Aku

Aku is the Hawaiian name for skip jack tuna. Also referred to as bonito.  Aku can be steamed, grilled and even dried and flaked.  Aku is also the preferred tuna for making poke, a Hawaiian dish made of raw tuna and various seasonings such as green onion and soy sauce. Read more about Skipjack Tuna

If you don't have aku you can substitute Ahi tuna OR, depending on the preparation you could use another oily fish such as salmon.