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 distrib-
uted 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).
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.
Troll-caught aku is marketed through fish auctions in Honolulu and Hilo, through inter-
mediary 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
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 the deep red color of the meat to a brownish-red or
rainbow color, accompanied by loss of firm texture.
Aku (Skipjack Tuna)