Fish

Fish Temporal range:Mid Cambrian–Recent PreЄ Є O S D C P T J K Pg N
Giant groupersoummin amangschuilso ither fish
Heid-on view o areid lionfish
Scienteefic clessification
Kinrick:	Animalia
Phylum:	Chordata
Clade:	Olfactores
Subphylum:	Vertebrata
Groups included
Jawless fish †Airmoured fish †Spiny sharks Cartilaginous fish Banie fish Ray-finned fish Lobe-finned fish
Cladeesticallyincludit but tradeetionally excludit taxa
Tetrapods

Fishare thegill-beirinaquaticcraniateainimals that lacklimmswideegits.Thay form a sister group tae thetunicates,thegither formin theolfactores.Includit in this defineetion are the leevinhagfish,lampers,ancartilaginousanbanie fishas weel as various extinct relatit groups.Tetrapodsemerged athinlobe-finned fishes,saecladisticallythay are fish as weel. Houiver, tradeetionally fish are renderedparaphyleticbi excludin the tetrapods (i.e., theamphibians,reptiles,birdsanmammals). Acause in this manner the term "fish" is defined negatively as a paraphyletic group, it is nae conseedert a formal taxonomic groupin inseestematic biology.The tradeetional termpisces(an aaichthyes) is conseedert a teepological, but nae aphylogeneticclessification.

The earliest organisms that can be clessifee'd as fish war saft-bodiedchordatesthat first appeared in theCambrianperiod. Awtho thay lacked atrue spine,thay possessednotochordsthat alloued them tae be mair agile nor thair invertebrate coonterpairts. Fish wad conteena tae evolve throu thePaleozoicera, diversifeein intae a wide variety o forms. Mony fish o the Paleozoic developedexternal airmourthat pertectit them frae predators. The first fish wijawsappeared in theSilurianperiod, efter that mony (sic asshairks) becam formidable marine predators raither than juist the prey oarthropods.

Maist fish areectothermic( "cauld-bluidit" ), allouin thair bouk temperaturs tae vary as ambient temperaturs cheenge, tho some o the lairge active soummers likwhite sharkantunacan hauld a heichercore temperatur.Fish are abundant in maist bouks o watter. Thay can be foond in nearly aw aquatic environments, frae heich moontain streams (e.g.,Salvelinusangudgeon) tae theabyssalan evenhadaldeepths o the deepest oceans (e.g.,gulpersananglerfish). Wi 33,600 descrived species, fish exhibit greater species diversity than ony ither group o vertebrates.

Fish are an important resoorce for humans warldwide, especiallyas fuid.Commercial an subsistence fishers hunt fish inwild fisheries(seefishin) orfermthem in ponds or in cages in the ocean (seeaquacultur). Thay are an aa catcht birecreautional fishers,kept as pets, raised bifishkeepers,an exhibitit in publicaquaria.Fish hae haed a role in cultur throu the ages, servin asdeities,releegious seembols, an as the subjects o airt, beuks an films.