Osmoregulatory ability of chum salmon,Oncorhynchus keta, reared in fresh water for prolonged periods

1987 ◽  
Vol 4 (2) ◽  
pp. 101-110 ◽  
Author(s):  
S. Hasegawa ◽  
T. Hirano ◽  
T. Ogasawara ◽  
M. Iwata ◽  
T. Akiyama ◽  
...  
Keyword(s):  
Fresh Water ◽  
Chum Salmon ◽  
Oncorhynchus Keta ◽  
Chum Salmon Oncorhynchus Keta ◽  
Osmoregulatory Ability

Decreased Seawater Adaptability of Chum Salmon (Oncorhynchus keta) Fry Following Prolonged Rearing in Freshwater

1982 ◽  
Vol 39 (3) ◽  
pp. 509-514 ◽  
Author(s):  
Munehico Iwata ◽  
Sanae Hasegawa ◽  
Tetsuya Hirano
Keyword(s):  
Body Weight ◽  
Chum Salmon ◽  
Sea Water ◽  
Oncorhynchus Keta ◽  
Direct Transfer ◽  
Chum Salmon Oncorhynchus Keta ◽  
Salmon Fry ◽  
Seaward Migration ◽  
Osmoregulatory Ability

Chum salmon (Oncorhynchus keta) fry weighing about 1 g maintained plasma Na+ concentrations at 134–140 mmol/L during seaward migration in the Otsuchi River. The plasma Na+ level increased slightly in the estuary, and reached 150–160 mmol/L in the fry caught in the bay. On direct transfer from freshwater to seawater, the plasma Na+ concentrations of the fry weighing 0.4–2.3 g increased markedly after 1 h and reached a maximum after 3–12 h. The fry of < 1.4 g attained sea water-acclimated plasma Na+ level of 156 mmol/L within 24 h after transfer, whereas fry of 1.8–2.3 g failed to adapt to seawater within 24 h. When seawater adaptability of fry of different lots was examined simultaneously in late April, 83–109 d after hatch, the smaller fry adjusted their plasma Na+ levels more easily than the larger fry: the smallest fry attained seawater level after 12 h without showing any peak. Changes in seawater adaptability of the same lots of fry were also followed until 5 mo after hatching, and the osmoregulatory ability of the fry in seawater decreased gradually with an increase in body weight or in the time spent in freshwater.Key words: chum salmon fry, seaward migration, plasma Na+ concentration, seawater adaptability, Oncorhynchus keta

Loss of seawater preference in chum salmon (Oncorhynchus keta) fry retained in fresh water after migration season

1986 ◽  
Vol 240 (3) ◽  
pp. 369-376 ◽  
Author(s):  
Munehico Iwata ◽  
Hiroyuki Ogura ◽  
Shichiko Komatsu ◽  
Keiji Suzuki
Keyword(s):  
Fresh Water ◽  
Chum Salmon ◽  
Oncorhynchus Keta ◽  
Chum Salmon Oncorhynchus Keta
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