Why Round Scad and Horse Mackerel Look Alike but Have Different Names
Sep 25, 2025
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In common usage, "round scad" and "horse mackerel" may sound like two very different kinds of fish, but in fact they are close relatives. Both belong to the family Carangidae, which includes many slender, silvery fish often confused with true mackerel. The round scad (Decapterus maruadsi) is commonly found in the Pacific and is generally called "scad." Meanwhile, the Japanese jack mackerel (Trachurus japonicus), another member of the Carangidae family, is widely known in Europe and Japan as "horse mackerel"-even though it is not part of the true mackerel family (Scombridae).
This difference in names comes mainly from fishing traditions and regional habits. Early fishermen often named fish based on appearance: if a species looked slim and shiny like a mackerel, it was given the "mackerel" label. At the same time, "scad" developed as a common English name for many Carangid fishes. As a result, two similar species within the same family ended up with very different names-one called scad, the other called mackerel. This shows how local naming customs can be confusing, and why scientific names are essential for clarity and accuracy
