coefficient associated with water flow plumb to the cylinder.The value of the drag coeffi-cient(CN90) was determined based on the Reynolds number(Re) of the study object.

Intra-individual behavioral variability displayed by tuna at fish aggregating devices (FADs)

Fishers have exploited the associative behavior displayed by several pelagic fish species with floating objects for decades, through the use of man-made fish aggregating devices (FADs), which facilitate the capture of such species. However, our understanding of this associative behavior and its adaptive value is poor and the scientific community is ill-equipped to provide fishery managers with science-based recommendations on the impacts of FADs on ecosystems. In an array of 13 anchored FADs around Oahu, Hawaii, USA, 72 yellowfin tuna Thunnus albacares were equipped with internal acoustic tags, which facilitated the continuous monitored of their presence and absence around each FAD using automated acoustic receivers. Data were analyzed using survival curves with the objective of determining the behavioral dynamics of fish joining and leaving the FADs. Residence times at FADs were characterized by 4 behavioral modes: briefly passing near a FAD (average 13.1 min), short association (average 2.9 d), and 2 long association behaviors (13.8 and 23.2 d, respectively). Statistical analyses suggest that different behavioral modes were likely dependent upon local conditions around the FAD at a given time (environmental factors or social interactions). We observed 2 behavioral modes for absence times from FADs: short (2.8 d) and long (infinite). More importantly, individuals exhibited behavioral variability, switching between short and long residence times at FADs. This suggests that large pelagic fish can display a range of behavioral responses while in an array of FADs, challenging the common hypothesis of a single behavioral pattern, which could ultimately lead to an ecological trap. Survival curves were best fitted with exponential models, suggesting that underlying behavioral processes were time independent.

Vertical behavior of juvenile yellowfin tuna Thunnus albacares in the southwestern part of Japan based on archival tagging

The behavior of juvenile yellowfin tuna Thunnus albacares in southwestern Japan was investigated using archival tag data from five fish (fork length 52.5–92 cm, days at liberty 26–280 days) released near the Nansei Islands (24–29°N, 122–130°E). Vertical behavior was classified into three patterns: “shallow” (≥50 % of daytime hours at depth of <50 m), “deep” (≥50 % of daytime hours at ≥100 m), and “intermediate” (other than “shallow” or “deep”). The pooled proportion of the number of days of each behavior was 29, 25 and 46 %, respectively. The proportion of “shallow” behavior increased with fish size. The proportion of time spent near the surface at nighttime increased in the colder season, when the thermal gradient was relatively small. Surface-oriented behavior (fish remained at a depth of <10 m for more than 10 min) occurred mainly during nighttime and between November and January. Dives exceeding 500 m were occasionally observed (0.02 day−1), and one fish dived to 1230 m. The results of our study show that yellowfin tuna were typically distributed in the mixed layer or upper thermocline where the water temperature was close to the sea surface temperature and that the vertical behavior was variable.

Mitochondrial DNA analysis reveals three stocks of yellowfin tuna Thunnus albacares (Bonnaterre, 1788) in Indian waters

Yellowfin tuna (Thunnus albacares) is an epipelagic, oceanic species of family Scombridae found in tropical and subtropical region of Pacific, Indian and Atlantic Ocean. It is commercially important fish and accounts for 19 % of total tuna catches in Indian waters. In present study, population structure of yellowfin tuna was examined using sequence analysis of mitochondrial DNA from seven geographically distinct locations along the Indian coast. A 500 bp segment of D-loop region was sequenced and analysed for 321 yellowfin samples. Hierarchical analysis of molecular variance showed significant genetic differentiation among three groups (VE); (AG); (KO, TU, PO, VI, PB) analyzed (Φ ST = 0.03844, P ≤ 0.001). In addition, spatial analysis of molecular variance identified three genetically heterogeneous groups of yellowfin tuna in Indian waters. Results were further corroborated by significant value of nearest neighbour statistic (S nn = 0.261, P ≤ 0.001). Thus finding of this study rejects the null hypothesis of single panmictic population of yellowfin tuna in Indian waters.

