Longfin trevally

{{Short description|Species of fish}} {{Speciesbox | image = Longfin trevally.JPG | status = LC | status_system = IUCN3.1 | status_ref = <ref name="iucn status 19 November 2021">{{cite iucn |author=Smith-Vaniz, W.F. |author2=Borsa, P. |author3=Carpenter, K.E. |author4=Yahya, S. |author5=Obota, C. |author6=Jiddawi, N. |date=2018 |title=''Carangoides armatus'' |volume=2018 |article-number=e.T20257156A46664044 |doi=10.2305/IUCN.UK.2018-2.RLTS.T20257156A46664044.en |access-date=19 November 2021}}</ref> | taxon = Atropus armatus | authority = ([[Eduard Rüppell|Rüppell]], 1830) | synonyms = *''Sciaena armata'' [[Peter Forsskål|Forsskål]], 1775 *''Caranx armatus'' (Forsskål, 1775) *''Citula armata'' (Forsskål, 1775) *''Citula armatus'' (Forsskål, 1775) *''Citula armata'' Rüppell, 1830 *''Caranx armatus'' (Rüppell, 1830) *''Carangoides armatus'' (Rüppell, 1830) *''Caranx ciliaris'' [[Georges Cuvier|Cuvier]], 1833 *''Citula ciliaria'' Rüppell, 1830 *''Caranx schlegeli'' [[Yojiro Wayima|Wayima]], 1924 *''Citula pescadorensis'' Oshima, 1924 *''Caranx pescadorensis'' (Oshima, 1924) | range_map = C. aramatus distribution.png | range_map_caption = Approximate range of the longfin trevally }}

The '''longfin trevally''' ('''''Atropus armatus'''''), also known as the '''longfin kingfish''', '''longfin cavalla''' or '''armed trevally''', is a [[species]] of [[inshore]] [[marine (ocean)|marine]] [[fish]] in the jack [[Family (taxonomy)|family]], [[Carangidae]]. The species is common in [[tropical]] to subtropical waters of the [[Indo-Pacific]], ranging from [[South Africa]] in the west to [[Japan]] in the east, typically inhabiting inshore [[reef]]s and bays. The species is easily distinguished by its elongate [[dorsal fin|dorsal]] and [[anal fin]] lobes and filamentous dorsal rays, as well as its scaleless breast. Longfin trevally are pelagic [[predator]]s, taking a variety of small fish, [[cephalopod]]s and [[crustacean]]s, and reach sexual maturity at around 21 cm. The species has a maximum known length of 57 cm and weight of 3.5 kg. The longfin trevally has a very complex [[Taxonomy (biology)|taxonomic history]] which is closely intertwined with another currently valid species, ''Carangoides ciliarius'', which may yet prove to be synonymous. Longfin trevally are of minor importance to [[fisheries]] throughout their range and are considered good [[fish (food)|table fish]], and are occasionally taken by [[angling|anglers]].

==Taxonomy and naming== The longfin trevally is classified within the genus ''[[Carangoides]]'', a group of fish commonly called jacks and trevallies. ''Carangoides'' falls into the jack and horse mackerel family [[Carangidae]], the Carangidae are part of the [[Order (biology)|order]] [[Carangiformes]].<ref name = Nelson5>{{BioRef |fotw5 |pages=380–387}}</ref>

The species was first [[scientific classification|scientifically described]] by the [[Germany|German]] [[naturalist]] [[Eduard Rüppell]] in 1830, based on a specimen taken from the [[Red Sea]], which was designated to be the [[holotype]].<ref name = "Zoocat" >{{cite book | last = Hosese | first = D.F. |author2=Bray, D.J. |author3=Paxton, J.R. |author4=Alen, G.R. | title = Zoological Catalogue of Australia Vol. 35 (2) Fishes | publisher = CSIRO | year = 2007 | location = Sydney | page = 1150 | isbn =978-0-643-09334-8 }}</ref> Rüppell named the species ''Citula armata'', placing his new species in what was at the time a valid jack genus created by [[Georges Cuvier]] in 1816. ''Citula'' was later synonymised with ''[[Pseudocaranx]]'', and all its members were re-examined and placed in a number of different jack genera. ''C. armata'' became ''Caranx armatus'', also masculinising the species name. Then the species was placed in ''Carangoides'' after re-examinations of its [[anatomy]] by a number of authors as part of a larger investigation into the [[Taxonomy (biology)|taxonomy]] of the carangid fishes.<ref name = "Williams">{{cite journal | last = Williams | first = F. |author2=Heemstra, P. C.|author3=Shameem| title = Notes on Indo-Pacific carangid fishes of the genus ''Carangoides'' Bleeker II. The ''Carangoides armatus'' group | journal = Bulletin of Marine Science | volume = 30 | issue = 1 | pages = 13–20 | year = 1980 }}</ref> Finally, the species was placed into ''[[Atropus]]'' in 2022.<ref>{{cite journal|author=Kimura, S.|author2= Takeuchi, S.|author3= Yadome, T. |year=2022|title= Generic revision of the species formerly belonging to the genus ''Carangoides'' and its related genera (Carangiformes: Carangidae)|journal= Ichthyological Research|volume= 69|issue=4|pages= 433-487 |doi=10.1007/s10228-021-00850-1}}</ref> The species has been described independently under three different names, with Cuvier applying ''Caranx ciliaris'' to the species, [[Masamitsu Ōshima]] applying ''Citula pescadorensis'' and Yojiro Wakiya ''Caranx schlegeli''.<ref>{{cite journal | last = Nichols | first = J. T. | title = On ''Citula ciliaria'' Rüppell | journal = Copeia | volume = 1940 | issue = 3 | pages = 201–202 | publisher = American Society of Ichthyologists and Herpetologists | year = 1940 | jstor = 1437985| doi = 10.2307/1437985}}</ref> These are all considered to be invalid [[junior synonym]]s under [[International Code of Zoological Nomenclature|ICZN]] rules.

