Summary

Description

Spring Creek National Fish Hatchery traditionally operates an adult ladder, without closure, from the start of the tule fall Chinook salmon run in late August until the run ceases in early October. Ladder operation is continuous during the tule fall Chinook salmon run to receive all hatchery origin fish. In recent years, Spring Creek NFH has recorded large returns of adult tule fall Chinook salmon often with several thousand fish entering the hatchery each day of the hatchery run. An alternative approach to ladder operations at Spring Creek NFH was attempted in 2003 with several half day and one full day ladder closure near the end hatchery run. Another large hatchery escapement 40,000 fish was expected during 2004 and during 2005 50,000. An assessment of the 20042005 ladder closures was planned with the following objectives: to determine if hatchery brood stock includes tule fall Chinook salmon not allowed access to the hatchery during a ladder closure; and to determine if the behavior of tule fall Chinook salmon changes during intermittent ladder closure, specifically if intermittent ladder closure increases natural spawning and straying of Spring Creek NFH returning adults.