Mackerel (in the family Scombridae) can refer to several different species of ocean fish that are found in tropical as well as temperate water. The smaller species of mackerels often travel in schools. Mackerel is a widely consumed fish around the world. Since it spoils quickly if not properly refrigerated, many of the common preparations of mackerel (especially in the past) involved curing or smoking the fish. However, today, it is commonly prepared grilled, seared, or roasted.
At this point you may be wondering, is mackerel kosher? Good news: According to Chabad, who received their information from the Orthodox Union, mackerel is a kosher fish.
If it’s kosher where are the scales ?
The type species of mackerel that is most commonly eaten in Europe, the Mediterranean, and North America is the Atlantic Mackerel (Scomber Scombrus).
It has gills, fins, and scales. The scales on its body are small and inconspicuous if you aren’t looking out for them. Most fish are also descaled before packaging (or burnt off during smoking process), so that may be a reason why you aren’t finding any.
But, there should be some bigger scales behind the head and around the pectoral fins.
There are a lot of other mackerel species, not all of them have scales, most of them do have scales though.