The complexities of this naming process has led to extensive confusion between this species, originally described as ''Citula armata'', and a very closely related species, ''Sciaena armata'', now probably a synonym of ''[[Carangoides ciliarius]]''. ''Sciaena armata'', originally named by [[Peter Forsskål]] in 1775, has never been definitively identified,<ref name = "smith">{{cite journal | last = Smith | first = Margaret M. | title = Identity of ''Caranx armatus'' (Pisces: Carangidae) | journal = Copeia | volume = 1973 | issue = 2 | pages = 352–355 | publisher = American Society of Ichthyologists and Herpetologists | year = 1973 | jstor = 1442982 | doi = 10.2307/1442982}}</ref> but in the same volume he described ''C. armatus'' in, Rüppell created ''Citula ciliaria''. He was unsure if this species was the same fish Forsskål described as ''S. armatus'', and subsequent reviews of this species complex tend to keep Rüppell as the author. ''Carangoides armatus'' and ''Carangoides ciliarius'' were considered synonymous in a 1975 review of the species,<ref name = "smith"/> however some authorities still consider them both to be valid species.<ref name = "fishbase">{{FishBase | genus = Carangoides | species = armatus | year = 2008 | month = January}}</ref><ref>{{FishBase | genus = Carangoides | species = ciliarius | year = 2008 | month = January}}</ref>

==Description== [[File:Carangoides armatus.png|thumb|The male longfin trevally has trailing dorsal and anal fin filaments]]The longfin trevally has a similar body profile to most other jacks, having a deep, strongly [[Compression (zoology)|compressed]] body. It is a medium-sized fish, growing to a maximum known length of 57 cm, and at least 3.5 [[kilogram|kg]] in weight.<ref name = "Oman">{{cite book | last = Randall | first = John E. | title = Coastal Fishes of Oman | publisher = University of Hawaii Press | year = 1995 | location = Honolulu | page = 183 | isbn = 0-8248-1808-3 }}</ref> The profile of the head is very steep from the mouth to the [[nape]], especially in adults. There is a weak [[adipose eyelid]] covering the [[eye]], which is about equal to or smaller than the snout length.<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 5. Bony fishes part 3 (Menidae to Pomacentridae) | publisher = FAO | year = 2001 | location = Rome | page = 2684 | url = ftp://ftp.fao.org/docrep/fao/009/y4160e/y4160e00.pdf | isbn = 92-5-104587-9 }}</ref> Both [[jaw]]s are lined with [[Ichthyology terms#V|villiform]] [[teeth]], although larger specimens have small conical teeth in bands. The [[gill raker]]s are one of the diagnostic features of the species, having 30 to 37 rakers on the first arch.<ref name = "Williams"/> The [[dorsal fin]] is in two parts, the first consisting of 13 [[Fish anatomy#Spines and rays|spines]] and the second of 1 spine followed by 19 to 22 [[Fish anatomy#Spines and rays|soft rays]].<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 = 23 April 1999 }}</ref> The second dorsal fin is [[sexual dimorphism|sexually dimorphic]], with mature males longer than 21 cm having 3 to 12 of the central soft rays extended into thin filaments of varying lengths. The [[anal fin]] has 2 [[Anatomical terms of location#Anterior and posterior|anteriorly]] detached spines followed by a single spine connected to 16 to 18 soft rays. The lobes of both the anal and dorsal fin are highly extended, giving the species its name. The anal fins also show extension into filaments to a lesser degree.<ref name = "FAO"/> The [[pectoral fin]]s are falcate to subfalcate with 18–20 rays, while the [[caudal fin]] is deeply forked with bilateral, paired caudal keels. The [[pelvic fin]]s are short, and fit in fairly pronounced [[anatomical terms of location#Dorsal and ventral|ventral]] grooves, similar to that of ''[[Atropus atropos]]'' The [[lateral line]] is moderately arched anteriorly, with the curved section containing 57 to 77 [[scale (zoology)|scales]], while the straight section contains 25 to 43 elements, 11 to 24 of which are weak [[scute]]s.<ref name = "Williams"/> Another of the diagnostic traits of the longfin trevally is the scaleless breast, extending from the origin of the pelvic fins to the base of the pectoral fin and anteriorly to the gill cover.<ref name = "Lin1999"/> There are 24 [[vertebrae]] in the species.

