Growth, maturation and seawater adaptability of Kamchatka kokanee, Oncorhynchus nerka, implanted in Nikko [Japan].
1991
Iwata M. | Muto K. | Akutsu U. | Klyashtorin L.B. | Smirnov B.P. | Varnavsky V.S. | Kurenkov S.I. | Maruyama T.
A mixture of kokanee eggs from two Kamchatka lake stocks (Kronotsky Lake and Karimsky Lake) were transported to Nikko Branch, National Research Institute of Aquaculture in November 1988. Karimsky population was initiated by stocking with adult kokanee form Kronotsky Lake in 1976. The survival rate in September 1990 at their first spawning season was 34.4%. The maturation rate was 53.9% at the same period, and 14.2% were female. The body length and weight of 2 years old kokanee were 212.0 +- 3.1mm and 157.5 +-8.2g, respectively. Although implanted fish matured 2 or 3 years earlier than the donor populations in Karimsky Lake of Kronotsky Lake, the body size was similar to that of the Kronotsky population, but smaller than the kokanee of Karimsky Lake. Eggs from matured kokanee were fertilized and the survival rate at hatching period was 29.8%. Immature 1+ kokanee and Nikko strain produced from residual sockey (hime) in Lake Chuzenji were transferred to 30 ppt salt water. Plasma osmolality and chloride concentration of kokanee reached 414.9 +- 8.0 mOsm/kg and 201.5 +- 3.3 mEq/l 4 hours after the transfer. These values are significantly higher than those of the Nikko strain. Also the kokanee could not survive in 35 ppt salt water for 24 hours. The present results show that Kamchatka kokanee possess flexibility to adapt to new freshwater environment but not to sea water.
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