Editing Haddock (section)

==Habitat and biology==
[[File:Haddock fins.tiff|thumb|left|[[Fish fin|Fins]], [[barbel (anatomy)|barbel]] and [[lateral line]] on a haddock. Haddock have three [[dorsal fin]]s and two [[anal fin]]s.]]
The haddock is a [[demersal fish|demersal species]] which occurs at depths from {{convert|10|to|450|m|ft fathom|abbr=on|sigfig=2}}, although it is most frequently recorded at {{convert|80|to|200|m|ft fathom|sigfig=1|abbr=on}}. It is found over substrates made up of rock, sand, gravel or shells and it prefers temperatures of between {{convert|4|and|10|°C|°F}}. Off Iceland and in the Barents Sea, haddock undergo extensive migrations, but in the north western Atlantic its movements are more restricted, consisting of movements to and from their spawning areas. They reach sexual maturity at 4 years old in males and 5 years old in females, except for the population in the North Sea which matures at ages of 2 years in males and 3 years in females. The overall sex ratio is roughly 1:1, but in shallower areas, females predominate, while the males show a preference for waters further offshore.<ref name = FAO/>

The fecundity of the females varies with size: a fish of {{convert|25|cm|in|frac=2|abbr=on}} length bears 55,000 eggs while a fish at {{convert|91|cm|in|frac=2|abbr=on}} has 1,841,000 eggs. Spawning takes place from depths of around {{convert|50|to|150|m|ft fathom|abbr=on|sigfig=1}}. In the northwestern Atlantic spawning lasts from January to July, although it does not occur simultaneously in all areas, and in the northeastern Atlantic the spawning season runs from February to June, peaking in March and April.<ref name = FAO/> The eggs are pelagic with a diameter of {{convert|1.2|to|1.7|mm|in|frac=128}}, and they take one to three weeks to hatch. Following metamorphosis, the past larval fish remain pelagic until they attain a length of around {{convert|7|cm|in|frac=2|abbr=on}}, when they settle to a demersal habit.<ref name="ICES">{{cite web |title=Haddock |url=http://www.ices.dk/explore-us/projects/EU-RFP/EU%20Repository/ICES%20FIshMap/ICES%20FishMap%20species%20factsheet-haddock.pdf |url-status=dead |archive-url=https://web.archive.org/web/20180415063505/http://www.ices.dk/explore-us/projects/EU-RFP/EU%20Repository/ICES%20FIshMap/ICES%20FishMap%20species%20factsheet-haddock.pdf |archive-date=15 April 2018 |access-date=14 April 2018 |work=ICES Fish Map |publisher=[[International Council for the Exploration of the Sea]]}}</ref> Their growth rate shows considerable regional variation and fish at one year old can measure {{convert|17|to|19|cm|in|frac=2|abbr=on}}, at 2 years old {{convert|25|to|36|cm|in|frac=2|abbr=on}}, up to {{convert|75|to|82|cm|in|frac=2|abbr=on}} at 13 years old. Their lifespan is around 14 years.<ref name = FAO/> The most important spawning grounds are in the waters off the central coast of [[Norway]], off the southwest of [[Iceland]], and over the [[Georges Bank]].<ref name = ICES/><ref name = NOAA/> The fish which spawn in inshore waters are normally smaller and younger fish than those which occur in offshore areas. The younger fish have a spawning season which is less than half of that of the larger and older stock offshore. Once hatched the larvae do not appear to travel far from their spawning grounds, however some larvae spawning off the west coast of [[Scotland]] are transported into the North Sea through the [[Fair Isle]]-[[Shetland]] Gap or to the northeast of Shetland.<ref name = ScotGov>{{cite web | url = http://www.gov.scot/Topics/marine/marine-environment/species/fish/demersal/haddock | title = Haddock | access-date = 13 April 2018 | publisher = [[Scottish Government]] Riaghaltas na h-Alba | work = Topics Marine & Fisheries | archive-date = 14 March 2020 | archive-url = https://web.archive.org/web/20200314193902/https://www2.gov.scot/Topics/marine/marine-environment/species/fish/demersal/haddock | url-status = dead }}</ref>

