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We regularly post short Marine Wildlife Videos an Photographs with a short explanation regarding the subject and the technique used to capture the image.

All videos are made by Olivier Van den Broeck using Light & Motion video lights

and all photographs are by Greet Meulepas unless stated otherwise.

97. A difficult to identify yellow Weedy Scorpionfish (Rhinopias frondosa)



Subject: Considered the "Holy Grail" of underwater photography and videography, the Rhinopias is a seldom-seen Scorpionfish. The moment the light beams of our video lamps illuminated the odd fish, we knew we had struck gold, again! Only two weeks before this discovery, we did spot another Rhinopias in the same area (see our previous vlog post number 96).

Identification of this particular individual is difficult because at first sight it bears characteristics of both the Paddleflap Scorpionfish (Rhinopias eschmeyeri) and the Weedy Scorpionfish (Rhinopias frondosa). However, let's take a closer look at this individual and compare them with some of the characteristics that separate both species.

Both species live in the same regions, inhabiting the tropical waters of the Indian Ocean and the west Pacific Ocean and are found from South Africa to Australia, north to Japan, and to the Caroline Islands in the east. Additionally, both species grow to a maximum size of 23cm/9inch, so location and size cannot be used to identify or differentiate between both species.

Habitat, however, can be used, although it is far from conclusive. R. eschmeyeri is more often found on sandy bottoms, whereas R. frondosa tends to prefer venturing amongst rubble and in weedy areas.

Regarding colour and markings, R. eschmeyeri exhibits a uniform body colour with no distinct pigmentation or markings, while R. frondosa usually has round and oblong pale spots and blotches (these can be less distinguishable in some individuals). Although both species come in different colours, such as yellow, green, brown, pink, and red, R. eschmeyeri is more often spotted in different pink hues.

Regarding anatomical appearances, the first dorsal fin of R. eschmeyeri is virtually sail-like in most individuals, in comparison with that of R. frondosa, which is severely cut, giving the dorsal fin a jagged appearance. The tentacles above their eyes (supraorbital tentacles) of R. eschmeyeri are unbranched and flattened (leaf-like), whereas those of R. frondosa are branching but the branching is not necessarily pronounced. R. eschmeyeri also lacks distinct tentacles and appendages underneath its eyes and on the lateral surface of its body, in comparison with R. frondosa, who has 2 to 4 tentacles below the eyes. However, the number of appendages of R. Frondosa’s body varies with their habitat. Species living in algae-rich environments have more weed-like appendages compared to the ones living around soft coral and sponges, which have fewer appendages. R. eschmeyeri has only two tentacles on the underside of its lower jaw, and R. frondosa has many, however some are small.

Some ichthyologists do not recognise both of these Rhinopias species as different species but rather as one and the same. However, if we assume that these are two distinctive species occurring in Mauritian waters, the other four species in this genus, namely the Lacey Scorpionfish (Rhinopias aphanes), the Easter Island Scorpionfish (Rhinopias cea), the Japanese Scorpionfish (Rhinopias argoliba), and the Strange-eyed Scorpionfish (Rhinopias xenops), do not inhabit the waters of the Mascareignes (La Réunion, Mauritius, and Rodrigues). Therefore, based upon all characteristics in this individual (round and oblong pale spots and blotches, branched tentacles above their eyes, a jagged dorsal fin and more than two tentacles on the underside of its lower jaw) we can carefully conclude that the specimen in this underwater videoclip is just as the one we previously spotted in the same area; a Weedy Scorpionfish (Rhinopias frondosa).


Technique: The importance of good video lights is illustrated here. Without our illumination this Weedy Scorpionfish was as greyish green as the Halimeda weeds it was hiding in. Ou underwater video lights revealed the real colours of our subject, colours that were absorbed by the 25m/82ft high water column that separated our subject from the sunlight.


For a more in-depth description about the Weedy Scorpionfish please go to our vlog post 124 or click on this link:

https://www.beyondscuba.com/post/a-weedy-scorpionfish-rhinopias-frondosa-yawns

and vlog post 96 or click on this link:

https://www.beyondscuba.com/post/weedy-scorpionfish-rhinopias-frondosa


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