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Formal approaches to physiological energetics, such as the Dynamic Energy Budget (DEB) theory, enable interspecies comparisons by uniformly describing how individuals of different species acquire and utilise energy. We used the DEB theory to infer the energy budgets of three commercial tuna species (skipjack, Pacific bluefin, and Atlantic bluefin) throughout all stages of ontogenetic development—from an egg to an adult individual and its eggs. Energy budgets were inferred from exhaustive datasets fed into a DEB-based mathematical model tailored for tuna fish until reaching a high goodness of fit and thus reliable estimates of the model parameters. The life histories of all three species are strongly influenced by morphological and physiological adaptations that accelerate ontogeny during the larval stage, although the effect is more pronounced in bluefin than skipjack tuna. Accelerated ontogeny in energetic terms is a simultaneous improvement of energy acquisition (higher intake) and utilisation (higher expenditure) without changing the capacity of fish to build energy reserve as intake and expenditure increase in unison. High energy expenditure, an even higher intake by necessity, and a limited capacity to build energy reserve, make all three tuna species vulnerable to starvation, thereby theoretically underpinning the description of tuna as “energy speculators”. Energy allocation to reproduction maximises fecundity of all three tuna species, thus suggesting that the evolution of tuna favours higher fecundity at the expense of growth. Thinking beyond just physiological energetics (e.g., wild stock projections), DEB-based models are a natural foundation for physiologically-structured population dynamics wherein the environment influences the population growth rate via metabolism.

Formal approaches to physiological energetics, such as the Dynamic Energy Budget (DEB) theory, enable interspecies comparisons by uniformly describing how individuals of different species acquire and utilise energy. We used the DEB theory to infer the energy budgets of three commercial tuna species (skipjack, Pacific bluefin, and Atlantic bluefin) throughout all stages of ontogenetic development—from an egg to an adult individual and its eggs. Energy budgets were inferred from exhaustive datasets fed into a DEB-based mathematical model tailored for tuna fish until reaching a high goodness of fit and thus reliable estimates of the model parameters. The life histories of all three species are strongly influenced by morphological and physiological adaptations that accelerate ontogeny during the larval stage, although the effect is more pronounced in bluefin than skipjack tuna. Accelerated ontogeny in energetic terms is a simultaneous improvement of energy acquisition (higher intake) and utilisation (higher expenditure) without changing the capacity of fish to build energy reserve as intake and expenditure increase in unison. High energy expenditure, an even higher intake by necessity, and a limited capacity to build energy reserve, make all three tuna species vulnerable to starvation, thereby theoretically underpinning the description of tuna as “energy speculators”. Energy allocation to reproduction maximises fecundity of all three tuna species, thus suggesting that the evolution of tuna favours higher fecundity at the expense of growth. Thinking beyond just physiological energetics (e.g., wild stock projections), DEB-based models are a natural foundation for physiologically-structured population dynamics wherein the environment influences the population growth rate via metabolism.

Formal approaches to physiological energetics, such as the Dynamic Energy Budget (DEB) theory, enable interspecies comparisons by uniformly describing how individuals of different species acquire and utilise energy. We used the DEB theory to infer the energy budgets of three commercial tuna species (skipjack, Pacific bluefin, and Atlantic bluefin) throughout all stages of ontogenetic development—from an egg to an adult individual and its eggs. Energy budgets were inferred from exhaustive datasets fed into a DEB-based mathematical model tailored for tuna fish until reaching a high goodness of fit and thus reliable estimates of the model parameters. The life histories of all three species are strongly influenced by morphological and physiological adaptations that accelerate ontogeny during the larval stage, although the effect is more pronounced in bluefin than skipjack tuna. Accelerated ontogeny in energetic terms is a simultaneous improvement of energy acquisition (higher intake) and utilisation (higher expenditure) without changing the capacity of fish to build energy reserve as intake and expenditure increase in unison. High energy expenditure, an even higher intake by necessity, and a limited capacity to build energy reserve, make all three tuna species vulnerable to starvation, thereby theoretically underpinning the description of tuna as “energy speculators”. Energy allocation to reproduction maximises fecundity of all three tuna species, thus suggesting that the evolution of tuna favours higher fecundity at the expense of growth. Thinking beyond just physiological energetics (e.g., wild stock projections), DEB-based models are a natural foundation for physiologically-structured population dynamics wherein the environment influences the population growth rate via metabolism.

