Seawater Adaptability of Land-locked Masu Salmon Oncorhynchus masou masou by Acclimation

The seawater adaptability of land-locked masu salmon Oncorhynchus masou masou via acclimation was examined for aquaculture purposes. The survival, blood chemistry, and histological changes of masu salmon (150 g) were measured after 7-, 15-, and 30-day acclimation periods. After a total of 60 days in seawater cultures that incorporated the various acclimation periods, survival was 83.5, 87.2, and 91.0% for the 7-, 15-, and 30-day periods, respectively; thus, survival increased with longer periods of acclimation. Feeding efficiencies were 32.1, 52.0, and 40.6% for the 7-, 15-, and 30-day periods, and specific growth rates were 0.14, 0.26, and 0.23%, respectively. Generally, masu salmon appeared to exhibit better growth performance after an acclimation period of 15 days. Cortisol concentrations [mean SD] for 7, 15, and 30 days of acclimation were , , and , with the lowest values occurring with 15 days of acclimation. Osmolarities were , , and mOsm/kg, and glucose concentrations were , , and mg/dl for the 7-, 15-, and 30-day acclimation periods, respectively (P