The red lionfish is a predatory scorpionfish that lives on coral reefs of the Indo-Pacific Ocean and more recently in the western Atlantic. It gets its common name from its long, colorful fin rays that resemble a lion’s mane. Like in many scorpionfishes, this species has venom-filled spines in several of its fins. In addition to being a popular aquarium fish, this species has recently become well known for its successful, human-induced invasion of the western Atlantic Ocean.
The red lionfish is an ambush predator. It moves very slowly and often sits perfectly still, waiting for small fishes to approach too closely, at which point it lunges aggressively toward its prey. At the same time, it extends its jaws forward, creating a large amount of suction, and easily swallowing the prey whole. This species is not a picky eater and will eat just about any fish that it can swallow, limited only by the size of its mouth. As it grows larger, the size of the prey that it can attack and eat also grows larger. Some individuals have been observed slowly cornering prey with their large fins before attacking. In its natural geographic range, the red lionfish is eaten by large bony fishes and coastal sharks. In the western Atlantic, it has few (if any) natural predators. In both basins, it uses its venom-filled spines in an attempt to guard against predation (not to attack prey).
Male red lionfish are somewhat territorial and court females that enter the part of the reef that they defend. After successful courtship, a male-female pair reproduces by a behavior known as broadcast spawning. In this method, the female releases her eggs and the male releases his sperm in the water column, above the reef, at the same time. This behavior increases the likelihood that eggs will become fertilized and decreases the likelihood that fertilized eggs will be eaten by egg predators at the reef surface.
Red lionfish are eaten in some places but are not targeted heavily for human consumption. In the past, they have been captured alive, in large numbers, for display in public and private aquaria. They are naturally rare and have likely been depleted in some areas, but a more serious consequence of their live capture is the accidental establishment of large populations outside of their normal range. In the 1990s, one or several individuals were released by pet owners in Florida, USA, and over the course of the past twenty years, the red lionfish has become a very common, destructive invasion throughout the western Atlantic Ocean. Outside of its native range, there are few natural predators that can tolerate its venom. It also eats a wider variety of prey and lives in colder latitudes in the western Atlantic. It reaches densities up to ten times higher than in its natural range. On some Caribbean reefs, it is now the most common medium-sized predator. This invasion threatens coral reef food webs throughout the Caribbean Sea and other food webs in temperate areas. Though some eradication efforts are underway for the red lionfish, we have likely passed a point of no return with respect to this species’ invasion of the Atlantic Ocean. Scientists suspect that it will never be fully eliminated from that region and may, in fact, continue to increase its geographic range as a result of new invasions.