View source for Paddlefish

{{Short description|Family of fishes related to sturgeons}}
{{Distinguish|Oarfish}}
{{Good article}}{{use dmy dates|date=December 2024}}
{{Automatic taxobox
| name = Paddlefishes
| image = Paddlefish Polyodon spathula.jpg
| image_caption = [[American paddlefish]], ''Polyodon spathula''
| image2 = A_specimen_of_Psephurus_gladius,_Museum_of_Hydrobiological_Sciences,_Wuhan_Institute_of_Hydrobiology_(4).jpg
| image2_caption = [[Chinese paddlefish]], {{extinct}} ''Psephurus gladius''
| fossil_range = {{Fossil range|Barremian|Recent}}<ref name=FB>{{FishBase_family |family=Polyodontidae |year=2009 |month=January}}</ref>
| taxon = Polyodontidae
| authority = [[Charles Lucien Bonaparte|Bonaparte]], 1838
| subdivision_ranks = Genera
| subdivision =
Recent genera
* ''[[American paddlefish|Polyodon]]''
* {{Extinct}}''[[Chinese paddlefish|Psephurus]]''
Fossil genera
* {{Extinct}}''[[Crossopholis]]''
* {{Extinct}}''[[Paleopsephurus]]'' 
* {{Extinct}}''[[Parapsephurus]]''<ref name=Hilton2023/>
* {{Extinct}}''[[Protopsephurus]]''
* {{Extinct}}''[[Pugiopsephurus]]''<ref name=Hilton2023/>
}}

'''Paddlefish''' (family '''Polyodontidae''') are a family of [[ray-finned fish]] belonging to order [[Acipenseriformes]], and one of two living groups of the order alongside [[sturgeon]]s (Acipenseridae).<ref name=Crow2012>{{cite journal |last1 = Crow |first1 = K.D. |last2 = Smith | first2 = C.D. |last3 = Cheng |first3 = J.-F. |last4 = Wagner |first4 = G.P. |last5 = Amemiya |first5 = C.T. |year = 2012 |title = An independent genome duplication inferred from hox paralogs in the American Paddlefish – a representative basal ray-finned fish and important comparative reference |journal = Genome Biology and Evolution |volume = 4 |issue = 9 |pages = 937–953 |pmc = 3509897 |doi = 10.1093/gbe/evs067 |pmid = 22851613 }}</ref><ref name=TexasPWD-sp-dsc>{{cite web |title=Paddlefish (''Polyodon spathula'') |website=tpwd.texas.gov |url=https://tpwd.texas.gov/huntwild/wild/species/pad/ |access-date=2022-12-02 }}</ref> They are distinguished from other fish by their elongated [[Rostrum (anatomy)|rostra]], which are thought to enhance [[electroreception]] to detect prey. Paddlefish have been referred to as "[[primitive fish]]" because the Acipenseriformes are among the earliest diverging lineages of ray-finned fish, having diverged from all other living groups over 300&nbsp;million years ago. Both living and fossil paddlefish are found almost exclusively in North America and China.<ref name=Wilkens-Hofmann-2007>{{cite journal | last1=Wilkens | first1=Lon A. | last2=Hofmann | first2=Michael H. | year=2007 | title=The paddlefish rostrum as an electrosensory organ: A novel adaptation for plankton feeding | journal=BioScience | volume=57 | issue=5 | pages=399–407 | doi=10.1641/B570505 | doi-access=free }}</ref>

