Glossary - Ingredients

Aji/Horse mackerel


Located widely in warm sea waters throughout the world, horse mackerel are an adaptive migratory (wandering) fish species that ride warm currents. These fish can be classified into the species of horse mackerel, brownstriped mackerel scad, and striped jack mackerel. The horse mackerel is the most fished of the mackerel species, and it is sometimes classified according to size with those around 20 cm (7.9 in.) being called medium-sized horse mackerel and those under 10 cm (about 4 in.) being called small-sized horse mackerel (photo: horse mackerel).
Horse mackerel are available all year round, however the peak season for these fish is from June to August.



Contains protein and cholesterol-lowering polyunsaturated fatty acids (eicosapentaenoic acid, EPA). Horse mackerel extract contains high amounts of free amino acids including alanine, glycine and glutamic acid, and these extract components mix with lipids to create a characteristic umami flavor.

Connoisseur selection / storage

Horse mackerel with shiny eyes and bright metallic skin are fresh. Fish that are ungutted lose their freshness fast. Even when you do not plan to cook fish right away, gut and gill after purchase.

Cooking Tips

Fresh (sashimi-grade) horse mackerel can be used for tatataki (lightly seared, left raw in the middle), sashimi, and marinated dishes. These fish are also delicious grilled with salt, deep-fried, boiled, and as fishballs. Brownstriped mackerel scad are mostly used for dried fish products, and striped jack mackerel for sashimi, while small-sized mackerel are often first deep-fried and then pickled in sweetened vinegar and/or ‘nanbanzuke’ (spicy and sour marinade).

Cooking Basics

Horse mackerel - filleting

1. Remove scales (de-scale)

Spread a newspaper out over a cutting board and place the horse mackerel down. Move the tip of the knife from the tail towards the head to scrape off the scales.

2. Remove scutes (curved lateral line of hard scales)

Make a small angled cut with the tip of the knife from the tail and scrape off the scutes. Repeat in the same manner for the other side of the fish.

3. Chop off the head

Place the knife behind the pectoral fin and make an incision in the direction of the head with the knife at an angle (parallel to the gills). Slice in approximately half-way and then turn the horse mackerel over and repeat in the same manner on the opposite side making an incision with the knife to chop off the head.

4. Remove the innards

Insert the tip of the knife into the belly and make a shallow incision up to the anal fin, open the belly and remove the innards. At this point wrap up the innards in a newspaper, throw these away and rinse the horse mackerel with water and pat dry to remove excess moisture.

5. Fillet into 2-layers

Insert the knife from the flank until it reaches the backbone and slide the knife towards the head of the fish. Turn the horse mackerel over and repeat with the knife in the same manner from the belly. Lastly insert the knife facing the tail and slide it along the backbone to completely remove the fillet. Now you have a 2-layer fillet.

6. Fillet into 3-layers

Place the 2-layer filleted horse mackerel with the bones facing downwards, insert the knife from the flank until it reaches the backbone, slide the knife towards the tail to make an incision. Turn the horse mackerel over and make an incision with the knife in the same manner. Insert the knife at the base of the tail and slide it along the top of the backbone to remove the fillet from the backbone. Now you have a 3-layer fillet.

7. Remove the stomach bones

Lay the knife parallel to the cutting board and slice away the stomach bones.

8. Pull out small bones

Pull out small bones remaining in the mid-section of the fillet. These can be easily removed when pulled out in in the direction of from tail to head. To ensure no small bones go unnoticed, confirm with your fingers as you work to pull these out.

9. Remove the skin

Start skinning from an incision near the head and strip off the skin in the direction towards the tail.

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