The longfin trevally's colour is variable with age, although maintains a general colouration of greyish blue above, fading to a whitish silver near the [[Abdomen|belly]] region. Younger individuals show a more silver blue [[anatomical terms of location#Dorsal and ventral|dorsally]], and have six dark crossbars visible on the body past the pectoral fin base.<ref name = "Williams"/> There is a distinct blackish blotch on the upper margin of the [[operculum (fish)|operculum]].<ref name = "FAO"/> The first dorsal fin is pale grey to black, while the second dorsal fin and anal fin are both [[hyaline]] to black. The pectorals are dusty hyaline, the pelvics are usually black with a white leading edge and the caudal fin is also hyaline, with a dusty trailing edge.<ref name = "Williams"/>

==Distribution and habitat== The longfin trevally inhabits [[tropical]] to [[subtropical]] waters of the [[Indian Ocean|Indian]] and west [[Pacific Ocean]]s. It is distributed from [[East London, South Africa]] in the west, north to [[Madagascar]], [[eastern Africa]], [[India]], [[Thailand]], [[Hong Kong]], [[Taiwan]] and to [[Japan]] in the east.<ref name = "fishbase"/> The species is also common in the [[Red Sea]] and the [[Gulf of Oman]].<ref name = "Oman"/>

The species inhabits [[inshore]] [[coastal]] waters rarely venturing offshore, and is [[pelagic]], inhabiting both the upper and lower sections of the water column. Longfin trevally are commonly found on rocky and [[coral]] coastlines, often inhabiting [[reef]] complexes, with solitary individuals or groups of larger fish patrolling the edges of reefs.<ref name = "SAfrica">{{cite book | last = van der Elst | first = Rudy |author2=Peter Borchert | title =A Guide to the Common Sea Fishes of Southern Africa | publisher = New Holland Publishers | year = 1994 | page = 142 | isbn = 1-86825-394-5 }}</ref> They are also found in shallow, sandy [[bay]]s and [[lagoon]]s, with juveniles known to enter and use [[estuaries]] as [[nursery area]]s.<ref name = "SAfrica"/>

==Biology and fishery== The longfin trevally is a [[predator]]y fish, known to take a variety of small fishes, [[cephalopod]]s including [[squid]], and [[crustacean]]s such as [[crab]]s and [[mantis shrimp]]. The species' long gill rakers also help to filter minute organisms from the seawater, adding to the fish's diet.<ref name = "SAfrica"/> Longfin trevallies reach [[sexual maturity]] at 21 to 22 cm in length. There has been no research into their [[Spawn (biology)|spawning]] patterns, although it is known juveniles inhabit shallow bays and occasionally estuaries.<ref name = "FAO"/>

Longfin trevally are generally too rare to be a viable target for commercial [[fisheries]], although they are occasionally landed and sold fresh locally. The species is considered good table fare, although it is highly esteemed in Thailand and [[Cambodia]], where the filets are steamed or fried.<ref>{{cite book | last = Davidson | first = Alan | title = Seafood of South-East Asia: A Comprehensive Guide with Recipes | publisher = Ten Speed Press | year = 2004 | page = 70 | isbn = 1-58008-452-4}}</ref> Small quantities are taken by [[angling|recreational fishermen]] in South Africa, often from boats using fish baits on hook and line gear or lures, as well as by spear.<ref name = "SAfrica"/>

==References== {{Reflist|2}}

==External links== *[http://fishbase.org/summary/SpeciesSummary.php?id=1916 Longfin trevally at FishBase] *[https://web.archive.org/web/20090108155837/http://www.eol.org/taxa/17051423 Encyclopedia of Life page] * {{sealifephotos|218394}}

[[Category:Carangoides|longfin trevally]] [[Category:Fish of the Pacific Ocean]] [[Category:Fish of the Indian Ocean]] [[Category:Marine fish of East Africa]] [[Category:Taxa named by Eduard Rüppell]] [[Category:Fish described in 1830|longfin trevally]]