Eight species are known: Six of those species are extinct, and known only from fossils (five from North America, one from China),<ref name=Hilton2023>
<br/>{{cite journal
 |last1=Hilton |first1=E.J. |last2=During  |first2=M.A.D.
 |last3=Grande |first3=L.   |last4=Ahlberg |first4=P.E.
 |year=2023
 |title=New paddlefishes (Acipenseriformes, Polyodontidae) from the late Cretaceous Tanis site of the Hell Creek formation in North Dakota, USA
 |journal=Journal of Paleontology
 |volume=97 |issue=3 |pages=675–692
 |doi=10.1017/jpa.2023.19 |doi-access=free
 |s2cid=258095684
}}
</ref> one of the [[Extant taxon|extant]] species, the [[American paddlefish]] (''Polyodon spathula''), is native to the [[Mississippi River]] basin in the U.S. The other is the [[Chinese paddlefish]] (''Psephurus gladius''), which was declared extinct in 2022 following a 2019 recommendation;<ref name=Reuters2022>{{cite news |title=Chinese paddlefish and wild Yangtze sturgeon extinct - IUCN |agency=[[Reuters]] |date=2022-07-22 |df=dmy-all |lang=en |url=https://www.reuters.com/business/environment/chinese-paddlefish-wild-yangtze-sturgeon-extinct-iucn-2022-07-22/ |access-date=2022-07-22 |archive-date=23 July 2022 |archive-url=https://web.archive.org/web/20220723155510/https://www.reuters.com/business/environment/chinese-paddlefish-wild-yangtze-sturgeon-extinct-iucn-2022-07-22/ |url-status=live }}</ref><ref name=SD2019>{{cite journal | last1=Zhang | first1=Hui | last2=Jarić | first2=Ivan | last3=Roberts | first3=David L. | last4=He | first4=Yongfeng | last5=Du | first5=Hao | last6=Wu | first6=Jinming | last7=Wang | first7=Chengyou | last8=Wei | first8=Qiwei | display-authors=6 | year=2020 | title=Extinction of one of the world's largest freshwater fishes: Lessons for conserving the endangered Yangtze fauna | journal=Science of the Total Environment | volume=710 | pages=136242 | issn=0048-9697 | doi=10.1016/j.scitotenv.2019.136242 | pmid=31911255 | bibcode=2020ScTEn.71036242Z | s2cid=210086307 }}</ref><ref name=Oceanographic-2020>{{cite web | title=Study declares ancient Chinese paddlefish extinct | magazine=Oceanographic magazine | date=2020-01-09 | url=https://www.oceanographicmagazine.com/news/chinese-paddlefish-extinct/ | access-date=2022-04-23 | df=dmy-all }}</ref> the species has not been sighted in the [[Yangtze River Basin]] in China since 2003.<ref name=SCMPost-2020>{{cite web | title=Chinese paddlefish, native to the Yangtze River, declared extinct by scientists | newspaper=[[South China Morning Post]] | date=2020-01-04 | df=dmy-all | url=https://www.scmp.com/news/china/society/article/3044520/chinese-paddlefish-native-yangtze-river-declared-extinct | access-date=2020-01-04}}</ref><ref name=IUCN-Chinese>{{cite iucn |last=Qiwei |first=W. |year=2010 |title=''Psephurus gladius'' |volume=2010 |page=e.T18428A8264989 |doi=10.2305/IUCN.UK.2010-1.RLTS.T18428A8264989.en <!-- |access-date=11 November 2021 --- access date requires a URL --> }}</ref> Chinese paddlefish are also commonly referred to as "Chinese swordfish", or "elephant fish".<ref name=FAO>{{cite web | title=''Psephurus gladius'' (Martens, 1862) | department=Species Fact Sheet | publisher=[[Food and Agriculture Organization of the United Nations]] | series=Fisheries and Aquaculture Department | url=http://www.fao.org/fishery/species/14620/en | access-date=June 10, 2014 | url-status=live | archive-url=https://web.archive.org/web/20150707033220/http://www.fao.org/fishery/species/14620/en | archive-date=July 7, 2015 }}</ref> The earliest known paddlefish is ''[[Protopsephurus]]'', from the [[early Cretaceous]] ([[Aptian]]) of China, dating to around 120&nbsp;million years ago.

Paddlefish populations have declined dramatically throughout their historic range as a result of [[overfishing]], pollution, and the encroachment of human development, including the construction of dams that have blocked their seasonal upward migration to ancestral spawning grounds.<ref>{{cite news |title=Hooking the dinosaur of fish |date=2018-05-26 |newspaper=[[The New York Times]] |lang=en-US |issn=0362-4331 |url=https://www.nytimes.com/2018/05/26/science/paddlefish-caviar-conservation.html |access-date=2018-05-27 |df=dmy-all }}</ref>  Other detrimental effects include alterations of rivers which have changed natural flows resulting in the loss of spawning habitat and nursery areas.<ref name=NatGeo>{{cite web |title=Chinese paddlefish |website=[[National Geographic magazine|National Geographic]] |url=http://environment.nationalgeographic.com/environment/freshwater/chinese-paddlefish/ |access-date=May 28, 2014 |url-status=dead|archive-url=https://web.archive.org/web/20140714034603/http://environment.nationalgeographic.com/environment/freshwater/chinese-paddlefish/ |archive-date=July 14, 2014 |df=dmy-all }}</ref>

