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Rhinopias Scorpionfish

What can you tell me about the Rhinopias scorpionfish?

By Scott W. Michael

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Q. I recently saw an unusual, very expensive fish that was new to me. I considered buying it, but because I knew nothing about it, and it appeared to have excess slime, I decided to first find more information on it. Looking at photos in my Burgess Atlas I decided it is either Rhinopias aphanes or possibly R. frondosa. There is no aquarium care information in any of my books. A store employee told me that it ate feeder fish and was poisonous. What can you tell me about this fish? By the time you get this it will probably be gone, but I figured in case I see another one I would like to know if I should buy it or not.

A. For your sake I hope that fish has not been sold! In my opinion the Rhinopias species are some of the most fascinating fishes inhabiting the world's oceans, and I would jump at the opportunity to purchase another one.

I've had only two myself. One was a beautiful brick red Rhinopias eschmeyeri that Julian Sprung located at a fish wholesaler in Miami and was kind enough to send me, and the other was a Rhinopias frondosa that was sent to me by a purveyor of rare and unusual marines, Dennis Reynolds of Aqua Marines.

These fish are available in the marine aquarium trade very infrequently. In fact, I would be surprised if you ever saw another one in a fish store again. Should it not be too late to buy the fish you saw, or if anyone else out there owns or ever has the opportunity to purchase one of these exquisite fishes, I will answer your question and give you details on some of the other species in the genus.

The Rhinopias species belong to the scorpionfish family, which is known scientifically as the Scorpaenidae. The genus contains only five species, and none are considered to be common. However, their apparent 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.

The species that comprise the genus are: Merlet's scorpionfish (Rhinopias aphanes), the Japanese scorpionfish (Rhinopias argoliba), Eschmeyer's scorpionfish (Rhinopias eschmeyeri), the weedy scorpionfish (Rhinopias frondosa) and the strange-eyed scorpionfish (Rhinopias xenops). All of the Rhinopias have deep, laterally compressed bodies and eyes set high on top of their heads, and some species have dermal appendages above their eyes, on the jaws and on the body surface.

Most of the species are known to shed their cuticle, or the outer epidermal layer — hence the excessive slime you saw hanging from the specimen you observed at the stores. This is a normal process that helps rid the animals body of algae, parasites or encrusting organisms. In some individuals, shedding can occur quite often. For example, in one specimen of R. eschmeyeri it was reported to occur every 12.6 days.

These fish rarely swim, but move about by crutching along the bottom on their pectoral and pelvic fins. When hunting they remain motionless and wait for their prey to approach within striking distance, or they slowly stalk their quarry. When a specimen is very hungry and if used to food presentation in the aquarium, it may "hop" rapidly toward a prey item rather than approaching it slowly. When it gets close enough to its prey the Rhinopias will lunge forward and suck in its victim. Although the mouth does not look very capacious, they can ingest relatively large prey items. Rhinopias will also rock forward and backward in order to mimic a piece of debris sitting on the bottom.

You mentioned you were not sure whether the species you saw was R. frondosa or R. aphanes. These species have different color patterns. R. aphanes has dark reticulations on its body, head and fins, whereas R. frondosa has round and oblong pale spots and blotches.

The weedy scorpionfish is usually considered the rarer of the two. It is a wide-ranging species that occurs from East Africa to the Caroline Islands, north to Japan and south to Mauritius. This scorpaenid attains a maximum length of 9 inches. The weedy scorpionfish has been reported at depths from 10 to 300 feet on bottoms consisting of macroalgae and rocks. I kept my specimen in a small tank full of live rock, where it adapted quickly to its new home.

Merlet's scorpionfish has been reported from north east Australia, New Guinea, New Caledonia and southern Japan. It is found on coral reefs and rocky substrates at depths from 15 to 100 feet, and often associates with crinoids, which it is thought to mimic. It apparently is quite site specific, remaining in the same area, or even spot, for long periods of time (weeks or even months). If you want to see one of these fish in their natural habitat you should go diving in Milne Bay, Papua New Guinea. Rob Vanderloos, the owner of the live-aboard dive boat the Chertan, is a great Rhinopias hunter and will assist you in locating a specimen to observe and photograph.

Eschmeyer's scorpionfish has been reported from Mauritius to Sri Lanka, but the specimen that was sent to me by Julian Sprung was apparently from the Philippines. This species differs from other genus members in having a more uniform body color and unbranched, flattened skin appendages. It comes in variety of bright colors, including light blue, lilac, yellow, orange or brick red, and attains a maximum length of 7½ inches. Rhinopias eschmeyeri is reported to occur on open sand bottoms at depths from 10 to 130 feet. I kept mine in a tank with crushed coral substrate and a few medium-sized pieces of bleached coral, and it spent most of its time sitting in exposed portions of the tank.

The Japanese scorpionfish, as the name suggests, has only been reported from Japanese waters and it is unlikely that it will ever make it to North American fish stores. This species has no dermal appendages on its lower jaw and few on its body. The closely related strange-eyed scorpionfish has been reported from the Hawaiian islands, where it is typically found in water between 200 and 330 feet deep, and from Japan. I have never seen nor heard of either of these species in the North American aquarium trade.

All the Rhinopias readily adapt to captivity, and because of they are relatively inactive they can be kept in smaller aquariums. For example, I housed one of my Rhinopias in a 10-gallon tank and the other in a 20-gallon. Because these fish tend to spend most of their time out in the open, they would be great additions to the reef aquarium that did not contain small fish or ornamental shrimp.

Although live food (e.g., ghost shrimp, mollies, guppies) may be necessary to initiate feeding, these fish can be trained to take pieces of shrimp, squid and fish off of a feeding stick. They can be housed with other fish, but I would avoid keeping them with species that eat encrusting invertebrates, because they mistake the Rhinopias as a rock covered with food! Although on some occasions these fish may not harm your Rhinopias, in my mind it is not worth the risk.

You should also be careful when putting them in tanks with other predatory fish. Although the deep body and venomous spines of these fish may dissuade most predators, smaller specimens may be eaten by frogfishes, other scorpionfishes or large groupers. My Eschmeyer's scorpionfish met a tragic end when its head was engulfed by a smaller striated frogfish (Antennarius striatus). I had placed several feeder fish in the tank and was watching these two fish stalk them. The Rhinopias was moving around a piece of coral when the frogfish decided to try and eat it! I quickly grabbed the frogfish by the tail and it released the Rhinopias, but the eye of the scorpionfish was damaged, became infected and it died several days later.

Another problem I had with one of the Rhinopias I kept was that during the shipping process it had abraded the tip of the lower jaw by swimming up and down against the bag. This wound gradually healed, but for a while it was raw and bloody, and I was concerned it might become infected.

I hope you're not too late to purchase a Rhinopias. If you are and want to see more of these awesome fish, I would recommend going diving in New Guinea or visiting the Waikiki Aquarium. They often have specimens of Rhinopias xenops on display.

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