text: australian swellshark not to be confused with the draughtsboard shark , cephaloscyllium isabellum , of new zealand . the australian swellshark or shark ( cephaloscyllium laticeps ) is a species of catshark , and part of the family scyliorhinidae , endemic to southern australia . this bottom - dwelling species can be found on the continental shelf down to a depth of 220 m ( 720 ft ) . usually measuring 1 m ( 3 ft ) long , it is a stout - bodied , broad - headed shark with a short tail and a first dorsal fin much larger than the second . it can be identified by its variegated dorsal coloration of brown or gray patches and numerous spots . australian swellsharks are sedentary and mainly nocturnal , with most individuals remaining within the same local area throughout the year . it feeds on small crustaceans , cephalopods , and fishes . when threatened , it responds by rapidly taking in water or air to inflate its body , hence the name " swellshark " . this shark is oviparous and females lay pairs of distinctively ridged egg capsules at 20 – 30 day intervals . the eggs hatch after 11 – 12 months . harmless and of little commercial interest , many australian swellsharks are caught incidentally in gillnets and bottom trawls but usually survive to be released because of their extreme hardiness . as a result , the international union for conservation of nature ( iucn ) has assessed this species as of least concern . taxonomy the first scientific description of the australian swellshark , as scyllium laticeps , was published in 1853 by french zoologist auguste duméril , in the scientific journal revue et magasin de zoologie . the type specimen was a 79 cm ( 31 in ) long male caught off tasmania . the specific epithet laticeps is derived from the latin latus , meaning " broad " , with the suffix ceps , meaning " head " . other common names for this species include ( a reference to its ability to inflate ) , isabell 's swell shark , nutcracker shark , rock shark , sleepy joe , and spotted swellshark . this species is almost identical to the draughtsboard shark ( c. isabellum ) of new zealand ; the two species differ in coloration and the form of their egg cases ( ridged in c. laticeps versus smooth in c. isabellum ) . description the australian swellshark has a stocky , rounded body that tapers significantly to the short caudal peduncle . the head comprises no more than a fifth of the total length and is broad and moderately flattened , with a very short , thick , blunt snout . the nostrils are divided into small incurrent and excurrent openings by short , triangular flaps of skin that do not reach the mouth . the mouth is extremely large , without furrows at the corners . the teeth are numerous and small with multiple cusps ; the upper teeth are exposed when the mouth is closed . the large , oval eyes are placed somewhat on the upper surface of the head , and have rudimentary nictitating membranes ( protective third eyelids ) and ridges underneath . there are two dorsal fins , the first much larger than the second . the first dorsal originates over the forward half of the pelvic fin bases , while the second is located over the anal fin . the pectoral fins are large and broad , and the anal fin is larger than the second dorsal fin . the short and broad caudal fin has an indistinct lower lobe and a prominent ventral notch near the tip of the upper lobe . the skin is thick and covered by well - calcified , arrowhead - shaped dermal denticles , which are more sparse in young sharks . the back and sides are light gray to brown , with an irregular pattern of close - set darker saddles and blotches along with many dark ( sometimes light ) spots , and a dark stripe from under the eye to the pectoral fin origins . the fins do not have sharply lighter margins . the underside is cream - colored , with some mottling on the fins and often a dark stripe running down the middle in adults . the maximum known length is 1 . 5 m ( 4 . 9 ft ) , though few exceed 1 . 0 m ( 3 . 3 ft ) . distribution and habitat the australian swellshark inhabits the continental shelf of southern australia , from the recherche archipelago off western australia to jervis bay in new south wales , including tasmania . it is commonly found on or near the bottom amongst rocky reefs or seaweed beds , from close to shore to a depth of 220 m ( 720 ft ) . biology and ecology the most abundant catshark species in the coastal waters of southern australia , the australian swellshark is a generally sluggish swimmer that is more active at night . during the day , it is often found resting singly or in groups under ledges or inside caves . tracking studies have shown that some individuals are continuously active for months at a time , while others alternate activity with periods of stationary rest lasting up to five days . most australian swellsharks present within a given region tend to remain there year - round , frequenting established feeding areas or preferred habitats . on the other hand , a minority of sharks have been recorded covering distances of up to 300 km ( 190 mi ) . this extremely hardy species can survive for more than a day out of water . one of the higher - level predators within its ecosystem , the australian swellshark feeds on crustaceans ( particularly crabs and rock lobsters ) , cephalopods ( including squid and octopus ) , and small fishes . even large - sized prey tends to be swallowed whole ; the long periods of rest exhibited by some sharks may relate to digestion . like the other members of its genus , this shark is capable of rapidly inflating its body by taking water or air into its stomach , as a defense against predators . these include larger fishes , such as the broadnose sevengill shark ( notorynchus cepedianus ) , and marine mammals . by inflating , the shark may be able to wedge itself inside crevices , make itself harder to swallow , or simply intimidate a would - be predator . marine snails are known to prey upon this shark 's eggs . the australian swellshark serves as a host to a number of parasite species , but these are poorly documented . life history the australian swellshark is oviparous . males have larger teeth than females , with which to bite and hold onto them for copulation . whether there is a specific mating season is uncertain , though in terms of sperm production males are capable of breeding year - round . females have a single functional ovary and two oviducts , ovulating a single egg into each at a time . they can store sperm for at least 15 months . females produce eggs throughout the year , laying them in pairs approximately once every 20 days from january to june , and once every 30 days the rest of the year . the second egg in a pair is deposited 12 – 24 hours after the first . the pale , flask - shaped egg capsules measure 13 cm ( 5 in ) long and 5 cm ( 2 in ) across , and bear 19 – 27 crosswise ridges . there are long , curling tendrils at the four corners , which allow the female to attach the capsule to seaweed or other bottom structures . in captivity , the embryo develops external gills at two months old , which are retained until it is five months old , at which time the internal gills take over and the first pigmentation appears . at six months , embryonic growth accelerates and the yolk sac begins to shrink , disappearing by nine to ten months of age . hatching usually occurs at eleven to twelve months ; the newly emerged young are miniature versions of the adults measuring 14 cm ( 6 in ) long . males mature sexually at a length of 71 – 87 cm ( 28 – 34 in ) , and females at 75 – 86 cm ( 30 – 34 in ) . human interactions the australian swellshark is harmless to humans and seldom utilized , though recently in parts of tasmania some have begun to be marketed as a source of " flake " . it is regarded as a nuisance by lobster fishers due to its habit of entering traps to eat the contents . every year , substantial numbers of australian swellsharks are caught as bycatch in the southeast australian shark gillnet fishery , and more in bottom trawls and on longlines . these animals are usually released , and likely suffer minimal mortality due to their resilience . since this species at present faces little risk from fisheries , the international union for conservation of nature ( iucn ) has listed it under least concern . although commercial fisheries reported drops in australian swellshark catches from 1973 to 1976 and 1998 to 2001 , these appeared to have resulted from changing fishing habits rather than actual population declines . nevertheless , as a precaution the government of tasmania has instituted a possession limit of two sharks per person or five sharks per boat per day .