Editing Blue cod (section)

==Economic and population management issue==
[[File:New Zealand blue cod dish, Corner House, Singapore Botanic Gardens - 20170126.jpg|thumb|A dish of blue cod and Hokkaido scallops in a restaurant in [[Singapore]]]]

Blue cod is well known by the public due to its commercial and recreational importance.<ref name="Paul.a" /><ref name="Paul.b" /> As mentioned before, we fish 2000 to 2500 tones of ''P. colias'' per year.<ref name="MPI2014" /> The value of ''P. colias'' as being the third popular recreational fishing species cannot be ignored,<ref name="MPI2018" /> this includes using their flesh as rock lobster bait.<ref name="Robertson1980" >{{cite journal| last1=Robertson |first1=D.A.| year=1980 |title=Hydrology and the quantitative distribution of planktonic eggs of some marine fishes of the Otago Coast, South-eastern New Zealand |journal=Fisheries Research Bulletin | volume=21 |url=http://docs.niwa.co.nz/library/public/frb21.pdf}}</ref>  It is estimated that the marginal willingness to pay for an additional ''P. colias'' is $1.61 per fish and the average willingness to pay is $24.46 per fish.<ref name="Williamson2000">{{cite conference| last1=Williamson| first1=S.| year=2000 | title=The Economic Value of New Zealand Marine Recreational Fishing and its Use as a Policy Tool |conference=International Institute of Fisheries Economics & Trade (IIFET) 2000, "Microbehavior and Macroresults" |location=Corvallis, Oregon, USA |book-title=IIFET 2000 Proceedings| url=https://ir.library.oregonstate.edu/downloads/fx719n336}}</ref> It is estimated that in 1999, 1.2 million ''P. colias'' was harvested, of which 70% were from the [[South Island]].<ref name="Williamson2000" /> Thus, [[Ministry for Primary Industries (New Zealand)]] has set minimum capture length and maximum capture limit of ''P. colias'', which varies between areas mainly depending on abundance, to avoid [[Natural resource|depletion]].  For example, in the South-East area (of [[South Island]] from [[Clarence Point]] to [[Southland, New Zealand|Southland]] and extended to the [[Chatham Islands]], [[New Zealand]]), no fish shorter than 30&nbsp;cm can be taken and each fisher has a limit up to 30 fish per day.<ref name="MPI2018" />

To achieve [[Sustainable fishery|sustainable fishing]], it is crucial to persist healthy [[population]] structure with continuous monitoring and quotas set to date.<ref name="MPIs" >{{cite book| author=Ministry for Primary Industries |year=2016| title=New Zealand's Sustainable Fisheries| url=http://www.mpi.govt.nz/dmsdocument/11096-new-zealands-sustainable-fisheries}}</ref>  However, as the largest fish in the [[population]] would be the male, males are often being caught and is thought to affect the females changing their sex earlier.<ref name="BeentjesCarbines" />  This is an emerging issue to all hermaphrodites.<ref name="Robinson" >{{cite journal| last1=Robinson |first1=O. J.|last2=Jensen|first2=O. P |last3=Provost | first3=M. M.|last4=Huang | first4=S.| last5=Fefferman| first5=N. H.| last6=Kebir| first6=A.| last7=Kebir| first7=A.| last8=Lockwood| first8=Julie | year=2016| title=Evaluating the impacts of fishing on sex-changing fish: a game-theoretic approach| journal=ICES Journal of Marine Science| volume=74| issue=3| pages=652–659| doi=10.1093/icesjms/fsw222| doi-access=free}}</ref>  Surprisingly, the sex ratio male to females of ''P. colias'' is about 5:1<ref name="Carbines.b" /> which is biologically implausible. This suggests that sex changes might not purely depend on fish length, but we cannot ignore the fact that fishery has changed the natural population composition of "P. colias".  To understand the direct impact on P. colias despite population decline<ref name="BeentjesCarbines" /> further research is required.

In addition, the fundamental unit of concern of its management of [[population]] is the [[Genetics|genetic]] structure that can lead to the reduction of the evolutionary potential for responding to [[environmental change]], the increase of [[inbreeding]] risk and the force of selective [[Genetics|genetic]] change.<ref name="Smith" /> Since a number of evidence indicated that blue cod are relatively sedentary,<ref name="ColeVilloutaDavidson" /><ref name="MaceJohnston" /><ref name="RodgersWing" /><ref name="Smith" /> the [[Overfishing|fishing pressure]] may lead to potential local [[Natural resource|depletion]].<ref name="CarbinesMcKenzie" /> Recent studies showed that the [[Genetics|genetic]] differences were significant between mainland [[List of islands of New Zealand]] [[population]] and [[Chatham Island]] [[population]].<ref name="Gebbie" /><ref name="Smith" /> On the other hand, the differences within mainland[[List of islands of New Zealand]] [[population]]s were limited while the pattern of the isolation by distance was detected.<ref name="Smith" /> Further research using [[microsatellite]] [[Genetic marker|DNA markers]] suggested that some significant [[Genetics|genetic]] differences between [[List of islands of New Zealand|mainland]] [[population]] exist which indicate the potential long-distance [[Biological dispersal|dispersal]], but the [[Biological dispersal|dispersal]] rate is too low to have [[Demography|demographic]] effect in the [[population]].<ref name="Gebbie">{{cite book| last1=Gebbie| first1=C. L.| year=2014| title=Population genetic structure of New Zealand blue cod (''Parapercis colias'') based on mitochondrial and microsatellite DNA markers (Master thesis)| publisher=Victoria University of Wellington| url=http://researcharchive.vuw.ac.nz/handle/10063/4245}}</ref>