This paper provides an overview of why the bathyscaphe FNRS III came to Japan in May 1958 and how it explored Japan Trench with Japanese and French scientists. Launched in Toulon in 1953, the FNRS III was the most advanced submersible in the world at the time. Professor Tadayoshi Sasaki of Tokyo University of Fisheries who had been conducting deep-sea research in Japan, spent seven months at the Institut océanographique of Paris from January 1956. Then, he met Professor Louis Fage of the Museum National dʼHistoire naturelle and the Institut océanographique who was President of Comité de Direction du Bathyscaphecf et de la Calypso. After some persuasion by Professor Sasaki, Professor Fage promised to send the bathyscaphe to Japan. Professor Sasaki with another Japanese organisations prepared to accept FNRS III in Japan. The bathyscaphe arrived in Japan in May 1958 and descended into the Japan Trench and surrounds to achieve valuable findings. Based on them, the Japanese-French Oceanographic Society （SFJO） was established in Japan in April 1960 to develop and deepen French-Japanese cooperation in oceanography and fisheries science. The SFJO has been promoting and contributing to cooperations between the two countries in the fields of oceanography and fisheries science since then.

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In 1960, the Japanese-French Oceanographic Society （SFJO） was established and cooperation with France on oceanography began. In the late 1960s, oysters farmed in France died in large numbers due to diseases, and oyster farming was in danger of extinction. French researchers then approached SFJO member Professor Takeo Imai of Tohoku University to see if Sanriku oysters resistant to the diseases could be exported to France. The research team led by Professor Imai conducted quarantine and pathological tests to succeed in exporting 10, 000 t Sanriku single-seeded oysters （spat） to France. This export brought the French oyster farming industry out of crisis. Subsequently, French-Japanese cooperation also extended to fisheries science, and SFJO France was set up in 1984. On 11 March 2011, a huge tsunami hit off the coast of Sanriku, devastating aquaculture facilities. Immediately afterwards, SFJO France and French oyster farmers including another French groups contacted SFJO to support oyster farmers in Sanriku in return for their spat export. These organisations and SFJO donated essential equipment for oyster seed collection, such as microscopes and plankton nets, to the prefectural fisheries experiment stations and prefectural fisheries cooperatives in Sanriku. This article outlines the French-Japanese exchange on these fisheries science.

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This article outlines the creation of the French-Japanese Ocean Development Sub- Committee, which was established under the Agreement on Scientific and Technological Cooperation between France and Japan signed in 1974 and its subsequent activities. In July 1974, the French side expressed interest in krill harvesting and utilization, fish pathology, and manganese nodules at the Japan-France Joint Committee on Cooperation in Science and Technology. The first meeting of the French-Japanese Ocean Development Sub-Committee was held in April 1975, during which the Japanese side expressed interest in diving technology, coastal development and marine structures, and marine observation equipment. In October of the same year, at the second meeting of the sub-committee, discussions were held on bluefin tuna farming and marine energy in both France and Japan. In recent years, the conference of the sub-committee has been expanding with reports on continuing, new and completed projects under the main themes of marine research, marine technology and research infrastructure, marine resources, marine biotechnology, deep-sea ecosystems, coastal ecosystems and social ecosystems. The sub-committee plays a significant role in promoting cooperation between France and Japan in the ocean development.

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With annual global production of artificial polymers （plastics） exceeding 400 million tonnes, the oceans are among the areas most affected by plastic pollution. The distribution of plastics in these oceans is influenced by human activities. Plastic pollution is found on beaches, on the surface and, for more than 90%, on the seabed worldwide. Plastic degrades at sea into microplastics or nanoplastics, constituting, together with industrial pellets or primary microplastics, a heterogeneous group of particles, varying in size, shape, colour, chemical composition and density. Little is known about the extent of the impacts caused by marine litter and microplastics. Some of the most important are the entanqlement of organisms, ingestion by organisms, release of contaminants and long-range transport of species. There are also impacts on certain sectors of the economy, including tourism and fisheries, but also risks to navigation and health impacts. In addition to reduction measures based on circular economy, recycling, water purification, selective cleaning and education, global initiatives （United Nations Environment Assembly, G7 and G20）, establish a framework within which states must take management measures to achieve a better state of the environment. However, the risks remain high, environmentally, socially, economically and for human health.

