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wobbegongs? Text by Mark Baker and Simon L Hartley The family Orectolobidae is found worldwide and is one of the commonest families of shark. Members of this family tend to be tropical however the cold waters of Australia's southern states supports several varieties of these colourful and intricately patterned sharks. Commonly known as wobbegongs and occasionally as carpetsharks they are demersal and are encountered around rocky foreshores, algal and coral reefs, under piers and in caves. Like other bottom dwelling sharks wobbegongs possess a spiracle which helps facilitate water movement over the gills enabling them to remain motionless on the bottom. Their cryptic colours and habits (hiding in holes and under crevices) make them difficult to spot and smaller individuals particularly often go unnoticed by divers. Wobbegongs appear sluggish during the day (except when roused by the chance of a meal) but are more active at night (Grant, 1985; Hartley personal observation). Connell (1998) has noted that large reef predators are more active at night and this would appear to explain their docile daylight habits. Attacks by wobbegongs on scuba divers and fishermen occur only if the sharks are disturbed or provoked (Goadby, 1959; Whitley, 1983; Last & Stevens, 1994). The sharks have been known to mollest spearfishers returning to shore with a catch (Hannan pers. comm.). The Two species of Wobbegong found in northern New South Wales are the banded wobbegong and the spotted wobbegong both species are endemic to Australian waters. Banded (or ornate) wobbegong (Orectolobus ornatus): The distinguishing features of this species include; a groove connecting the mouth and nostrils, five to six dermal lobes anterior to the eyes, branched simple barbels on the nose and large spiracles. Two large dorsal fins of equal size are set well back on the body and there is a reduced ventral lobe on the caudal fin (Last & Stevens, 1994; Grant, 1985; Allen & Swainston, 1988). Colouration is yellowish brown to greyish brown with corrugated saddles outlined in black over the back, elsewhere bluish white patches. Two white spots feature behind the spiracles (Last & Stevens, 1994). O. ornartus grow to about 290cm reaching maturity at 175cm. Last & Stevens (1994) have observed a mature male in Queensland at 63cm (also refer to the copulation record presented on this site). Females give birth to live young (viviparous) about 20cm in length (Grant, 1985; Allen & Swainston 1994). The range is extensive stretching from the Houtman Abrolhos in Western Australia south to Flinders Island and north along the East Coast to Papua New Guinea. The species has been recorded from close inshore to depths of one hundred meters (Last & Stevens, 1994). Spotted Wobbegong (Orectolobus maculatus): This species is similar in appearance to O. ornatus but can be distinguished by the presence of six to ten branched dermal lobes around the head anterior to the eyes (not on the chin), nasal barbels with one or two branches at the base. Colour varies from pale yellow to greenish brown, with four distinctive darker saddles highlighted in white by white spots in ring formations and a brown triangle between the eyes. Elsewhere the colouration is blotchy providing excellent camouflage in reef environments (Last & Stevens, 1994; Grant, 1985; Allen & Swainston, 1988). O. maculatus is the larger and most common species of wobbegong within its range growing up to 300cm although one specimen netted at Jibbon New South Wales measured 318cm. Litters can number up to 37 and are born viviparously at 20cm. This species reportedly reaches maturity at a smaller size than O. ornatus (Chidlow pers. comm.), males mature at 60cm or 3 years old. O. maculatus are distributed from Fremantle Western Australia across southern Australia and north to Moreton Island Queensland. They range from inshore reefs to depths of 110m (Last & Stevens, 1994; Whitley, 1983; Grant, 1985). Both species prey on crabs, lobsters, octopus and fish and represent one group of top end predators. Some canabalism or predation by larger individuals of either species may also occur. Predation of pups at birth by yellowtail kingfish has been observed (Murrel Pers. Comm.). Mortality rates of young in the wild is not know nor is the significance of inter or intra species canabalism. It is unclear from the literature whether wobbegongs are keystone predators with a positive relationship with prey species richness, however they do preform an important ecological role by reducing sick or weak specimens thus keeping a check on prey populations. Despite being relatively common the biology of Orectolbus sp. has not been well studied (Eggleston et al., 1997; Last & Stevens, 1994; Whitley, 1983; Grant, 1985). References cited:
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