The members of the integration group will work together to evaluate and synthesize the results of all the research projects to provide an overall understanding of ocean biosystems and formulate a new “view of life in the ocean”, which can hopefully be useful to help reduce some of the harmful changes to the ocean-atmosphere system, such as pollution and climate change. The individual research programs of the members of this group are listed below.

Information about the migrations of organisms in the ocean can be very important for understanding the dynamics of ocean biosystems. We are investigating the spawning locations, migratory behavior, early life history and the evolution of spawning migrations of anguillid eels, as well as the behavior and phylogeny of sea turtles. Although temperate anguillid species such as the European, American, and Japanese eel make very long spawning migrations, we have shown that some tropical anguillid species only make relatively short migrations and that their larvae, or leptocephali, have faster growth rates and smaller maximum sizes. Phylogenetic analysis indicated that anguillid eels probably originated near present day Indonesia, where about seven tropical species are now found, and that the ancestor of the Atlantic eels likely moved through the ancient Tethes Sea, and other lineages moved into other regions such as the South Pacific. These findings along with those about the scales of migrations of anguillid eels, suggest that anguillid eels evolved from a tropical ancestor with a small-scale spawning migration. It appears that anguillid eels evolved from a completely marine ancestor, and this is supported by our discovery of “sea eels” that never enter freshwater, which has changed the view of “freshwater” eels as catadromous fishes and has revealed previously unknown levels of plasticity in their migratory behavior. By synthesizing information on the phylogeny, migration, larval ecology, and biodiversity of freshwater eels, a greater understanding of these ecologically important fishes and marine organisms in general can be obtained.

I study population dynamics of marine organisms such as fish and dolphins with special attentions to their management or conservation. I mainly use theoretical or statistical approaches, but also carry out field surveys on coastal dolphins from a boat or a helicopter. Recent works are statistical estimation of migration rates using
mark-recapture experiments, developing a method for fishery resource management using marine procted areas, abundance estimation of finless porpoises, and geographical distribution of Indo-Pacific bottlenose dolphins.

For the purpose to establish the sustainable development of marine bio-resources, the better understanding of the capture process will be urgently required for reducing impact of fishing technology, from the view points of the interactions among fish, fishing gear and environment. The Behavioral Physiology as the response of the target and unwanted species/sizes can be the key issue for improving the capture process from the view point of Stimuli-Response system according to the species and sizes. Visual function of fish is one topic for understanding the maximum sighting distance by means of estimated value of visual accuracy through the microscopic examination of retina. The swimming performance is another topic for estimating the maximum swimming speed, together with the examination of swimming curve in the flume tank. These results can be employed to understand the background mechanism of fish response to the fishing gear, in the capture process to recognize the gear with the sensory system, and then to avoid and escape from the gear.

Using anadromous salmon as a main research model, physiological research on the mechanism of salmon homing to their natal river as well as environmental biological research on the interaction between aquatic environment and salmon resources are studied. By means of the most advanced analytical techniques in salmon research, we are trying to establish a new subject of field bioscience that elucidates a better understanding of human activity that is in harmony with the natural environment. Three different physiological studies ranging from molecular biology to behavioral biology are applied to investigate mechanisms of salmon homing migration using chum salmon from the Bering Sea to Hokkaido, as well as lacustrine sockeye salmon and masu salmon in Lake Toya and Shikotsu, Hokkaido, Japan. Three different environmental biological studies are being carried out in lakes, rivers, and the coastal sea of Hokkaido. Problems of destruction of environments and shortage of foods at the global levels threaten human survival. It is necessary to protect stream and ocean environments for salmon homing, since 1g salmon fry can grow up to 4kg adults at the time of homing, and salmon are also a rare carrier of marine nutrients to land. We would like to make a contribution to solve the global environment and bioresources problems by studying salmon research in our laboratory.