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Barbara A Block - One of the best experts on this subject based on the ideXlab platform.
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Skeletal muscle and cardiac transcriptomics of a regionally endothermic fish, the Pacific Bluefin Tuna, Thunnus orientalis.
BMC Genomics, 2020Co-Authors: Adam Ciezarek, Luke D Gardner, Vincent Savolainen, Barbara A BlockAbstract:The Pacific Bluefin Tuna (Thunnus orientalis) is a regionally endothermic fish that maintains temperatures in their swimming musculature, eyes, brain and viscera above that of the ambient water. Within their skeletal muscle, a thermal gradient exists, with deep muscles, close to the backbone, operating at elevated temperatures compared to superficial muscles near the skin. Their heart, by contrast, operates at ambient temperature, which in Bluefin Tunas can range widely. Cardiac function in Tunas reduces in cold waters, yet the heart must continue to supply blood for metabolically demanding endothermic tissues. Physiological studies indicate Pacific Bluefin Tuna have an elevated cardiac capacity and increased cold-tolerance compared to warm-water Tuna species, primarily enabled by increased capacity for sarcoplasmic reticulum calcium cycling within the cardiac muscles. Here, we compare tissue-specific gene-expression profiles of different cardiac and skeletal muscle tissues in Pacific Bluefin Tuna. There was little difference in the overall expression of calcium-cycling and cardiac contraction pathways between atrium and ventricle. However, expression of a key sarcoplasmic reticulum calcium-cycling gene, SERCA2b, which plays a key role maintaining intracellular calcium stores, was higher in atrium than ventricle. Expression of genes involved in aerobic metabolism and cardiac contraction were higher in the ventricle than atrium. The two morphologically distinct tissues that derive the ventricle, spongy and compact myocardium, had near-identical levels of gene expression. More genes had higher expression in the cool, superficial muscle than in the warm, deep muscle in both the aerobic red muscle (slow-twitch) and anaerobic white muscle (fast-twitch), suggesting thermal compensation. We find evidence of widespread transcriptomic differences between the Pacific Tuna ventricle and atrium, with potentially higher rates of calcium cycling in the atrium associated with the higher expression of SERCA2b compared to the ventricle. We find no evidence that genes associated with thermogenesis are upregulated in the deep, warm muscle compared to superficial, cool muscle. Heat generation may be enabled by by the high aerobic capacity of Bluefin Tuna red muscle.
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skeletal muscle and cardiac transcriptomics of a regionally endothermic fish the Pacific Bluefin Tuna thunnus orientalis
BMC Genomics, 2020Co-Authors: Adam Ciezarek, Luke D Gardner, Vincent Savolainen, Barbara A BlockAbstract:The Pacific Bluefin Tuna (Thunnus orientalis) is a regionally endothermic fish that maintains temperatures in their swimming musculature, eyes, brain and viscera above that of the ambient water. Within their skeletal muscle, a thermal gradient exists, with deep muscles, close to the backbone, operating at elevated temperatures compared to superficial muscles near the skin. Their heart, by contrast, operates at ambient temperature, which in Bluefin Tunas can range widely. Cardiac function in Tunas reduces in cold waters, yet the heart must continue to supply blood for metabolically demanding endothermic tissues. Physiological studies indicate Pacific Bluefin Tuna have an elevated cardiac capacity and increased cold-tolerance compared to warm-water Tuna species, primarily enabled by increased capacity for sarcoplasmic reticulum calcium cycling within the cardiac muscles. Here, we compare tissue-specific gene-expression profiles of different cardiac and skeletal muscle tissues in Pacific Bluefin Tuna. There was little difference in the overall expression of calcium-cycling and cardiac contraction pathways between atrium and ventricle. However, expression of a key sarcoplasmic reticulum calcium-cycling gene, SERCA2b, which plays a key role maintaining intracellular calcium stores, was higher in atrium than ventricle. Expression of genes involved in aerobic metabolism and cardiac contraction were higher in the ventricle than atrium. The two morphologically distinct tissues that derive the ventricle, spongy and compact myocardium, had near-identical levels of gene expression. More genes had higher expression in the cool, superficial muscle than in the warm, deep muscle in both the aerobic red muscle (slow-twitch) and anaerobic white muscle (fast-twitch), suggesting thermal compensation. We find evidence of widespread transcriptomic differences between the Pacific Tuna ventricle and atrium, with potentially higher rates of calcium cycling in the atrium associated with the higher expression of SERCA2b compared to the ventricle. We find no evidence that genes associated with thermogenesis are upregulated in the deep, warm muscle compared to superficial, cool muscle. Heat generation may be enabled by by the high aerobic capacity of Bluefin Tuna red muscle.
