BENTHOS RESEARCH
Online ISSN : 2186-4535
Print ISSN : 0289-4548
ISSN-L : 0289-4548
Volume 1995, Issue 49
Displaying 1-5 of 5 articles from this issue
  • HIDEO SEKIGUCHI, MICHITAKA UCHIDA, AKIHISA SAKAI
    1995 Volume 1995 Issue 49 Pages 1-14
    Published: August 31, 1995
    Released on J-STAGE: August 07, 2009
    JOURNAL FREE ACCESS
    The mouths of two rivers in Japan, the Ano and the Shitomo, are adjacent to each other but show a marked difference in their bivalve assemblages on the tidal flats. From the results of a four-year field investigation on the densities of larvae and recruitants of three dominant bivalves (Nuttallia olivacea, Ruditapes philippinarum, Musculista senhousia), we sought to see whether pre- or post-settlement processes are the important factors determining the features of the bivalve assemblages in each river. They were found to be determined basically by post-settlement processes. However, in some years, they were determined after larval recruitment (>1.0mm in shell length), and in other years immediately after the larvae had settled on the tidal flats or after the bivalves had reached a certain size but before larval recruitment.
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  • SATOSHI KOBAYASHI, SHUHEI MATSUURA
    1995 Volume 1995 Issue 49 Pages 15-28
    Published: August 31, 1995
    Released on J-STAGE: August 07, 2009
    JOURNAL FREE ACCESS
    The reproductive ecology of the Japanese mitten crab Eriocheir japonicus in the sea was investigated by sampling and rearing crabs from Tsuyazaki, Fukuoka Prefecture, Japan, in 1990 -1991. Crabs, including ovigerous females, were collected in the field from early September to early July. Carapace width distributions for field-collected dead and live specimens did not differ. Crabs of both sexes reared in the laboratory died without moulting by August. These deaths were concentrated in two periods - November to December and again in April to June; this agreed with the periods of collection of dead crabs in the sea. Therefore, in the sea most crabs seem to die after reproduction without further moulting and growth. Female crabs oviposited and hatched eggs up to a maximum of three times. The volume of the egg mass tended to decrease in later ovipositions. There seemed to be two groups that differed in the timing of oviposition and death. Crabs that migrated to the sea in September and October tended to be larger than those migrating later.
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  • RAYMOND NAKAMURA, MASAO TANAKA
    1995 Volume 1995 Issue 49 Pages 29-37
    Published: August 31, 1995
    Released on J-STAGE: February 05, 2010
    JOURNAL FREE ACCESS
    The growth and survival of marked individuals of Capitulum mitella were examined for one year of Tomioka, Japan. Survival rates of individuals on the edges of aggregates did not differ significantly from those of individuals on the interior, nor did isolated individuals differ significantly from aggregated ones in this respect. Overall, annual survivorship was about 80%. A power function best described the relationship between specific growth rate and size. The growth of individuals on the edges of aggregates did not differ from that of interior individuals, nor did growth differ significantly between isolated and aggregated individuals. The integrated form of the power function indicates that it would take five years for an individual in an aggregate to reach its mature size at a rostral-carinal length of 10mm.
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  • NOZOMU IWASAKI
    1995 Volume 1995 Issue 49 Pages 39-50
    Published: August 31, 1995
    Released on J-STAGE: August 07, 2009
    JOURNAL FREE ACCESS
    The small-scale spatial distribution of meiobenthic harpacticoid copepods was studied in a sea bream nursery pond on Momo Island, Hiroshima, Japan. Sampling was carried out twice in daylight in July and August, 1980. Sediment samples were collected by hand coring using a 7×7 cells multiple contiguous corer. All the abundant species in both samples showed aggregated spatial patterns. For each abundant species, except in two cases, cores with a lower density and cores with a higher density than the mean were randomly distributed in the grid. There was no significant avoidance between species and some species significantly overlapped. Within species, ovigerous females and mating cou-ples were predominantly distributed in densely populated areas. The results suggest that interspecific competition was not the cause of patch generation, but that breeding behavior probably played an important role in patch formation during the breeding season.
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  • 1995 Volume 1995 Issue 49 Pages 55-64
    Published: August 31, 1995
    Released on J-STAGE: August 07, 2009
    JOURNAL FREE ACCESS
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