An integrated habitat index for yellowfin tuna in waters near Gilbert Islands based on GAM

The aim of this study is to contribute to the sustainable utilization of yellowfin tuna(Thunnus albacares)resources.In this study,generalized additive model(GAM)was applied to develop the integrated habitat index(IHI)models on the basis of the data which were collected in waters near Gilbert Islands from October,2009 through December,2009.The profiles of environmental variables and the yellowfin tuna catch rate data were collected at 34 sites.These models were used to predict the corresponding potential catch rate.The Wilcoxon test was used to test if there was significant relationship between the predicted catch rates predicted by the models and the nominal catch rates.The integrated habitat indexes(IHI)in different water strata of yellowfin tuna were estimated by the catch rate predicted by the models.Comparing the nominal CPUE with the average integrated habitat index(IHI)in different water strata,the predicted power of the models was evaluated.The correlation coefficients between the nominal CPUE and the average integrated habitat index(IHI)in different water strata were calculated.This correlation coefficient was also used to evaluate the prediction power of the models.In addition,the Gilbert Islands survey data in 16 sites from Nov.2010 through Jan.2011 were used to verify the effectiveness of the models.These data were input into the models for water stratum of 40-80 m and the whole water bin(0-240 m),and the IHIs of the yellowfin tuna were estimated.The results showed that:(1)The IHI distributions of different water strata were different from each other.The environmental variables which influenced the distribution of yellowfin tuna were different in the different water strata.The yellowfin tuna are mainly distributed in the water stratum of 40-120 m;(2)The prediction power of the models was good on the basis of the verification data obtained in 16 sites from Nov.2010 through Jan.2011;(3)GAM is suitable for the environmental variable selection,which influenced the distribution of yellowfin tuna,and shows the nonlinear relationship between the environmental variables and the catch rate;(4)GAM can be used to study the spatial distribution of the pelagic fish by building the IHI model.

大西洋中部延绳钓黄鳍金枪鱼渔场时空分布与温跃层的关系

We evaluated the isoline distribution of thermocline characteristics(the upper and lower boundary temperatures and depths) in the yellowfin tuna(Thunnus albacares) fishing grounds in the tropical Atlantic Ocean. We plotted the thermocline characteristics contour on a spatial overlay map using data collected on a monthly basis from Argo buoys and monthly CPUE(catch per unit effort) from yellowfin tuna longlines from the International Commission for the Conservation of Atlantic Tunas(ICCAT). In addition,frequency analysis and the empirical cumulative distribution function(ECDF)were used to calculate the optimum ranges for the thermocline characteristics of the central fishing grounds. Our analysis suggested that there were significant seasonal variations in the upper boundary temperature and depth of the thermocline in the central fishing grounds,which significantly influenced the temporal and spatial distribution of the yellowfin tuna population. However,the lower boundary temperature and depth of thermocline has little seasonal variation. The lower boundary depth of the thermocline isoline depth showed that the higher depth area( 250 m) was shaped like the letter‘W'. Similarly,the lower boundary temperature of the thermocline isoline depth suggests that the temperature is higher besides the equator and lower around the equatorial Zonal. The overlay map suggest that the upper boundary of the thermocline in the fishing grounds of the yellowfin tuna ranges from 20 to 60 m in the equatorial zone during January to June.It is between 60 and 80 m from July to September,but increases to 100 m offshore of Namibia during July to September. The upper boundary of the thermocline in the fishing grounds decreases to about 60 m from October to December. The fishing grounds are distributed where the upper boundary temperature of the thermocline is between 26 and 29 ℃ all year in the equator zonal,whereas the hooking rates are low where the temperature falls below 24 ℃. The lower boundary depth of the thermocline of the fishing grounds in the equatorial zone ranges from 160 to 250 m and concentrates on 230 m. The lower boundary temperature of the thermocline in the fishing grounds is between 12 and 14 ℃ all year in the equatorial zone.Conversely,if the temperature is outside this range,the hooking rates are very low. The upper boundary of the temperature thermocline in the fishing grounds extends to 20 ℃ offshore of Namibia during July to November,and the lower boundary of the temperature and depth of the thermocline lies between 14 and 15 ℃ and 140 and 160 m,respectively. Frequency analysis and the empirical cumulative distribution function(ECDF) were used to calculate the optimum range of thermocline characteristics. The optimum depth range of the upper boundary temperature was 26—28. 9 ℃. The optimum depth range of the lower boundary and the lower boundary temperature were 150—249 m and 12—14.9 ℃,respectively.The results were confirmed by using the Kolmogorov—Smirnov test. However,the upper boundary temperature was shown as insignificant from the statistical results. A preliminarily indication of the optimum distribution interval and seasonal change characteristics of each thermocline in the longline central fishing ground of yellowfin tuna was obtained in this paper. The conclusion could provide a reference for improving the efficiency of yellowfin tuna longline fishing and aid tuna resource management in the Atlantic Ocean.

