Best sources of DHA omega-3 essential fatty acid

This is surprisingly difficult to find out, so I decided to share the results with everyone. But first, background:

• Animals need omega-3 and omega-6 essential fatty acids
• The same enzymes are used for omega-3 and omega-6 processing, so too much of one will interfere with the other. People used to have diets with about 1:1 omega-3:omega-6. Today ratio is more like 1:20, and that little omega-3 we eat is mostly ALA.
• Three most important omega-3 are ALA (18 carbons), EPA (20 carbons), and DHA (22 carbons).
• Brains are made largely out of DHA.
• Land plants produce no EPA / DHA. None whatsoever. Zero.
• Some land plants produce adequate amounts of ALA, but even this is uncommon.
• Algae produce quite a lot of EPA / DHA.
• Animals including humans can convert ALA to EPA, and then DHA, but this is a painfully slow and inefficient process; and over-saturation of omega-6 and many conditions interfere with even that much.

Based on this some people believe it would be wise to try to increase amount of omega-3 fatty acids in diets. Hard evidence is rather lacking, this is however to be expected as hard evidence of anything about diet is essentially nil. It's almost only short term studies of crappy proxies, and there are millions of reasons why this is just wrong. Anyway, concerning supplementation:

• All mixed omega-3/omega-6/omega-9 supplements are waste of money - you're eating too much omega-6 already, and you can make as much omega-9 as you wish yourself.
• You don't want generic "omega-3" supplements - most of these are ALA, which is of very limited use. You want DHA. At worst EPA. ALA is little more than filler, it's not bad for you but it's less relevant, and much easier to get via normal diet anyway.
• If you're surprised why it's so hard to get DHA, this is possibly highly relevant.

Hopefully now you see why I'm measuring DHA, not anything else. And to keep science proper what I'm interested in is "% of calories coming from DHA", not "grams of DHA per portion" or anything like it. Portions are whatever manufacturer says they are, "per 100g" measures mostly tell you how much water foods have, and only "% of calories from" measures the right thing.

Best Sources of DHA

I digged through USDA National Nutrient Database, and this is what I found.

• The data only contains "food" not supplement pills and such. These will of course contain highest concentrations. Rarely eaten foods like dolphin meat are not in the database, so I have no idea how nutritious dolphin sashimi would be.
• The best source of DHA is unsurprisingly - fish oil. Salmon oil is 18.2% DHA and 34.2% omega-3 altogether; other fish oils are pretty good too, but not so much. Other oils like cod liver, sardine, and menhaden are 8.5%-10.9% DHA, 18.8%-26.6% total omega-3. Herring oil is less impressive 4.2%/11.1%. Fish oil also contains most mercury and other poisoning, so enjoy that. Once ultra-refined you won't need to worry about poisoning but it's more supplementation than food.
• The second best source is caviar/roe, with 7.7%-13.6% DHA, and 13.7%-24.2% total omega-3. Might be expensive to turn it into a major part of your diet.
• The third best source is seal oil with 6.5-12% DHA, 14.0-27.7% omega-3. Let's see if you can buy some legally outside Canada. So far we're totally out of luck.
• Finally something more useful. The fourth best source is salmon. There's wide range of nutritious value from 2%/4% to 8.9%/13.7% - depending on where they're caught and what's their diet. Fortunately there doesn't seem to be a big difference between wild and farmed salmon, so either will work. Unfortunately the same mercury poisoning problem applies as to fish oil - poisonous substances are stored in oil so the oilier (and more useful for us) the fish the more toxic, and there is no way to escape that.
• Fifth best source is mackerel. Like salmon, it can have as little as 1.5%/2.8% or as much as 8.7%/14.7%.

USDA says the next best source is dried parsley leaves at 7.3%/9.9% - which is most likely a massive measurement error, as there are no other plants anywhere, and it really makes little sense.

Other than that, it's fish, fish, fish, mollusks, jellyfish, crustaceans, and more fish. My hopes for finding something that's not fish are getting slimmer and slimmer, so I'm just going to skip all of them now (you can probably see the pattern), and only focus on things which are not fish/seafood.

• Brains. Beef/lamb/pork brains have 3%-5.4% DHA and 4.4%-7.7% total omega-3. Not surprisingly, as that's what animals primary need DHA for. And we simply throw away this most nutritious part.
• Whale oil - 3.9%/8.3%. Whale meat on the other hand is pretty useless at 0.2%/0.5%. Not that you'll find much of either at the nearest supermarket. It's technically not a fish. Anyway, between brains and ocean creatures we pretty much ran out of good sources, the next source is:
• Roasted squirrel - and that at mere 0.5%/0.6%
• Chicken can be anywhere from 0.1%/0.2% to 0.5%/0.8%
• Egg yolk - 0.3%-0.4% DHA, 0.4%-0.7% total.
• Whole egg - 0.2%-0.3% DHA, 0.2%-0.8% total. Pretty much all of that in yolk.
• We're long past useful concentrations anyway, so I won't be listing them. Next on the list are caribou, green turtles, turkeys, lamb kidneys, frog legs, guineahen, lamb hearts, squab/pigeon, pork livers, bear, raccoon, pork lung (and other beef/lamb/pork offal), and emu. Pork/beef/lamb meat doesn't register other than as rounding error.

So to summarize:

• Get supplements;
• Or eat a lot of fish and other seafood;
• Or eat ridiculous amount of poultry, eggs, and game meat;
• Or you're fucked.

There's no way to get enough DHA in anything resembling standard Western diet. Simply no way. Fruits and vegetables contain none, even "organic" ones. Actually fast food contains more as it often uses eggs and poultry as ingredients, but that's still not that useful.

One more long-term option would be to genetically engineer some common oily plants like soy or canola to produce some EPA/DHA - even if humans wouldn't eat them, if they're used as animal feed, we'd benefit indirectly quite a lot.

Actually someone already genetically engineered pigs to produce 4x omega-3 fatty acids, including 2x DHA, which sounds like the most urgent reminder that we need GMO now, and Luddites should not be in charge of policy.

EDIT: GM soybeans with more omega-3 (this most likely means ALA) and higher stability so they don't need partial hydrogenation has just been approved in US. If people moved from usual partially hydrogenated soybean oil to that it would be a massive health benefit. Of course our Euro-Luddites + CAP-paid farmer lobby coalition will probably ban it until long after "America vs Europe" picture get reversed. It's already much closer than you think.