== Morphology ==
[[File:General Morphology of Paddlefish.png|thumb|270px|General [[Morphology (biology)|morphology]] of paddlefish]]
Paddlefish as a group are one of the few organisms that retain a [[notochord]] past the embryonic stage. Paddlefish have very few [[bone]]s and their bodies mostly consist of cartilage with the notochord functioning as a soft spine. During the initial stages of development from embryo to fry, paddlefish have no [[Rostrum (anatomy)|rostrum]] (snout).  It begins to form shortly after hatching.<ref name=LSU>{{cite report | title=Biology of the Paddlefish | publisher=Lamer-Louisiana State University | series=NFC Section&nbsp;I  | url=http://www.lamer.lsu.edu/pdfs/NFC_Section1.pdf | access-date=June 9, 2014 | url-status=dead | archive-url=https://web.archive.org/web/20140714195741/http://www.lamer.lsu.edu/pdfs/NFC_Section1.pdf | archive-date=2014-07-14 }}</ref> The rostrum of the [[Chinese paddlefish]] was narrow and sword-like whereas the rostrum of the American paddlefish is broad and paddle-like. Some common morphological characteristics of paddlefish include a spindle-shaped, smooth-skinned scaleless body, [[Heterocercal|heterocercal tail]], and small poorly developed [[eye]]s.<ref name=FAO/><ref name=LSU/> Unlike the filter-feeding American paddlefish, Chinese paddlefish were [[piscivores]], and highly predatory.  Their jaws were more forward pointing which suggested they foraged primarily on small fishes in the water column, and occasionally on shrimp, [[benthic]] fishes, and crabs.<ref name=FAO/><ref name=Miller>{{cite book | last=Miller |first=Michael J. | date=2006-01-20 | chapter=Chapter&nbsp;4 – The ecology and functional morphology of feeding of North American sturgeon and paddlefish | title=Sturgeons and Paddlefish of North America | publisher=Springer Science & Business Media | isbn=9781402028335 | pages=87–101 |editor1-first=G.T.O |editor1-last=le&nbsp;Breton |editor2-first=F. William H. |editor2-last=Beamish  |editor3-first=Scott R. |editor3-last=McKinley |series = Fish & Fisheries Series |volume=27 |url=https://books.google.com/books?id=M-2cxIjeuMIC | chapter-url=https://books.google.com/books?id=M-2cxIjeuMIC&q=Chinese+paddlefish+have+electroreceptors&pg=PA87 | access-date=June 10, 2014 | url-status=live | archive-url=https://web.archive.org/web/20140728044150/http://books.google.com/books?id=M-2cxIjeuMIC&pg=PA87&lpg=PA87&dq=Chinese%2Bpaddlefish%2Bhave%2Belectroreceptors%3F&source=bl&ots=1KDmJpKIFj&sig=h7tdiFolHfCG4QsOer5TQPGU2hU&hl=en&sa=X&ei=G0aXU6S2M6HG0AXK1YAI&ved=0CDkQ6AEwAw#v=onepage&q=Chinese%20paddlefish%20have%20electroreceptors%3F&f=false | archive-date=July 28, 2014 }}</ref> The jaws of the American paddlefish are distinctly adapted for filter feeding only. They are [[Aquatic feeding mechanisms#Ram feeding|ram suspension filter feeders]] with a diet that consists primarily of [[zooplankton]], and occasionally small insects, insect larvae, and small fish.<ref name=Wilkens-Hofmann-2007/>
[[File:DSC08833 - Open Wide (36823357680).jpg|thumb|270px|Closeup of the head, showing the presence of [[Electroreception and electrogenesis|electrorecepting]] organs ([[ampullae of Lorenzini]])]]
The largest Chinese paddlefish on record measured {{convert|23|ft|m|abbr=on}} in length, and was estimated to weigh a few thousand pounds.<ref name=IUCN-Chinese/> They commonly reached {{convert|9.8|ft|m|abbr=on}} and {{convert|1100|lb|kg|abbr=on}}.<ref name=IUCN-Chinese/><ref name=FAO/><ref name=BBC>{{cite news | last=Bourton |first=Jody | date=September 29, 2009 | title=Giant fish 'verges on extinction' | website=[[BBC News]] | department=Earth News | url=http://news.bbc.co.uk/earth/hi/earth_news/newsid_8269000/8269414.stm | access-date=June 9, 2014 | url-status=live | archive-url=https://web.archive.org/web/20141006072635/http://news.bbc.co.uk/earth/hi/earth_news/newsid_8269000/8269414.stm | archive-date=October 6, 2014 }}</ref> Although the American paddlefish is one of the largest [[freshwater fish]]es in North America, their recorded lengths and weights fell short in comparison to the larger Chinese paddlefish. American paddlefish commonly reach {{convert|5|ft|m|abbr=on}} or more in length and can weigh more than {{convert|60|lb|kg|abbr=on}}. The largest American paddlefish on record was caught in 1916 in Okoboji Lake, Iowa.{{efn|"Okoboji Lake" could refer to either of two attached lakes: [[West Okoboji Lake]] and [[East Okoboji Lake]]. The source does not state which one is meant.}}<ref name=Nichols>{{cite journal |last=Nichols |first=J.T. |date=24 August 1916 |title=A large ''Polyodon'' from Iowa |journal=Copeia |volume=34 |issue=34 |page=65 <!-- |publisher=JSTOR --> |jstor=1436920 }}</ref> The fish was taken with a spear, and measured {{convert|7|ft|1|in|m|abbr=on}} long and {{convert|45.5|in|m|abbr=on}} in the girth.<ref name=Nichols/> A report published by J.R. Harlan and E.B. Speaker (1969) in ''Iowa Fish and Fishing'' states that the fish weighed over {{convert|198|lb|kg|abbr=on}}.<ref name=AFS-7>{{cite book |last=Gengerke |first=Thomas W. |date=August 1986 |section=The paddlefish: Status, management and propagation |title=Distribution and Abundance of Paddlefish in the United States |id=AFS-7 }}</ref> The world record paddlefish caught on rod and reel weighed {{convert|144|lb|kg|abbr=on}} and was {{convert|54.25|in|m|abbr=on}} long. The fish was caught by Clinton Boldridge in a 5&nbsp;acre pond in [[Atchison County, Kansas]] on 5&nbsp;May 2004.<ref name=Kansas>{{cite web | title=State Record Fish | department=Kansas angler online edition | date=May 2004 | publisher=[[Kansas Department of Wildlife, Parks and Tourism]] | url=http://ksoutdoors.com/Fishing/State-Record-Fish | url-status=live | access-date=June 9, 2014 | archive-url=https://web.archive.org/web/20150326215821/http://www.kansasangler.com/archive/0502riley.html | archive-date=March 26, 2015 }}</ref><ref name=KWPT>{{cite web |title=State record fish |publisher=Kansas Wildlife Parks & Tourism |via=ksoutdoors.com |url=http://ksoutdoors.com/Fishing/State-Record-Fish |access-date=September 8, 2017}}</ref> However, the record would be broken an additional two times in 2020: On 28&nbsp;June 2020, an Oklahoma man caught a 146&nbsp;pound paddlefish in [[Keystone Lake]], west of [[Tulsa]]. Later on 23&nbsp;July 2020, the record was broken again when another Oklahoma man caught a 151&nbsp;pound, nearly 6&nbsp;foot long paddlefish in the same lake.<ref>{{cite news | last=Wilkinson |first=Joseph | date=July 31, 2020 | title=Oklahoma man catches world-record 150&nbsp;pound paddlefish — breaking record set last month in the same lake |newspaper=[[The New York Daily News]] | via=NYDailyNews.com | url=https://www.nydailynews.com/news/national/ny-oklahoma-man-paddlefish-world-record-cory-watters-20200731-3j7ueb3fhjczfaychucyegviva-story.html | access-date=August 3, 2020 }}</ref>