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temperature dependent pre and postprandial activity in Pacific Bluefin Tuna thunnus orientalis
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2019Co-Authors: Adrian C Gleiss, Jonathan J Dale, Charles J. Farwell, Ethan E. Estess, Dane H Klinger, Luke D Gardner, Benjamin Machado, Alexander G Norton, Barbara A BlockAbstract:Bluefin Tunas are highly specialized fish with unique hydrodynamic designs and physiological traits. In this study, we present results in a captive population that demonstrate strong effects of ambient temperature on the tail beat frequency and swimming speed of a pelagic fish in both pre- and post-prandial states. We measured the responses of a ram ventilator, the Pacific Bluefin Tuna (Thunnus orientalis), after digestion of a meal to explore the impacts of the metabolic costs of digestion on behavior and respiration. A combination of respirometry, physiological biologging of visceral temperatures, and activity monitoring with accelerometry were used to explore the metabolic costs of digestion and the impacts on ventilation and swimming speed. Experiments were conducted at temperatures that are within the metabolic optimum for Pacific Bluefin Tuna (17 °C), and at a second temperature corresponding to the upper distributional limit of the species in the California Current (24 °C). Warmer temperatures resulted in higher tail-beat frequency and greater elevation of body temperature in pre-prandial Pacific Bluefin Tuna. Specific dynamic action (SDA) events resulted in a significant postprandial increase in tail-beat frequency of ~0.2 Hz, compared to pre-prandial levels of 1.5 Hz (17 °C) and 1.75 Hz (24 °C), possibly resulting from ventilator requirements. Data of fish exercised in a swim-tunnel respirometer suggest that the observed increase in tail-beat frequency comprise 5.5 and 6.8% of the oxygen demand during peak SDA at 24 °C and 17 °C respectively. The facultative increase in swimming speed might increase oxygen uptake at the gills to meet the increasing demand by visceral organs involved in the digestive process, potentially decreasing the available energy of each meal for other metabolic processes, such as growth, maturation, and reproduction. We hypothesize that these post-prandial behaviors allow Tuna to evacuate their guts more quickly, ultimately permitting fish to feed more frequently when prey is available.
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Appendix A. A table of amino acid compound-specific results for migrant and resident Pacific Bluefin Tuna Thunnus orientalis and eastern Pacific Ocean residents yellowfin Tuna (T. albacares), jack mackerel (Trachurus symmetricus), and Pacific saury (
2016Co-Authors: Daniel J Madigan, Zofia Baumann, Aaron B Carlisle, Danielle K Hoen, Brian N Popp, Heidi Dewar, Owyn E Snodgrass, Barbara A Block, Nicholas S. FisherAbstract:A table of amino acid compound-specific results for migrant and resident Pacific Bluefin Tuna Thunnus orientalis and eastern Pacific Ocean residents yellowfin Tuna (T. albacares), jack mackerel (Trachurus symmetricus), and Pacific saury (Cololabis saira)
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Appendix C. A table showing Pacific Bluefin Tuna white muscle bulk δ15N values, age, size, and classification as migrant or resident by discriminant analysis.
2016Co-Authors: Daniel J Madigan, Zofia Baumann, Aaron B Carlisle, Danielle K Hoen, Brian N Popp, Heidi Dewar, Owyn E Snodgrass, Barbara A Block, Nicholas S. FisherAbstract:A table showing Pacific Bluefin Tuna white muscle bulk δ15N values, age, size, and classification as migrant or resident by discriminant analysis
Nicholas S. Fisher - One of the best experts on this subject based on the ideXlab platform.
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isotopic insights into migration patterns of Pacific Bluefin Tuna in the eastern Pacific ocean
Canadian Journal of Fisheries and Aquatic Sciences, 2018Co-Authors: Daniel J Madigan, Zofia Baumann, Aaron B Carlisle, Heidi Dewar, Owyn E Snodgrass, Nicholas S. FisherAbstract:Understanding regional migration, residency dynamics, and associated trophic ecology can inform recovery strategies for pelagic species such as Pacific Bluefin Tuna (Thunnus orientalis) (PBFT). PBF...
