Measurements of key life history metrics of Coho salmon in Pudding Creek, California
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Since 2005, a life cycle monitoring project in Pudding Creek, California, has utilized a variety of methodologies including an adult trap, spawning surveys, PIT tags, electro-fishing, and a smolt trap to estimate coho salmon adult escapement, juvenile abundance, juvenile growth, winter survival, and marine survival. Adult coho salmon escapement and smolt abundance are closely related when spawner abundance is high. However, with decreasing escapement, smolt abundance appears to stabilize. Adult abundance has declined dramatically, from 1200 in 2005 to 20 in 2010. Corresponding smolt abundance initially declined from 24,000 to approximately 15,000 but maintained at that level despite continued declines in escapement. Winter survival ranged from 17 to 80 percent, and appeared to increase as the juvenile population decreased. Juvenile growth rates within the upper watershed were low during summer and significantly higher in spring and fall. PIT tag detections indicated that thirteen percent of all coho outmigrants were two year old smolts that were smaller at tagging than one year old outmigrants, but larger than one year old fish at outmigration. Over three complete coho life cycles (2006 to 2010), ocean survival appeared to strongly affect adult returns. In all years since 2006, ocean survival for Pudding Creek spawners was notably lower than reported by others in streams throughout the Pacific Northwest in previous years.