NOTES Reproduction of Aquaculture Atlantic Salmon in a Controlled Stream Channel on Vancouver Island, British Columbia

—Sightings and captures of Atlantic salmon Salmo salar that have escaped from aquaculture facilities have become common in coastal British Columbia, Canada. A lack of empirical data has prevented the forecast of what effects may result from the presence of this species in the Pacific Northwest. A first step towards this objective is to evaluate the spawning potential of escaped Atlantic salmon. We report results from a study of Atlantic salmon spawning in a simulated stream channel at the Little Qualicum River, British Columbia. Adults were obtained from a local commercial marine net-pen operation; 17 of 19 males and 24 of 30 females matured sexually, and up to 9 females successfully deposited eggs in six redds, five of which yielded viable progeny when the eggs were collected and incubated in Heath trays. Results suggest Atlantic salmon escaping from aquaculture facilities are likely to experience low spawning success in coastal British Columbia. However, based on the high proportion of sexual maturation, and even though successful spawning may be limited, we conclude that adult Atlantic salmon escapees, particularly those observed in freshwater, should be considered potential spawners. The coastal marine waters of southern British Columbia (B.C.) around Vancouver Island support one of the world’s most prolific salmon culture industries. Over 47,000 metric tons of salmon were produced by B.C. salmon farmers in 1999, 81% of which was Atlantic salmon Salmo salar, an exotic species in this region. Atlantic salmon cultured in B.C. are a composite of strains imported from Scotland, Ireland, USA, and New Brunswick (Atlantic Canada; Alverson and Ruggerone 1997). Eleven private hatcheries (mostly on Vancouver Island) select broodstock and supply smolts to ma* Corresponding author: [email protected] Received November 5, 1999; accepted October 10, 2000 rine grow-out facilities (Alverson and Ruggerone 1997). Atlantic salmon were first imported for commercial culture in 1984 (Keller and Leslie 1996), and free ranging escapees have been reported in both the marine and freshwater environments since 1987 (McKinnell et al. 1997). During the following 11 years a total of 236,974 Atlantic salmon have been reported to have escaped (Thomson and Candy 1998). It is likely additional fish have been lost due to ‘‘leakage’’ (i.e., chronic, undocumented loss of fish; Alverson and Ruggerone 1997; Moring 1989). The adjacent waters of Washington State also support Atlantic salmon culture facilities. Three recent events occurring over 3 years liberated an estimated 591,000 Atlantic salmon into coastal Washington waters (Amos and Appleby 1999). These escaped fish have prompted debate over the colonization potential of Atlantic salmon in the Pacific Northwest. On the Atlantic Coast, spawning success of farm-raised Atlantic salmon escapees has been shown to be inferior relative to wild counterparts (reviewed by Fleming et al. 1996). In a Norwegian study, farm-raised females retained more eggs, had greater egg mortality, and overall were 20–40% as successful as wild females (Fleming et al. 1996). Restrained and inappropriate behaviors of farm-raised males resulted in less than 3% of the success of wild males (Fleming et al. 1996). Poor spawning performance and presumed poor competitive ability of any wild-reared Atlantic salmon progeny have led to suggestions that escapees from aquaculture facilities pose little threat to native species in coastal B.C. (Needham 1995; Alverson and Ruggerone 1997). Atlantic salmon reproduction in the wild has been documented in B.C. (Volpe et al. 2000); how-