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Isotopic insights into migration patterns of Pacific Bluefin Tuna in the eastern Pacific Ocean
Canadian Journal of Fisheries and Aquatic Sciences, 2018Co-Authors: Daniel J Madigan, Zofia Baumann, Aaron B Carlisle, Heidi Dewar, Owyn E Snodgrass, Nicholas S. FisherAbstract:Understanding regional migration, residency dynamics, and associated trophic ecology can inform recovery strategies for pelagic species such as Pacific Bluefin Tuna (Thunnus orientalis) (PBFT). PBFT residency duration in the eastern Pacific is uncertain, particularly for larger individuals (here, >100 cm or ∼3+ years of age). We applied a previously tested “chemical tracer toolbox” (Fukushima-derived radiocesium and 13C and 15N stable isotope signatures) to examine migratory and residency patterns and dietary inputs of 428 age 1–6+ PBFT collected from 2012 to 2015 in the eastern Pacific Ocean. Age 1–3 individuals were a mix of residents and recent (≤500 day) migrants, while 98% of age 3–4 and 100% of age 4–6.3 year old PBFT were resident for >500 days in the eastern Pacific. Zooplanktivorous forage (e.g., sardine, anchovy, pelagic red crab, and trophically similar species) of the California Current Ecosystem constituted 57%–82% of diet across PBFT sizes. Migration timing estimates show that PBFT may spend...
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Appendix C. A table showing Pacific Bluefin Tuna white muscle bulk δ15N values, age, size, and classification as migrant or resident by discriminant analysis.
2016Co-Authors: Daniel J Madigan, Zofia Baumann, Aaron B Carlisle, Danielle K Hoen, Brian N Popp, Heidi Dewar, Owyn E Snodgrass, Barbara A Block, Nicholas S. FisherAbstract:A table showing Pacific Bluefin Tuna white muscle bulk δ15N values, age, size, and classification as migrant or resident by discriminant analysis
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Appendix A. A table of amino acid compound-specific results for migrant and resident Pacific Bluefin Tuna Thunnus orientalis and eastern Pacific Ocean residents yellowfin Tuna (T. albacares), jack mackerel (Trachurus symmetricus), and Pacific saury (
2016Co-Authors: Daniel J Madigan, Zofia Baumann, Aaron B Carlisle, Danielle K Hoen, Brian N Popp, Heidi Dewar, Owyn E Snodgrass, Barbara A Block, Nicholas S. FisherAbstract:A table of amino acid compound-specific results for migrant and resident Pacific Bluefin Tuna Thunnus orientalis and eastern Pacific Ocean residents yellowfin Tuna (T. albacares), jack mackerel (Trachurus symmetricus), and Pacific saury (Cololabis saira)
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reconstructing transoceanic migration patterns of Pacific Bluefin Tuna using a chemical tracer toolbox
Ecology, 2014Co-Authors: Daniel J Madigan, Zofia Baumann, Aaron B Carlisle, Danielle K Hoen, Brian N Popp, Heidi Dewar, Owyn E Snodgrass, Barbara A Block, Nicholas S. FisherAbstract:Large pelagic predators play important roles in oceanic ecosystems, and may migrate vast distances to utilize resources in different marine ecoregions. Understanding movement patterns of migratory marine animals is critical for effective management, but often challenging, due to the cryptic habitat of pelagic migrators and the difficulty of assessing past movements. Chemical tracers can partially circumvent these challenges by reconstructing recent migration patterns. Pacific Bluefin Tuna (Thunnus orientalis; PBFT) inhabit the western and eastern Pacific Ocean, and are in steep decline due to overfishing. Understanding age-specific eastward transPacific migration patterns can improve management practices, but these migratory dynamics remain largely unquantified. Here, we combine a Fukushima-derived radiotracer (134Cs) with bulk tissue and amino acid stable isotope analyses of PBFT to distinguish recent migrants from residents of the eastern Pacific Ocean. The proportion of recent migrants to residents decreased in older year classes, though the proportion of older PBFT that recently migrated across the Pacific was greater than previous estimates. This novel toolbox of biogeochemical tracers can be applied to any species that crosses the North Pacific Ocean.
Daniel J Madigan - One of the best experts on this subject based on the ideXlab platform.
