shark shark species requiem shark family occurring tropical warm temperate continental seas worldwide apex predator shark found coast outer continental shelf adjacent waters recorded depth populations migrate poles summer equator winter traveling hundreds thousands kilometers largest members genus shark reaches length weight slender streamlined body identified short round snout long shaped pectoral fins ridge second dorsal fins marked fins adult sharks broad varied diet consisting bony fishes sharks rays cephalopods occasionally crustaceans sea stars sea turtles marine mammals garbage species viviparous year reproductive cycle females bear litters young gestation period months year rest pregnant females capable storing sperm long periods encounters suitable mates far nomadic lifestyle low overall abundance sharks slowest growing latest sharks reaching adulthood years age slow reproductive rate shark vulnerable human caused population species highly valued commercial fisheries fins shark fin soup meat skin liver oil recreational assessed species worldwide vulnerable eastern united_states populations dropped 1970s levels shark regarded potentially dangerous humans large size attacks taxonomy french naturalist published scientific description shark issue placed genus gave specific epithet latin dark dim referring coloration subsequent authors recognized species belonging genus designate type specimen presumably working shark caught north american waters early sources gave scientific shark later originated account jordan gilbert referred set jaws came shark type specimen designated later discovered copper shark considered synonym common names species include bay shark black brown common gray shark brown shark brown shark common ground shark river slender shark phylogeny evolution teeth belonging shark fairly represented fossil record assigning teeth species problematic shark teeth dating recovered formations formation egypt florida possibly northern venezuela teeth dating late early abundant north_carolina chesapeake_bay region teeth differ slightly modern shark belonging oceanic shark shark teeth recovered vicinity north_carolina preserved dating late mud dating years ago published phylogenetic analysis based morphology placed shark shark center group group consisted large triangular toothed sharks ridge dorsal fins included shark caribbean reef shark shark oceanic shark interpretation largely upheld study sequence study able resolve ridge backed branch finding shark shark oceanic shark blue shark comprise derived clade distribution habitat range shark extends worldwide albeit tropical warm temperate waters western atlantic_ocean found massachusetts southern brazil including bahamas cuba reported western central mediterranean_sea cape_verde sierra possibly including portugal spain morocco indian_ocean found south_africa madagascar sporadic records red_sea pacific_ocean occurs japan mainland china taiwan vietnam australia west southern california possibly northern chile east records sharks northeastern eastern central atlantic tropical islands fact sharks mitochondrial dna evidence suggest indonesian australian sharks represent distinct populations residing continental coastlines surf zone outer continental shelf adjacent oceanic waters shark occupies intermediate habitat overlaps specialized relatives shark silky shark oceanic shark shark shark shark tracking study northern gulf_of_mexico found spends time depths making occasional species known dive deep prefers water temperatures avoids areas low shark nomadic strongly migratory undertaking recorded movements adults generally longer distances juveniles sharks coasts north_america shift northward warmer summer temperatures retreat equator winter south_africa young males females long disperse southward northward respectively overlap nursery area join adults years later unidentified route addition juveniles spend spring summer surf zone fall winter offshore waters approach length begin conduct north south migration winter summer larger sharks long migrate far southern western_australia adult juvenile sharks migrate coast summer fall occupied description largest members genus shark commonly reaches length weight maximum recorded length weight respectively females grow larger males shark slender streamlined body broadly rounded snout longer width mouth nostrils preceded barely developed flaps skin medium sized circular eyes equipped membranes protective mouth short subtle furrows corners contains typically tooth rows jaws upper teeth broad triangular slightly oblique strong coarse lower teeth narrower upright finer pairs gill slits fairly long large pectoral fins measure fifth long body like shape tapering point dorsal fin moderate size somewhat pointed apex strongly concave rear margin origin lies pectoral fin free rear tips second dorsal fin smaller positioned opposite anal fin low dorsal ridge present dorsal fins caudal fin large high developed lower lobe ventral notch near tip upper lobe dermal denticles diamond shaped closely set bearing horizontal ridges leading teeth posterior margin species bluish gray white extends flanks faint lighter stripe fins particularly underside pectoral fins lower caudal fin lobe tips obvious juveniles biology ecology apex predator positioned highest level web shark generally abundant sharks share range high concentrations