Swordfish Identification Guide

The Swordfish (Xiphias gladius) is a large open-ocean predator named for its long, flattened bill. It is often grouped with billfish like marlin and sailfish but differs in key ways.

Key identification features

• A long, broad, flattened 'sword' (bill) — wider and more blade-like than a marlin's round bill.
• A tall, stiff, crescent first dorsal fin that does not fold down, set well forward.
• No pelvic fins and a smooth, scaleless adult body.
• Large eyes and a dark, blackish-brown back fading to lighter below.

Swordfish vs. marlin and sailfish

• Marlin: round, spear-like bill and a long dorsal that can fold into a groove; pelvic fins present.
• Sailfish: enormous sail-like dorsal fin and a slimmer body.
• Only the swordfish has the flat, wide blade and lacks pelvic fins.

Where you'll see one

Swordfish roam temperate and tropical open oceans worldwide. The flat, broad sword plus the tall rigid dorsal fin and absence of pelvic fins confirm the identification.