Revealed: Bali Wobbegong Shark
By Annabel Thomas
For The Bali Times
SEMINYAK ~ Andrea and Antonella Ferrari â€“ marine-life book authors, associate editors of Fins Magazine and www.ReefWonders.net – were lucky enough during a recent trip with AquaMarine Diving – Bali to encounter and photograph the elusive and as-yet-undescribed Bali Wobbegong, a local subspecies of the Ornate wobbegong shark.
Much darker than the normal Ornate wobbegong, this beautiful shark has also been found by famed marine biologist Robert Myers in the Komodo area. The Ferraris photographed this one under an overhang at 15 meters in Nusa Penidaâ€™s Crystal Bay at a chilling 19 degrees Celsius, confirming that it uniquely seems to prefer cold upwellings.
There are seven described species plus several undescribed forms within the Wobbegong (Orectolobidae) family.
Wobbegongs are instantly identifiable due to the distinctively flattened body and broad head with large, nearly terminal mouth positioned in front of the eyes, long barbels (whiskery protrusions used for sensing and touching near the nostrils and mouth) and skin flaps around the mouth and nasal grooves (the number varies between the species). Their name comes from the aborigine for â€œbeard.â€
Ovoviviparous, they hatch from eggs but develop inside the motherâ€™s body â€“ however there is no placenta to nourish the babies; hence the alternative name aplacental viviparity. It seems that wobbegongs have either a two- or three-year reproductive cycle, including a gestation time of one year.
Wobbegongs are cryptic (have coloring that conceals them), benthic (bottom-dwelling) sharks that occur on the continental shelves of warm-temperate to tropical waters of the western Pacific. They inhabit rocky and coral reefs or sandy bottoms, from the intertidal area to depths of around 200 meters.
They ambush their prey using a strategy called passive luring: they attract potential prey because they resemble a food source. They donâ€™t change their behavior or adopt a specific posture in order to attract prey; they just stay still. Their entire bodies are covered with spots, dots, bands and reticulations which help them to disappear among coral, coralline algae and larger macroalgaes. The skin flaps around the mouth help to break up the sharkâ€™s outline, further increasing the resemblance to reef substrate. Both the skin and skin flaps of wobbegongs resemble certain algaes and encrusting invertebrates. Many bony fishes and crustaceans feed on such marine plants and animals and so mistake the inactive wobbegong for food-ridden substrate. Protective resemblance is another way that Wobbegongs ambush potential prey: where space is limited, a motionless wobbegong (because it resembles the substrate) may attract fishes or invertebrates looking for shelter.
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Ornate Wobbegong (Orectolobus ornatus).
Alternate Common Names: Banded wobbegong, Gulf wobbegong.
My references all say Ornate wobbegongs are born at 20 centimeters; however the maximum size is quoted at between 1.7 and 2.9 meters, with males maturing 1.7 meters.
Distribution: Australia, Papua New Guinea and Indonesia.
Habitat: Ornate wobbegongs can sometimes be seen in such shallow water that the dorsal fins break the water’s surface; but itâ€™s not unusual to sight them at 30 meters. On coral reefs, they are found on the reef flat, in tidal pools (especially juveniles), in reef channels and on the fore reef. On rocky reefs, younger specimens often hide in crevices and among boulders, with adults often seen lying out in the open on boulders or on flat table corals.
Feeding: Ornate wobbegongs eat cephalopods (octopus, squid), crustaceans, and other (same size or smaller) sharks as well as bony fish. It is not unusual to find a school of Bullseye fishes oblivious to the presence of an Ornate wobbegong below them. The wobbegong moves at such speed that other individuals donâ€™t realize members of the school have been grabbed. Anything else that comes within striking distance, including larger fishes looking for a meal within the Bullseye school, can also become a meal.
Behavior: They occur singly or in groups. Unless disturbed, Ornate wobbegongs are rarely active during the day. They often take up daytime residence in one place for years, only leaving to search for food at night.
Distinguishing Characteristics: The Ornate wobbegong has five or six skin flaps located under and in front of the eyes. The body has black-bordered saddles and spots; the lighter areas in between have paler centered spots. The patterns themselves vary greatly between individuals.
Interaction with Divers: It is said that the wobbegongs bite more divers than any other shark â€“ because theyâ€™re found in such shallow waters, they are easily stood on. In deeper water, well â€“ if you follow the â€œDonâ€™t Touchâ€ rule, youâ€™d be unlikely to rest/lean on one.
The writer is director of AquaMarine Diving â€“ Bali.Filed under: The Island