This well-camouflaged ambush predator spends most of its time resting motionless on the seafloor, looking more like part of the reef than a fish. When smaller fishes venture near, the scorpionfish makes a quick lunge and opening its huge mouth in a fraction of a second inhales the prey into its large mouth. Its excellent camouflage also helps it escape detection by predators.

But this slow-moving fish has another defense one that has earned it the name scorpionfish. Running down its back, within the dorsal fin, is a row of venomous spines. At the base of each grooved spine is a sac of venom, and if a predator bites down on the fish, the venom is forced up a groove the spine and into the predator. Like many venomous marine animals, the nohu also has warning coloration. While the top of the fish is a perfect match for its surroundings, the bottom surfaces of the pectoral fins are brightly colored with bold bands of orange, yellow and black. When the fish is at rest, the fins are held close to the body and the colors are concealed. But, when threatened, the nohu flares the fins, revealing the colors as a warning to would-be predators.

There are about 25 scorpionfish species in Hawai’i, some are small, just 4 inches (10 cm) long, others can reach 24 inches (61 cm) in length. All are well camouflaged and all have the venomous spines. Because they blend in so well with the reef, waders, snorkelers and divers sometimes can be stung if they accidentally step on or touch any member of the scorpionfish family. The primary symptom is severe pain which can last as long as twelve hours if left untreated. The best treatment for a scorpionfish sting is to soak the wound in the hottest water the person can stand to denature the protein venom. But, you should always consult a physician for the most current treatment options. A Hawaiian scorpionfish sting, while very painful, is not considered life threatening. However, its South Pacific relative, the stonefish, has potentially deadly venom. Fortunately, this species does not occur in Hawai’i. The best protection against scorpionfish stings is prevention: always move slowly when exploring the reef; be careful where you put your hands and feet; and never attempt to handle a scorpionfish.