The Scorpaeniformes are a diverse order of ray-finned fish. It is one of the five largest orders of bony fishes by number of species with over 1,320.
Scorpaeniform fishes are carnivorous, mostly feeding on crustaceans and on smaller fish. Most species live on the sea bottom in relatively shallow waters, although species are known from deep water, from the midwater, and even from fresh water. They typically have spiny heads, and rounded pectoral and caudal fins. Most species are less than 30 cm in length, but the full size range of the order varies.
Here I have a few species from the families of Dactylopteridae, Synanceiidae, Platycephalidae and Scorpaenidae.
Dactylopteridae have been observed to “walk” along sandy sea floors by using their pelvic fins. Like the true gurnards, they possess a swim bladder with two lobes and a “drumming muscle” that can beat against the swim bladder to produce sounds. They have heavy, protective scales and the undersides of their huge pectoral fins are brightly coloured, perhaps to startle predators.The adults live on the sea bottom, but many species have an extended larval stage, which floats freely in the oceans.
- Helmut gurnard (Dactyloptena orientalis), also known as Oriental flying gurnard, has huge, round Pectoral fins. The fins are usually held against the body, but when threatened they can expand their wings (fins) to scare off a predator. Their name is derived from the French word ‘gurnard’ meaning to grunt, for the grunting sound this fish makes.
Synanceiidae is a family of Actinopterygii, ray-finned fish, found in the Indo-Pacific oceans. They are primarily marine, though some species are known to live in fresh or brackish waters. The various species of this family are known informally as stonefish, stinger, stingfish and ghouls. Its species are known to have the most potent neurotoxins of all the fish venoms, secreted from glands at the base of their needle-like dorsal fin spines. The vernacular name of the species derives from their behaviour of camouflaging as rocks. The type species of the family is the stonefish.
- Demon stinger (Inimicus didactylus) is also known as Goblinfish, Spiny devilfish and Bearded ghoul. It is nocturnal and typically lies partially buried on the sea floor or on a coral head during the day, covering itself with sand and other debris to further camouflage itself. Once dug in, it is very reluctant to leave its hiding place. When it does move, it displays an unusual mechanism of subcarangiform locomotion — it crawls slowly along the seabed, employing the four lower rays (two on each side) of its pectoral fins as legs.
Platycephalids are small to medium-sized fish. Most species are small, reaching an average of 10 cm in length. However, a few species are known to grow up to a meter in length. Their most distinctive characteristic is the flattened shape of their heads. Flatheads are mostly marine fish, often resting directly on the seabed, sometimes partially buried in sand or mud. They can be found in a wide range of depths, ranging from 10m to the edge of the continental shelf at depths of about 300m.
- Flathead crocodilefish (Cymbacephalus beauforti), or De Beaufort’s flathead or Giant flathead has the elongated body and head that particularly appears to look like a duck bill. Crocodilefish dwell in sandy patch and detritic zone where their camouflage is most effective, usually associated with reefs or mangroves in shallow water and protected areas. Juveniles begin black with few white spots and a white line behind the head.
Scorpeanidae, the scorpionfish, are a family of mostly marine fish that includes many of the world’s most venomous species. The family is a large one, with hundreds of members. They are widespread in tropical and temperate seas, but mostly found in the Indo-Pacific.
Most species are bottom-dwellers, many inhabit shallow waters, but a few live as deep as 2,200m. Most scorpionfish wait in disguise for prey to pass them by before swallowing, while lionfish often ambush their prey. When not ambushing, lionfish may herd the fish, shrimp, or crab into a corner before swallowing. Scorpionfish are suction feeders that capture prey by rapidly projecting a suction field generated by expansion of the fish’s buccal cavity. All lionfish are immune to each other’s venom and all are solitary fish.
- Longspine lionfish (Pterois sp.) is quite similar to Common lionfish except much taller dorsal spines. Sparsely scattered small black spots on the rear dorsal, anal and tail fins.
- Indian lionfish (Pterois muricate) is also very similar to a Common lionfish. Has long pectoral and dorsal fins with numerous black spots.
- Zebra lionfish (Dendrochirus zebra), or a Zebra turkeyfish, has wider brown bars and whitish fan-like pectoral fins. Can grow up to 25cm. Zebra lionfish feed only on small crustaceans, and are in turn preyed upon by groupers.
- Shortfin lionfish (Dendrochirus brachypterus), or a Dwarf lion fish, grows up to 17cm and is a popular specie for aquariums. Lionfish can be found during the day, hovering above the ground, in caves or crevices, often upside down. At night they are out in the open hunting.
- Bandtail scorpionfish (Scorpaenopsis neglecta), also known as the Yellowtail Scorpionfish, this species can be highly variable in colour.
- Tasseled scorpionfish (Scorpaenopsis oxycephala) can vary considerably in color. Adults are bearded with a number of tassels below the jaw.
- Devil scorpionfish (Scorpaenopsis diabolus), also know as a False stonefish, has a pronounced hump on a back. Devil scorpionfish exhibits biofluorescence, that is, when illuminated by blue or ultraviolet light, it re-emits it as red, and appears differently than under white light illumination. Biofluorescence may assist in intraspecific communication and camouflage.
- Cockatoo waspfish (Ablabys taenianotus) is an opportunistic predator and ambushes passing prey while mimicking a crumpled, dead leaf or a drifting piece of seaweed. It allows itself to drift with the moving water in the way that an inert object would do.
- Leaf scorpionfish (Taenianotus triacanthus) grows only up to 10cm. The leaf scorpionfish resembles a dead leaf lying in the water. To enhance this camouflage, it even makes gentle sideways movements in its pelvic area which make it resemble a drifting inert object. It is an ambush predator, waiting until suitable prey, a small fish or shrimp, approaches. Then it slowly moves with its pectoral fins close to the victim. When the leaf scorpionfish is close enough, the prey is sucked in by a sudden opening of its mouth. It eats small crustaceans, fishes, and larvae.