individuals especially juveniles found particular locations adults found following ships far land tracking study mouth north_carolina reported average swimming speed mph shark hosts known parasites species include larvae sea grown sharks significant natural predators major predators young sharks include ragged tooth shark great white shark bull shark tiger shark use shark nets protect beaches reduced populations large predators leading dramatic increase number juvenile sharks phenomenon called predator release turn juvenile sharks populations small bony fishes negative consequences biodiversity local ecosystem feeding shark takes wide variety prey levels water column favors hunting near large individual consume tenth body weight single sitting bite force exerted long shark measured area tip tooth highest figure far measured shark reflects concentration force tooth tip dense young sharks forming response feeding opportunities documented indian_ocean known diet shark encompasses fishes including herring fishes including reef fishes including fishes including angel sharks sharks smaller requiem sharks butterfly rays invertebrates including cephalopods crustaceans sea stars rarely largest sharks consume sea turtles marine mammals mainly human refuse northwestern atlantic shark diet consists bony fishes families summer especially important fishes mainly egg cases second important component lady crab relatively significant food source south african australian waters bony fishes important prey type newborn juvenile sharks mainly small prey squid older sharks long include larger bony fishes run southern african occurring eastern coast south_africa winter attended medium large sized sharks pregnant post females join possibly energy cost gestation leaves unable pursue swift prey south african study reported sharks examined preyed life history like requiem sharks shark viviparous developing embryos initially yolk sac converted connection mother yolk supply exhausted mating occurs spring northwestern atlantic appears reproductive regions south_africa females capable storing masses sperm possibly multiple males months years organ egg cases given sharks low natural abundance encounters suitable mates unpredictable gestation period estimated months year resting period female sharks bear litter young years litter size ranges typical female size sharks western atlantic tend produce slightly smaller litters southeastern atlantic averaging versus pups litter depending region occur year span months newborn sharks reported late winter summer northwestern atlantic summer fall western_australia year peak fall southern africa females shallow habitats birth areas offer pups rich food supplies shelter predation including species leave immediately afterward nursery areas known coasts southwestern australia california eastern united_states new_jersey north_carolina newborn sharks measure long size increases female size decreases litter size evidence females determine size pups born improve chances survival better worse environmental conditions females provision young energy reserves stored liver comprises fifth weight newborn learns hunt shark slowest growing shark species reaching sexual maturity substantial size age table studies found growth rates largely similar geographical regions sexes annual growth rate years life maximum lifespan believed years human interactions shark considered potentially dangerous humans large size little known people underwater lists responsible attacks people boats fatal attacks attributed species bermuda islands probably reality caused sharks shark nets protect beaches south_africa australia adult larger juvenile sharks numbers average individuals caught annually nets species specific data available nets australia young sharks adapt display public shark sought species shark fin trade fins large contain high number internal rays addition meat sold fresh frozen dried smoked skin leather liver oil processed sharks taken targeted commercial fisheries operating eastern north_america southwestern australia eastern south_africa multi species southwestern australian fishery began 1940s expanded 1970s yield tons year fishery utilizes selective exclusively young sharks years old captured year demographic models suggest fishery sustainable provided mortality rate sharks long addition commercial shark fisheries sharks caught meant usually kept valuable fins recreational large numbers sharks juveniles caught sport south_africa eastern australia shark important species florida trophy shark tournaments population collapsed conservation assessed species worldwide vulnerable northwestern atlantic gulf_of_mexico assessed north american shark populations vulnerable low reproductive rate renders shark extremely susceptible stocks eastern united_states severely stock assessment survey showed population dropped 1970s levels shark identified species concern meaning conservation concern insufficient information listing commercial recreational retention sharks prohibited limited effectiveness high mortality multi species gear addition sharks caught recreational despite ban north_carolina implemented time area closure reduce impact recreational fishing aid conservation efforts molecular techniques chain reaction developed identify marketed shark parts fins prohibited species like shark versus similar allowed species shark
Dusky shark