Like other scorpionfish, Rhinopias species are camouflaged to blend in with their surroundings. The scorpionfish’s cryptic camouflage is an invaluable tool for hunting prey and avoiding becoming prey itself. Both prey and predators mistake the well camouflaged fish for a piece of seaweed. These very beautiful scorpionfish are rare, so an encounter by a fortunate diver is a highlight. Their rareness may be due in part to their cryptic behavior, excellent camouflage and the fact some species live in habitats that are not readily explored
For locomotion, they crutch along the bottom on their pectoral and pelvic fins. They rarely swim. When hunting, they remain motionless waiting for unsuspecting prey to approach within striking distance. Lunging forward, a weedy scorpionfish sucks in its victim. For added camouflage, the scorpionfish may sway back and forth mimicking debris or seaweed moved by the ocean currents.
The scorpionfish has a highly compressed body, can reach a maximum length of 23 cm, and can vary considerably in color as well as appendages depending on its environment. Specimens found in rocky, algae rich waters are covered in weed-like appendages, whereas specimens found in deeper soft-bottomed waters with soft corals and sponges have fewer appendages. Color can range vastly from dark red and purple to yellow and lavender. The variations differ so vastly that the specimens are often misidentified.
Like most Scorpaenidae, weedy scorpionfish are mostly nocturnal ambush hunters, using their camouflageto prey on unsuspecting fish and invertebrates. They rarely swim, but rather move along the bottom propelling themselves with their fins.
There are 3 members of this genus that are commonly seen by divers in South East Asia -Rhinopias aphanes, Rhinopias eschmeyeri and Rhinopias frondosa.
Lacy Scorpionfish / Rhinopias aphanes – is endemic to the Coral Sea area of Papua New Guinea, Great Barrier Reef, Solomon Islands and New Caledonia. They differ in habitat preference from the other two species as a result of the predominant environmental conditions in the Coral Sea. They are found on rich coral bommies and walls sitting out in the open, mimicking crinoids. The patterning on the body is made up of a network of line rather than spots and colouration is quite variable as with the other species.
- many tentacles on the underside of the lower jaw
- 2-4 tentacles below the eyes
- distinct tentacles on the lateral surface
- long tentacles
- markings on the body
- deep incisions between the dorsal spines
Paddle Flap Scorpionfish / Rhinopias eschmeyeri – This is the easiest species to identify. The body is generally only one colour with very few other markings. There are also hardly any filaments on the skin and the dorsal fins are completely lacking in skin filaments or indentations adjacent to the spines, hence the common name. I have seen red, pink and purple individuals. The range is throughout much of the tropical Indo West Pacific. It prefers ‘muck’ dive sites with black sand and algal beds.
- two tentacles on the underside of the lower jaw
- no tentacles below the eyes
- no distinct tentacles on the lateral surface
- short tentacles
- no distinct pigmentation or markings
- the first dorsal fin (the one on the back) is sail-like with no or only small incisions between the dorsal spines
Weedy Scorpionfish / Rhinopias frondosa – The weedy scorpionfish, commonly called popeyed scorpionfish. Basically this is the only species of filamentous Rhinopias that is found in Indonesia and Philippines but is often incorrectly identified as the Lacy Scorpionfish / Rhinopias aphanes species. It shares the same habitat as Rhinopias eschmeyeri and the two often co-occur. The weedy scorpionfish has a highly compressed body, can reach a maximum length of 23 cm. This species is found in white, yellow, purple, red and all manner of other colours. It has circles rather than lines covering the body. It is also found throughout the Indo West Pacific as far west as Mozambique. It can therefore occur in the Coral Sea but habitat type and body patterning easily distinguish it from Lacy Scorpionfish / Rhinopias aphanes.
The weedy is also difficult to tell apart from the lacy Rhinopias. The easiest way to tell them apart are the markings.
- Weedy: circular and oblong dark-margined or pale spots, rings and blotches
- Lacy: elongate black-margined markings each with a central region of yellow, green or brown
There are in fact a total of six species of Rhinopias but the other three are very restricted in range and found only in Japan (Rhinopias argoliba), Hawaii (Rhinopias xenops) and Easter Island also known as Rapa Nui (Rhinopias cea). Actually geography plays a much greater part in the identification of Rhinopias than people realize.
Where to dive and see the Rhinopias: The best destinations to see weedy and paddleflap rhinopias are Ambon, Alor, Lembeh and Bali in Indonesia. Less frequently they can be encountered in Anilao in the Philippines. The best place to see lacy rhinopias is Milne Bay in Papua New Guinea.
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