Abstract
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 0.1mg・l−1 to a maximum of about 6mg・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 LC values ranged from 1.53 to 3.68mg・l−1, from 2.79 to3.90mg・l−1, and from 1.28 to 3.22mg・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 4mg・l−1 or at least 3mg・l−1 is necessary to conserve populations of these 3 species.
