Fish
Cobia
Rachycentron canadum · also called cobias, black kingfish
A cobia gets mistaken for a shark by some observers and a remora by others, and it is neither, occupying an entirely lonely branch of the fish family tree as the only living species in its own family. It often swims alongside actual sharks and sea turtles anyway, picking up scraps and disturbed prey along the way.
Overview
The cobia, Rachycentron canadum, is a large, fast-growing predator of warm coastal waters worldwide, the sole living member of family Rachycentridae. It hunts crabs, squid, and smaller fish, often trailing larger animals like sharks and rays for easy opportunities.
Fast growth, wide appeal
Cobia grow remarkably quickly for a large fish, making it a favoured aquaculture species, while its size, strength, and powerful fight have also made it a prized recreational catch across nearshore reefs and wrecks worldwide.
Status
Least Concern — widespread and resilient thanks to fast growth and early maturity, with growing aquaculture production helping ease pressure on wild stocks.
Cobia: common questions
Why is the cobia often mistaken for a shark or a remora?
Its elongated, somewhat flattened body shape, broad flat head, and a dark horizontal stripe running along its side combine to give the cobia a silhouette that can look sharklike from a distance, while its habit of swimming alongside larger marine animals is reminiscent of the well-known hitchhiking behaviour of remoras, even though the cobia is neither a shark nor closely related to remoras at all, making the resemblance purely superficial.
What does it mean that cobia has no close living relatives?
The cobia is the only living species classified within its own taxonomic family, Rachycentridae, meaning that unlike most fish, which belong to families containing numerous related species, the cobia stands essentially alone on its particular branch of the fish family tree, an unusual evolutionary position for a species that is otherwise so widely distributed and commercially significant.
Why has cobia become popular for fish farming?
Cobia grow unusually quickly compared with many other large marine fish species, reaching a substantial market size within just a few years under good conditions, and this fast growth rate, combined with generally good flesh quality, has made cobia an attractive candidate for aquaculture operations looking to produce a large, valuable fish efficiently.
Why does a cobia follow sharks and other large animals?
By swimming alongside or trailing a larger animal such as a shark, ray, or sea turtle, a cobia can take advantage of food scraps left over from the larger animal's own feeding, prey disturbed or flushed out by its movement through the water, or occasionally parasites dislodged from the larger animal's body, making this association a low-effort way to access additional food opportunities.