Short mackerel

Short mackerel (Rastrelliger brachysoma), or shortbodied mackerel, are a species of mackerel in the scombrid family (family Scombridae) of order Perciformes. Its habitat is the shallow waters of Southeast Asia and Melanesia, where the surface temperatures range from 20 to 30 degrees Celsius. It feeds mainly on microzooplankton.

As food
Pla thu (ปลาทู) is a very important fish in Thai cuisine, where it is sold in the market with the head bent downwards, which gives it a characteristic shape. Pla thu is typically fried and eaten with nam phrik kapi, boiled and raw vegetables and leafy greens, as well as pieces of cha-om omelette, but there are many other preparations in which it is essential. The name pla thu is sometimes also applied to the Indian mackerel (Rastrelliger kanagurta), which is prepared in the same way.

In the traditional way of processing the pla thu for preservation, the gills are removed and the head of the fish is bent downwards forcefully towards the belly by breaking its backbone. This is done to allow three fishes to fit into a small open-work bamboo basket of a predetermined size. Once in the baskets, the fishes are boiled for a few minutes in large basins of sea-water with salt added at 1 kg of salt for every 4 l of water. In Thai cuisine, the thus processed pla thu is most often eaten fried in combination with nam phrik kapi, a spicy dip made with shrimp paste, dried prawns, lime juice, fish sauce and the small pea eggplant, with rice and steamed, raw or fried vegetables.

The pla thu prepared in this way will keep for a very long time in the refrigerator. In former times, it kept for about two weeks without refrigeration as long as it was boiled for a few minutes every two days. In this manner, this sea fish could reach many places in interior Thailand, like the Chiang Mai area in the far north and even remote places in Isan, where it is much appreciated.

Fresh pla thu is commonly used to make soups such as tom yam pla thu. This fish is so popular in Thai culture that the Samut Songkhram F.C. has a pla thu in its emblem.

Already in 1870 CE, Anna Leonowens describes the importance of this fish for Thailand in her book The English Governess at the Siamese Court: "The stream is rich in fish of excellent quality and flavour, such as is found in most of the great rivers of Asia; and is especially noted for its plathu, a kind of sardine, so abundant and cheap that it forms a common seasoning to the labourer's bowl of rice. The Siamese are experts in modes of drying and salting fish of all kinds, and large quantities are exported annually to Java, Sumatra, Malacca, and China".

The innards of this mackerel are one of the main ingredients of Tai pla sauce, used in the preparation of the well-known Kaeng tai pla curry.

This type of mackerel is also very important in the cuisine of other regions of Southeast Asia, such as Cambodia, the Philippines (where it is the most commercially important variety of mackerel) and Malaysia.