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isotopic insights into migration patterns of Pacific Bluefin Tuna in the eastern Pacific ocean
Canadian Journal of Fisheries and Aquatic Sciences, 2018Co-Authors: Daniel J Madigan, Zofia Baumann, Aaron B Carlisle, Heidi Dewar, Owyn E Snodgrass, Nicholas S. FisherAbstract:Understanding regional migration, residency dynamics, and associated trophic ecology can inform recovery strategies for pelagic species such as Pacific Bluefin Tuna (Thunnus orientalis) (PBFT). PBF...
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Isotopic insights into migration patterns of Pacific Bluefin Tuna in the eastern Pacific Ocean
Canadian Journal of Fisheries and Aquatic Sciences, 2018Co-Authors: Daniel J Madigan, Zofia Baumann, Aaron B Carlisle, Heidi Dewar, Owyn E Snodgrass, Nicholas S. FisherAbstract:Understanding regional migration, residency dynamics, and associated trophic ecology can inform recovery strategies for pelagic species such as Pacific Bluefin Tuna (Thunnus orientalis) (PBFT). PBFT residency duration in the eastern Pacific is uncertain, particularly for larger individuals (here, >100 cm or ∼3+ years of age). We applied a previously tested “chemical tracer toolbox” (Fukushima-derived radiocesium and 13C and 15N stable isotope signatures) to examine migratory and residency patterns and dietary inputs of 428 age 1–6+ PBFT collected from 2012 to 2015 in the eastern Pacific Ocean. Age 1–3 individuals were a mix of residents and recent (≤500 day) migrants, while 98% of age 3–4 and 100% of age 4–6.3 year old PBFT were resident for >500 days in the eastern Pacific. Zooplanktivorous forage (e.g., sardine, anchovy, pelagic red crab, and trophically similar species) of the California Current Ecosystem constituted 57%–82% of diet across PBFT sizes. Migration timing estimates show that PBFT may spend...
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east not least for Pacific Bluefin Tuna
Science, 2017Co-Authors: Daniel J Madigan, Andre Boustany, Bruce B. ColletteAbstract:High market values have incentivized extensive fisheries for Pacific Bluefin Tuna ( Thunnus orientalis , see the photo), a species whose longevity, commercial value, and long generation time make it particularly susceptible to overfishing ( 1 , 2 ). Today, the population of Pacific Bluefin Tuna stands at an estimated 2.6% of prefished levels ( 1 ). Yet, knowledge of its basic life history is incomplete. Recent studies ( 3 , 4 ) suggest that the fundamental distribution of Pacific Bluefin across the North Pacific has been misunderstood. The results underscore the need for basic movement ecology information to assist science-based fisheries management.
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Appendix C. A table showing Pacific Bluefin Tuna white muscle bulk δ15N values, age, size, and classification as migrant or resident by discriminant analysis.
2016Co-Authors: Daniel J Madigan, Zofia Baumann, Aaron B Carlisle, Danielle K Hoen, Brian N Popp, Heidi Dewar, Owyn E Snodgrass, Barbara A Block, Nicholas S. FisherAbstract:A table showing Pacific Bluefin Tuna white muscle bulk δ15N values, age, size, and classification as migrant or resident by discriminant analysis
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Appendix A. A table of amino acid compound-specific results for migrant and resident Pacific Bluefin Tuna Thunnus orientalis and eastern Pacific Ocean residents yellowfin Tuna (T. albacares), jack mackerel (Trachurus symmetricus), and Pacific saury (
2016Co-Authors: Daniel J Madigan, Zofia Baumann, Aaron B Carlisle, Danielle K Hoen, Brian N Popp, Heidi Dewar, Owyn E Snodgrass, Barbara A Block, Nicholas S. FisherAbstract:A table of amino acid compound-specific results for migrant and resident Pacific Bluefin Tuna Thunnus orientalis and eastern Pacific Ocean residents yellowfin Tuna (T. albacares), jack mackerel (Trachurus symmetricus), and Pacific saury (Cololabis saira)
Yoshifumi Sawada - One of the best experts on this subject based on the ideXlab platform.
