In North American waters, and 2 others in the Asian waters. In North American waters, we have: chinook/king, coho, chum, sockeye, and pink. In Asia waters, we have masu and amago. There is 1 species of Atlantic salmon. The largest salmon is chinook/king, and it can get up to 1.5 meters long and 57.2 kg. The smallest salmon is pink salmon, which can get up to 0.8 meters long and 5.4 kg, averaging 1.3-2.3 kg (3-5 pounds). Sometimes people classify steelhead trout as an eighth Pacific salmon, but they don't die after spawning just like the other Pacific salmons, and they have the ability to do repeat spawning, so they are often grouped with other fish as " Pacific trout".
The controversy between farm raised salmons and wild caught salmons still exists, and it was widely discussed in media, forums, news, scientific and academic publications. The viewpoints seem to have contradictory among them, which are mainly classified into 3 major categories: concerns for the environment, contamination lies within, and omega-3 fatty acid level in the edible part of the salmon.
Transfer of disease is the first environmental concern. Atlantic salmon eggs are introduced to the Pacific for farming purposes, people are worried that there might be a disease transfer to wild stocks. However, there are solutions, which include more testings on the fish from which eggs are taken, decrease the egg importation, and disinfecting the process can all minimize the disease transfer. Another thing we can do is to reduce the number of the fish stockings, because too high density can increase the chance of the disease spreading, which can lead to an outbreak later on.
Second concern would be the Atlantic salmon are escaping from their habitat and going into the Puget Sound and Pacific Northwest Rivers. The fact is that, some juvenile Atlantic salmon have escaped, there are no other escapes documented despite with the effort of the government agencies. One thing that people have to know is that when Atlantic salmon and Pacific salmon mate, they don't produce fertile offsprings, they can't mate successfully, so we don't have to worry about the interaction between the two species. Furthermore, studies have shown that farm raised Atlantic salmon has low survival rate in the wild because they are so used to being fed. At least in the state of Washington, there has been no signs of Atlantic salmon (farm raised or wild) successfully interacting with the Pacific salmon.
Pollution - third concern, normally happens under the net pens, and it includes fish feces excretion and uneaten feed. Most pens are located in high water currents area, however, if the water currents are low, then there is a large possibility that pollution can happen. Once pollutions do happen, they may influence the bottom water body habitat negatively. But, this influence is temporary and the habitats can recover over inactive periods.
Fourth concern is the sea lice. Sea lice from farmed fish might pass on to the native salmon populations if there is a mix happening. There is, however, a solution for it, British Columbia and US have rules and regulations set to check and monitor the number of sea lice in the farm raised salmon population monthly. Also, they are required to report to the authorities and receive treatment if they found out that there are more than 3 sea lice per fish.
Nowadays, most of the salmon that we buy in the store are farmed salmons. Early studies indicate there are higher PCB and other contaminants levels in the farmed salmons than in the wild salmons like pink salmon. Follow-up studies have not confirmed the previous findings, the scientists and regulators all reach a conclusion that farmed salmon and wild salmon are both safe to consume. Studies of farmed salmon in Washington State markets reveal low levels of organic contaminants in them. There are also strict rules in the limit of contaminants in the feeding materials, in other words feed changes make a difference on the contaminant level of the fish.
In conclusion, we were able to explain the concerns that have been mentioned regarding farm raised salmon and wild salmon. We can see that for each and every concern, we were able to find a solution for that problem. So don't worry about consuming salmon, it is completely safe, just make sure you read the production place, expiration date, type of salmon, production company information.
<Above information is taken from the Washington State Department of Health.>
Incidents about finding parasites/worms in the salmon?
The fact is that the appearance of parasites/worms is a natural occurrence in all living organisms. It is as if we sometimes find insects/bugs in our plants in our bakyard garden. Presence of parasites are not raising a health concern if we THOROUGHLY COOK the fish. That parasites does become a concern when you are eating them raw, or lightly preserved like sushi, sashimi, gravlax and ceviche. We can use commercially frozen fish as an alternative, or freeze the fish to -4 degree Fahrenheit internal temperature for 7 days to kill any parasites that can possibly be there. It's hard to reach this low freezing temperature using home freezers. The health risk from parasites are way less than those hidden unseen bacteria. It is NOT appropriate to consume the salmon or most other fish RAW in supermarkets here in the US. The "Sushi Grade" / "Sashimi Grade" labels you see on the packages of seafood when you are shopping around are just a marketing strategy by the sellers/manufacturers. Since there is no quality levels of "Sushi Grade" being discussed by FDA. But if you really want to purchase them and make Sushi/Sashimi yourself, you may follow the safe and practical steps recommended by the FDA:
"The FDA recommends the following for seafood preparation or storage to kill parasites.
On the other hand, the fish normally pass stricter examinations and special parasites removing process under extremely low temperatures in those Japanese Sushi/Sashimi restaurants. Make sure to check the restaurant's standard when you choose to eat there.