In their larval stages, haddock mainly feed on the immature stages of [[copepod]]s, [[Ostracod|ostracods]] and [[limacina]] with their diet changing as they grow, moving on to larger pelagic prey such as [[Amphipoda|amphipods]], [[Krill|euphausiids]], eggs of invertebrates, zoea larvae of [[Decapoda|decapods]] and increasing numbers of copepods.<ref name=":5">{{Cite journal |last1=Bastrikin |first1=Dorota K. |last2=Gallego |first2=Alejandro |last3=Millar |first3=Colin P. |last4=Priede |first4=Imants G. |last5=Jones |first5=Emma G. |date=2014-10-01 |title=Settlement length and temporal settlement patterns of juvenile cod (Gadus morhua), haddock (Melanogrammus aeglefinus), and whiting (Merlangius merlangus) in a northern North Sea coastal nursery area |url=https://academic.oup.com/icesjms/article/71/8/2101/753583 |journal=ICES Journal of Marine Science |language=en |volume=71 |issue=8 |pages=2101–2113 |doi=10.1093/icesjms/fsu029 |issn=1095-9289|url-access=subscription }}</ref><ref>{{Cite journal |last1=Rowlands |first1=William Ll. |last2=Dickey-Collas |first2=Mark |last3=Geffen |first3=Audrey J. |last4=Nash |first4=Richard D.M. |date=July 2008 |title=Diet overlap and prey selection through metamorphosis in Irish Sea cod (Gadus morhua), haddock (Melanogrammus aeglefinus), and whiting (Merlangius merlangus) |url=http://www.nrcresearchpress.com/doi/10.1139/F08-041 |journal=Canadian Journal of Fisheries and Aquatic Sciences |language=en |volume=65 |issue=7 |pages=1297–1306 |doi=10.1139/F08-041 |bibcode=2008CJFAS..65.1297R |issn=0706-652X|url-access=subscription }}</ref> Once they have reached the settled, demersal, post-larval stage, they gradually switch from pelagic to [[benthic]] prey.<ref name=":5" />  Adults primarily feed on benthic invertebrates such as [[sea urchins]], [[Brittle star|brittlestar]]s, [[Bivalvia|bivalves]] and worms,<ref>{{Cite journal |last1=Schückel |first1=S. |last2=Ehrich |first2=S. |last3=Kröncke |first3=I. |last4=Reiss |first4=H. |date=July 2010 |title=Linking prey composition of haddock Melanogrammus aeglefinus to benthic prey availability in three different areas of the northern North Sea |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1095-8649.2010.02657.x |journal=Journal of Fish Biology |language=en |volume=77 |issue=1 |pages=98–118 |doi=10.1111/j.1095-8649.2010.02657.x |pmid=20646141 |bibcode=2010JFBio..77...98S |issn=0022-1112|url-access=subscription }}</ref> however, they will feed opportunistically on smaller fish such as [[capelin]], [[Sand eel|sandeels]] and ''[[Trisopterus esmarkii|'''Norway pout''']].''<ref>{{Cite journal |last1=Jónsdóttir |first1=I G |last2=Björnsson |first2=B |last3=Ragnarsson |first3=S á |last4=Elvarsson |first4=B þ |last5=Sólmundsson |first5=J |date=2024-04-25 |editor-last=Ojaveer |editor-first=Henn |title=Spatial distributional shifts and associated body condition changes of haddock ( Melanogrammus aeglefinus ) following population expansion |url=https://academic.oup.com/icesjms/article/81/3/587/7219434 |journal=ICES Journal of Marine Science |language=en |volume=81 |issue=3 |pages=587–599 |doi=10.1093/icesjms/fsad108 |issn=1054-3139|doi-access=free }}</ref><ref>{{Cite journal |last=Adlerstein |first=S |date=June 2002 |title=Comparison of stomach contents of haddock (Melanogrammus aeglefinus) from the 1981 and 1991 North Sea International Stomach Sampling Projects |url=https://academic.oup.com/icesjms/article-lookup/doi/10.1006/jmsc.2002.1197 |journal=ICES Journal of Marine Science |language=en |volume=59 |issue=3 |pages=497–515 |doi=10.1006/jmsc.2002.1197|bibcode=2002ICJMS..59..497A |url-access=subscription }}</ref> Juvenile haddock are an important prey for larger demersal fish, including other [[Gadiformes|gadoids]], while seals prey on the larger fish.

The recorded growth rates of haddock underwent significant change over the 30 to 40 years up to 2011.<ref name = ICES/> Growth has been more rapid in recent years, with haddock attaining adult size much earlier than was noted 30–40 years ago. However, the degree to which these larger, younger fish contribute to reproductive success of the population is unknown. The growth rates of haddock, however, have slowed in recent years. There is some evidence which indicates that these slower growth rates may be the result of an exceptionally large year class in 2003.<ref name = NOAA>{{cite web | url = http://www.nefsc.noaa.gov/nefsc/publications/crd/crd0216/ | title = NEFSC Ref Doc | access-date = 14 April 2018 | publisher = NOAA}}</ref> The haddock stock periodically has higher than normal productivity; for example in 1962 and 1967, and to a lesser extent, 1974 and 1999. These result in a more southerly distribution of the fish and have a strong effect on the biomass of the spawning stock, but because of high fishing mortality, these revivals do not have any lasting effect on the population. In general, there was above average recruitment from the 1960s up to the early 1980s, similar to recruitment for Atlantic cod and [[Merlangius merlangus|whiting]], this has been called the ''gadoid outburst''. There was strong recruitment in 1999 but since then, the recruitment rate has been very low.<ref name = ICES/>