Weird fish of the week: Sea moth


This week's scuttling sea bed oddity is the Sea moth or Little dragon fish, Eurypegasus draconis.

The more weird fish we look at, the more normal it seems for fish to walk around the seabed rather than swim, and the Sea moth is another well practiced perambulator at the expense of swimming ability – they've even dispensed with their swimbladder to make trundling around the sea bed easier. Check out the video below:

This walking behaviour is made possible by their specially adapted pelvic fins which are little more than the fin spine and the first ray joined to form an odd tentacle like structure used for this purpose.

Coming from the order Gasterosteiformes which is also home to the sticklebacks, they share similar armoured body characteristics to their prickly cousins, but taken to far greater extremes. Growing to around 12cm/4.5in, the Sea moth's depressed, flattened body is covered in hard bony plates, giving them a lumpy protective carapace which is so complete the fish sheds the whole structure in one piece when growing, rather like an aquatic insect.

This seemingly odd behaviour also helps rid them of algae, parasites and other hangers-on.

They have greatly enlarged pectoral fins which they can fan out from their sides, flashing bright edges in the process probably as a way of scaring off would be predators. When forced to swim these fins can be tucked back making these cumbersome creatures more streamlined. These wing like fins give rise to their common name.

They have a long, pointed rostrum, (nose) and underslung mouth with which they forage around the substrate in search of their prey, which consists largely of tiny crustaceans and worms found just under the surface.

Observations of these fish in the wild reports them often in pairs and they are thought to be monogamous. They show no parental care as they are broadcast spawners with breeding pairs leaving their sea floor sanctuary at dusk, swimming upwards into the water column where they release and fertilise eggs.

They are found at depths between 3-90m in the tropical Indo-Pacific but little is known of their lives.

Unfortunately their dried bodies,(and those of the four other Sea moth species) are increasingly being used in the Chinese medicine trade, often in place of the seahorses to which they are distantly related.

This has led to the IUCN red list of threatened species listing the fish as "data deficient" in a call for more research and scrutiny of Sea moths, and the trading of them. They are occasionally found for sale in the aquarium trade.

Why not check out some of our other Weird fish of the week features? 

Mega mouth shark

Flying gurnard

Pinecone fish

Sea lamprey

Slender snipe eel

Tripod fish


Ocean sunfish

Two-headed arowana


Giant oarfish

Kroyer's deep sea anglerfish

Halimeda ghost pipefish