Scientists once believed paddlefish used their rostrums to excavate bottom substrate,<ref name=LSU/><ref name=Nachtrieb>{{cite journal |last=Nachtrieb |first=Henry F. |year=1910 |title=The primitive pores of ''Polyodon spathula'' (Walbaum) |journal= Journal of Experimental Zoology |volume=9 |issue=2 |pages=455–468 |doi=10.1002/jez.1400090211 |url=https://zenodo.org/record/1426858 |via=zendo.org }}</ref> but have since determined with the aid of [[electron microscopy]] that paddlefish rostrums are covered in [[electroreception and electrogenesis|electroreceptors]] called [[Ampullae of Lorenzini|ampullae]].<ref name=Jorgensen>{{cite journal |last1=Jørgensen |first1=J. Mørup |last2=Flock |first2=Å. |last3=Wersäll |first3=J. |date=September 1972 |title=The Lorenzinian ampullae of ''Polyodon spathula'' |journal=Zeitschrift für Zellforschung und Mikroskopische Anatomie |issue=3 |volume=130 |pages=362–377 |doi=10.1007/BF00306949 |pmid=4560320 |s2cid=28712903 }}</ref> These ampullae are densely packed within star-shaped bone projections that branch out from the rostrum.<ref name=Grande1991>{{Cite journal |last1=Grande |first1=Lance |last2=Bemis |first2=William E. |date=1991-03-28 |title=Osteology and phylogenetic relationships of fossil and recent paddlefishes (Polyodontidae) with comments on the interrelationships of Acipenseriformes |journal=Journal of Vertebrate Paleontology |volume=11 |issue=sup001 |pages=1–121 |doi=10.1080/02724634.1991.10011424 |issn=0272-4634 |lang=en |url=http://www.tandfonline.com/doi/abs/10.1080/02724634.1991.10011424 |url-access=subscription }}</ref> The electroreceptors can detect weak electrical fields which not only signal the presence of prey items in the water column, such as [[zooplankton]] which is the primary diet of the American paddlefish, but they can also detect the individual feeding and swimming movements of zooplankton's [[appendages]].<ref name=Wilkens-Hofmann-2007/><ref name=LSU/> Paddlefish have poorly developed eyes, and rely on their electroreceptors for foraging. However, the rostrum is not the paddlefish's sole means of food detection. Some reports incorrectly suggest that a damaged rostrum would render paddlefish less capable of foraging efficiently to maintain good health. Laboratory experiments, and field research indicate otherwise. In addition to electroreceptors on the rostrum, paddlefish also have sensory pores covering nearly half of the skin surface extending from the rostrum to the top of the head down to the tips of the [[operculum (fish)|operculum]] (gill flaps). Paddlefish with damaged or abbreviated rostrums are still able to forage adequately.<ref name=Wilkens-Hofmann-2007/><ref name=LSU/>

