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John Hampton – 1st expert on this subject based on the ideXlab platform
vertical movements behavior and habitat of Bigeye Tuna thunnus obesus in the equatorial central pacific oceanFisheries Research, 2015Co-Authors: Daniel W Fuller, John Hampton, Kurt M Schaefer, Sylvain Caillot, Bruno Leroy, David ItanoAbstract:
Abstract 8217 days of data downloaded from 47 archival tags, recovered from Bigeye Tuna ( Thunnus obesus ) 51–134 cm in length ( x ¯ = 86.9 c m ) , 0.87–3.44 years of age ( x ¯ = 1.89 years ) at liberty from 36 to 851 days ( x ¯ = 183 days ) in the equatorial central Pacific Ocean, are evaluated herein. Analyses of depth and temperature records resulted in the classification of three daily behavior types: characteristic, associative (associated with floating objects), and other. For three defined length classes, 54–79.9 cm, 80–99.9 cm, and 100–134 cm, when exhibiting characteristic behavior, the proportions of time and average durations of events were 45.3% ( x ¯ = 5.1 days ) , 62.6% ( x ¯ = 8.5 days ) , 79.2% ( x ¯ = 17.5 days ) , and the average daytime depths and temperatures were 284 m and 12.6 °C, 305 m and 12.7 °C, and 312 m and 12.1 °C, respectively. For the same three length classes, when exhibiting associative behavior, the proportions of time and average durations of events were 9.5% ( x ¯ = 1.9 days ) , 4.8% ( x ¯ = 1.9 days ) , and 6.0% ( x ¯ = 1.8 days ) , and the average daytime depths and temperatures were 101 m and 23.2 °C, 105 m and 23.1 °C, and 74 m and 22.3 °C, respectively. There is a significant positive correlation between the proportion of time fish exhibits characteristic behavior and fish length, and significant negative correlations between the proportion of time Bigeye Tuna exhibit associative and other behavior with fish length. Behavior and habitat preferences of Bigeye Tuna should be considered for standardizing catch-per-unit of effort (CPUE) data from both longline and purse-seine fisheries targeting tropical Tunas in the Pacific, in an effort to provide more reliable estimates of relative abundance.
movements dispersion and mixing of Bigeye Tuna thunnus obesus tagged and released in the equatorial central pacific ocean with conventional and archival tagsFisheries Research, 2015Co-Authors: Kurt M Schaefer, John Hampton, Daniel W Fuller, Sylvain Caillot, Bruno Leroy, David ItanoAbstract:
Abstract A total of 31,242 Bigeye Tuna was captured, tagged, and released, 30,793 with dart tags (DTs) and 449 with geolocating archival tags (ATs), in the equatorial central Pacific Ocean along the 140° W, 155° W, 170° W, and 180° meridians, during 2008 through 2012, of which 10,029 (32.1%) of the DTs and 74 (16.5%) of the ATs were returned. A subset of high-confidence filtered DT data was retained for 5807 fish at liberty for 30 d or more, for evaluating linear displacements from release to recapture positions. For the filtered DT data, days at liberty ranged from 30 to 1701 d (median = 187 d). Linear displacements ranged from 1 to 5372 nautical miles (M) (median = 936 M), with 71% eastward and 29% westward, and 95% within 3614 M of their release positions. The data indicate significant differences in the linear displacements by release locations, days at liberty, and fish length at release. An unscented Kalman filter model with sea-surface temperature measurements integrated (UKFsst) was used to process 48 AT data sets from Bigeye Tuna at liberty for 30 d or longer, to obtain most probable tracks, improved estimates of geographic positions, and movement parameters. The 95% volume contours surrounding the position estimates, along the most probable tracks from Bigeye Tuna releases along the 140° W, 155° W, 170° W, and 180° meridians show substantial overlap. For the pooled AT data sets, the median parameter estimates from the UKFsst model for errors in longitude ( σ x ) and latitude ( σ y ) were 0.52° and 1.75°, for directed eastward and northward movements ( u and v ) were −2.01 M/d and −1.41 M/d, and for dispersive movement ( D ) was 496.7 M 2 /d. The linear displacements and most probable tracks obtained from these tagging data demonstrate constrained latitudinal dispersion, some regional fidelity, some extensive eastward longitudinal dispersion, and substantial mixing of Bigeye Tuna between release longitudes. The amount of mixing of Bigeye Tuna among these release areas in the equatorial central Pacific Ocean, with those in adjacent areas of the equatorial eastern and western Pacific Ocean, is dependent on distances between areas, with, in general, the greatest mixing occurring between the areas that are closest to one another.