Assessment of Commercial Quality Evaluation of Yellowfin Tuna Thunnus albacares Meat Based on Myoglobin Properties

Four quality grades (excellent, good, acceptable, and “not acceptable”) of yellowfin tuna meat (Thunnus albacares), as judged by a professional appraiser, were compared based on the red/ox state and extractability of myoglobin (Mb). As a result, the metMb ratio of the “not acceptable” grade of meat was significantly higher than that of the other higher-grade samples. In contrast, the highest ratio of oxyMb was found in the “excellent” meat, followed by good > acceptable > “not acceptable” meats. Color measurement revealed significant differences in a* value between the different grades of meat, but showed essentially no difference in L* and b* values. Both a* value and redness index (a*/b*) showed high correlation coefficients with metMb ratio. Mb extractability tended to be higher in the higher grade of meat. In conclusion, the commercial appraisal of tuna meat quality was demonstrated to be reliable.

Schooling behavior of juvenile yellowfin tunaThunnus albacaresaround a fish aggregating device (FAD) in the Philippines

A fish aggregating device (FAD) called a payao is conventionally installed to catch pelagic species in the Philippines. The waters around the Philippines are important regions for yellowfin tuna stocks because they include spawning grounds and nurseries. To understand the schooling behavior of juvenile yellowfin tuna Thunnus albacares around a payao, 13 juveniles (20.5−24.0 cm fork length) double tagged with ultrasonic transmitters (V7-2L-R256; Vemco Ltd.) and data loggers (DST-micro; Star-Oddi Ltd.) were released around a payao. A self-recording receiver (VR2-DEL; Vemco Ltd.) was attached on the mooring rope of the payao to follow the horizontal movements and data loggers recorded the vertical movements of tagged juveniles. Nine juveniles were recaptured simultaneously by ring net at the same payao after 4-7 days. One juvenile was recaptured by hand line at another payao 12 km away from the tagging site after 6 days. Recaptured juveniles showed a diurnal schooling pattern suggesting different school shape and foraging strategy between daytime and nighttime. Juveniles showed a diurnal horizontal moving pattern, concentrated near the payao during daytime, while they were distributed around the payao at nighttime. The fluctuations of swimming depth were synchronized among fish. Juveniles also showed a diurnal vertical movement pattern in surface mixed layer. They concentrated in a shallow and narrow range (11.2±8.2 m, mean ± SD) at nighttime, while they were distributed to a deep and wide range (20.0 ± 11.8 m) during daytime. The maximum vertical neighbor distance indicated the vertical thickness of the school and showed a peak around noon. Higher vertical movement speed during daytime indicated vertical foraging in a water column, while at nighttime the juveniles might forage horizontally following the diurnal migration patterns of prey in the surface layer.

Biomagnification of mercury and its antagonistic interaction with selenium in yellowfin tuna Thunnus albacares in the trophic web of Baja California Sur, Mexico

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.

