Editing American paddlefish (section)

==Reproduction and life cycle==
[[File:Paddlefish transformation from embryo to larval stage of development.webm|thumb|260px|Development of paddlefish from embryo to larval stage]]
[[File:American paddlefish fry at 30 days of age - 2013.jpg|thumb|260px|Stages of rostrum development|right]]

American paddlefish are long-lived, sexually late maturing [[pelagic fish]]. Females do not begin [[spawn (biology)|spawning]] until they are seven to ten years old, some as late as sixteen to eighteen years old. Females do not spawn every year; rather they spawn every second or third year. Males spawn more frequently, usually every year or every other year beginning around age seven, some as late as nine or ten years of age.<ref name="LSU"/><ref name="ND">{{cite web|url=http://gf.nd.gov/fishing/other-fishing-information/paddlefish-snagging-season/paddlefish-questions-and-answers |publisher=North Dakota Game and Fish Department |title=Paddlefish Questions and Answers |date=2012 |access-date=June 9, 2014 |url-status=dead |archive-url=https://web.archive.org/web/20150624063851/http://gf.nd.gov/fishing/other-fishing-information/paddlefish-snagging-season/paddlefish-questions-and-answers |archive-date=June 24, 2015 }}</ref>

American paddlefish begin their upstream spawning migration sometime during early spring; some begin in late fall.<ref name="ND"/> They spawn on 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 |url=https://nature.mdc.mo.gov/discover-nature/field-guide/search/paddlefish |publisher=Missouri Department of Conservation |title=Paddlefish, ''Polyodon spathula'' |work=Discover Nature Field Guide |access-date=June 9, 2014 |url-status=live |archive-url=https://web.archive.org/web/20170824024506/https://nature.mdc.mo.gov/discover-nature/field-guide/search/paddlefish |archive-date=August 24, 2017 }}</ref> Although availability of preferred spawning habitat is essential, there are three precise environmental events that must occur before American paddlefish will spawn.<ref name=EWS>{{cite web|url=http://www.earthwave.org/paddlefish|publisher=Earthwave Society|title=Paddlefish|author=Betty Wills|date=2004|access-date=October 3, 2014|url-status=live|archive-url=https://web.archive.org/web/20141006103219/http://www.earthwave.org/paddlefish|archive-date=October 6, 2014}}</ref><ref name="LSU" /> The water temperature must be from {{convert|55|to|60|F|C}}; the lengthened [[photoperiodism|photoperiod]] which occurs in spring triggers biological and behavioral processes that are dependent on increasing day length; and there must be a proper rise and flow in the river before a successful spawn can occur. Historically, American paddlefish did not spawn every year because the precise environmental events occurred just once every 4 or 5 years.<ref name="EWS" />

American paddlefish are [[broadcast spawner]]s, also referred to as mass spawners or synchronous spawners. [[Gravid]] females release their [[egg (biology)|eggs]] into the water over bare rocks or gravel at the same time males release their [[spermatozoon|sperm]]. Fertilization occurs externally. The eggs become sticky after they are released into the water and will attach to the bottom substrate. Incubation varies depending on water temperature, but in {{convert|60|F|C|abbr=on}} water the eggs will hatch into [[larval fish]] in about seven days.<ref name="ND" /> After hatching, the larval fish drift downstream into areas of low flow velocity where they forage on zooplankton.<ref name="ND"/>

Young American paddlefish are poor swimmers which makes them susceptible to predation. Therefore, rapid first-year growth is important to their survival.<ref name="ND" /> [[Juvenile fish|Fry]] can grow about {{convert|1|inch|cm|abbr=on}} per week,<ref name="PA">{{cite journal|url=https://www.fish.state.pa.us/anglerboater/1999/jf99/padlfish.htm |title=Progress with Paddlefish Restoration |journal=Pennsylvania Angler and Boater |author=Dudley Parr |issue=January/February 1999 |access-date=August 28, 2014 |url-status=dead |archive-url=https://web.archive.org/web/20140903095036/https://www.fish.state.pa.us/anglerboater/1999/jf99/padlfish.htm |archive-date=September 3, 2014 }}</ref> and by late July the [[fingerling (fish)|fingerlings]] are around {{convert|5|-|6|in|cm|abbr=on}} long.<ref name="ND"/> Their rate of growth is variable and highly dependent on food abundance. Higher growth rates occur in areas where food is not limited.  The feeding behavior of fingerlings is quite different from that of older juveniles and adults. They capture individual plankton one by one, which requires detection and location of individual ''[[Daphnia]]'' on approach, followed by an intercept maneuver to capture the selected prey.<ref name="OhioEdu" /> By late September fingerlings have developed into juveniles, and are around {{convert|10|-|12|in|cm|abbr=on}} long. After the 1st year their growth rate slows and is highly variable. Studies indicate that by age 5 their growth rate averages around {{convert|2|in|cm|abbr=on}} per year depending on the abundance of food and other environmental influences.<ref name="TSU"/>