Bentstick Pipefish, Trachyrhamphus bicoarctatus (Bleeker 1857)

Widespread in the tropical Indo-west Pacific. Bentstick Pipefish are known in Australian waters from the central coast of Western Australia, northwards throughout the waters of the Northern Territory and Queensland to central New South Wales. They live in sheltered coastal lagoon and reef areas on sandy and rubble habitats amongst seagrasses and macroalgae at 1– 30 m.

Meristic features: D 24-32; P 15-19 (usually 16-18); trunk rings 21-24; tail rings 55-63; subdorsal rings 4.0-2.0 + 1.75-3.5 = 4.75-6.5.

Head and Body: Body slender, elongate, encased in a series of bony rings; superior trunk and tail ridges discontinuous; trunk ridge arched dorsally on subdorsal rings; inferior trunk ridge ends on anal ring; lateral trunk ridge confluent with inferior tail ridge; snout length 1.5-2.0 in head length; snout depth 5.2-11.1 in snout length; snout straight in small fish (<150 mm SL), curved in subadults-adults; median dorsal snout ridge a little elevated above nares, entire to irregularly denticulate; opercle usually with a low, complete or incomplete ridge angled upward toward gill opening; principle body ridges low, essentially entire; scutella not keeled.

Fins: Dorsal fin originates on trunk, the fin base somewhat elevated; caudal fin tiny, elongate and rounded in juveniles, but often lost, regenerated, vestigial or represented by stubby rudimentary rays in subadults-adults; pectoral fin base with no distinct ridges.

To 40 cm.

Colour variable from whitish, green, grey or brown to black, and either uniform, or spotted and mottled, or with light bands, often matching the substrate.

Carnivore - preys on small crustaceans such as amphipods, caprellids and mysids which are sucked in through the long, tubular snout. Bentstick Pipefish raise their head and face into the water column to capture the passing zooplankton.

Reproduction: Females lay eggs that are drooded by the male in a semi-enclosed pouch under the anterior portion of the tail; pouch plates a little enlarged; pouch folds present; males likely to be brooding at 26 cm.

Larvae: Newly hatched individuals and pelagic young have 13 pairs of elongate dermal appendages on the back of the body that may aid buoyancy. Individuals up to 10 cm TL have been found amongst plankton.

Sometimes collected for sale in the aquarium industry or sold for use as medicine or curios.

Australian Government Legislation: Marine listed under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act).

State Government Legislation: Listed as Protected species under the New South Wales Fisheries Management Act.

Found singly or in pairs. In strong currents Bentstick Pipefish use their tails to grip the substrate which may lead to abrasion or loss of tail in adults.

The similar Trachyrhamphus longirostris generally has a straight body posture rather than the bent-neck posture of T. bicoarctatus.

Trachyrhamphus is from the Greek trachys meaning rough and rhamphos meaning bill.

Syngnathus bicoarctatus Bleeker 1857, Act. Soc. Sci. Indo-Neerl. 2: 99, Ambon, Indonesia (as Amboina).

Dianne J. Bray