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Farmed Salmon Get More Lice, Lose Omega-3s
Omega-3 levels in farmed salmon drop drastically; aqua farms losing fight against the lice they spread to wild fish

09/03/2018 By Craig Weatherby

Farmed salmon has always been a Faustian bargain.

Consumers pay lower prices, in return for fish that’s less healthful, kills wild salmon, and drains the oceans of smaller fish used as feed.

And in recent years, that false, Faustian bargain has begun to look increasingly bogus.

Two trends that don’t bode well for farmed salmon have been worsening simultaneously.

One is a decline in the omega-3 content of farmed salmon — which, as we’ll explain, worsens their existing “omega imbalance”.

The second trend is an accelerating failure to control the sea lice that afflict farmed salmon, which they spread to passing wild salmon.

Omega-3 levels dropped drastically in farmed salmon
Average omega-3 levels in farmed salmon dropped by half between 2005 and 2016.

British researcher Douglas Tocher of Stirling University put it this way to BBC News:
“About five years ago, a 130 gram [4.6 ounce] portion of Atlantic salmon was able to deliver 3,500mg of beneficial omega-3.”

As he said, “Now, the level of omega-3 has halved. Therefore, instead of eating one portion of farmed salmon, we would need to eat two portions of farmed salmon.”

To put these amounts in perspective, U.S. and global health authorities advise adults to get 250-500 mg of seafood-source omega-3s (DHA + EPA) every day.

What’s the explanation for this steep decline in the levels of omega-3s in farm-raised salmon?

Salmon farms have been replacing omega-3-rich fish and fish oil with soy, grains, and vegetable oils that deliver loads of omega-6 fats, but no seafood-source omega-3s.

Previously, fish like anchovies and herring provided 60 to 80 percent of farmed salmon feed. Today, the proportion of fish in farmed salmon feed has dropped to about 20 percent.

Salmon farmers’ desire to speed growth dictates a high-calorie diet that loads these farmed fish with more total fat — mostly added saturated and omega-6 fat — than their wild counterparts.

As a result, farmed salmon deliver many more calories — and fat-soluble pollutants such as PCBs — versus their wild counterparts.

Attempts to shift salmon feed away from fish and fish oil — due to rising costs and reduced availability — causes other concerns:

  • Genetically modified feed – Farmed salmon can be fed GM foods (soy, corn, canola oil).
  • Animal byproducts – Farmed salmon can be fed byproducts from poultry processing, such as feathers, necks, and intestines.

Salmon farms have been making this change to their fish feed for three reasons:

  1. Growing demand for cheap farmed fish, including farmed salmon.
  2. The higher cost of fish and fish oil versus soy, grains, and vegetable oils.
  3. Growing protests against depletion of wild fish like herring to feed farmed salmon.

To be clear, despite the drastic decline in their average omega-3 levels, farmed salmon remain rich in these healthful fats.

Using Dr. Tocher’s data, one 4.6-oz. serving of farmed salmon now averages 1,750mg of DHA plus EPA — the equivalent of consuming 250 mg of these omega-3s daily for a full week.

However, the changes to salmon feed mean these farm-raised fish — which were already very high in omega-6 fatty acids — now deliver even more omega 6s.

And omega-6 fatty acids — mostly from cheap vegetable oils (soy, corn, safflower, sunflower, cottonseed) — already overwhelm the standard American diet, to sickening effect.

(To learn more about the consequences of America’s “omega imbalance”, visit our Omega-3/6 Balance page, and browse the articles in the Omega-3/Omega-6 Balance section of our news archive.)

Long before the recent drop in omega-3s and rise in omega-6s in farmed salmon, a Norwegian clinical study found that farmed salmon's unnatural omega-3/6 fat profile produces harmful impacts on heart health: see Farmed Salmon's Diet Yields Unhealthful Cardiovascular Effects.

Subsequent studies confirmed that — for the same feed-related reasons — all farmed fish suffer by comparison with their wild counterparts: see Farmed Fish Possess Unhealthful Fat Profiles and Tilapia Taken to Task.

And a recent mouse study from U.S. and Danish researchers found that farmed salmon raised on feed featuring soybean oil — a growing salmon-farm measure meant to cut costs — harmed the rodents’ metabolisms and livers while inciting inflammation (Midtbø LK et al. 2015).

Industrial salmon farms want to replace fish and fish oils with omega-3-rich oils from algae or genetically modified canola oil.

But neither option is currently available, and it’s unclear whether their costs would be low enough to meet salmon farmers’ required profit margins.

Salmon farms losing fight against sea lice
Sea lice occur naturally worldwide, and attach to fish to eat their blood and skin.

Adult salmon are not normally susceptible to being crippled or killed by sea lice, but they will succumb if unusually large numbers grab hold.

Wild salmon populations rarely suffer from dangerous concentrations of sea lice, because the fish and the lice are widely dispersed in the ocean.

That changed with the start of salmon farming in the 1970s. The ocean net pens holding farmed salmon constitute perfect breeding grounds, proven to spread sea lice to passing wild salmon.

This ugly side effect of salmon farming is blamed in part for the near-extinction of wild Atlantic salmon: see Farmed Salmon Seen Spreading Sea Lice, Court Vindicates Claim that Fish-Farm Lice Kill Wild SalmonSea Lice from Salmon Farms Threaten Wild Stocks, and Threat to Salmon from Farm-Spawned Sea Lice Grows.