==Habitat and historic range==

Over the past half century, paddlefish populations have been on the decline. Attributable causes are overfishing, pollution, and the encroachment of human development, including the construction of dams which block their seasonal upward migration to ancestral spawning grounds. Other detrimental effects include alterations of rivers which have changed the natural flow, and resulted in the loss of spawning habitat and nursery areas. American paddlefish have been extirpated from much of their Northern peripheral range, including the [[Great Lakes]] and Canada, [[New York (state)|New York]], [[Maryland]] and [[Pennsylvania]].  There is growing concern about their populations in other states.

The Chinese paddlefish was considered [[anadromous]] with upstream migration, however little is known about their migration habits and population structure. They were endemic to the [[Yangtze River Basin]] in China where they lived primarily in the broad surfaced main stem rivers and shoal zones along the [[East China Sea]].<ref name=IUCN-Chinese/><ref name=UN-HFAO>{{cite web | title=FAO Fisheries & Aquaculture | ref={{sfnref | Home | Food and Agriculture Organization of the United Nations }} | url=https://www.fao.org/fishery/en/aqspecies/14620/enn | access-date=2022-04-24 }}</ref> Research suggests they preferred to navigate the middle and lower layers of the water column, and occasionally swam into large lakes.<ref name=IUCN-Chinese/> There have been no sightings of Chinese paddlefish since 2003, and were declared extinct in 2019.<ref name=SD2019/> Past attempts of [[artificial propagation]] for restoration purposes failed because of difficulties encountered in keeping captive fish alive.<ref name=Conservation>{{cite book  | last=Helfman | first= Gene | year=2007 |publisher=Island Press |title=Fish Conservation: A guide to understanding and restoring global aquatic biodiversity and fishery resources }}</ref>

American paddlefish are native to the Mississippi River basin from New York to Montana and south to the Gulf of Mexico.<ref name=TPW>{{cite web | title=Paddlefish (''Polyodon spathula'') | publisher=Texas Parks & Wildlife | url=http://tpwd.texas.gov/huntwild/wild/species/pad/ | access-date=April 20, 2016 | url-status=live | archive-url=https://web.archive.org/web/20160505071851/http://tpwd.texas.gov/huntwild/wild/species/pad/ | archive-date=May 5, 2016 }}</ref> They have been found in several Gulf Slope drainages in medium to large rivers with long, deep sluggish pools, as well as in backwater lakes and bayous.<ref name=INHS>{{cite report |title=INHS padfish |date=Spring 2002 |series=Prairie Research Institute |publisher=[[University of Illinois]] |place=Urbana-Champaign, IL |url=http://wwx.inhs.illinois.edu/resources/inhsreports/spring-02/padfish/ |url-status=live |access-date=May 28, 2014 |archive-url=https://web.archive.org/web/20140529051611/http://wwx.inhs.illinois.edu/resources/inhsreports/spring-02/padfish/ |archive-date=May 29, 2014 }}</ref> In Texas, paddlefish occurred historically in the [[Angelina River]], [[Big Cypress Bayou]], [[Neches River]], tributaries of the [[Red River of the South|Red River]], [[Sabine River (Texas–Louisiana)|Sabine River]], [[San Jacinto River (Texas)|San Jacinto River]], [[Sulphur River]], and [[Trinity River (Texas)|Trinity River]].<ref name=TPW/> Their historical range also included occurrences in Canada in [[Lake Huron]] and [[Lake Helen (Ontario)|Lake Helen]], and in 26~27&nbsp;other states in the United States. The [[Ontario Ministry of Natural Resources]] listed the paddlefish as extirpated from [[Ontario, Canada]] under their Endangered Species Act.<ref name=SAR>{{cite web | title=SAR Paddlefish | url=http://www.mnr.gov.on.ca/en/Business/Species/2ColumnSubPage/MNR_SAR_PADDLEFISH_EN.html | access-date=June 9, 2014 | url-status=live | archive-url=https://web.archive.org/web/20140714154356/http://www.mnr.gov.on.ca/en/Business/Species/2ColumnSubPage/MNR_SAR_PADDLEFISH_EN.html | archive-date=July 14, 2014 }}</ref> The [[IUCN Red List]] lists the Canadian populations of paddlefish as extirpated, noting there have been no Canadian records since the early 1900s and distribution in Canada was highly peripheral. As a species, the American paddlefish is classified as vulnerable (VU) on the IUCN Red List, and its international trade has been restricted since June 1992 under Appendix&nbsp;II of the [[CITES|Convention of International Trade in Endangered Species of Wild Flora and Fauna]] ([[CITES]]).<ref name=Redlist>{{cite iucn |last=Grady |first=J. |year=2019 |collaboration=[[United States Fish and Wildlife Service]] |title=''Polyodon spathula'' |volume=2019 |page=e.T17938A174780447 |doi=10.2305/IUCN.UK.2019-3.RLTS.T17938A174780447.en |access-date=11 November 2021}}</ref>