shifting from marine reserves to maritime zoning for conservation of pacific Bigeye Tuna thunnus obesusProceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: John R Sibert, Patrick Lehodey, Inna Senina, John HamptonAbstract:
Over 50% of the total Bigeye Tuna (BET) landed in the Western Central Pacific Ocean is caught incidentally in the purse seine fishery and sold for canning at prices less than US$2/kg. The remainder is landed in longline fisheries directed at BET and sold as fresh or frozen Tuna at prices greater than US$10/kg. The combined fishing mortality by all gears will soon reduce the BET biomass in the Pacific Ocean to less than that capable of producing maximum sustainable yield. Closure of the high-seas enclaves in 2009 was hailed as a conservation measure, but was not scientifically evaluated before implementation and appears to have had no beneficial effect on the BET stock. A spatially explicit age-structured ecosystem model, SEAPODYM, is used to simulate alternative area-based fishery management policies to conserve Bigeye Tuna in the Western Central Pacific Ocean. Closing the high-seas enclaves to purse seine fishing has negligible effect on the BET biomass. Fishery management policies that control mortality on both juveniles and adults, through prohibition of fish aggregation devices in the purse seine fishery and restrictions on longline fishing in spawning areas, are the most efficient conservation policies. Large-scale benefits from Bigeye conservation measures will become apparent only in the 2030s, assuming timely implementation and minimal effects of climate change.
Richard W Brill – 2nd expert on this subject based on the ideXlab platform
transectional heat transfer in thermoregulating Bigeye Tuna thunnus obesus a 2d heat flux modelThe Journal of Experimental Biology, 2009Co-Authors: Jess Boye, Richard W Brill, Michael K Musyl, Hans MalteAbstract:
SUMMARY We developed a 2D heat flux model to elucidate routes and rates of heat
transfer within Bigeye Tuna Thunnus obesus Lowe 1839 in both
steady-state and time-dependent settings. In modeling the former situation, we
adjusted the efficiencies of heat conservation in the red and the white muscle
so as to make the output of the model agree as closely as possible with
observed cross-sectional isotherms. In modeling the latter situation, we
applied the heat exchanger efficiencies from the steady-state model to predict
the distribution of temperature and heat fluxes in Bigeye Tuna during their
extensive daily vertical excursions. The simulations yielded a close match to
the data recorded in free-swimming fish and strongly point to the importance
of the heat-producing and heat-conserving properties of the white muscle. The
best correspondence between model output and observed data was obtained when
the countercurrent heat exchangers in the blood flow pathways to the red and
white muscle retained 99% and 96% (respectively) of the heat produced in these
tissues. Our model confirms that the ability of Bigeye Tuna to maintain
elevated muscle temperatures during their extensive daily vertical movements
depends on their ability to rapidly modulate heating and cooling rates. This
study shows that the differential cooling and heating rates could be fully
accounted for by a mechanism where blood flow to the swimming muscles is
either exclusively through the heat exchangers or completely shunted around
them, depending on the ambient temperature relative to the body temperature.
Our results therefore strongly suggest that such a mechanism is involved in
the extensive physiological thermoregulatory abilities of endothermic Bigeye
temperature sensitivity of cardiac function in pelagic fishes with different vertical mobilities yellowfin Tuna thunnus albacares Bigeye Tuna thunnus obesus mahimahi coryphaena hippurus and swordfish xiphias gladiusPhysiological and Biochemical Zoology, 2009Co-Authors: Gina L J Galli, Holly A Shiels, Richard W BrillAbstract:
Abstract We measured the temperature sensitivity, adrenergic sensitivity, and dependence on sarcoplasmic reticulum (SR) Ca2+ of ventricular muscle from pelagic fishes with different vertical mobility patterns: Bigeye Tuna (Thunnus obesus), yellowfin Tuna (Thunnus albacares), and mahimahi (Coryphaena hippurus) and a single specimen from swordfish (Xiphias gladius). Ventricular muscle from the Bigeye Tuna and mahimahi exhibited a biphasic response to an acute decrease in temperature (from 26° to 7°C); twitch force and kinetic parameters initially increased and then declined. The magnitude of this response was larger in the Bigeye Tuna than in the mahimahi. Under steady state conditions at 26°C, inhibition of SR Ca2+ release and reuptake with ryanodine and thapsigargin decreased twitch force and kinetic parameters, respectively, in the Bigeye Tuna only. However, the initial inotropy associated with decreasing temperature was abolished by SR inhibition in both the Bigeye Tuna and the mahimahi. Application of …
Bigeye Tuna behavior and physiology their relevance to stock assessments and fishery biologyCollective Volume of Scientific Papers; 57(2) pp 142-161 (2005), 2005Co-Authors: Richard W Brill, K A Bigelow, Michael K Musyl, Kerstin A Fritsches, Eric J WarrantAbstract:
