There has been a big debate here in British Columbia about salmon farming along the coastal waters. Personally, I think informed consumers are in a better position to make an educated decision whether to eat wild or farmed salmon, when you are at a dinner table, whether at home or in some restaurant. Not only the salmon farming practice is disastrous for the environment, but also the fish may have an adverse effect on your health..
http://www.farmedanddangerous.org/index.htm
here are some excerpts from the site, but check it out for more details..
Why You Should Think Twice About Eating Farmed Salmon
Farmed salmon is much higher in saturated fats than wild salmon. This can contribute to health problems.
A single serving of salmon, wild or farmed, gives you the suggested daily requirement of omega 3 fatty acids. These essential fatty acids are also found in other wild fish like tuna, sardines or anchovies. Farmed salmon, however, contains more unhealthy fats. Preliminary research also shows that farmed salmon has higher levels of PCBs and other contaminants than wild salmon.
Farmed salmon are frequently fed antibiotics which contribute to the growth of drug-resistant bacteria .
Preliminary findings suggest that farmed salmon contain higher levels of PCBs and dioxins than wild salmon .
Farmed salmon are often given additives in their food to colour their flesh pink with chemicals to resemble its wild counterparts - otherwise, it would remain an unappetizing grayish-brown color
All Atlantic salmon sold in restaurants and grocery stores are farmed. There is no longer any commercial fishery for wild Atlantic salmon.
In BC, over 70% of farmed salmon are Atlantic salmon. Atlantic salmon are considered exotic (non-native, or alien) species in Pacific waters since they do not naturally occur in the Pacific Ocean.
With only a very few exceptions, farmed salmon are raised in open net cages in the ocean. These nets can tear, allowing farmed salmon to escape into the wild. Over a million farmed salmon have been reported by the industry to have escaped into Pacific waters since 1988; because many escapes over the years have gone unreported, experts believe the real figure is much higher.
Atlantic salmon have been found in 78 BC rivers and streams, but only a small portion of our rivers have been surveyed so far - meaning non-native Atlantic salmon could be inhabiting many more.
Atlantic salmon compete with wild salmon for habitat, particularly steelhead, and have been known to eat wild salmon fry and eggs. Atlantic salmon have been found spawning, and juveniles surviving in the wild .