Horse mackerel

One of the cheapest fish in the games, the Horse Mackerel (アジ, Aji) is a common fish that can be found in the ocean. It can be caught at any given time, month, or season. When this fish is given to Wendell the walrus in City Folk, the player is rewarded with a Horizontal Track pattern.

In Wild World
Blathers will say this when handed the fish:

"How do you like to eat your fried horse mackerel? With tartar sauce? Vinegar? ...Ah! Cocktail sauce?! Hoo, I see. Fascinating."

In City Folk
Blathers will say this when handed the fish:

"Horse mackerel are not at all related to horses... Rather obvious, I should think... It's quite a strange name, given how many fish are related to this one, like yellowtail and amberjack."

In New Leaf
The plaque by the tank in which the fish is housed says the following:

"With their appealing flavor, horse mackerel have long been a cheap and common food source. However, in certain regions, they have actually been branded as something of a luxury dish. They have tough scales on both sides of their bodies that must be removed before preparing. Though small, they are formidable carnivores. Since they go after bait, they are popular with fishers."

Further information
The Japanese jack mackerel has a depth range of 0 - 275 m, but usually 50 - 275 m. It is tropical. It is an important fish in the fishing trade and can be found in the northwest Pacific Ocean. It is vulnerable.