The Spawning Success of Early Maturing Resident Hatchery Chinook Salmon in a Natural River System

AbstractHatchery propagation of spring Chinook Salmon Oncorhynchus tshawytscha has been shown to increase the proportion of males maturing as minijacks (age 2) or microjacks (age 1) relative to those proportions in wild populations. However, little is known about the success of early maturing males when they spawn in the wild. A captive broodstock program for spring Chinook Salmon in the White River (a tributary of the Wenatchee River, Washington) has a high rate of early male maturity. We used genetic parentage analysis to evaluate the spawning success of anadromous males in comparison with inferred early maturing resident, hatchery-origin males that spawned naturally. Based on samples of juvenile offspring (n = 1,007–1,368 fish/year) and a nearly complete sample of the potential anadromous parents, we found that during 2006–2009, 26–45% of the progeny did not have a male parent in the anadromous sample. In contrast, 0–23% of the progeny did not have a female parent represented in the sample. Using grand...