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Analysis of sinking death using video images of the swimming performance of Pacific Bluefin Tuna (Thunnus orientalis) larvae
Aquacultural Engineering, 2020Co-Authors: Y. Ina, Yoshifumi Sawada, Michio Kurata, Shigeru Miyashita, Hiromu Fukuda, Tomoki Honryo, T. Takagi, Shinsuke TorisawaAbstract:Abstract In this study, we aimed to clarify the mechanism of sinking death during the larval stage of Pacific Bluefin Tuna Thunnus orientalis by investigating the effects of swimming performance on sinking death, using a behavioral approach. Swimming performance was examined 3–9 days after hatching (DAH) under day and night light conditions in cuboid experimental tanks. Swimming behavior variables such as swimming speed and swimming angle were measured under both light conditions. Larvae in the daytime experiment and larvae with inflated swim bladders at night were distributed on the surface layer of the water column. In contrast, larvae with uninflated swim bladders at night were frequently observed swimming vertically or sinking to the bottom of the tank. Larvae with inflated swim bladders at night were always distributed beneath the surface until the next morning (survival rates were 100 %). However, larvae with uninflated swim bladders at night swam upward repeatedly and later sank to the bottom of the tank (survival rates were 60 % and 38 % at 5 and 9 DAH, respectively). Larvae with uninflated swim bladders were not always able to maintain their swimming depth by swimming until the next morning. Additionally, their swimming speed and vertical swimming frequency (ratio) depended on the illumination and swim bladder conditions. Our findings show that larvae with uninflated swim bladders at night were associated with a higher risk of sinking death. The swimming energy capacity of Pacific Bluefin Tuna larvae, which indicates the total amount of the energy that enables individuals to swim throughout the night without feeding, was found to be linked to sinking death.
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Blood chemistry of Pacific Bluefin Tuna (Thunnus orientalis) juveniles showing abnormal swimming behavior
Aquaculture, 2019Co-Authors: Tomoki Honryo, Yasunori Ishibashi, Tokihiko Okada, Michio Kurata, Yasuo Agawa, Yoshifumi SawadaAbstract:Abstract We conducted a chemical analysis of the blood of juvenile Pacific Bluefin Tuna (PBF; Thunnus orientalis) showing abnormal swimming (AS) behavior, such as irregular and/or frantic patterns, and compared them to normally-swimming (NS) fish in order to elucidate causes of death in aquaculture-reared Tuna. This study found three abnormal characteristics in the blood chemistries of AS specimens; 1) hyperventilation accompanied by significantly higher PO2 and lower PCO2 than NS, 2) metabolic alkalosis owing to excessive excretion of protons, and 3) hyperkalemia. Hence, PBF juveniles are subject to mortality due to respiratory failure and homeostatic imbalances in acid-base regulation, even in the absence of physical injury. This indicates that since PBF juveniles are ram ventilators, even light collision impacts can be fatal for PBF juveniles if swimming activities are affected.
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Identification of male sex-linked DNA sequence of the cultured Pacific Bluefin Tuna Thunnus orientalis
Fisheries Science, 2014Co-Authors: Yasuo Agawa, Toru Kobayashi, Naoki Yagishita, Tomoki Honryo, Mayui Iwaki, Takafumi Komiya, Kouhei Tamura, Tsukasa Okada, Yoshifumi SawadaAbstract:A male-specific marker of a DNA sequence for the Pacific Bluefin Tuna Thunnus orientalis, Male delta 6 (Md6), was identified by comparative study of the sequences obtained by F3-cultured male and female AFLP-selective DNA amplification products, followed by high-throughput DNA sequencing. Md6 was characteristic in continuous 6-bp nucleotide deletions compared to redundant sequences that could be seen in both sexes. The PCR genotyping primers were developed based on the Md6 sequence, which showed that 29 of 32 F3 males (90.6 %) and 9 of 13 (69.2 %) F2 parental males were genotyping positive, whereas in females, the genotyping test was negative in parental F2 (n = 12), and 1 of 32 (3.1 %) F3 female was Md6-positive. Parentage allocation tests suggested that Md6-positive F2 males were more attendant in spawning than Md6-negative males, suggesting that Md6 was passed from male parents to male progeny under aquaculture conditions.
