There are several species of fishes in the San Francisco Estuary that are highly vulnerable to extinction or endangered status. These include the longfin smelt, Sacramento splittail, Sacramento perch, green sturgeon, delta smelt, Chinook salmon and steelhead trout. A leading conservation strategy for preserving these species is to rear fish in hatcheries for release in the wild—restocking. This approach, however, has its own set of environmental risks, including the risk of spreading disease and/or reducing genetic diversity. In this project, the fellow is studying various stocking strategies to identify those that might best maintain the genetic integrity of supplemented wild fishes. Findings may be of assistance to ongoing, mandated and proposed hatchery operations in the Central Valley.