==Life cycle==

Paddlefish are long-lived, and sexually late maturing.  Females do not begin spawning until they are six to twelve years old, some even as late as sixteen to eighteen years old. Males begin spawning around age four to seven, some as late as nine or ten years of age.<ref name=LSU/><ref name=ND>{{cite web | title=Paddlefish questions and answers | publisher=North Dakota Game and Fish Department | url=https://gf.nd.gov/fishing/paddlefish-snagging/faq | access-date=June 9, 2014 | url-status=live | archive-url=https://web.archive.org/web/20161129140952/https://gf.nd.gov/fishing/paddlefish-snagging/faq | archive-date=November 29, 2016 }}</ref><ref name=TexasPWD-sp-dsc/> Paddlefish spawn in late spring if the proper combination of events occur; these include water flow, temperature, photoperiod, and availability of gravel substrates suitable for spawning. If all the conditions are not met, paddlefish do not spawn. Research suggests females do not spawn every year, rather they spawn every second or third year while males spawn more frequently, typically every year or every other year.<ref name=LSU/>

Paddlefish migrate upstream to spawn, and prefer silt-free gravel bars that would otherwise be exposed to air, or covered by very shallow water were it not for the rises in the river from snow melt and annual spring rains that cause flooding.<ref name=MDC>{{cite web | title=Paddlefish | website=MDC online | url=http://mdc.mo.gov/node/1002 | access-date=June 9, 2014 | url-status=dead | archive-url=https://archive.today/20140611082939/http://mdc.mo.gov/node/1002 | archive-date=June 11, 2014 }}</ref> They are [[broadcast spawner]]s, also referred to as mass spawners or synchronous spawners. Fertilization occurs externally: [[Gravid]] females release their [[egg (biology)|eggs]] into the water over bare rocks or gravel at the same time males release their sperm. The eggs are adhesive and stick to the rocky substrate. The young are swept downstream after hatching and grow to adulthood in deep freshwater pools.<ref name=EoF>{{cite book |last=Wiley |first=Edward G. |year=1998 |editor1-last=Paxton |editor1-first=J.R. |editor2-last=Eschmeyer |editor2-first=W.N. |title=Encyclopedia of Fishes |publisher=Academic Press |place=San Diego, CA |pages=77–78 |isbn=0-12-547665-5 }}</ref>

==Propagation and culture==

The advancements in biotechnology in paddlefish propagation and rearing of captive stock indicate significant improvements in reproduction success, adaptation and survival rates of paddlefish cultured for broodstock development and stock rehabilitation.  Such improvements have led to successful practices in reservoir ranching and pond rearing, creating an increasing interest in the global market for paddlefish polyculture.<ref name=WAS>{{cite conference | last=Mims |first=Steven | year=2013 | title=Current global status of American paddlefish aquaculture | conference=World Aquaculture Society | type=meeting abstract | url=https://www.was.org/meetings/ShowAbstract.aspx?Id=28396 | access-date=April 28, 2015 | url-status=live | archive-url=https://web.archive.org/web/20160303233953/https://www.was.org/meetings/ShowAbstract.aspx?Id=28396 | archive-date=March 3, 2016 }}</ref><ref name=Mims>{{cite report | first=Steven D. |last=Mims | date=February 2006 | title=Paddlefish culture: Development expanding beyond U.S., Russia, China | publisher=[[Global Aquaculture Alliance]] | url=http://pdf.gaalliance.org/pdf/GAA-Mims-Feb06.pdf | access-date=April 28, 2015 | url-status=dead | archive-url=https://web.archive.org/web/20140714141327/http://pdf.gaalliance.org/pdf/GAA-Mims-Feb06.pdf | archive-date=July 14, 2014 }}</ref>

