Author/Authors :
Kurihara, Takeo Seikai National Fisheries Research Institute - Japan Fisheries Research and Education Agency, Japan , Nakano, Shoji Seikai National Fisheries Research Institute - Japan Fisheries Research and Education Agency, Japan , Matsuyama, Yukihiko Seikai National Fisheries Research Institute - Japan Fisheries Research and Education Agency, Japan , Hashimoto, Kazumasa Seikai National Fisheries Research Institute - Japan Fisheries Research and Education Agency, Japan , Yamada, Katsumasa Seikai National Fisheries Research Institute - Japan Fisheries Research and Education Agency, Japan , Ito, Atsushi National Research Institute of Fisheries and Environment of Inland Sea - Japan Fisheries Research and Education Agency, Japan , Kanematsu, Masaei National Research Institute of Fisheries and Environment of Inland Sea - Japan Fisheries Research and Education Agency, Japan
Abstract :
Survival time of juvenile pen shell Atrina pectinata (shell length ~ 34 mm) exposed to hyposaline water without sediments was investigated in laboratory experiments. The bivalves were individually maintained in rearing cups in which salinity was decreased either gradually (over 1–11 h to 12 salinities ranging from 0 to ca. 34 ppt) or rapidly (directly to 21 salinities) at 12 and 24 °C. When the environmental salinity was gradually decreased, survival time differed markedly between the bivalves exposed to: salinities B 18.6 ppt (survival time<20 h in general) vs. > 21.1 ppt (>83 h) at 24 °C; and between salinities B 15.1 ppt (<34 h) vs. > 17.2 ppt (>83 h) at 12 °C. When the environmental salinity was rapidly decreased, survival time, again, differed markedly between the bivalves exposed to: salinities B 15.9 ppt (<20 h in general) vs. > 17.7 ppt (>140 h) at 24 °C; and salinities < 21.3 ppt (<38 h in general) vs. > 22.3 ppt (>140 h) at 12 °C. Such sharp decreases in survival time due to reduced salinity led to the selected, statistical models that assume either a sharp exponential increase or stepwise hike in hazard (instantaneous mortality rate) according to salinity reduction. These data and models indicate that juvenile A. pectinata should not be kept at salinities<21 ppt for periods>1 day in environments without sediments.
Keywords :
Pen shell , Atrina pectinata Lineage 2 , Survival analysis , Low salinity , Gradual and rapid decreases , Temperature
