Editing Atlantic cod (section)

==Reproduction==
[[File:Gadus morhua (High Arctic, Canada).png|thumb|Atlantic cod in a High Arctic Lake in Canada. These cod resemble those of past Atlantic catches. Measuring {{cvt|47|-|53|in|cm|order=flip}} long and weighing between {{cvt|44|and|57|lb|kg|order=flip}}, it is easy to see that today's {{cvt|16|-|20|in|cm|order=flip}} commercially caught cod are less than half this size. A cod 2.7 times as long would weigh 20 times as much.]]
<gallery mode="packed">
File:Gravid female cod.jpg|Spawning female in captivity
File:Jonge kabeljauwen of gul nieuwsgierig bij een wrak-4885743.webm|Juveniles on a wreck in the [[North Sea]]
File:Gadus morhua (head).jpg|Atlantic cod juvenile
File:Gadus morhua Cod-2b-Atlanterhavsparken-Norway.JPG|Adult
</gallery>

Atlantic cod will attain sexual maturity between ages two and eight with this varying between different populations and has also varied over time with a population.<ref name=":1" /><ref name=":2" /> Their [[gonad]]s take several months to develop and most populations will spawn from January to May.<ref>{{Cite journal |last=ICES |date=2005 |title=Spawning and life history information for North Atlantic cod stocks |url=https://ices-library.figshare.com/articles/_/18624242 |doi=10.17895/ICES.PUB.5478}}</ref><ref>{{Cite journal |last1=Kjesbu |first1=Olav Sigurd |last2=Righton |first2=David |last3=Krüger-Johnsen |first3=Maria |last4=Thorsen |first4=Anders |last5=Michalsen |first5=Kathrine |last6=Fonn |first6=Merete |last7=Witthames |first7=Peter R. |date=April 2010 |editor-last=Marshall |editor-first=C. Tara |title=Thermal dynamics of ovarian maturation in Atlantic cod (Gadus morhua) |url=http://www.nrcresearchpress.com/doi/10.1139/F10-011 |journal=Canadian Journal of Fisheries and Aquatic Sciences |language=en |volume=67 |issue=4 |pages=605–625 |doi=10.1139/F10-011 |bibcode=2010CJFAS..67..605K |hdl=11250/108908 |issn=0706-652X|hdl-access=free }}</ref> For many populations, the spawning grounds are located in a different area than the feeding grounds so require the fish to migrate in order to spawn.  On the spawning area, males and females will form large schools. Based on behavioral observations of cod, the cod mating system has been likened to a [[lekking]] system, which is characterized by males aggregating and establishing dominance hierarchies, at which point females may visit and choose a spawning partner based on status and sexual characteristics.<ref name="Ponomarenko 1965 349–354" /> Evidence suggests male sound production and other sexually selected characteristics allow female cod to actively choose a spawning partner. Males also exhibit aggressive interactions for access to females.<ref name="Hutchings">{{cite journal |last=Hutchings |first=Jeffrey A |author2=Bishop, Todd D |author3=McGregor-Shaw, Carolyn R |date=1 January 1999 |title=Spawning behaviour of Atlantic cod: evidence of mate competition and mate choice in a broadcast spawner |journal=Canadian Journal of Fisheries and Aquatic Sciences |volume=56 |issue=1 |pages=97–104 |doi=10.1139/f98-216}}</ref>

Atlantic cod are batch spawners, in which females will spawn approximately 5–20 batches of eggs over a period of time with 2–4 days between the release of each batch.<ref>{{Cite journal |last1=Kjesbu |first1=O S |last2=Solemdal |first2=P |last3=Bratland |first3=P |last4=Fonn |first4=M |date=1996-03-01 |title=Variation in annual egg production in individual captive Atlantic cod ( Gadus morhua ) |url=http://www.nrcresearchpress.com/doi/10.1139/f95-215 |journal=Canadian Journal of Fisheries and Aquatic Sciences |language=en |volume=53 |issue=3 |pages=610–620 |doi=10.1139/f95-215 |bibcode=1996CJFAS..53..610K |hdl=11250/109284 |issn=0706-652X}}</ref><ref>{{Cite journal |last=Kjesbu |first=O. S. |date=February 1989 |title=The spawning activity of cod, Gadus morhua L. |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1095-8649.1989.tb03302.x |journal=Journal of Fish Biology |language=en |volume=34 |issue=2 |pages=195–206 |doi=10.1111/j.1095-8649.1989.tb03302.x |bibcode=1989JFBio..34..195K |issn=0022-1112}}</ref> Each female will spawn between 2 hundred thousand and 15&nbsp;million eggs, with larger females spawning more eggs.<ref>{{Cite journal |last1=Skjæraasen |first1=Jon Egil |last2=Nilsen |first2=Trygve |last3=Kjesbu |first3=Olav S |date=2006-02-01 |title=Timing and determination of potential fecundity in Atlantic cod (''Gadus morhua'') |url=http://dx.doi.org/10.1139/f05-218 |journal=Canadian Journal of Fisheries and Aquatic Sciences |volume=63 |issue=2 |pages=310–320 |doi=10.1139/f05-218 |bibcode=2006CJFAS..63..310S |issn=0706-652X}}</ref> Females release gametes in a ventral mount, and males then [[fertilization|fertilize]] the released eggs. The eggs and newly hatched larvae float freely in the water and will drift with the current, with some populations relying upon the current to transport the larvae to nursery areas.<ref>{{Cite book|title=The DK Nature Encyclopedia|last=Burnie|first=David|publisher=DK Publishing, Inc|year=1998|isbn=0-7894-3411-3|location=New York|pages=[https://archive.org/details/dknatureencyclop0000unse/page/189 189]|url=https://archive.org/details/dknatureencyclop0000unse/page/189}}</ref>