Investigation of winter-run Chinook Salmon vital rates
Carlton

The current drought (up through 2016), in combination with other long-term stressors, is threatening survival of Sacramento River winter-run Chinook Salmon population. Given the circumstances, data on vital rates for the population are urgently needed to better guide management efforts.  The study directly links adults and offspring (within brood year) using genetic mark-capture, parentage, and relatedness methods, to characterize reproductive success (recruitment, differential survival) among individuals and hatchery contribution to in-river juvenile production.  Independent estimates of adult escapement, breeder abundance and other important metrics can be obtained by incorporating genetic techniques into existing monitoring activities.  Effectively, genetic methods can link adult winter Chinook encountered at the Keswick trap and in carcass surveys with juvenile outmigrants (encountered at Red Bluff Diversion Dam) through genotypes.  These procedures enable specific vital rate metrics to be generated such as spawner census and the number of contributing breeders.  An accurate estimate of the number of female breeders contributing to recruitment (less prespawn mortality) would provide enhanced information about the underlying winter-run population (egg-to-smolt survival), as there is an information gap currently between observed unspawned carcasses and juveniles captured at Red Bluff Diversion Dam.  Generalized linear model approaches are used to explore factors that may influence fitness.  Factors included to evaluate recruitment of juveniles to Red Bluff Diversion Dam are origin (hatchery, natural), environment (temperature, discharge), adult sampling location, emigration date (family average, family variation).