{{Short description|Species of ray-finned fish}} {{Speciesbox | image =Shadow trevally 2.JPG | status = LC | status_system = IUCN3.1 | status_ref = <ref name = iucn>{{cite iucn | author1 = Smith-Vaniz, W.F. | author2 = Williams, I. | name-list-style = amp | year = 2016 | title = ''Carangoides dinema'' |errata=2017 | volume = 2016 | article-number = e.T20429438A115372384 | doi = 10.2305/IUCN.UK.2016-3.RLTS.T20429438A65927713.en | access-date = 12 November 2022}}</ref> | taxon = Carangichthys dinema | authority = ([[Pieter Bleeker|Bleeker]], 1851) | range_map = Carangoides dinema distribution.png | range_map_caption = Approximate range of the shadow trevally | synonyms_ref = <ref name="ECoF species" /> | synonyms = *''Carangoides dinema'' <br /><small>[[Pieter Bleeker|Bleeker]], 1851</small> *''Caranx dinema'' <br /><small>([[Pieter Bleeker|Bleeker]], 1851)</small> *''Carangichthys typus'' <br /><small>[[Pieter Bleeker|Bleeker]], 1853</small> *''Caranx longipes'' <br /><small>[[Franz Steindachner|Steindachner]], 1906</small> }}
The '''shadow trevally''' ('''''Carangichthys dinema'''''), also known as the '''shadow kingfish''', '''twothread trevally''' or '''Aldabra trevally''', is a [[species]] of inshore [[marine (ocean)|marine]] [[fish]] in the jack [[Family (taxonomy)|family]] [[Carangidae]]. The species is patchily distributed throughout the [[tropical]] and subtropical waters of the [[Indian Ocean|Indian]] and west [[Pacific Ocean]]s, from [[South Africa]] in the west to [[Japan]] and [[Samoa]] in the east, reaching as far south as [[Indonesia]] and [[New Caledonia]]. It is most easily distinguished from similar species by as series of dark rectangular blotches under the second [[dorsal fin]], giving a 'shadowed' appearance, from which its [[common name]] is derived. The shadow trevally is a reasonably large fish, growing to 85 cm in length and at least 2.6 kg in weight. It inhabits shallow [[coastal]] waters, including [[reef]]s, [[bay]]s, and [[estuaries]], where it takes small fish and benthic [[crustacean]]s as prey. Nothing is known of the species' [[ecology]] and [[reproductive biology]]. It is of little importance to [[fisheries]], and is occasionally taken by bottom [[fishing trawler|trawl]]s and other [[artisanal fishing]] gear.
==Taxonomy and naming== The shadow trevally is presently classified within the [[genus]] ''[[Carangichthys]]'', one of a number of genera referred to as trevallies.<ref name="ECoF species">{{Catalog of Fishes |genus=Carangichthys |list=species |date=12 February 2026}}</ref> ''Carangichthys'' is further classified in the family [[Carangidae]], and Carangidae is part of the [[Order (biology)|order]] [[Carangiformes]].<ref name = Nelson5>{{cite book |title=Fishes of the World |edition=5th |author1=J. S. Nelson |author2=T. C. Grande |author3=M. V. H. Wilson |year=2016 |pages=380–387 |publisher=Wiley |isbn= 978-1-118-34233-6 |url=https://sites.google.com/site/fotw5th/ }}</ref>
The species was first [[scientific classification|scientifically described]] and named by the Dutch [[ichthyologist]] [[Pieter Bleeker]] in 1851 based on a specimen collected from the waters off [[Jakarta]], located on [[Java]] in [[Indonesia]], which was designated to be the [[holotype]].<ref name = "Lin1999">{{cite journal | last = Lin | first = Pai-Lei |author2=Shao, Kwang-Tsao | title = A Review of the Carangid Fishes (Family Carangidae) From Taiwan with Descriptions of Four New Records | journal = Zoological Studies | volume = 38 | issue = 1 | pages = 33–68 | url = http://cat.inist.fr/?aModele=afficheN&cpsidt=10055944 | date = 28 March 1999 }}</ref> He named this new species ''[[Carangoides]] dinema'', with the specific name derived from the Latin ''dis'', meaning two and the Greek ''nema'', meaning thread, referring to the fin anatomy of the species. The species is quite unique in the comparatively simple [[Taxonomy (biology)|taxonomic history]] it has, with other related species often renamed and transferred between genera many times. The species is most [[common name|commonly termed]] the 'shadow trevally' or 'shadow kingfish' in reference to a series of small dark blotches positioned on the upper side, underneath the second dorsal fin, giving the appearance of shadow from the fin itself. Other names used for the species include 'two-thread trevally' and 'Aldabra trevally'.<ref name = "fishbase">{{FishBase | genus = Carangoides | species = dinema | year = 2008 | month = September}}</ref>
