billfishes

Billfishes are a group of large, highly migratory predatory fishes distinguished by elongated bills. The group includes marlins, sailfish, swordfish, and spearfish. Taxonomically they are divided into two families: Xiphiidae, which contains the swordfish, and Istiophoridae, comprising marlins, sailfish, and spearfishes. They inhabit warm and temperate seas worldwide, typically in the pelagic zone from near the surface to mid-water depths.

A hallmark is the rostrum, used to slash or stun prey. Sailfish have the largest dorsal fin and a prominent sail; marlins and spearfish have slender, streamlined bodies with long bills; swordfish possess a broad, flat bill. Several species exhibit regional endothermy, enabling higher body temperatures in the mouth and eyes, which supports rapid pursuit in cooler waters.

Diet consists mainly of smaller fishes, squid, and other cephalopods. They are highly migratory, forming seasonal movements and feeding across different ocean regions. Reproduction is typically ovoviviparous, with embryos developing inside the female and being born live after internal fertilization; exact timings vary by species.

Billfishes are targets of commercial and recreational fisheries, often valued for meat and sport. Stocks are affected by overfishing and bycatch, and management measures such as quotas, size limits, and seasonal protections have been implemented in various regions to sustain populations.