According to Dr Ng, the Smallhead dragonet (Callionymus erythraeus) has been mistaken for Callionymus enneactis and Callionymus schaapii when seen at Changi Beach. Indeed, I made that mistake! So it's good to finally get this corrected! He also explains that it is not certain whether this fish is an introduced alien species. He says:
Previously known only from the Persian Gulf and the Gulf of Mannar (Fricke, 2002), it is recorded from Singapore waters for the first time here. As it has not been previously recorded from this part of the world, its presence in Singapore might possibly have been from introductions via the discharge of ballast water from commercial shipping (R. Fricke, pers. comm.). As the first specimen from Singapore was obtained in 1968, this may represent an early introduction that has remained undetected. However, it is also possible that the species is native to the region, but had been overlooked as the marine fish fauna of Singapore has not been sampled adequately. This is also supported by the fact that other callionymid species (e.g., Callionymus hindsii) are known to have a similar distribution. Therefore, without evidence from more extensive surveys throughout the region, it is difficult to ascertain if this species is, indeed, an alien in Singapore.
So yes, we need to study our shores more thoroughly!
Dragonets (Family Callionymidae) are fascinating bottom-dwelling fishes. When resting, most are buried in the sand. They pick off small animals from the surface with their cute pointed, downward facing mouth. Instead of scales, the body is covered in a tough skin and usually coated with mucous that often has a bad taste and smell. So they are sometimes also called stinkfishes. The gill opening is just a small hole, usually on the upper side of the head, with a strong spine near it. Most of these fishes are well camouflaged but some species can be quite colourful. In many species the males and females appear different. The males usually have an enlarged first dorsal fin that is colourful with intricate patterns.
Another commonly encountered dragonet on our shores is the Mosaic dragonet (Callionymus enneactis). It's tiny and very well camouflaged!
Fingered dragonet (Dactylopus dactylopus) which not seen often. Here is a videoclip of this amazing fish, shared by Kok Sheng.
Pretty dragonet fish at Cyrene Reef from Loh Kok Sheng on Vimeo.
Read more about our dragonets on Ng, H. H., 2012. The dragonets of Singapore (Actinopterygii: Perciformes: Callionymidae). Nature in Singapore, 5: 27–38. [PDF, 1.55 MB] on the Nature in Singapore website of the Raffles Museum of Biodiversity Research.