Bull. Jpn. Soc. Fish. Oceanogr. 78(1), Page 45-53, 2014   Effects of hypoxic water on planktonic larvae of swimming crab (Portunus trituberculatus), kuruma prawn (Marsupenaeus japonicus) and greasyback shrimp (Metapenaeus ensis) Satoshi Yamada1†, Satoru Kamohara1, Ryota Sone1, Toshihiro Horiguchi2 and Teruaki Suzuki3 1 Aichi Fisheries Research Institute, 97 Wakamiya, Miyacho, Gamagori, Aichi 443-0021, Japan 2 National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan 3 Graduate School of Environmental and Human Sciences, Meijo University, 1-501 Shiogamaguchi, Tempaku, Nagoya, Aichi 468-8502, Japan † E-mail: satoshi_5_yamada@pref.aichi.lg.jp We carried out laboratory experiments about adverse effects of hypoxic water on planktonic larvae of swimming crab, kuruma prawn and greasyback shrimp which are important target species in commercial fisheries. For the experiments, flow-through exposure systems with low dissolved oxygen (DO) concentrations were used; six different DO concentration groups (at least about 0.1 mg·l−1 to a maximum of about 6 mg·l−1) were tested for larvae and juveniles of each species, which were produced at the Aichi fish farming center. The larvae and juveniles exposed to various DO concentrations were observed for their death or survival under a stereomicroscope and their lethality were evaluated by LC5 (5% lethal concentration) calculated from logistic curves expressing relationship between the average DO concentration and the mortality every 24 h. Estimated LC5 values ranged from 1.53 to 3.68 mg·l−1, from 2.79 to 3.90 mg·l−1, and from 1.28 to 3.22 mg·l−1 for swimming crab (from zoea to juvenile), kuruma prawn (from nauplius to juvenile) and greasyback shrimp (from protozoea to juvenile), respectively. These results suggest that DO concentration of 4 mg·l−1 or at least 3 mg·l−1 is necessary to conserve populations of these 3 species. Key words: hypoxic water, flow-through exposure system, planktonic larvae, swimming crab, kuruma prawn, greasyback shrimp