Life in 3-D: life history strategies in tunas, mackerels and bonitos

The scombrids (tunas, bonitos, Spanish mackerels and mackerels) sustain some of the most important fisheries in the world and their sustainable management depends on better understanding of their life history strategies. Here, we first assemble life history information on maximum size, growth, longevity, maturity, fecundity and spawning duration and interval for all scombrid species. Second we characterize their life history patterns and trait co-variation and evaluate how many principal axes of trait variation underlie scombrid life history strategies. Most of their life history variation can be explained along three axes or dimensions: size, speed, and reproductive schedule. Body size governs the first axis ranking species along a small-large continuum. The second axis was mostly influenced by time-related traits, such as longevity, growth rates, spawning duration, time between spawning events, ranking species along a slow-fast continuum of life histories. Scombrid species with the slowest life histories such as Atlantic bluefin tuna Thunnus thynnus and Atlantic mackerel Scomber scombrus tend to inhabit more temperate waters while species with faster life histories such as yellowfin tuna Thunnus albacares and short mackerel Rastrelliger brachysoma are typically found in more tropical waters. The third axis comprises the negative relationship between number of eggs produced at length of maturity and rate in gain of fecundity with size describing the schedule of reproductive allocation which reflects a fundamental trade-off between reproduction and growth. Finally, in addition we show that the life history strategies of scombrids conform more closely to the Periodic and Opportunistic strategists within the triangular model of fish life histories.

Nursery origin of yellowfin tuna in the Hawaiian Islands

Stable isotopes of carbon (! 13 C) and oxygen (! 18 O) in otolith cores (first 2 mo of age) of young-of-the-year (YOY) yellowfin tuna Thunnus albacares were used as natural tracers to pre- dict the nursery origin of sub-adults (age-1) collected from the Hawaiian Islands. YOY fish were first collected from nurseries throughout the western and central Pacific Ocean (WCPO) to deter- mine whether ! 13 C and ! 18 O values of otolith cores (! 13 Cotolith and ! 18 Ootolith) were sufficiently dif- ferent to discriminate individuals from different nurseries used during the YOY period. Nurseries examined included both nearshore Hawaiian Islands and offshore Hawaiian Islands (Cross Seamount), and 4 locations in the equatorial Pacific Ocean: Line Islands, Marshall Islands, Solomon Islands, and Philippines. Significant differences existed in ! 13 Cotolith and ! 18 Ootolith among YOY yellowfin tuna from different nurseries for each year of the 2 yr study period (2008!2009). Individuals from the nearshore Hawaiian Islands were most enriched in ! 18 Ootolith, while samples obtained from the Philippines were most depleted in both ! 13 Cotolith and ! 18 Ootolith relative to other regions. Inter-annual variability in otolith core chemistry was minor and only observed for individ- uals collected from the Philippines. Overall classification success from quadratic discriminant function analysis of YOY yellowfin tuna to their respective nursery of collection was 63 and 87% for 2008 and 2009, respectively. Mixed-stock analysis indicated 91% of the sub-adult yellowfin tuna collected from the nearshore Hawaiian Islands originated from this same nursery. In addition, sub-adults from the offshore location within the Hawaiian Islands appear to originate from the nearshore Hawaiian Islands, highlighting the importance of local production and retention of yellowfin tuna to the standing stock and domestic fisheries of Hawaii.

Application of satellite multi-sensor techniques to detect upwellings and potential fishing grounds in Wakatobi Marine National Park, Southeast Sulawesi, Indonesia

Information about Yellowfin Tuna fishing grounds is needed to develop the capture fisheries sector, which could be obtained through satellite multi-sensor mapping techniques. Fishermen often have difficulty determining where the fish are and when they can be caught in abundance. Knowing this information would sufficiently reduce operating costs. Mapping the fishing ground of Yellowfin Tuna would also avoid overfishing due to the concentration of fishing boats in one particular location, thus allowing the operation to be more effective and efficient. The long-term aim of this research is to improve the welfare of fishermen in the Wakatobi district, Southeast Sulawesi, while the short-term goal is to map the fishing ground of Yellowfin Tuna (Thunnus albacares) with the application of multi-sensor satellite technology to detect upwellings. The benefits of this research are cost savings for the fishermen and providing a reference for the arrangement of management strategies of Yellowfin Tuna (Thunnus albacares) for sustainablity and continuity. This study indicated that the average sea surface temperature in the west was 29.79°C, in the west-east an average of 29.70°C, in the east an average of 27.40°C and the east-west an average of 29.13°C. Chlorophyll-a in both the west and the west-east averaged 0.15 mg m−3, in the east 0.27 mg m−3 and in the east-west 0.21 mg m−3. High temperatues started in December and continued until February in the Wakatobi region, which moved from west to east. Low temperature moved from east to west from June until August. Fronts occured arround Kaledupa and Koromaha reef in December, January and February, as well as in March, April and May around Kaledupa reef and Runduma Island. In June, July, August, September, October and November fronts were observed around Kapota reef, Kaledupa reef, Koromaha reef and Koka reef. Upwelling occured in Kapota reef, Kaledupa reef and Koka reef in June, and in July and August around Runduma Island, Kapota reef, and Kaledupa reef. Furthermore, upwelling in Kapota reef, Wangi-wangi Island, and Kaledupa reef was observed in September.

