Artificial propagation of aquatic organisms is increasing globally and currently accounts for approximately 32% of total world fishery production (Vannuccini, 2004). Between 1970 and 2000, aquaculture production of salmonids has grown from less than 200,000 metric tons per year to over 1.5 million metric tons (Tacon, 2003). In 1995, the number of Atlantic salmon (Salmo salar) far exceeded the carrying capacity of salmon in the wild but over 94% of all adult Atlantic salmon were in aquaculture environments (Gross, 1998).

Since the 1970’s, concerns have arisen about interactions of hatchery and wild produced salmonids in native habitats. In response, research has addressed concerns about domestication and genetic impacts (Reisenbichler and McIntyre, 1977; Hindar et al., 1991; Waples, 1991; Clifford et al., 1998a; Fleming et al., 2000, 2002; Hard et al., 2000), transfer of disease and parasites (Johnsen and Jensen, 1994; Bakke and Harris, 1998), behavior of spawning adults (Fleming and Gross, 1992; Fleming et al., 1994; Økland et al., 1995; Youngston et al., 1998), differences in fitness traits and life history (Jonsson et al., 1991; Thodesen et al., 1999; McGinnity et al., 2003), and behavioral interactions between hatchery and wild juvenile salmon (Swain and Riddell, 1990; Johnsson et al., 1996; Clifford et al., 1998b). Much of this research has been driven by concerns about the impacts of escaped farmed Atlantic salmon in the North Atlantic Ocean (Hansen et al., 1991). Studies of the interactions between hatchery and wild salmonids, with few exceptions (see Myers et al., 2000), have primarily focused on interactions in freshwater environments.

Interactions between hatchery and wild fishes in estuarine and marine environments have not received the same attention, but may have signifi- cant impacts on wild populations. To address this issue, we organized a symposium held at the 2003 annual meeting of the Western Division of the American Fisheries Society in San Diego, California. The session was titled Interactions of Hatchery and Wild Fishes in Marine and Estuarine Environments and included nine presentations. All but one presentation focused on salmonids. This Special Issue of Reviews in Fish Biology and Fisheries includes five papers that were submitted to the symposium.