The monitoring of marine top predators, primarily fish species, provides important insights into marine ecosystems. Recently, biologging techniques involving electronic data-storage tags and acoustic transmitters have been increasingly used to understand migratory fish movements and behaviours. The number of tags, however, is normally limited due to costs, and the tag recovery rate is still low. In this study, therefore, to reveal the population and community dynamics of fishes in open waters, we will develop a new variety of small, low-cost, large-data-capacity and multifunctional tags, and implement the high recovery rate of the data. This study consists of the following four development: (1) two types of archival tags (small-sized tags and customizable-multifunctional tags), (2) the energy harvesting system installed in the tag, (3) the data receiving system onboard multi-platforms, and (4) the inter-individual communication system based on hydro-acoustic methods. Lastly, combining them, we will develop a new biologging system and test the practical utility of this system using wild herrings and bonitos in open waters off Japan. The new technology will overcome the bottleneck of conventional biologging techniques, and will lead to a breakthrough in marine ecosystem studies.

Using an advection and diffusion model for particle tracking in three dimensions, the hatchling transport process of loggerhead, Caretta caretta and green turtles, Chelonia mydas in the North Pacific was investigated. Loggerhead hatchlings were transported eastward to northeastward by the Kuroshio from their nest, Yakushima Island, and were transported 2770 km on average over 60 days (46 km/d). These indicate that the Kuroshio enables loggerhead hatchings and juveniles to spread out without them using up their energy. In addition, transported by the Kuroshio provides them with a significantly lower mean ambient water temperature (20.7±4.1℃) than that around the nest (24.0±0.5℃). In contrast, green turtle hatchlings were transported northwestward from their nest, the Ogasarawa islands, and their mean location after 60 days was no more than 323 km away from their nest. The mean ambient water temperature during transport showed little difference from that around the nesting islands (24.5℃). These suggest that their thermal condition relatively stable in their early life in comparison with loggerhead turtles., Southeast Asia Sea Turtle Associative Research, Bangkok, Thailand, 16-19 December 2002

Emergence success of loggerhead turtles in Inakahama beach is decreasing and this phenomenon seems to be related to human beach use. To clarify this relationship, locations and numbers of loggerhead turtle's nests and beach users were recorded at each area. Some nests were excavated and development of embryos was checked. Pressure, temperature, and humidity in the nests were also measured (40cm under the surface) at each examination area. In Inakahama Beach, mean rate of emergence success was lower than the areas which are frequently used by visitors. In this area, visitors stomping on the nests cause the decrease of emergence success of the turtles. Visitors stomping on the nests cause overheating in the nests, resulting in retarding of hatchling emergence from their nests., Southeast Asia Sea Turtle Associative Research, Bangkok, Thailand, 16-19 December 2002

Using an advection and diffusion model for particle tracking in three dimensions, the hatchling transport process of loggerhead, Caretta caretta and green turtles, Chelonia mydas in the North Pacific was investigated. Loggerhead hatchlings were transported eastward to northeastward by the Kuroshio from their nest, Yakushima Island, and were transported 2770 km on average over 60 days (46 km/d). These indicate that the Kuroshio enables loggerhead hatchings and juveniles to spread out without them using up their energy. In addition, transported by the Kuroshio provides them with a significantly lower mean ambient water temperature (20.7±4.1℃) than that around the nest (24.0±0.5℃). In contrast, green turtle hatchlings were transported northwestward from their nest, the Ogasarawa islands, and their mean location after 60 days was no more than 323 km away from their nest. The mean ambient water temperature during transport showed little difference from that around the nesting islands (24.5℃). These suggest that their thermal condition relatively stable in their early life in comparison with loggerhead turtles.

Emergence success of loggerhead turtles in Inakahama beach is decreasing and this phenomenon seems to be related to human beach use. To clarify this relationship, locations and numbers of loggerhead turtle's nests and beach users were recorded at each area. Some nests were excavated and development of embryos was checked. Pressure, temperature, and humidity in the nests were also measured (40cm under the surface) at each examination area. In Inakahama Beach, mean rate of emergence success was lower than the areas which are frequently used by visitors. In this area, visitors stomping on the nests cause the decrease of emergence success of the turtles. Visitors stomping on the nests cause overheating in the nests, resulting in retarding of hatchling emergence from their nests.