Post-Release Performance of Chinook Salmon Reared in Circular Vessels Compared to Traditional Flow-through Raceways

Dual-drain circular vessels (CV) were evaluated as a means to maintain or enhance the performance of hatchery reared summer Chinook salmon relative to standard flow-through raceways (FT).  Passive integrated transponder (PIT) tags were utilized to evaluate travel time and survival to McNary Dam of juveniles by rearing vessel type. PIT tags were utilized to evaluate smolt-to-adult survival and corresponding age structure by rearing vessel type for seven release groups.  Juvenile outmigration survival to McNary was not significantly different for five of the release groups, but was significantly greater for fish reared in CV for two release groups.  Juvenile outmigration travel time to McNary was shorter for fish reared in CV versus fish reared in FT for six of the release groups.   PIT-tagged based estimates of mini-jacks were significantly lower for fish reared in CVs in six of the release groups.  PIT tag based adult age at return data is complete for two release groups; fish reared in CV exhibited higher rates of age-5 and age-6 returns compared to fish reared in FT. Dual-drain circular vessels are a hatchery rearing tool that has the potential to improve juvenile hatchery fish performance and hatchery male adult reproductive success.