(Salmon farms also breed viruses that can spread from farmed to wild salmon … see Salmon-Killing Virus Found in Pacific NorthwestWild Salmon Advocates Win Fight vs. Fish Farms, and Salmon Farm Sickness Caught on Video.)

Now, this ocean-going parasite threatens to wipe out a multibillion-dollar global industry that feeds millions of people … though never as their only viable source of protein and omega-3s.

Because of lice, Norway produced 1.2 million fewer pounds of farmed salmon than expected last year — with salmon farms in Canada and many other countries suffering comparably serious lice-related losses.

And sea lice now afflict about half of all Scottish salmon farms, killing thousands of tons of farmed salmon annually and causing skin lesions and secondary infections in millions more.

As a Scottish salmon farmer told The Guardian newspaper earlier this month, “They are everywhere now, and just a few can kill a fish. When I started in fish farming 30 years ago, there were barely any. Now they are causing great problems.”

Consequently, world production of farmed salmon has fallen, causing the world price for these fish to soar.

Pesticide use and pollution on the rise
Salmon farmers feed their fish a pesticide called Slice (emamectin benzoate) to control sea lice ... which can become resistant to it.

The U.S. FDA says Slice should not be used on fish destined for dinner plates, and it can kill or cripple shellfish on the seafloor below salmon pens.

Slice is fed to most farmed salmon from British Columbia — over 80 percent of which go to the U.S. market.

Attempts to get rid of the lice now cost the Scottish farmed salmon industry alone around $375 million annually.

And data recently forced out of Scottish government files revealed two disturbing facts:

  • The amounts of toxic chemicals rising continuously
  • 45 Scottish lochs are seriously polluted by the chemicals used to kill lice and treat related infections on farmed salmon.

According to The Guardian’s recent report, “… the levels of chemicals used to kill sea lice have breached environmental safety limits more than 100 times in the last 10 years … and have been discharged into the waters by 70 fish farms”.

Although Scotland suffers from the worst lice infestations, the problem is growing globally and is proving much harder to fight than the industry thought and has claimed.

Globally, industrial salmon companies are spending more than $1 billion every year trying to eradicate lice and protect their salmon against lice and the viruses and diseases carried by these parasites.

Desperate measures against sea ice
Salmon farms have been trying some pretty bizarre lice-control methods.

One involves use of hydro-dousers, which function like huge car washes.

Another, called thermal delousing, pumps farmed salmon into a lukewarm water bath for about 30 seconds, and that sudden temperature change kills the lice.

But both measures are costly and can kill fish during the process of corralling and pumping them through the machines.

According to the Financial Times, Marine Harvest — the huge, Norwegian-owned industrial salmon farming firm — lost about 3.4 million pounds of salmon to sea lice treatment in Scotland last year.

Small fish called wrasse — which love to eat sea lice — are seen as the smartest, environmentally safest solution.

Salmon farms have been testing this approach successfully, but have been using wild caught wrasse.

And recent studies found that fish farms may be depleting wild wrasse stocks to a dangerous extent.

It’s possible to farm-raise wrasse, but that may not be sustainable, and breeding enough wrasse to protect just Scottish farms could take several years.

One possible solution is to raise salmon in onshore containment tanks — but that would likely be very costly and could create waste-disposal challenges.

Or, the huge companies that run most salmon farms could simply face facts and abandon salmon farming, which was ill-conceived from the start.

Note: This report was originally published on April 13, 2017.


Sources

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  • Henriques J, Dick JR, Tocher DR, Bell JG. Nutritional quality of salmon products available from major retailers in the UK: content and composition of n-3 long-chain PUFA. Br J Nutr. 2014 Sep 28;112(6):964-75. doi: 10.1017/S0007114514001603. Epub 2014 Jul 14.
  • Midtbø LK, Borkowska AG, Bernhard A, Rønnevik AK, Lock EJ, Fitzgerald ML, Torstensen BE, Liaset B, Brattelid T, Pedersen TL, Newman JW, Kristiansen K, Madsen L. Intake of farmed Atlantic salmon fed soybean oil increases hepatic levels of arachidonic acid-derived oxylipins and ceramides in mice. J Nutr Biochem. 2015 Jun;26(6):585-95. doi: 10.1016/j.jnutbio.2014.12.005. Epub 2015 Feb 4
  • Miller MR, Nichols PD, Carter CG. Replacement of dietary fish oil for Atlantic salmon parr (Salmo salar L.) with a stearidonic acid containing oil has no effect on omega-3 long-chain polyunsaturated fatty acid concentrations. Comp Biochem Physiol B Biochem Mol Biol. 2007 Feb;146(2):197-206. Epub 2006 Oct 21.
  • Sprague M, Dick JR, Tocher DR. Impact of sustainable feeds on omega-3 long-chain fatty acid levels in farmed Atlantic salmon, 2006-2015. Sci Rep. 2016 Feb 22;6:21892. doi: 10.1038/srep21892.
  • Sprague M, Walton J, Campbell PJ, Strachan F, Dick JR, Bell JG. Replacement of fish oil with a DHA-rich algal meal derived from Schizochytrium sp. on the fatty acid and persistent organic pollutant levels in diets and flesh of Atlantic salmon (Salmo salar, L.) post-smolts. Food Chem. 2015 Oct 15;185:413-21. doi: 10.1016/j.foodchem.2015.03.150. Epub 2015 Apr 10.