Bigeye Tuna (Thunnus obesus) have distinctive depth distributions and vertical movement patterns. They remain in the uniformed temperature surface layer at night and can descend to greater than 500 m depth at dawn. They thus mirror the vertical migrations of the small nektonic organisms of the deep sound scattering layer and extensively exploit these as a food resource. At their maximum depths, Bigeye Tuna frequently experience prolonged exposure to ambient temperatures (.5 EC) that are up to 20EC colder than surface layer temperature, and oxygen concentrations less than 1.5 ml O2 l-1. In contrast, skipjack Tuna (Katsuwonus pelamis) and yellowfin Tuna (T. albacares) generally limit their forays to depths where water temperatures are no more than 8EC below surface layer temperatures, and ambient oxygen levels are above 3.5 ml O2 l-1. Understanding the vertical movements and depth distribution of Bigeye Tuna, as well as the physiological abilities/tolerances and oceanographic conditions controlling them, has been shown key for improving longline catch-per-unit effort analysis and long-term populations assessments in the Pacific. Similar work is needed in the Atlantic. (Less)
Yingqi Zhou – 3rd expert on this subject based on the ideXlab platform
Growth and mortality rates of Bigeye Tuna Thunnus obesus (Perciformes: Scombridae) in the central Atlantic Ocean.Revista De Biologia Tropical, 2013Co-Authors: Liuxiong Xu, Yingqi Zhou, Xinjun ChenAbstract:
Age and growth parameters were estimated for Bigeye Tuna Thunnus obesus Lowe, 1839 sampled from China longline fisheries in the central Atlantic Ocean from October 2002 to July 2003 and from August 2004 to March 2005. The von Bertalanffy growth parameters were estimated at L ∞ =217.9 cm fork length, k=0.23 year-1, and t 0 =-0.44 year. The total mortality rate (Z) was estimated to be from 0.82 to 1.02, the fishing mortality (F) and the natural mortality were 0.54 year-1 and 0.39 year-1, respectively. The exploitation ratio (E) was 0.35. This study provides the detailed estimates of growth and mortality rate for Bigeye Tuna in the central Atlantic Ocean, which can be used as biological input parameters in further stock evaluations in this region. However, age analysis, additional validation of the size composition and stock structure are needed for future studies. Rev. Biol. Trop. 57 (1-2): 79-88. Epub 2009 June 30.
developing an integrated habitat index for Bigeye Tuna thunnus obesus in the indian ocean based on longline fisheries dataFisheries Research, 2010Co-Authors: Liming Song, Yingqi ZhouAbstract:
Abstract Two surveys were conducted in 2005 and 2006 aboard Chinese longliners in the Indian Ocean to evaluate how environmental variables might influence the spatial distributions of Bigeye Tuna, Thunnus obesus. Models were developed to estimate integrated habitat indices (IHI) for Bigeye Tuna at eight depth strata between 80 m and 400 m and to predict the spatial distributions of Bigeye Tuna in these depths. Catch rates and environmental variables (water temperature, salinity, chlorophyll-a, and dissolved oxygen) at these depth strata were obtained at 30 sampling stations in the survey, and the quantile regression method was used to develop the IHI models. This study suggests that the weighted average temperature, chlorophyll-a, and dissolved oxygen (when the dissolved oxygen was less than 0.85 mg L−1) had significant impacts on the spatial distribution of Bigeye Tuna. The IHI models developed in this study performed well in predicting catch rates with selected environmental variables. The key environmental parameters in the IHI models differed among the depth strata, suggesting impacts of the environmental variables on the Tuna distribution differed among different depth strata. This study provides an effective approach to identify optimal habitats for the Bigeye Tuna.
reproductive biology of Bigeye Tuna thunnus obesus scombridae in the eastern and central tropical pacific oceanEnvironmental Biology of Fishes, 2010Co-Authors: Liuxiong Xu, Yingqi ZhouAbstract:
Understanding the reproductive potential of any species is of great importance for resource assessment and management. We studied the reproductive biology of Bigeye Tuna, Thunnus obesus, based on 1283 samples taken from the Chinese longline vessels in the eastern and central Tropical Pacific Ocean during February through November 2006. The female-male ratio was 1.0 : 1.5 and males were predominant in all length classes except for the length class of 166–170 cm (fork length). Males dominated in sizes larger than 171 cm, all specimens of 192 cm or larger were males. The main spawning period of Bigeye Tuna was between March and November. Gonadosomatic rates of males were larger than those of females. Statistically, female and male Bigeye Tuna had no significant reproductive seasonality. The observed minimum length at sexual maturity for female Bigeye Tuna was 94 cm. Length at 50% sexual maturity of female Bigeye Tuna was estimated at 107.8 cm, and maturation rate was 0.106 cm−1. The results derived in this study provide the information critical to our understanding of key life history parameters of Bigeye Tuna in tropic Pacific Ocean.