nervous shark nervous shark species requiem shark family named behavior regard humans common shallow coastal waters northern australia small brownish grayish shark typically measuring long species short blunt snout oval eyes relatively large second dorsal fin leading margins fins finely edged black lower caudal fin lobe black tipped small bony fishes main prey nervous shark crustaceans snakes eaten viviparous developing embryos connection details life history vary depending latitude example timing breeding season length gestation period females produce litters young annually harmless nervous shark caught incidentally coastal fisheries line fisheries lacks sufficient data assess conservation status species australian waters population healthy listed concern taxonomy phylogeny australian originally described nervous shark subspecies junior synonym shark issue scientific journal australian zoologist gave meaning cautious latin demeanor confronted people later authors recognized shark distinct species placed genus type specimen consists preserved skin teeth long female caught western australia based morphology suggested nervous shark closely related reef shark tentatively grouped species shark copper shark silky shark night shark close relationship nervous reef sharks upheld phylogenetic study based study based nuclear mitochondrial genes description nervous shark stout shaped body short broadly rounded snout anterior margin extended slender shaped lobe moderately large eyes horizontally oval shape equipped membranes mouth lacks conspicuous furrows corners contains upper lower tooth rows upper teeth narrow angled edges lower teeth slender upright shape finer pairs gill slits medium length pectoral fins moderately long narrow pointed dorsal fin originates free rear tips pectoral fins large shaped pointed apex second dorsal fin positioned opposite anal fin relatively large high ridge dorsal fins crescent shaped notch present caudal upper caudal fin origin caudal fin strong lower lobe longer upper lobe ventral notch near tip dermal denticles overlapping bear horizontal ridges larger individuals leading marginal teeth species bronze gray white white stripe flank thin black line runs leading margins dorsal fins pectoral fins upper caudal fin lobe caudal fin trailing margin lower caudal fin lobe pectoral fins tipped black nervous shark typically reaches length grow long females attain larger sizes males distribution habitat nervous shark found continental shelves northern australia west east common sharks species generally inhabits shallow waters depth particularly favor lined areas sandy muddy bottoms avoids areas dense cover biology ecology diet nervous shark consists mainly small fishes including crustaceans including crabs predominantly cephalopods constitute secondary food sources shark known occasionally prey snakes known parasite nervous shark like requiem sharks nervous shark viviparous embryos exhaust initial supply yolk mother connection formed depleted yolk sac adult females single functional right functional male bites sides female prelude mating mating female stores sperm approximately weeks prior mating occurs january march occurs october november following gestation period months mating occurs late october early november occurs time following year following gestation period months slower development likely reflects cooler temperatures females produce litters annual cycle cycle litter size ranges size female relatively large measuring long shallow nursery areas juvenile growth rate high shark males females mature sexually respectively respectively age maturity years males years females maximum lifespan years males years females human interactions shy difficult approach nervous shark harmless humans occasionally marketed food species susceptible caught incidentally coastal fishery operating northern australia caught line gear australian nervous shark population appear threatened fishing activities assessed concern data impact fishing available range iucn listed overall
Nervous shark