Seafood markets designate salmon as being wild, wild-caught or farmed. Each of these terms has a commonly accepted meaning based on the life cycle of the salmon. Most jurisdictions monitor and control the numbers of each type of salmon caught, both by commercial and recreational fishermen. All species of salmon may have any of these designations attached to them.
Wild salmon have not had their life cycle interrupted or manipulated by humans. These fish have hatched from spawned eggs in native streams or rivers, and grown to maturity in rivers and oceans. Wild salmon are always native to the area in which they were caught.
Fish hatcheries produce large numbers of young salmon, called fry, and release them into streams and rivers. These salmon are species native to the area, and complete the remainder of their natural life cycle after their release. A harvested salmon which had any portion of its life cycle manipulated by humans, including a hatchery birth, is designated as wild-caught. Wild-caught salmon are genetically very similar to wild salmon.
Salmon raised in confined areas, without living any portion of their life in the wild, are farmed fish. These fish may not be native to the area, and critics rate them as the lowest quality of the three types. Farmed salmon are prone to parasites such as sea lice, and the farming operations are potentially damaging to the local ecosystems.
Identifying Wild Salmon
Since wild and wild-caught salmon are often the same species, hatcheries typically mark each hatchery-raised fry. Hatcheries typically clip the adipose fin, a small fin on the top of the fish, of any young salmon born in captivity. This fin never grows back during the salmon's life, so the mark is permanent. Any fish with an intact adipose fin is likely to have hatched and grown without human intervention.
There is evidence that wild and wild-caught salmon provides better nutrition than farmed fish, a result of different diets. Farmed fish may have a lower level of omega-3 oils, a beneficial oil found in salmon. Farmed salmon may also have higher levels of Polychlorinated Biphenyls (PCB), a carcinogen found in fish. Both farmed and wild salmon PCB levels are typically below the level considered hazardous to humans.
Because of the pressure on natural fisheries, most salmon offered for sale in the United States is farm-raised. New farming techniques, including improved feed, have narrowed the gap between the quality of wild and farmed salmon. PCB levels are also changing in wild salmon, reducing the difference between farm-raised and wild salmon.