Common Jack Mackerel, Trachurus declivis (Jenyns 1841)

Other Names: Chows, Cowan Young, Cowanyoung, Greenback Horse Mackerel, Greenback Scad, Horse Mackerel, Jack Mackerel, Scad, Scaly Mackerel

Common Jack Mackerel, Trachurus declivis. Source: Rudie H. Kuiter / Aquatic Photographics. License: All rights reserved


The Common Jack Mackerel is one of three species of Trachurus in Australian waters, and the three are difficult to distinguish. All have strong scutes in the straight part of the lateral line, some scutes in the curved part, long falcate pectoral fins, an additional lateral line just below the dorsal fin base to the beginning of the second dorsal fin.

T. declivis is almost cylindrical and has the anterior raised part of the lateral line running parallel to the dorsal profile of the body, and the accessory lateral line at the dorsal-fin base terminates below the 5th-11th (usually 7th-9th) segmented ray.

The Common Jack Mackerel is dark bluish-green above fading to silvery-grey below, with a yellowish tinge to the scutes and fins, and a dark blotch on the rear of the gill cover.

Cite this page as:
Dianne J. Bray, Trachurus declivis in Fishes of Australia, accessed 21 Jun 2024,

Common Jack Mackerel, Trachurus declivis (Jenyns 1841)

More Info


Widespread in southern Australia, from Southern Queensland to Shark Bay (Western Australia) and around Tasmania; depth range 0-500 metres. Elsewhere in New Zealand.

These planktivores form large schools of uniformly-sized individuals; smaller fishes usually occur at shallower depths.


Meristic features.
Dorsal fin spines/rays: VIII; I, 29-35
Anal fin spines/rays: II; I, 24-29
Caudal fin rays: 17
Pectoral fin rays: 20-21
Pelvic fin spines/rays: I, 5
Lateral line scales/scutes: 71-89
Gill rakers: 11-16 + 32-34


To 50cm TL


Dark bluish-green above, fading to silvery-grey below the body midline, with a yellow tinge to the scutes and fins, and a black spot on the rear margin of the gill cover. Estuarine individuals tend to be brownish above.




A commercial and gamefish species, although not widely fished in Australian waters; has strongly-flavoured flesh.

Similar Species

Differs from the Yellowtail Scad (Trachurus novaezelandiae) in having the anterior raised part of the lateral line parallel to the dorsal profile of the body, and having a longer accessory lateral line below the dorsal fin base that terminates below the 5th-11th dorsal-fin ray (vs the anterior part of the lateral line curved slightly upwards, and the accessory lateral line terminating below the 1st -5th dorsal-in ray).

The Peruvian Jack Mackeral (Trachurus murphyi) has a shorter accessory lateral line (only reaching to below the1st-5th dorsal fin ray), a more compressed body (vs body somewhat cylindrical in the Common Jack Mackerel) 71-89 scales and scutes in the lateral line (vs 93-106 scales and scutes in the Common Jack Mackerel).

Species Citation

Caranx declivis Jenyns, 1841, in Darwin, Zool. Voy. H.M.S. Beagle Part 4, Fishes: 68, pl. 14. Type locality: Princess Royal Harbour, King George Sound, WA.


Dianne J. Bray

Common Jack Mackerel, Trachurus declivis (Jenyns 1841)


Berry, F.H. & Cohen, L. 1974. Synopsis of the genus Trachurus (Pisces, Carangidae). Quarterly Journal of the Florida Academy of Science 35(4): 177-211 figs 1-4

Jenyns, L. 1841. Part 4 Fishes. 65-96 pls 16-20 in Darwin, C. (ed.). The Zoology of the Voyage of H.M.S. Beagle under the Command of Captain Fitzroy, R.N. during the years 1832 to 1836. London : Smith, Elder & Co.

Gomon, M.F. 1994. Family Carangidae. pp. 582-590 figs 516-522 in Gomon, M.F., Glover, C.J.M. & Kuiter, R.H (eds). The Fishes of Australia's South Coast. Adelaide : State Printer 992 pp. 810 figs

Grant, E.M. 2002. Guide to Fishes. Redcliffe : EM Grant Pty Ltd 880 pp.

Hoese, D.F. & Gates, J.E. 2006. Family Carangidae. pp. 1148-1173 in Beesley, P.L. & Wells, A. (eds). Zoological Catalogue of Australia. Volume 35 Australia : ABRS & CSIRO Publishing Parts 1-3 2178 pp.

Hutchins, J.B. & Swainston, R. 1986. Sea Fishes of Southern Australia. Complete field guide for anglers and divers. Perth : Swainston Publishing 180 pp.

Kuiter, R.H. 1993. Coastal Fishes of South-eastern Australia. Bathurst : Crawford House Press 437 pp. 

Neira, F.J., R.A. Perry, C.P. Burridge, J.M. Lyle & J.P. Keane. 2014. Molecular discrimination of shelf-spawned eggs of two co-occurring Trachurus spp. (Carangidae) in southeastern Australia: a key step to future egg-based biomass estimates. ICES J. Mar. Sci.  doi: 10.1093/icesjms/fsu151 Abstract

Roughley, T.C. 1957. Fish and Fisheries of Australia. Sydney : Angus & Robertson 341 pp. (59, as T. novaezelandiae)

Smith-Vaniz, W.F. 1999. Family Carangidae. pp. 2659-2756 in Carpenter, K.E. & Niem, T.H. (eds). The Living Marine Resources of the Western Central Pacific. FAO Species Identification Guide for Fisheries Purposes. Rome : FAO Vol. 4 2069-2790pp.

Smith-Vaniz, W.F. 2008. Family Carangidae. pp. 575-581 in Gomon. M.F., Bray, D.J. & Kuiter, R.H (eds). Fishes of Australia's Southern Coast. Sydney : Reed New Holland 928 pp.

Stephenson, A.B. & Robertson, D.A. 1977. The New Zealand species of Trachurus (Pisces : Carangidae). Journal of the Royal Society of New Zealand 7(2): 243-253.

Yearsley, G.K., Last, P.R. & Ward, R.D. (eds) 1999. Australian Seafood Handbook. Hobart : CSIRO Marine Research 460 pp.

Wilson, D.T., Curtotti, R. & G.A. Begg.  2010.  Fishery Status Reports, 2009: status of fish stocks and fisheries managed by the Australian Government. Australian Bureau of Agricultural and Resource Economics - Bureau of Rural Sciences, Canberra.

Quick Facts

CAAB Code:37337002

Behaviour:Forms large schools

Depth:0-500 m

Fishing:Commercial & gamefish


Max Size:50cm TL

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