Over 99% of the Atlantic salmon found in the market comes from farmed sources as historical commercial fisheries for wild stocks have ceased. Atlantic salmon is farmed around the world, primarliy in net pens and cages in protected open water bays and increasingly in land-based closed-containment aquaculture systems. The majority of these farms are located in Australia, Canada, Chile, Norway, Russia, and the U.K.. In many cases, Atlantic salmon takes on the name of the country where it was farmed, i.e. 'Norwegian salmon.' Atlantic salmon should have bright silver skin and with it's black cross spottings, it closely resembles coho salmon. The flavor is more mild than wild salmon and the flesh coloration ranges from a deep orange to a pinkish-orange and this variation comes from different types of feed in the different farms. When raw, the meat almost looks marbled and when cooked the large moist flakes retain the raw color of the flesh.
The quality of data from recirculating aquaculture systems tends to be relatively high and specific. Given that these systems are a fairly new development, however, long-term scientific data may not be available. The outbreak of infectious salmon anemia in Chile that began in 2007 and began to reverse in 2011 prompted improvements to transparency and public data availability in the industry. Seafood Watch considers data quality and availability for pen net salmon farming in Scotland, Norway, and British Columbia to be good.
Atlantic salmon are farmed around the world including the United States, Canada, Chile, Scotland, Denmark, and Norway. The land-based closed containment recirculating aquaculture systems primarily used in North America and Denmark treat and recycle water. This nearly eliminates effluents. For the small volumes produced, discharging aquaculture waste requires a permit and is highly regulated, according to Seafood Watch. The waste can be disposed at municipal treatment plants.
However, the net pens used in other regions allow for large amounts of effluent to be discarded into waterways. Some countries with net pens do regulate and monitor the waste, but even the highest Seafood Watch effluent scores for Scotland, British Columbia, and the largest salmon farm in Chile respectively, were moderate at best.
Recirculating aquaculture systems used to farm Atlantic salmon are closed and contained, which means there is very little interaction with local habitats. Open systems can have a significant negative impact on local habitats, although this tends to vary by country and by farm. In Norway, net pen salmon farms produce substantial nutrient pollution, but recent data indicated a low risk to local habitats near the farm areas, according to Seafood Watch.
Floating net pens at the largest salmon farm in Chile had few direct habitat impacts, but Seafood Watch found that chemicals, fish waste, and uneaten feed settled underneath the farm. Elsewhere in Chile the seabed impacts from floating net pens can be severe. The industry there is also rapidly expanding into pristine areas. Floating net pens in Scotland and British Columbia received moderate scores because the habitat impacts are reversible and impact relatively small areas.
The feed formulations used for Atlantic salmon farming vary greatly. In North America and Denmark, some farms used feed containing moderate amounts of fish oil and fishmeal from wild sources. Chile’s largest salmon farm uses feed made from genetically-modified yeast instead of protein from wild fish. Other farms in Chile have substantially reduced wild fish use in salmon feeds with more than 60% of ingredients coming from terrestrial sources, Seafood Watch reported. Fish farmers in Scotland are increasingly using alternative proteins and oils in their feed. Norwegian salmon farmers have also made progress in reducing wild fish for feed.
Source of Stock
Globally, the Atlantic salmon farming industry uses domestic broodstock and hatcheries, keeping sourcing independent from wild salmon populations, according to Seafood Watch.
Disease, Pathogen and Parasite Interaction
Land-based recirculating aquaculture systems allow for greater control over the farming environment than open net pens, reducing the risk of pathogens and transmission to wild populations. There is also less need for chemicals or antibiotics at these biosecure facilities.
Diseases and high chemical usage are common problems for open net pen Atlantic salmon farming globally. Bacterial and viral diseases along with sea lice parasites cause serious concern in Chile. An infectious salmon anemia virus outbreak that started in 2007 and didn’t begin to reverse until 2011 prompted better monitoring, enforcement, and compliance in the country. Seafood Watch gave Atlantic salmon farming there a moderate score for its disease criterion. However, Chilean salmon farmers use extremely high amounts of antibiotics and pesticides, prompting a “critical” score on chemical use from Seafood Watch.
Parasitic sea lice from Scottish Atlantic salmon farms have caused significant wild species population declines. On the farms, pesticide use has gone up over the past several years. A 2014 Seafood Watch report also noted that farmers were using hydrogen peroxide and more toxic chemicals like teflubenzuron.
While antibiotic use in Norway used to be considered fairly low, but then increased nearly 300% between 2011 and 2012, according to Seafood Watch. In addition, there are no regulations on antibiotic use if there is an outbreak. Overuse has led to antibiotic-resistant parasitic sea lice, prompting toxic alternative treatments. Pesticide use is also substantial.
Seafood Watch gave net pen salmon farming in British Columbia’s disease and chemical use a red/avoid recommendation over concerns about disease transmission to wild populations and substantial quantities of antibiotics in open systems.
Escapes and Introduced Species
Land-based recirculating aquaculture systems for Atlantic salmon farming tend to be enclosed in secure buildings, reducing the risk of escapes. Net pens have an inherent escape risk since they are located offshore.
Chile’s largest salmon farm uses best management practices that exceed national standards to prevent escapes. Seafood Watch also noted that escaped farmed Atlantic salmon are unlikely to become established in the wild in Chile.
Tens of thousands of salmon have escaped from farms in Scotland with very few recaptured. Seafood Watch reported that this is an ongoing catastrophic failure that has impacted wild salmon populations. About a quarter of salmon found in the wild in Scotland are actually hybrids. Norwegian farms have also reported large escape events. In 2011, more than 300,000 salmon escaped. Improved management and pen design have reduced the number of escapes, but previous events have already had negative effects on wild salmon populations.
Escape numbers have varied in British Columbia over the past several years, ranging from a dozen to more than 100,000. However, Seafood Watch concluded that escapees are unlikely to become established in the wild.