Bigfin Reef Squid

Overview

The Bigfin Reef Squid (Sepioteuthis lessoniana) is a widely distributed, neritic cephalopod known for its distinctive, broad fins that run the length of its mantle. Often mistaken for cuttlefish due to this body shape, it is a highly active, schooling species frequently encountered in shallow tropical and temperate waters.

Distribution & habitat

This species is found throughout the tropical and temperate Indo-Pacific, ranging from the Red Sea to Hawaii and across northern Australian coastal waters. It has also expanded its range into the Mediterranean Sea as a Lessepsian migrant. They typically inhabit shallow coastal areas, including coral reefs, seagrass meadows, and rocky shorelines, often moving into shallower zones at night to feed.

Appearance

Characterized by a robust, fusiform mantle, the Bigfin Reef Squid features large, oval-shaped fins that extend along the entire margin of its body. Their coloration is highly variable, ranging from nearly transparent to dark with distinct black bands, and they often display a pair of iridescent transverse spots on the mantle. A narrow white or blue line is typically visible along the base of the fins where they attach to the body.

Biology & behavior

These squids are known for their rapid growth rates—among the fastest of any large marine invertebrate—and a short lifespan of less than a year. They exhibit complex social behaviors, including forming schools of similar-sized individuals, which may help mitigate the risks of cannibalism. They are capable of sophisticated visual communication through dynamic body patterning and color changes.

Feeding

As voracious predators, their diet consists primarily of small fish and crustaceans, including prawns, crabs, and stomatopods.