210Po Activity and Concentrations of Selected Trace Elements (As, Cd, Cu, Hg, Pb, Zn) in the Muscle Tissue of Tunas Thunnus albacares and Katsuwonus pelamis from the Eastern Pacific Ocean

Daily mineral intake (DMI) of Cu and Zn, percentage weekly intake (PWI) of As, Cd, Hg, Pb, and doses of (210)Po were estimated by using their elemental concentration in muscle of two tuna species and the average tuna consumption in Mexico. Skipjack tuna Katsuwonus pelamis had significantly (p < 0.05) higher levels of As (1.38 μg g(-1) dw) and Cu (1.85 μg g(-1) dw) than yellowfin tuna Thunnus albacares, whereas Pb concentrations (0.18 μg g(-1) dw) were significantly (p < 0.05) higher in T. albacares. The sequence of elemental concentrations in both species was Zn > Cu > As > Hg > Pb > Cd. In T. albacares, concentrations of Cd and Pb in muscle tissue were positively correlated (p < 0.05) with weight of specimens, while Cu was negatively correlated. DMI values were below 10 %. PWI figures (<2 %) are not potentially harmful to human health. (210)Po concentration in T. albacares and K. pelamis accounts for 13.5 to 89.7 % of the median individual annual dose (7.1 μSv) from consumption of marine fish and shellfish for the world population.

아세트산처리 황다랑어(Thunnus albacares) 껍질 유래 젤라틴으로 제조한 바이오필름의 생체 접착 특성

This study aimed to demonstrate the bioadhesive characteristics of gelatin biofilm to rat skin. The biofilm was manufactured from gelatin extracted from the acetic acid treated-skin of the yellowfin tuna Thunnus albacares. The bioadhesive strength of tuna gelatin biofilm was compared to that of porcine gelatin biofilm. The tuna gelatin biofilm exhibited a higher bioadhesive strength than the porcine gelatin biofilm. Gelatin biofilm was subjected to glutaraldehyde treatment at different concentrations, temperatures and pH in order to improve its bioadhesive strength. Glutaraldehyde treatment improved the bioadhesive strength of gelatin biofilm up to three-fold. The bioadhesive strength of glutaraldehyde treated-biofilm was significantly decreased by application of sodium borohydride.

아세트산 처리 황다랑어(Thunnus albacares) 껍질 유래 젤라틴으로 제조한 바이오필름의 물리적 특성

The present study examined the physical properties of biofilms manufactured from yellowfin tuna Thunnus albacares skin gelatin with the aim of developing a biofilm from fisheries by-products to replace mammalian sources. The physical properties of biofilms from yellowfin tuna gelatin were compared with those of biofilms from porcine gelatin. The yellowfin tuna gelatin biofilm exhibited higher tensile strength (69.08 MPa) and greater elongation (14.32%) than did porcine gelatin biofilm (50.50 MPa and 10.21%, respectively). The <TEX>${\Delta}E$</TEX> and YI (yellowness index) Huntercolor values of yellowfin tuna gelatin biofilm were three-fold and 15-fold higher, respectively, than values for porcine gelatin biofilm. The opacity value of yellowfin tuna gelatin biofilm was higher than that of porcine gelatin biofilm. The stability against water of yellowfin tuna gelatin biofilm was lower than that of porcine gelatin biofilm at pH 3 to pH 11. Thermogravimetric analysis (TGA) indicated that the thermal stability of the biofilms was about <TEX>$270^{\circ}C$</TEX> for porcine gelatin biofilm and about <TEX>$250^{\circ}C$</TEX> for yellowfin tuna gelatin biofilm.