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Isolation and characterization of 25 microsatellite loci from the Pacific Bluefin Tuna Thunnus orientalis (Perciformes, Scombridae)
Conservation Genetics Resources, 2013Co-Authors: Naoki Yagishita, Yoshifumi Sawada, Yasuo Agawa, Toru KobayashiAbstract:The Pacific Bluefin Tuna (PBT) Thunnus orientalis is one of the most important species for fisheries in the world. This species has been highly exploited in fisheries, resulting in dwindling of its natural resources. The artificial hatching of a third generation of fully cultured PBT was a success in 2007, suggesting the possibility of mass production of PBT for food and for seed release. To enhance stock structure studies and investigate genetic feature of seedlings, we isolated 25 polymorphic microsatellite loci (2–18 alleles/locus; expected heterozygosity, 0.042–0.941) from PBT.
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Visual spectral sensitivity of photopic juvenile Pacific Bluefin Tuna (Thunnus orientalis)
Fish Physiology and Biochemistry, 2012Co-Authors: Taro Matsumoto, Tokihiko Okada, Yoshifumi Sawada, Yasunori IshibashiAbstract:Although Pacific Bluefin Tuna is a species that relies on vision, its photopic visual function is not well known; we therefore recorded electroretinograms to investigate photopic spectral sensitivity in juveniles of this species (49–81 days post-hatch; standard length 74–223 mm). The peak spectral sensitivity wavelength was 505 nm. We estimated that two (λ_max = 512–515 nm and 423–436 nm) or three (λ_max = 512–515 nm, 423–436 nm, and 473 nm) types of cone visual pigments contribute to photopic vision; these spectral sensitivities are adapted to surface water habitats in clear ocean and coastal water.
Harumi Yamada - One of the best experts on this subject based on the ideXlab platform.
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Immature Pacific Bluefin Tuna, Thunnus orientalis, utilizes cold waters in the Subarctic Frontal Zone for trans-Pacific migration
Environmental Biology of Fishes, 2009Co-Authors: Takashi Kitagawa, Akira Nitta, Shingo Kimura, Harumi Yamada, Hideaki Nakata, Yoshikazu Sasai, Hideharu SasakiAbstract:The habitat and movements of a Pacific Bluefin Tuna were investigated by reanalyzing archival tag data with sea surface temperature data. During its trans-Pacific migration to the eastern Pacific, the fish took a direct path and primarily utilized waters, in the Subarctic Frontal Zone (SFZ). Mean ambient temperature during the trans-Pacific migration was 14.5 ± 2.9 (°C ± SD), which is significantly colder than the waters typically inhabited by Bluefin Tuna in their primary feeding grounds in the western and eastern Pacific (17.6 ± 2.1). The fish moved rapidly through the colder water, and the heat produced during swimming and the thermoconservation ability of Bluefin Tuna likely enabled it to migrate through the cold waters of the SFZ.
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assessment of the nutritional status of field caught larval Pacific Bluefin Tuna by rna dna ratio based on a starvation experiment of hatchery reared fish
Journal of Experimental Marine Biology and Ecology, 2008Co-Authors: Yosuke Tanaka, Takayuki Takebe, Keisuke Satoh, Harumi Yamada, Hideki Nikaido, Satoshi ShiozawaAbstract:Abstract RNA/DNA ratio is a useful and reliable indicator of the nutritional status of fish larvae and juveniles. In order to assess the nutritional status of field-caught larval Pacific Bluefin Tuna Thunnus orientalis (Temminck et Schlegel), starvation experiments of hatchery-reared larvae were conducted and changes in the RNA/DNA ratio of fed and starved larvae were analyzed. Starvation experiments were conducted every 3 days after first feeding. The survival rate of Pacific Bluefin Tuna larvae ranged 10–50% after 1 day of starved conditions and growth retardation was observed immediately. These results suggest that Pacific Bluefin Tuna larvae have a very low tolerance to starvation. The RNA/DNA ratios of fed larvae were approximately 2.0–4.0. On the other hand, the value of starved larvae significantly decreased to 1.0–3.0. The nutritional status of 3 cohorts of field-caught Tuna larvae collected in the northwestern Pacific Ocean was examined based on the value of the RNA/DNA ratio of the 1 day starved larvae. 4.35–25.77% of the cohorts were regarded as the “starving condition”, which was negatively correlated to the ambient prey densities. These findings suggest that the nutritional condition of larval Pacific Bluefin Tuna was influenced by the ambient prey density, and starvation itself and starvation-induced predation could greatly contribute to mortality in the larval period of Pacific Bluefin Tuna.
