I. Biological Description
Aku (Katsuwonus pelamis) is commonly known as skipjack tuna. Other names for this species include striped tuna, oceanic skipjack and katsuo. This near-surface schooling tuna is widely distributed across the Pacific Ocean.
II. Of Special Interest For Buying/Distributing
Availability and Seasonality: Aku is historically the most important single commercial fish species in terms of landed weight and value in Hawaii, as well as throughout much of the central and western Pacific. Hawaii’s aku fishery, however, is characterized by wide annual and seasonal fluctuations in landings. Aku caught in Hawaii routinely range between 4 and 15 pounds in round weight, but larger fish (16 to 30 pounds in round weight), move into Hawaiian waters during the summer season of increased abundance (April-September).
Fishing Methods: Most of the aku catch in Hawaii is landed by commercial pole-and-line fishermen who induce aku to bite on feathered hooks by chumming with live bait. The pole-and-line catch is sorted according to fish size and is initially stored and sold in tubs head down so that blood drains away from the flesh. Trollers and longline boats land the remainder of the aku catch.
Distribution: Troll-caught aku is marketed through fish auctions in Honolulu and Hilo, through intermediary buyers on all islands, and by peddlers from the roadside. The pole-and-line aku, fleet, which is centered on the island of Oahu, markets its catch through intermediaries who sell to fresh fish outlets.
Substitution: Although ahi are often the preferred species for sashimi, aku can be substituted and, in fact, is preferred by some. When cooked, the red-fleshed aku lightens considerably in color, so it is interchangeable with ahi and a‘u in broiled or fried forms. Aku, ahi, and a‘u are also interchangeable for dried and smoked products, but due to their larger size, ahi and a‘u offer better yields.
III. Of Special Interest For Preparation/Quality Control
Shelf Life And Quality Control: Even with the best care, aku has a relatively short shelf life as a high quality product and is generally consumed within 6-7 days after landing (See Table 3). Aku which has been caught by trolling or pole-and-line is fresher and, hence, has a longer shelf life than that caught by longline boats, which make longer fishing trips.
Aku keeps longer if it is stored whole (especially if head down) and is not filleted until shortly before use. Larger summer fish (16-30 pounds in round weight) keep better than smaller fish. The first evidence of deterioration is a transformation of t