In a cooperative scientific effort in the early 1970s between the [[United States Fish and Wildlife Service|U.S. Fish & Wildlife Service]] and its former [[USSR]] counterpart, American paddlefish were imported into the former USSR for [[aquaculture]], beginning with five-thousand hatched larvae from [[Missouri]] hatcheries in the [[United States]]. They were introduced into several rivers in Europe and Asia, and provided the first brood stock that were successfully reproduced in 1984–1986 in Russia.<ref name=Lenhardt-Hegediš-etal-2006>{{cite journal |first1=Mirjana |last1=Lenhardt |first2=A. |last2=Hegediš |first3=B. |last3=Mićković |first4=Željka Višnjić |last4=Jeftić |first5=Marija |last5=Smederevac |first6=I. |last6=Jarić |first7=G. |last7=Cvijanović |first8=Z. |last8=Gačić. |display-authors=6 |year=2006 |title=First record of the North American paddlefish in the Serbian part of the Danube River |journal=Arch. Biol. Sci. |volume=58 |issue=3 |pages=27–28 |url=http://www.doiserbia.nb.rs/img/doi/0354-4664/2006/0354-4664060327PL.pdf |via=doiserbia.nb.rs |access-date=June 9, 2014 |url-status=live |archive-url=https://web.archive.org/web/20140714122704/http://www.doiserbia.nb.rs/img/doi/0354-4664/2006/0354-4664060327PL.pdf |archive-date=July 14, 2014  <!-- |publisher=Sinisa Stankovic Institute for Biological Research |place=Belgrade, RS --> }}</ref> Paddlefish are now being raised in [[Germany]], [[Austria]], the [[Czech Republic]], and the [[Plovdiv]] and [[Vidin]] regions in [[Bulgaria]]. Reproduction was successful in 1988 and 1989, and resulted in the exportation of juvenile paddlefish to [[Romania]] and [[Hungary]]. In May&nbsp;2006, specimens of different sizes and weights were caught by professional fisherman near [[Prahovo]] in the [[Serbia]]n part of the [[Danube River]].<ref name=Lenhardt-Hegediš-etal-2006/>

In 1988, fertilized paddlefish eggs and larvae from Missouri hatcheries were first introduced into China.<ref name=Lenhardt-Hegediš-etal-2006/> Since that time, China imports approximately 4.5&nbsp;million fertilized eggs and larvae every year from hatcheries in Russia, and the United States.  Some of the paddlefish are polycultured in carp ponds, and sold to restaurants while others are cultured for brood stock and caviar production. China has also exported paddlefish to Cuba, where they are farmed for caviar production.<ref name=Mims/>

==Classification==
[[File:Protopsephurus.png|thumb|270px|Restoration of the [[Cretaceous]] {{extinct}}''[[Protopsephurus]]'']]
[[File:Crossopholis.png|thumb|270px|Restoration of {{extinct}}''[[Crossopholis]]'']]
There is one currently [[extant taxon|extant]] genus in this family, one recently [[extinct]] and five extinct genera known exclusively from [[fossil]]s.

