Tuna and salmon often get grouped together as two high-protein fish, but nutritionally they do not do exactly the same job. Lean fresh tuna packs a lot of protein into very few calories; salmon provides less protein per calorie, but an amount of omega-3 that yellowfin tuna does not come close to matching.
If the priority is protein with very few calories, tuna has the edge. If you want EPA and DHA, salmon wins by a wide margin. And once mercury enters the discussion, the tuna species matters.
Start with a like-for-like comparison
To keep packing oil, added sodium and draining from muddying the picture, it helps to begin with cooked fresh fish: yellowfin tuna versus Atlantic salmon.
| Per 100 g cooked | Yellowfin tuna | Atlantic salmon |
|---|---|---|
| Calories | ~130 | ~205 |
| Protein | ~29 g | ~22 g |
| Fat | ~0.6 g | ~12 g |
| EPA + DHA | ~0.1–0.2 g | ~2.1 g |
The protein gap is real, but it is not the most striking part: tuna provides about 7 extra grams per 100 grams. The much larger contrast is fat and omega-3. In this example, salmon can supply more than ten times as much EPA+DHA.
Keeping serving size equal helps too. At 5 ounces, yellowfin would provide roughly 40 grams of protein while salmon would provide around 31 grams. Both are substantial protein servings; they simply package that protein differently.
Tuna packs protein unusually efficiently
With less than 1 gram of fat per 100 grams, almost all of yellowfin tuna’s calories come from protein. About 5 ounces can provide roughly 40 grams of protein for around 180 calories. That is a very high protein-to-calorie ratio.
Reaching a similar amount of protein with Atlantic salmon takes about 6 ounces. That serving is closer to 350–370 calories because it also provides roughly 20 grams of fat. That distinction can matter when someone is building a high-protein, lower-calorie meal, but it is not an argument that the salmon’s fat is nutritionally wasted.
But salmon’s fat is part of the reason to eat it
Calories alone would make the comparison incomplete. Salmon contains substantial amounts of EPA and DHA, the long-chain marine omega-3 fats. NIH data list about 1.83 grams of EPA+DHA in 3 ounces of cooked farmed Atlantic salmon.
The same amount of cooked yellowfin tuna is around 0.10 gram. In other words, salmon is higher in fat, but a meaningful part of that difference is exactly what gives it the omega-3 advantage. If omega-3 intake is one reason you eat fish, that makes the extra fat part of the point rather than a drawback to erase.
For mercury, “tuna” is too broad a label
FDA/EPA places canned light tuna in the Best Choices category, albacore/white and yellowfin tuna in Good Choices, and bigeye tuna in Choices to Avoid for people covered by the pregnancy and child fish-advice chart. Salmon is a Best Choice.
FDA commercial-fish data show the scale: canned light tuna averages about 0.13 ppm mercury, albacore and yellowfin about 0.35 ppm, bigeye about 0.69 ppm, and fresh or frozen salmon about 0.02 ppm.
So if mercury matters in the decision, the species and product matter more than the generic word “tuna.” For pregnancy, childhood, or frequent fish consumption, following the species-specific FDA/EPA categories is more useful than applying one mercury number to every tuna product.
Canned tuna deserves a separate comparison
Canned light tuna in water is not nutritionally identical to albacore, yellowfin or tuna packed in oil. Species, packing liquid, draining, fat, calories and sodium can all change.
Canned light tuna also tends to be lower in mercury than albacore. Using the numbers from a fresh yellowfin steak to describe every can of tuna would therefore mix unlike products. When comparing cans, use the drained serving and check whether calories and sodium refer to the fish after draining or include packing oil.
So which one should you choose?
There is no need to force a single winner. Lean tuna is excellent when you want a lot of protein for few calories; salmon provides less protein per calorie but far more EPA and DHA and is generally low in mercury.
In a real diet, rotating the two along with other fish usually makes more sense than treating this as a permanent either-or choice. The better pick depends on what the rest of the diet needs: lean protein, marine omega-3s, variety, or simply a fish you enjoy enough to eat regularly.
Sources
- USDA FoodData Central — Protein, fat and energy in cooked tuna and salmon.
- NIH Office of Dietary Supplements — Omega-3 Fatty Acids — EPA and DHA by fish serving.
- FDA/EPA — Advice about Eating Fish — Fish categories by mercury level.
- FDA — Technical Information on Mercury in Commercial Fish — Average mercury values for tuna types and salmon.