portuguese portuguese portuguese shark species sleeper shark family globally distributed species reported depth making deepest living shark known inhabits lower continental slopes plains usually staying near dark brown color portuguese distinguished similar looking species shark small spines dorsal fins dermal denticles unusual resembling scales bony fish species typically reaches length sharks mediterranean_sea smaller distinct depth food preferences relatively common portuguese active hunter capable fast large prey feeds mainly cephalopods fishes invertebrates shark acute vision detecting prey sunlight reach depths lives portuguese viviparous young yolk fluid females birth young gestation period year valued liver oil lesser extent meat portuguese important commercial fisheries operating portugal british isles japan australia fishing pressures low reproductive rate species led assess taxonomy scientific description portuguese published portuguese issue created new genus shark gave specific epithet derived greek hollow fish scale referring structure dermal denticles type specimen caught portugal destroyed fire distribution habitat widest ranging sharks portuguese distributed world western atlantic occurs grand banks newfoundland state delaware eastern atlantic found iceland sierra including western mediterranean_sea azores southern western south_africa indian_ocean species caught pacific shark occurs japan new_zealand australia new south wales including tasmania deepest living shark known portuguese reported depths lower continental slope plain common species found deeper mediterranean seldom occurring depth common deep mediterranean relatively constant temperature deep ocean temperature generally portuguese essentially benthic nature young sharks found considerable distance depth segregation size sex pregnant females found shallower water juveniles found deeper separate populations atlantic sharks mediterranean japan appear distinct description portuguese typically reaches length males females specimens long recorded sharks mediterranean smaller growing long species flattened broadly rounded snout shorter mouth wide nostrils preceded short flaps skin eyes large oval shape positioned head equipped reflective produces yellow green eye shine mouth wide slightly arched moderately thick smooth lips short furrows corners extending jaws upper teeth slender upright single numbering rows lower teeth short strongly angled number rows bases form continuous cutting surface pairs gill slits short nearly vertical body portuguese thick cylindrical flattened belly dorsal fins small similar size shape bearing tiny spine dorsal fin originates pectoral fins second dorsal originates middle pelvic fin bases pectoral fins medium sized rounded margin anal fin caudal fin short developed lower lobe prominent ventral notch near tip upper lobe large dermal denticles change shape age juveniles widely spaced heart shaped incomplete ridge posterior points adults overlapping roughly circular smooth flattened round central resembling scales bony fishes young sharks uniform blue black color adults brown black prominent fin markings partially individual pale body normal eyes caught northeastern atlantic represented documented case deep sea shark biology ecology living exclusively zone little sunlight portuguese relatively common dominant shark species deeper waters large rich liver shark allows maintain neutral minimal effort males contain females tracking study found portuguese average swimming speed remain particular area long species preyed larger fishes sharks known parasites species include genus active predator mobile relatively large organisms portuguese feeds mainly cephalopods including bony fishes including orange fishes known sharks invertebrates whale portuguese acute vision sharks addition having large pupil lens eyes contain high concentration cells concentrated horizontal streak center cells highly sensitive motion detection horizontal plane visual system species appears adapted detecting maximum absorption visual correspond light emitted favored prey mediterranean sea portuguese common sharks velvet belly shark shark abundant depth inhabiting deeper water portuguese mediterranean reduce competition species smaller size mediterranean sharks relative rest world limited food availability warmer environment diet portuguese mediterranean consists cephalopods bony fishes secondary food source immature sharks favor shrimp common environment unlike regions mediterranean sharks seldom life history portuguese viviparous female retaining eggs internally hatch embryos sustained yolk possibly fluid mother reported breeding seasons year portugal january august december fraction population active time previous accounts described continuous reproduction females stages pregnancy present year round time mature diameter studies females found traces sperm inside reproductive tracts suggests occurs immediately following trigger reproductive cycles portuguese atlantic pacific generally similar sharks japan tend produce larger numbers smaller sharks british isles exhibit larger litter size birth size smaller portugal record specimen right left early development embryos sexually possess external gills external yolk sac stage weighs recognizable sex organs develop length tissue complete length body appears embryo long external gills time internal yolk sac develops embryo long begins yolk external yolk sac time embryo long external yolk sac completely portugal young born december following gestation period year near giving birth females undergo suggesting enter resting period litter size ranges typically female size occur unknown nursery area rarely caught length birth reported atlantic pacific aside distinctive mediterranean population portuguese attain sexual maturity similar sizes world males females mature respectively respectively west british isles respectively japan respectively southeastern australia mediterranean males mature long human interactions portuguese small occurs deep pose danger humans species long commercially hook line mainly valued liver contains weight processed meat sold fresh dried human consumption converted important fishery portuguese exists liver oil catches peaked world war declined soon exploitation past years catches australia increasing seeking species covered commercial following mercury regulations shark landings fishery affected prohibition landing rest recently portugal european country utilize portuguese important black fishery tons shark landed annually weight value increasing exploitation likely continue french began fish portuguese sharks west british isles meat species referred catch peaked tons declining tons french joined norwegian irish scottish making portuguese significant component fisheries northwest atlantic stocks portugal stable stocks british isles diminished substantially recent years reflect portuguese fishery commercial french fishery assessed species commercial value low reproductive productivity
Portuguese dogfish