Side by Side

Blackfin Tuna Thunnus atlanticus

Typical: 20–28 in, 5–20 lb

Quickest tell: Dark finlets lacking bright yellow, on a deep football body with no back stripes, separate blackfin from the back-striped, fingerprint-spotted bonito/false albacore.

• Dark blue-black back, silver sides; deep football body with a chest corselet
• Finlets dusky/black, edged white-gray (NOT bright yellow as in other tunas)
• Short pectoral fins, not reaching past the second dorsal origin
• Smallest tuna; no oblique back stripes or fingerprint belly spots
• Faint yellow on the central finlets at most

Full Blackfin Tuna guide — season, gear and rules →

Yellowfin Tuna Thunnus albacares

Typical: 36–50 in, 30–80 lb

Quickest tell: Long, bright-yellow sickle-shaped dorsal and anal fins plus yellow black-edged finlets distinguish yellowfin from the much smaller blackfin, which keeps short fins and dark, dusky finlets.

• Dark metallic blue back, silvery-white belly, and a golden-yellow stripe down the side
• Greatly elongated, sickle-shaped (falcate) second dorsal and anal fins on larger adults
• Bright yellow finlets edged with a narrow black margin
• Lower flanks/belly often marked with alternating pale lines and rows of dots
• Pectoral fin moderately long, reaching to about the second dorsal origin (not past the anal fin as in bigeye)

Full Yellowfin Tuna guide — season, gear and rules →

When Each Is Running July — current month highlighted

Where Blackfin Tuna and Yellowfin Tuna Overlap

Both run in Gulf of Mexico — that is where telling them apart actually matters.

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