Akihide Kasai

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Recent surveys showed substantial aggregation of larvae of jack mackerel in the southern East China Sea, indicating intensive spawning grounds near Taiwan. A numerical model was applied to investigate transport and survival processes of eggs and larvae of jack mackerel from the spawning area to the nurseries. The results show that: (i) the distributions of(More)
Carbon and nitrogen isotopic ratios in tissue of the bivalve corbicula (Corbicula japonica) and particulate organic matter (POM) were measured along a salinity gradient in the Kushida Estuary, Japan. The bivalve exhibited a gradual isotopic enrichment from the uppermost estuarine site (σ13C=−24.8‰ and σ15N=8.6‰) to the marine site (σ13C=−16.1‰ and(More)
We examined the feeding niche of four species of molluscs by analysis of their stable isotope signatures and cellulase activities to determine if they could utilize terrestrial organic matter. The molluscs and potential food sources were collected from the upper, middle and lower estuary of the Yura River from spring 2007 to winter 2008. All species showed(More)
Juvenile temperate seabass Lateolabrax japonicus were sampled along the Yura River estuary from April to July 2008 to determine their distribution and feeding habits during migration within a microtidal estuary. Throughout the sampling period, juvenile seabass were distributed not only in the surf zone, but also in the freshwater zone, and they were(More)
It is important to know the characteristics of migration pattern and vital rates of juveniles to understand the early life history and its effect on the population dynamics of fishes. The relationship between growth and migration pattern of juvenile temperate seabass Lateolabrax japonicus in the Yura River estuary was examined by combination of stable(More)
Cellulose digestion by Corbicula japonica was investigated according to the hypothesis that without any symbiotic aid, this organism can utilize cellulose as a carbon source. Enzymatic studies revealed the complete cellulase activity of this species, and molecular cloning resulted in the isolation of cDNA with an ORF encoding a 596-amino-acid protein that(More)
The economic value of ecosystem services of vegetated habitats (seagrass and macroalgal beds) has been estimated to be among the highest of the various ecosystems on earth. However, fish production has not been included in the evaluations due to the difficulty of quantitative estimation of fish production in the field. In the present study, annual(More)
Carbon and nitrogen stable isotope ratios in tissue of the bivalve corbicula Corbicula japonica and particulate organic matter (POM) were measured in Lake Jusan, Lake Ogawara and Lake Shinji, which are the foremost fishing grounds for the corbicula in Japan, to determine their food sources. The bivalves in Lake Ogawara and Lake Shinji showed enriched(More)
We monitored hydrographic and biological conditions in the Yura Estuary and its coastal area from April 2006 to March 2008. Hydrographic conditions changed seasonally, and were mainly determined by river discharge and sea level, with tides playing a minor role. In summer, when river discharge was low and sea level was high, a salt-wedge regime was(More)
Diet-switch experiments with three different species of microalgae were conducted to estimate diet-tissue isotopic fractionation of carbon (C) and nitrogen (N) isotopes in the freshwater clam Corbicula sandai. The δ13C and δ15N values in the soft tissues of C. sandai changed in each experiment, with little inter-individual deviations, thereby reflecting the(More)
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