A maatje is a type of herring (Clupea harengus) that is caught in late spring. These are herring that are gorged, thanks to the abundant food supply in the spring. They are very fat and oily, and can contain up to 30% oil, a significant percentage of which is the much sought after Omega 3.

Traditionally, these herring are skinned and gutted (gekaakt), in such a way that the pancreas remains in the fish. Enzymes in the pancreas are said to “ripen” the herring. The bones are removed, but the tail remains attached, to keep both halves together. The fish is then lightly salted. They are eaten raw, and as such, they are the Dutch version of the better-known Japanese sashimi.

Raw seafish, including herring, is often infected by Anisakis, a group of nematode worms that can cause Anisakiasis. For that reason, maatjes consumed in the Netherlands and Belgium must be frozen for a period of 24 hours at a temperature that is not higher than -18°C. Anisakiasis, the illness caused by these worms, was once common but has now become rather rare, thanks to this safety measure.

Maatjes can be eaten with different accompaniments. The best known way to serve them is with raw onions and jenever (Dutch gin).

Maatjes are also called Hollandse nieuwe (New Dutch) or maatjesharing (maatjesherring). It is a uniquely Dutch dish that is somewhat popular in neighbouring countries like Belgium and Germany, but essentially unknown in the rest of the world.

Translations:
Dutch: maatje (plural: maatjes), maatjesharing, Hollandse nieuwe
English: Dutch herring