ABSTRACT
Wild steelhead (Oncorhynchus mykiss) from southeastern Alaska were spawned in 1986 and 1987 to determine the biological feasibility of rearing this species to market size and maturity in marine net-pens. For each brood year, most smolts were fin marked, tagged with binary-coded-wire tags, and released at age 2; some were retained for growout in marine net-pens. During the spring maturation period in 1990 and 1991, one net-pen was fitted with a waterproof barrier 1 m deep and fresh water was piped into the net to provide a freshwater layer for osmotic relief for maturing fish (artificial freshwater lens system [AFLS]). Reciprocal crosses between farmed and ocean-ranched adults indicated little difference in egg viability; however, farmed males had lower sperm viability than ocean-ranched males. Farmed spawners were maintained in an AFLS, and survival to second spawning exceeded 60%. Use of an AFLS allowed good growth, successful maturation, and production of high-quality gametes.
