Demand for seafood on a global scale is projected to increase by 70 percent in the next 30 years, though most fisheries are at or beyond their sustainable yields and many are in decline (Botsford et al. 1997). Fisheries management must be augmented by new strategies for protecting and enhancing marine resources, such as “no-take” marine reserves (Allison et al. 1998; Hastings and Botsford 1999) or enhancing natural stocks through artificial hatchery propagation. Despite criticisms from conservationists and fisheries biologists alike (e.g. Meffe 1992; MacCall 1989), large-scale hatchery supplementation programs are already in place for many anadromous and marine fisheries (Travis et al. 1998), and in Japan, a substantial fraction of marine production is attributable to enhancement programs (Masuda and Tsukamoto 1998). The global extent of enhancement of wild fisheries is poorly documented, however, especially for marine species (A.F. Born, A.J. Immink, and D.M. Bartley, FAO Fisheries, pers. com.). In Japan, to take just one example, nearly 70 marine species are supplemented, some at very high levels. To date there have been very few analyses of the potential genetic impact of these marine supplementation programs.