Distribution,life history,and production of three species of <Emphasis Type="Italic">Neomysis</Emphasis> in Akkeshi-ko estuary,northern Japan |
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Authors: | Katsumasa Yamada Kazutaka Takahashi Carole Vallet Satoru Taguchi Tatsuki Toda |
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Institution: | 1.Graduate school of Science and Technology, Chiba University,Chiba,Japan;2.Tohoku National Fisheries Research Institute,Miyagi,Japan;3.Centre d’Outreau,IUFM Nord-Pas de Calais,Outreau,France;4.Laboratoire d’ichtyoécologie marine (LIMUL),Université du Littoral-C?te d′Opale,Wimereux,France;5.Department of Environmental Engineering for Symbiosis,Faculty of Engineering, Soka University,Tokyo,Japan |
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Abstract: | Spatial and seasonal distribution pattern, life history and production of three species of Neomysis (Mysidacea) which commonly occur in northwestern subarctic Pacific coastal waters, were investigated throughout the year
in the Akkeshi-ko estuary, northern Japan. The most abundant species Neomysis awatschensis (annual mean density: 179.8 inds. m−2, biomass: 108.8 mg DW m−2) occurred at the inner part of the estuary including low salinity areas with no clear preference for the seagrass bed. The
second most abundant Neomysis mirabilis (mean density: 95.8 inds. m−2, biomass: 90.1 mg DW m−2) occurred at relatively saline seagrass site throughout the year. Occurrence of Neomysis czerniawskii in the estuary was limited to the seagrass bed during summer when their population mainly consisted of juveniles, suggesting
that this species is a seasonal migrant between the estuary and the marine environment. Both N. awatschensis and N. mirabilis populations were composed of two generation types, a larger sized overwintering and smaller sized spring/summer generations;
however, each species had a different reproductive strategy. N. awatschensis was characterized by fast growth to maturity at a smaller size than N. mirabilis with a relatively high fecundity during warm season, suggesting that this species is an r-strategist which can utilize opportunistically
a wide variety of habitats. In contrast, the seagrass bed resident N. mirabilis was a K-strategist which matures at a larger size producing fewer but larger offspring. The annual production of N. awatschensis (0.57–0.70 g DW m−2, mean of the whole estuary) and N. mirabilis (0.58–0.68 g DW m−2, mean of the seagrass bed) at their respective habitats was comparable. Consequently, species-specific life history and distribution
pattern are concluded to allow Neomysis spp. to coexist in the estuary and the high carrying capacity of seagrass bed is suggested to contribute to maintain their
high biomass level. |
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