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Marine litter is a global environmental concern affecting all the oceans and coastlines of the world. More than 8 million tons of plastic enter the oceans each year, contributing to an estimated total abundance of at least 24.4 trillion pieces of plastic particles in the world’s upper oceans. They can be found floating on the surface, in the sediments, in the ice or covering the ocean floor. Since 1990 Surfrider Foundation Europe, has put the fight against marine litter at the forefront of its action. Surfrider acts to better understand this pollution, to reduce the quantitative amount of litter entering the marine environment and its impacts on the marine environment and humans. The NGO’s leverages start with raising public awareness, stimulating scientific research to initiating political action in order to tackle at source this problem. The community and citizens are the heart of action programs, public engagement is the root. Citizens participate in collecting data and answering remaining questions about characteristics, distribution, transport pathways of marine litter and potential impacts on wildlife and humans as well as in policing-making. As a whistle-blower, an expert and an actor of change, Surfrider promotes the dialogue between citizens, scientists and decision-makers.

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Publications describing the concentration and distribution of plastic litter, microplastics（> 350 μm and < 5mm）, and small microplastics（< 350 μm）in seawater, sediments, and beaches around the coast of Japan are reviewed. Plastics from food packaging and polyethylene plastic bags are widely distributed along the Japanese coast. The concentration of expanded plastics and plastic bottles is high in the region of the East China Sea. Microplastics on the sea surface are widely distributed along the coast of Japan, and the average concentration of microplastics in seawater off the Japanese coast is very high compared with other regions of the world. A two-ply, double neuston net, comprising an internal net with a 350-μm mesh and an outer net with a 50-μm mesh, was used to quantify small microplastics（> 50 μm, < 350 μm） and microplastics（> 350 μm, < 5 mm）in Tokyo Bay. The concentration of small microplastics was about 10 times the concentration of microplastics. Conventional techniques used to quantify microplastics may underestimate plastic concentrations.

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Nutrient decrease and their effects on fisheries in the Seto Inland Sea, Japan were discussed. It suffered from heavy eutrophication during Japan’s period of high economic growth starting in the 1960s. At that time, red tides often occurred and fish culture was severely affected. Recently, water quality has dramatically improved. Although total nitrogen （TN） and total phosphorus （TP） runoff load from the land were reduced by 40% and 60%, respectively, TN and TP concentrations in seawater have apparently not decreased, despite the apparent nutrient concentration decrease. Nutrient decrease was not due to only nutrient runoff load from the land, and it was thought that nutrient release from the bottom sediment was also important. Despite the water quality improvement, fish catches have gradually decreased. Phytoplankton primary production did not response simply to nutrient decrease, and according to zooplankton, there is no data set to show their biomass variation. The conclusion is that the reason of fish catch decrease is still unknown. Whereas nutrient concentrations decreased, and presumably nutrient decrease will be a contributing factor, land reclamation, decreases in the area of tidal flats and algal/seagrass beds, global warming, and overfishing should be also thought as reasons contributing to fish catch decreases.

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The Mediterranean is a semi-enclosed temperate to locally warm sea. It is a hotspot of species, functional and ecosystem diversity, characterized by a high rate of endemism and a number of unique ecosystems. Between 12,000 and 17,000 marine species have been reported in the Mediterranean. Only one species is totally extinct and less than ten are extinct in the Mediterranean but still present elsewhere. In contrast, many species are functionally and/or regionally extinct. The progressive arrival of a thousand non-native species has in fact considerably increased the ε species diversity of the Mediterranean, contrary to the naive beliefs of some environmentalists. Several of the emblematic ecosystems of the Mediterranean （e.g. the dunebeach- banquette ecosystem, the Lithophyllum byssoides algal rim, the seagrass Posidonia oceanica meadow, the reef fucalean forests and the coralligenous） are currently in decline. Finally, the functioning of ecosystems （relative abundance of key species, carbon and nutrient flows, food webs, and interactions between ecosystems） has been profoundly altered. The causes of this impact on biodiversity are various; the three major causes are coastal development, overfishing, and biological invasions. Global warming is beginning to play a role, which will increase significantly over the course of the 21^st century, but it is currently far behind other human-induced causes. The concern over the growing and irreversible effects of global warming is totally justified; but the underestimation of other threats derives from issues which may be political or related to human perceptions and science funding, and which are discussed here.