==Description== [[File:Shadow trevally.jpg|thumb|left|An angler's catch of shadow trevally]] The shadow trevally is similar in form to a number of other jacks in the family Carangidae, having an almost [[Glossary of ichthyology#O|ovate]], strongly compressed body.<ref name = "FAO">{{cite book |editor-last=Carpenter |editor-first=Kent E. |editor2=Volker H. Niem | title = FAO species identification guide for fishery purposes. The living marine resources of the Western Central Pacific. Volume 4: Bony fishes part 2 (Mugilidae to Carangidae) | year = 2001 | location = Rome |page= 2694 | url = ftp://ftp.fao.org/docrep/fao/009/x2400e/x2400e52.pdf | isbn = 92-5-104587-9 | publisher = Food and Agriculture Organization of the United Nations | others = FAO}}</ref> It is fairly large fish, growing to a maximum known length of 85 cm<ref>{{cite book | last = Kuiter | first = Rudie H. |author2=T. Tonozuka | title = Pictorial guide to Indonesian reef fishes. Part 1. Eels- Snappers, Muraenidae - Lutjanidae| publisher = Zoonetics | year = 2001 | location = Australia | page = 302 | isbn = 979-98188-1-8 }}</ref> and a recorded weight of 2.6 [[kilogram|kg]].<ref name = "fishbase"/> The [[anatomical terms of location#Dorsal and ventral|dorsal]] profile is strongly convex, while the [[anatomical terms of location#Dorsal and ventral|ventral]] profile is less so, even tending to be concave between the snout and the [[anal fin]], while the [[nape]] is elevated and almost straight in profile.<ref name = "FAO"/> There are two separate [[dorsal fin]]s, the first consisting of 8 [[Fish anatomy#Spines and rays|spines]] and second of a single spine and 17 to 19 [[Fish anatomy#Spines and rays|soft rays]]. The lobe of the second dorsal fin is elongated, being greater than the head length. The anal fin is composed of two [[Anatomical terms of location#Anterior and posterior|anteriorly]] detached spines followed by a single spine and 15 to 17 soft rays.<ref name = "Tarp">{{cite book | last = Gloerfelt-Tarp | first = Thomas |author2=Patricia J. Kailola | title = Trawled Fishes of Southern Indonesia and Northeastern Australia | publisher = Australian Development Assistance Bureau | year = 1984 | location = Singapore | page = 285 | isbn = 0-642-70001-X }}</ref> The [[lateral line]] has a moderate arch anteriorly, with the junction of the curved and straight sections below the tenth or twelfth soft rays of the second dorsal fin. The curved section of the lateral line is slightly longer than the straight section, and contains 60 to 63 [[scale (zoology)|scales]], while the straight part contains no to six scales followed by 23 to 30 [[scutes]]. The breast is devoid of scales ventrally to behind the [[pelvic fin]] origin and up to the [[pectoral fin]] base, although in rare cases this is interrupted by a lateral band of scales.<ref name = "Tarp"/> Both [[jaw]]s contain bands of small teeth, with the bands becoming wider anteriorly, and the upper jaw also has an irregular outer series of moderately large teeth, with large specimens also showing this in the lower jaw. It has a total of 24 to 28 [[gill raker]]s and 24 [[vertebrae]].<ref name = "FAO"/>
