Weedy Sea Dragons

The Weedy Sea Dragon - or unfortunately named Common Sea Dragon - Phyllopteryx taeniolatus, is a fish related to seahorses in the family Syngnathidae.  This family also includes pipefish and the Weedy’s showy cousins, the Leafy Sea Dragons.

Description

Weedy Sea Dragons can reach lengths of around 45 cm, and have long bodies and tube-like snouts. Long leaf-shaped flaps of skin protrude from stalk-like bony projections at intervals along the top and bottom of the body. They have an amazing colour pattern, with an orange-red background colour, bright blue stripes and many white spots and yellow markings.

Weedy Sea Dragon by night, photo: Tim Nicol

As well as looking like seaweed, Weedy Sea Dragons move in a similar swaying motion as seaweed would in the water current. This enables them to camouflage themselves, deceiving unsuspecting prey. Tiny fins are found on either side of their head for balance and a long shimmering dorsal fin along their back propels their body through the water. They are, however, not strong swimmers and are often found washed ashore after storms.

Distribution

Weedy Sea Dragons are only found in shallow coastal water (approximately 3-50 meters deep) in southern Australian.  They are found from Port Stephens in New South Wales down to the southern coast of Australia including Tasmania, and up to Geraldton in Western Australia.  They inhabit kelp forests, reef edges, seagrass meadows, seaweed beds and are often found near pier pylons.

Diet

Weedy Sea Dragons lack teeth and use the powerful suction generated by their long, thin, tubular snout to draw water and prey into their mouths. Special muscles in the snout can widen it to capture different sizes of food, including plankton, larval fish, sea lice and small shrimp-like crustaceans called mysids. 

Reproduction

Like all sygnathids, it is the males who carry and care for their young.  Weedy Sea Dragons are independent and solitary, coming together only during mating season. Breeding occurs annually, usually in late spring. Prior to mating, the male Weedy Sea Dragon prepares the area of his tail where he will keep the eggs. His tail becomes slightly swollen, soft and spongy. The female lays up to 300 eggs on this area and it is during the transfer of the eggs from the female to the male that they are fertilized. The male Weedy Sea Dragon carries these eggs for two months after which hatching occurs over a period of 6 days.

Only a small percent (around 5%) of the eggs survive to form young sea dragons, which become completely independent soon after birth. The young feed on the remaining yolk sac and then graduate to consuming zooplankton.  Baby Weedy Sea Dragons hatch as miniature versions of the adults, just 2.5 cm long, which makes them vulnerable to predators like fish, crustaceans and sea anemones (only about 1 in 20 survive to become adults). Within 3 weeks they more than double in size to 7 cm. After around two years they will reach their maximum size. It is believed they can live for up to 10 years in the wild.

Status

Although there are few, if any, predators of adult Weedy Sea Dragons they are vulnerable to many threats, both natural and human induced. After sea storms they are often washed ashore, unable to cope with changes in water pressure or depth. Pollution and industrial runoff impacts their food availability and the loss of habitat is a major threat to its survival. Moreover, it is targeted by collectors for the aquarium trade although it is very difficult to maintain in an aquarium because of its strict dietary requirements.   

Weedy Sea Dragons are listed as 'near threatened' on the IUCN Red List because of illegal collections and are protected is all States they call home – except Western Australia.