One of the challenges of raising fish in hatcheries is reproduction. Many fish species are hard to spawn and it can be difficult to maintain genetic diversity and disease resistance in hatchery produced fish. This proposal highlights the emerging method of germ cell transplantation, a potentially important aquaculture tool that can magnify the numbers of specific genetic lines of males and females without genetic modification. The work proposes to develop and optimize the transplantation technology in two economically important Pacific Coast species in commercial production: steelhead and white sturgeon. It will be experimentally determined which stage of juvenile development can produce a high number of transplantable germ cells for the two species to be studied.