Seaward Migration of Juvenile Chinook Salmon without Elevated Gill (Na+K)-ATPase Activities

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Abstract
The hypothesis that juvenile anadromous salmonids which are migrating to sea have higher levels of gill [Na + K]-ATPase activity than nonmigrants was examined for wild and hatchery spring and fall chinook salmon (O. tshawytscha) from the Rogue River, Oregon [USA]. Although migrant juvenile chinook salmon captured at river km 173 had elevated gill (Na + K)-ATPase activity, migration from the more upstream portions of the Rogue River occurred without significant changes in gill (Na + K)-ATPase activity. High water flows stimulated migration without increasing gill (Na + K)-ATPase activity. Tributary-to-main-stem migration of juvenile fall chinook salmon did not result in elevated gill (Na + K)-ATPase activities. Juvenile spring chinook salmon released from Cole Rivers Hatchery (km 254) migrated rapidly to km 18 on the Rogue River without changes in gill (Na + K)-ATPase activity. Although the relationship between seaward migration and elevated gill (Na + K)-ATPase activity is demonstrable in chinook salmon in many cases, such elevated ATPase activity may not be a prerequisite for seaward movement of juvenile chinook salmon.