Association of early juvenile yellowfin tuna Thunnus albacares with a network of payaos in the Philippines

To understand how early juvenile yellowfin tuna use the habitat and environment provided by fish aggregating devices (FADs), fish (19–31 cm FL) implanted with ultrasonic transmitters into their abdominal cavities were released in a network of payaos in Panay Gulf, the Philippines. Self-recording receivers were attached to the anchor ropes of the payaos to detect the presence of the fish. Some aspects of the behavior of juveniles were similar to those reported in adults. One juvenile showed a diurnal vertical swimming pattern, swam within a limited shallow range during the nighttime, and dived to deeper waters during the daytime. Two juveniles performed deep dives over 100 m during payao-to-payao excursion. Three juveniles showed a diurnal horizontal swimming pattern that was synchronized. In contrast, juveniles stayed <6 days in the network, shorter than adults. No juveniles returned to the same payao after an interruption of over 24 h. It is suggested that juveniles in this area are just starting to migrate and are temporarily staying around a payao for a few days to forage before continuing their migration.

Total mercury in canned yellowfin tuna Thunnus albacares marketed in northwest Mexico

Mercury (Hg) was determined in Thunnus albacares canned in oil (from 7 to 10 samples per brand) and water (from 5 to 10 samples per brand) of five leading brands in Mexico in 2008. Potential health risk was estimated on the basis of Hg concentration and rate (1.43kgyear−1per capita) of tuna consumption in Mexico. Highest Hg concentrations were 0.51±0.26 and 0.40±0.24μgg−1 dry weight in water and oil, respectively. Averaged Hg concentrations in tuna canned in water in the current study were comparable to values in Katsuwonus pelamis from Alabama; regarding the oil presentation, Hg levels were lower than in canned tuna collected in Mexico and comparable to values in canned tuna (species not identified) from Turkey. Hazard quotients were 0.0166 and 0.012 in water and oil, respectively. For the analyzed brands and considering tuna consumption in Mexican population, reference dose for this element was not exceeded; therefore, no human health risk is likely to occur. More work is necessary in relation to exposure to Hg from other sources, rates of consumption in strata of population with elevated fish consumption, size of canned tuna and on the role of Se against Hg toxicity.

Growth and mortality rates of yellowfin tuna, Thunnus albacares (Perciformes: Scombridae), in the eastern and central Pacific Ocean

Age and growth parameters were estimated for the yellowfin tuna Thunnus albacares (Bonnaterre, 1788). Atotal of 443 individuals were sampled from China longline fisheries in the eastern and central Pacific Ocean from February to November 2006. The von Bertalanffy growth parameters were estimated at L∞ = 175.9 cm fork length, k = 0.52 year-1, and t0 = 0.19 year. The total mortality rate (Z) was estimated to be from 1.19 to 1.93 year-1, the fishing mortality (F) and the natural mortality (M) were calculated to be 0.91 year-1 and 0.65 year-1, respectively. The rate of exploitation (U) was estimated to be 0.46. This study provides estimates of growth and mortality rate for yellowfin tuna in the eastern and central Pacific Ocean, which may be used as biological input parameters in future stock assessments for the oceanic region. However, age analysis with other techniques, additional validation of the size composition and stock structure are also needed.

The effect of stimulation frequency on the transmural ventricular monophasic action potential in yellowfin tuna Thunnus albacares

Monophasic action potentials (MAPs) were recorded from the spongy and compact layers of the yellowfin tuna Thunnus albacares ventricle as stimulation frequency was increased. MAP duration decreased with increase in stimulation frequency in both the spongy and compact myocardial layers, but no significant difference in MAP duration was observed between the layers.

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.