In life, the shadow trevally is a bluish-green colour above, fading to a silvery white on the underside. It takes its common name from a series of small black-brown rectangular blotches which become larger posteriorly on its back between the bases of the second dorsal fin rays. Also, a dark-brown, diffuse blotch is present on the [[operculum (fish)|operculum]]. The spinous dorsal fin is pale to dusky, while the second dorsal fin lobe is dusky with the ray tips yellowish. The anal fin distal margin is whitish-blue, and the [[caudal fin]] has a yellowish upper lobe and pale trailing edges and lower lobe tip. The pectoral fins are [[hyaline]] and the pelvic fins are whitish to dusky.<ref name = "FAO"/>
==Distribution and habitat== The shadow trevally is distributed patchily throughout the [[tropical]] to subtropical waters of the [[Indian Ocean|Indian]] and west [[Pacific Ocean]]s. The species' westernmost limit is a section of the [[east Africa]]n coast from [[South Africa]] to [[Tanzania]]. No records exist for the species further north until [[India]] and [[Sri Lanka]].<ref>{{cite book |editor-last=Kapoor |editor-first=D. |editor2=R. Dayal |editor3=A.G. Ponniah | title = Fish Biodiversity of India | publisher = National Bureau of Fish Genetic Resources | year = 2002 | location = Lucknow | page = 228 | isbn = 81-901014-8-X }}</ref> In the Pacific, the species is known from [[China]], [[Korea]], [[Southeast Asia]], and the [[Indonesia]]n and [[Philippines]] island chains. Its easternmost limit extends to [[Taiwan]] and [[Japan]] in the north and a number of small island groups including [[Tonga]] and [[Samoa]] in the south.<ref name = "fishbase"/>
The shadow trevally inhabits [[coastal]] waters at depths generally less than 15 m. It is known to Kruise in small schools along the shallow edge of steep [[reef]] drop-offs,<ref name = "fishbase"/> and has also been recorded from [[bay]]s and [[estuaries]].<ref>{{cite journal | last = Kuo | first = S.R. | author2 = K.T. Shao | title = Species composition of fish in the coastal zones of the Tsengwen estuary, with descriptions of five new records from Taiwan | journal = Zoological Studies | volume = 38 | issue = 4 | pages = 391–404 | year = 1999 | url = http://zoolstud.sinica.edu.tw/Journals/38.4/391-404.pdf | access-date = 2008-09-21 | archive-date = 2008-12-04 | archive-url = https://web.archive.org/web/20081204093753/http://zoolstud.sinica.edu.tw/Journals/38.4/391-404.pdf | url-status = dead }}</ref> The species has been recorded around [[shipwreck]]s, and one study showed it was one of the first fish to move in after a ship was scuttled.<ref>{{cite journal | last = Wantiez | first = Laurent |author2=Pierre Thollotw | title = Colonisation of the F/V Caledonie Toho 2 Wreck by a Reef-Fish Assemblage Near Noumea (New Caledonia) | journal = Atoll Research Bulletin | volume = 485 | pages = 2–19 | year = 2000 | doi=10.5479/si.00775630.485.1}}</ref>
==Biology and fishery== The biology and [[ecology]] of the shadow trevally is poorly known. It is known to live either in small schools or individually, and is a [[predator]]y fish, taking small fish and benthic [[crustacean]]s.<ref name = "fishbase"/> Nothing is known of its movements or [[reproduction]].
The shadow trevally is of little importance to fisheries throughout its range, taken as [[bycatch]] and generally not distinguished from other carangid species. It is often taken by bottom [[trawl]]s and various kinds of [[artisanal]] fishing gear.<ref name = "FAO"/>
==References== {{Reflist|2}}
==External links== *[http://www.fishbase.org/summary/SpeciesSummary.php?id=1925 Shadow trevally at Fishbase] *[http://www.eol.org/taxa/17043863?category_id=1&expertise=expert Encyclopedia of Life page]{{dead link|date=May 2018 |bot=InternetArchiveBot |fix-attempted=yes }}
{{Taxonbar|from=Q2562214}}
[[Category:Caranginae]] [[Category:Fish of South Africa]] [[Category:Marine fish of Southern Africa]] [[Category:Marine fauna of South Asia]] [[Category:Marine fish of Southeast Asia]] [[Category:Fish of Micronesia]] [[Category:Fish described in 1851|shadow trevally]] [[Category:Taxa named by Pieter Bleeker]]