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Assessment of the nutritional status of field-caught larval Pacific Bluefin Tuna by RNA/DNA ratio based on a starvation experiment of hatchery-reared fish
Journal of Experimental Marine Biology and Ecology, 2008Co-Authors: Yosuke Tanaka, Takayuki Takebe, Keisuke Satoh, Harumi Yamada, Hideki Nikaido, Satoshi ShiozawaAbstract:Abstract RNA/DNA ratio is a useful and reliable indicator of the nutritional status of fish larvae and juveniles. In order to assess the nutritional status of field-caught larval Pacific Bluefin Tuna Thunnus orientalis (Temminck et Schlegel), starvation experiments of hatchery-reared larvae were conducted and changes in the RNA/DNA ratio of fed and starved larvae were analyzed. Starvation experiments were conducted every 3 days after first feeding. The survival rate of Pacific Bluefin Tuna larvae ranged 10–50% after 1 day of starved conditions and growth retardation was observed immediately. These results suggest that Pacific Bluefin Tuna larvae have a very low tolerance to starvation. The RNA/DNA ratios of fed larvae were approximately 2.0–4.0. On the other hand, the value of starved larvae significantly decreased to 1.0–3.0. The nutritional status of 3 cohorts of field-caught Tuna larvae collected in the northwestern Pacific Ocean was examined based on the value of the RNA/DNA ratio of the 1 day starved larvae. 4.35–25.77% of the cohorts were regarded as the “starving condition”, which was negatively correlated to the ambient prey densities. These findings suggest that the nutritional condition of larval Pacific Bluefin Tuna was influenced by the ambient prey density, and starvation itself and starvation-induced predation could greatly contribute to mortality in the larval period of Pacific Bluefin Tuna.
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growth dependent recruitment of Pacific Bluefin Tuna thunnus orientalis in the northwestern Pacific ocean
Marine Ecology Progress Series, 2006Co-Authors: Yosuke Tanaka, Keisuke Satoh, Masayuki Iwahashi, Harumi YamadaAbstract:To estimate the survival process of Pacific Bluefin Tuna Thunnus orientalis during the larval period, estimated growth histories were compared between larvae collected in late spring and juveniles collected in the boreal summer of 2004, which were considered to be survivors of the larval cohorts. Larval Tuna (3.3 to 9.6 mm standard length, SL) were collected from mid-May to early June around the Ryukyu Islands, northwestern Pacific Ocean, and juvenile Tuna were collected offshore of Kochi and Nagasaki prefectures in July-August. Preflexion, flexion and postflexion larvae were col- lected, and their ages ranged from 4 to 18 d. Back-calculated SLs by the biological intercept method showed that larval Tuna in the postflexion phase were larger-at-age than preflexion and flexion larvae, suggesting that only larger and faster growing larvae were able to survive to the postflexion phase. The logarithms of otolith radii (ln OR: proportional to SL) of larvae with slower growth and development were smaller than the minimum ln OR of surviving juvenile Tuna, which indicated the smallest possible size required for larvae to successfully recruit to the fishery. These results indicate that the survival of larvae of Pacific Bluefin Tuna depends largely on size and growth rates during early life history.
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Thermal adaptation of Pacific Bluefin Tuna Thunnus orientalis to temperate waters
Fisheries Science, 2006Co-Authors: Takashi Kitagawa, Shingo Kimura, Hideaki Nakata, Harumi YamadaAbstract:Immature Pacific Bluefin Tuna Thunnus orientalis, tagged with archival tags, were released near Tsushima Island in the East China Sea during the winters of 1995 through 1998. Time-series data for ambient and peritoneal cavity temperatures, recorded every 128 or 256 s for 23 fish recovered, were analyzed. The objective of this study was to clarify the process of development of thermoconservation ability with growth in relation to adaptive mechanisms to cooler temperate waters. According to the results, mean ambient temperatures ranged from 14.9 to 20.7°C, which is almost within the optimum temperature range according to previous reports. Mean peritoneal temperatures were higher than ambient temperatures (19.7–27.3°C), but never reached 35°C, which would induce overheating. Although the mean thermal differences between peritoneal and ambient temperatures increased with body size, the rate of increase decreased with body size. A heat budget model suggests that as the insulation of the body develops, the estimated mean values of internal heat production decrease with body size. This is probably due to the allometric scale effect and explains why the thermal difference does not increase quickly with body size. It is likely that Pacific Bluefin Tuna inhabit cooler temperate waters in mid-latitude regions to avoid overheating.
