Not all fish are created equal when it comes to omega-3 fatty acids. EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are the two marine omega-3s that drive the health benefits most people associate with eating fish — reduced cardiovascular disease risk, lower triglycerides, anti-inflammatory effects, and support for brain health. Cold-water, fatty fish are by far the richest sources. Atlantic mackerel tops the charts with roughly 2,600 mg of combined EPA and DHA per 100 g of cooked flesh, followed closely by wild Atlantic salmon (2,200 mg), sardines (1,480 mg), and anchovies (1,420 mg). By contrast, a lean white fish like cod delivers only around 200 mg per 100 g — still valuable, but in a different league.
Frequency of consumption matters as much as species choice. For most healthy adults, two to three servings of fatty fish per week — a serving being roughly 140 g (5 oz) cooked — delivers the 500–1,000 mg of EPA + DHA per day recommended by most cardiac health organisations. European sardines deserve special mention: they are one of the most sustainable fish you can eat, tend to be low in mercury due to their short lifespan and low position in the food chain, and deliver an outstanding omega-3 punch relative to cost. Anchovies are similarly impressive — a 30 g serving of canned anchovies in oil provides around 400 mg of EPA + DHA and contributes meaningfully to daily targets.
Mercury is the flip side of the omega-3 equation. Large, long-lived predators such as shark, swordfish, king mackerel, and tilefish bioaccumulate methylmercury to levels that can be harmful, particularly for pregnant women, nursing mothers, and young children. The FDA and EPA recommend these groups avoid high-mercury species altogether and limit albacore tuna to one serving per week. For the general population, the scientific consensus is clear: the cardiovascular and neurological benefits of consuming fatty fish two to three times per week substantially outweigh the risks from mercury exposure for most species. Choose small, oily, sustainably sourced fish — mackerel, sardines, anchovies, herring — and you'll get maximum omega-3 benefit with minimal risk.