Editing Orinoco (section)

== Ecology ==
The [[boto]] and the [[giant otter]] inhabit the Orinoco River system.<ref name=WWF>WWF: ''[http://wwf.panda.org/what_we_do/where_we_work/orinoco_river_basin/ Orinoco River Basin, South America.]'' Retrieved 24 May 2014</ref> The [[Orinoco crocodile]] is one of the rarest reptiles in the world.  Its range in the wild is restricted to the middle and lower Orinoco River Basin.<ref>{{Cite journal|last1=Thorbjarnarson |first1=John B. |last2=Hernández |first2=Gustavo  |year=1993 |title=Reproductive ecology of the Orinoco crocodile (''Crocodylus intermedius'') in Venezuela. I. Nesting ecology and egg and clutch relationships |journal=Journal of Herpetology |volume=27 |issue=4 |pages=363–370 |doi=10.2307/1564821 |jstor=1564821}}</ref>

More than 1000 fish species have been recorded in the river basin and about 15% are [[Endemism|endemic]].<ref name=Reis2016>{{Cite journal |doi = 10.1111/jfb.13016|pmid = 27312713|title = Fish biodiversity and conservation in South America|journal = Journal of Fish Biology|volume = 89|issue = 1|pages = 12–47|year = 2016|last1 = Reis|first1 = R. E.|last2 = Albert|first2 = J. S.|last3 = Di Dario|first3 = F.|last4 = Mincarone|first4 = M. M.|last5 = Petry|first5 = P.|last6 = Rocha|first6 = L. A.|url = https://zenodo.org/record/896303|doi-access = free| bibcode=2016JFBio..89...12R }}</ref> Among the fish in the river are species found in [[brackish]] or salt water in the Orinoco [[estuary]], but also many restricted to fresh water. By far the largest orders are [[Characiformes]] and [[Siluriformes]], which together account for more than 80% of the fresh water species.<ref name=FEW>Hales, J., and P. Petry: ''[http://www.feow.org/ecoregions/details/307 Orinoco Llanos]''. Orinoco Delta & Coastal Drainages. Retrieved 24 May 2014.</ref> Some of the more famous are the [[Pygocentrus cariba|black spot piranha]] and the [[cardinal tetra]]. The latter species, which is important in the aquarium industry, is also found in the [[Rio Negro (Amazon)|Rio Negro]], revealing the connection between this river and the Orinoco through the [[Casiquiare canal]].<ref>{{cite web|website=Seriously Fish|url=http://www.seriouslyfish.com/species/paracheirodon-axelrodi/|title=Paracheirodon axelrodi, Cardinal Tetra.|access-date=24 May 2014}}</ref> Because the Casiquiare includes both [[Blackwater river|blackwater]] and [[Clearwater river (river type)|clear-]] to [[Whitewater river (river type)|whitewater]] sections, only relatively adaptable species are able to pass through it between the two river systems.<ref name=Staeck2015>{{cite journal|last1=Staeck|first1=W.|last2=Schindler|first2=I.|title=Description of a new Heros species (Teleostei, Cichlidae) from the Rio Orinoco drainage and notes on Heros severus Heckel, 1840|year=2015|journal=Bulletin of Fish Biology|volume=15|issue=1–2|pages=121–136|url=http://www.ichthyologie.de/images/stories/gfi/publikationen/Bulletin_of_Fish_Biology/Volume_15/BoFB_Vol15_121_136_Staeck_and_Schindler.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.ichthyologie.de/images/stories/gfi/publikationen/Bulletin_of_Fish_Biology/Volume_15/BoFB_Vol15_121_136_Staeck_and_Schindler.pdf |archive-date=2022-10-09 |url-status=live}}{{Dead link|date=April 2020 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>