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Successive polychaete inventories have reported polydorids in the English Channel and there are some reports describing polydorids from the Pacific coast of Tohoku District, Japan. Species Richness in both areas is compared and discussed. Moreover, in March 2018, French-Japanese collaboration led to the collection of polydorid species from the shells of feral and cultured oysters Crassostrea gigas （THUNBERG, 1793）along the western coast of Normandy, France. Some species were also extracted from coralline algae and other calcareous substrates. Eight species were recorded belonging to four genera: Boccardia, Boccardiella, Dipolydora and Polydora. The two species Polydora hoplura Claparède, 1868 and Dipolydora giardi （Mesnii, 1893）were previously known in Normandy, along with another member of the genus Dipolydora that has not been identified to the species level. Boccardia proboscidea Hartman, 1940, Boccardiella hamata （Webster, 1879）and Polydora websteri Hartman in Loosanoff & Engle, 1943 represent new records in Normandy, while both Boccardia pseudonatrix Day, 1961 and Polydora onagawaensis Teramoto, Sato-Okoshi, Abe, Nishitani, Endo, 2013 are new species for European waters. We point out that collaboration with polychaete specialists to study wellknown seas such as the English Channel would allow us to discover new species, expanding the list of species actually present. This study also highlights the need to continue this partnership further identify which polychaete species infest English Channel oysters.

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The phytoplankton assemblages in Onagawa Bay were investigated by photosynthetic pigment analysis and DNA sequencing over two consecutive years, from January 2012 to December 2013. Chlorophyll a （Chl a） concentrations tended to be high from winter to spring, and fucoxanthin, the source of which is mainly diatoms, was also high. Chlorophyll b concentration, which is retained in picoprasinophytes, tended to be higher in June. Cyanobacteria tended to appear in the summer, although, at less than 2%, in relatively small amounts. Since picoeukaryotes and cyanobacteria are small, shellfish filters cannot trap them efficiently, so the amount of nutrition obtained from them is relatively low and inefficient. Dinophysis norvegica （the causative agent of diarrheal shellfish poisoning）was the dominant dinoflagellate species throughout the study. Two species of dominant cryptophyte that were found are food sources of ciliate Myrionecta rubra which is a food source for Dinophysis spp., so unfortunately, they render Onagawa Bay susceptible to the growth of Dinophysis spp.. Phaeocystis spp. was the dominant haptophyte. The combination of pigment analysis by HPLC and DNA Next Generation Sequencing provided good data on seasonal phytoplankton variation, which is necessary to understand the detailed feeding environment for shellfish raised in Onagawa Bay.

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There are several reports on the dynamics of thyroid hormones during metamorphosis in flatfish, but there are limited reports on the post-metamorphic juvenile stage. In this study, we investigated changes in thyroxine （T₄）, a thyroid hormone, from the larval to juvenile stages of the marbled flounder Pseudopleuronectes yokohamae. We found that the T₄ concentration from 20 days post-hatching （dph）（larval stage） to approximately 120 dph （juvenile stage） substantially increased in the juvenile stage. There was a local maximum T₄ concentration in the late developmental stage of juveniles. We also found considerable inter-annual variation in T₄ concentrations during this study（2015, 2016, 2018, and 2019）. The findings of this study can be used to inform treatment options and management of flatfish seed production to ensure the health and quality of the fish produced.

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