Classification following {{harvp|Grande|Bemis|1991}},<ref name=Grande1991/> with ''[[Parapsephurus]]'' and ''[[Pugiopsephurus]]'' added in {{harvp|Hilton|During|Grande|Ahlberg|2023}}:<ref name=Hilton2023/>
* genus {{extinct}} ''[[Protopsephurus]]'' <small>Lu, 1994</small> (Early Cretaceous, China)
** species {{extinct}} ''Protopsephurus liui'' <small>Lu, 1994</small>
* genus {{extinct}} ''[[Pugiopsephurus]]'' <small>Hilton ''et al.'', 2023<ref name=Hilton2023/></small> (Late Cretaceous, North America) (''[[Incertae sedis]]'')
** species {{extinct}} ''Pugiopsephurus inundatus'' <small>Hilton ''et al.'', 2023<ref name=Hilton2023/></small>
* clade Polyodonti
** genus {{extinct}} ''[[Paleopsephurus]]'' <small>MacAlpin, 1947</small> (Late Cretaceous, North America)
*** species {{extinct}} ''Paleopsephurus wilsoni'' <small>MacAlpin, 1947</small>
** genus {{extinct}}''[[Parapsephurus]]'' <small>Hilton ''et al.'', 2023<ref name=Hilton2023/></small> (Late Cretaceous, North America)
*** species {{extinct}} ''Parapsephurus willybemisi'' <small>Hilton ''et al.'', 2023<ref name=Hilton2023/></small>
** subfamily Polyodontinae
*** genus {{extinct}} ''[[Psephurus]]'' <small>[[Albert Günther|Günther]], 1873</small>
**** {{extinct}}''Psephurus gladius'' <small>[[Eduard von Martens|E. von Martens]], 1862</small> [[Chinese paddlefish]] (extinct c. 2003)
*** tribe Polyodontini
**** genus {{extinct}} ''[[Crossopholis]]'' <small>[[Edward Drinker Cope|Cope]]'','' 1883</small> ([[Paleogene]], North America)
***** species {{extinct}} ''Crossopholis magnicaudatus'' <small>Cope, 1883</small>
**** genus ''[[Polyodon]]'' <small>[[Bernard Germain de Lacépède|Lacépède]], 1797</small> ([[Paleocene]]-Recent, North America)
***** ''[[Polyodon spathula]]'' <small>[[Johann Julius Walbaum|Walbaum]], 1792</small> [[American paddlefish]]
***** {{extinct}} ''{{ill|Polyodon tuberculata|qid=Q25432127}}'' <small>Grande & Bemis, 1991</small>


Relationships of the genera are from {{harvp|Grande|Jin|Yabumoto|Bemis|2002}}.<ref>{{cite journal |last1=Grande |first1=Lance |last2=Jin |first2=Fan |last3=Yabumoto |first3=Yoshitaka |last4=Bemis |first4=William E. |date=2002-07-08 |title=''Protopsephurus liui'', a well-preserved primitive paddlefish (Acipenseriformes: Polyodontidae) from the lower Cretaceous of China |journal=Journal of Vertebrate Paleontology |volume=22 |issue=2 |pages=209–237 |doi=10.1671/0272-4634(2002)022[0209:plawpp]2.0.co;2 |s2cid=86258128 |issn=0272-4634 }}</ref>{{clade
 |style=font-size:100%;line-height:80%
 |label1=Polyodontidae
 |1={{clade
   |1={{clade
      |1={{extinct}} ''[[Protopsephurus]]''
       }}      
    |2={{clade
     |label1=
      |1={{clade
        |1={{extinct}} ''[[Paleopsephurus]]''
         }}
       |label2=Polyodontinae
       |2={{clade
         |1={{extinct}} ''[[Psephurus]]''
         |2={{clade
          |1={{extinct}} ''[[Crossopholis]]''
          |2=''[[Polyodon]]''
          }}
        }}
      }}
    }}
 }}

==Notes==
{{notelist}}

==References==
{{reflist|25em}}

== External links ==

{{Commons category|Polyodontidae}}
* [https://www.youtube.com/watch?v=FONx-LEly0k&list=UUDccenSZMiOc93B6BF6OSbA&index=7 One hour PBS documentary]
* [https://web.archive.org/web/20070703112348/http://www.capachi.com/paddlefish.htm The Chinese Paddlefish Website] – containing many photographs of ''Psepherus''.
* [https://web.archive.org/web/20060422092004/http://www.arkive.org/species/GES/fish/Polyodon_spathula/ images and movies of the paddlefish ''(Polyodon spathula)'' ARKive]
* [http://www.fishbase.org/Summary/FamilySummary.cfm?ID=33 FishBase entry for Polyodontidae]
* [https://web.archive.org/web/20040819002327/http://www.umesc.usgs.gov/aquatic/fish/paddlefish/main.html USGS UMESC Paddlefish Study]
* [https://fisheries.org/2016/10/mississippi-river-basin-paddlefish-population-dynamics-implications-for-the-management-of-a-highly-migratory-species/ Fisheries.org]
* [https://gfp.sd.gov/fishing-boating/paddlefish.aspx Paddlefish Fisheries Management]
* [https://web.archive.org/web/20090916013046/http://www.phy.ohiou.edu/~neiman/synchronization/ Stochastic synchronization of electroreceptors in the paddlefish]

{{Chondrostei|state=collapsed}}
{{Acipenseriformes}}
{{Taxonbar|from=Q858011}}
{{Authority control}}

[[Category:Polyodontidae]]
[[Category:Acipenseriformes]]
[[Category:Freshwater fish of North America]]
[[Category:Taxa named by Charles Lucien Bonaparte]]
[[Category:Extant Barremian first appearances]]