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Aku (Skipjack Tuna) Katsuwonus pelamis

Typical: 18–30 in, 5–20 lb

Quickest tell: Straight horizontal stripes running along the belly and a plain unmarked back separate Aku from Kawakawa, whose markings are wavy, confined to the upper back, with spots low on the chest.

• 4-6 bold straight horizontal dark stripes on the LOWER sides/belly
• Dark blue-purple back; silvery belly
• Back plain and unmarked above the lateral line
• Streamlined tuna body, short pectoral fins, finlets
• Scaleless except for the corselet and lateral line

Full Aku (Skipjack Tuna) guide — season, gear and rules →

Kawakawa Euthynnus affinis

Typical: 18–28 in, 5–15 lb

Key field mark: Broken wavy markings confined to the UPPER back, plus a few dark spots low between the pectoral and pelvic fins, distinguish Kawakawa from Aku, which has clean horizontal stripes on the LOWER belly and a plain back.

• Wavy/scribbled dark bars on the back ABOVE the lateral line, not extending below it
• A few (usually 2-5) small dark spots low on the body between pectoral and pelvic fins
• Scaleless except for the corselet and along the lateral line
• Stout, football-shaped tuna body; finlets behind dorsal and anal fins
• Belly silvery and unmarked (no horizontal stripes)

Full Kawakawa guide — season, gear and rules →

When Each Is Running July — current month highlighted

Where Aku (Skipjack Tuna) and Kawakawa Overlap

Both run in Hawaiian Islands — that is where telling them apart actually matters.

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