Seasonal changes in seawater adaptability of the hatchery reared juvenile sockeye salmon, Oncorhynchus nerka
1991
Ban, M. (Hokkaido Salmon Hatchery, Sapporo (Japan)) | Yamauchi, K.
Seawater (33%) challenge test was performed to assess the development of seawater adaptability in the underyearling and yearling sockeye salmon, Oncorhynchus nerka, from July, 1989 to July, 1990. The body silvering were observed throughout the experimental period, whereas the pigmentation of both dorsal and tail fin margins appeared during from July to October, 1989, and from May to June, 1990. A survival rate of 100% was observed on the 7th day after transfer into seawater in August and September 1989, and in May and June, 1990. Serum sodium contents after the 7th day of transfer into seawater were low in August and September, 1989 and June, 1990. High gill Na(+), K(+)-ATPase activities were observed in August, 1989 and June, 1990. These results suggest that the underyearling and yearling sockeye salmon develop seawater adaptability in August and in June, respectively
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