Interannual variation in quantitative relationships among egg production and densities of larvae and juveniles of the Japanese mantis shrimp <Emphasis Type="Italic">Oratosquilla oratoria</Emphasis> in Tokyo Bay,Japan |
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Authors: | Keita Kodama Masaaki Oyama Jeong-Hoon Lee Yoshiaki Akaba Yoshihiro Tajima Takamichi Shimizu Hiroaki Shiraishi Toshihiro Horiguchi |
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Institution: | (1) Research Center for Environmental Risk, National Institute for Environmental Studies, Tsukuba Ibaraki, 305-8506, Japan;(2) Graduate School of Science and Technology, Nagasaki University, Nagasaki 852-8521, Japan;(3) Chiba Prefectural Fisheries Research Center, Awa Chiba, 295-0024, Japan;(4) Kanagawa Prefectural Fisheries Technology Center, Miura Kanagawa, 238-0237, Japan;(5) Present address: Marine Science Institute, University of Texas at Austin, Port Aransas TX, 78373, USA;(6) Present address: Faculty of Fisheries, Nagasaki University, Nagasaki Nagasaki, 852-8521, Japan |
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Abstract: | To explore which lifestages affect the stock size of young-of-the-year mantis shrimp Oratosquilla oratoria in Tokyo Bay, Japan, we investigated interannual variations in the quantitative relationships among egg production, larval
density, and juvenile density. We collected adult females, larvae, and juveniles during monthly field surveys from 2004 to
2007. The interannual trend for the juvenile density index differed from those for egg production and larval density; although
indices of both egg production and larval density were high in 2004 and 2007, the juvenile density index was high only in
2007, suggesting high mortality during the pelagic larval stage or the early phase of the postsettlement juvenile stage in
2004. We found that larval settlement started at the end of August and peaked in October, although larvae from the early spawning
season (May–June) should have settled in August or earlier. Juveniles were found throughout the bay except in areas where
bottom hypoxia occurred, suggesting that hypoxia restricts the spatial distribution of juveniles. Our results suggest that
mortality during the early life history fluctuates among years, probably because of changes in environmental conditions in
the bay, resulting in interannual variation in the stock size of young-of-the-year juvenile O. oratoria. |
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Keywords: | Early life history Hypoxia Mortality Oratosquilla oratoria Pelagic larvae Population dynamics Recruitment Tokyo Bay |
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