The stout whiting (Sillago robusta), also known as the yellow-cheek whiting or school whiting, is a species of benthic marine fish in the smelt-whiting family Sillaginidae. Like other sillaginids, it is an elongate, slightly compressed fish, growing to a maximum known length of 30 cm. The stout whiting is endemic to Australia, with the species divided into western and eastern populations, with the western population ranging from Shark Bay to Fremantle and the eastern population from Bustard Head, Queensland to northern New South Wales. The species inhabits deep, sandy continental shelf regions to a depth of at least 70 m.
The stout whiting is a benthic carnivore, consuming a variety of polychaetes and crustaceans. The species grows rapidly, and sexual maturity is reached at a length of 13 cm, with spawning occurring between December and March. Juveniles of the eastern population move to protected inshore waters, while those of the western population remain offshore their entire life.
Stout whiting are the subject of a major export fishery operating out of southern Queensland and to a lesser extent New South Wales, with fishery authorities limiting the yearly catch to 1000 tonnes in Queensland. Most of the catch is exported frozen to a number of Asian countries, although small quantities are sold in Australia, with the net worth of the fishery values at around 3 million Australian dollars per year.
Taxonomy and naming
The stout whiting is one of over 30 species in the genus Sillago, which is one of five genera belonging to the smelt whiting family Sillaginidae, this family was previously considered to be part of the Percoidea, a suborder of the Perciformes. The 5th edition of Fishes of the World classifies the Sillaginidae in the order Spariformes.
The species was first scientifically described by Stead in 1908 based on a specimen collected from Rose Bay in Port Jackson, New South Wales, which was designated to be the holotype. After this description and naming, the species was once again described and named by William Ogilby in 1910 as Sillago auricomis, based on a specimen taken from near Hervey Bay in Queensland. This is considered to be junior synonym under ICZN naming rules and has subsequently been discarded. During a comprehensive revision of the sillaginids in 1985, Roland McKay noted that the eastern and western populations of fish varied slightly in their fin osteology and swimbladder morphology, but recommended a full osteological comparison before placing them in subspecies ranks. McKay also postulates that the two populations became separated during the last ice age, when a land bridge closed the Torres Strait to the movement of the species.
The species is most commonly known as the 'stout whiting', and is recognised as such by the Australian Government. The species is occasionally called the 'yellow-cheek whiting' and also 'school whiting', a broad name applied to a number of Australian sillaginids.
Description
The stout whiting is similar in appearance to a number of Australian sillaginids, with dorsal fin and swimbladder morphology the best identification features. It is a small fish, reaching a known maximum length of 30 cm, but more commonly seen below 23 cm. Like most sillaginids, the stout whiting has a slightly more convex dorsal profile compared to the ventral profile, reflecting the benthic nature of the species. The dorsal fin is composed of 2 sections; the first consisting of 11 spines and the second of 1 spine followed by 16 to 18 soft rays. Large specimens show a distinct anterior keel on the first spine of the first dorsal fin, with this feature being more pronounced in the eastern population. The anal fin is similar to the second dorsal fin, having 2 spines followed by 16 or 19 soft rays. The lateral line has 65-70 scales, whilst the cheek has 2 to 3 rows of cteniod scales, and there are 33 vertebrae in total. The swimbladders of the two populations are slightly different, with the eastern population having small anterolateral extensions, while the western population lack these. There is a single tapering posterior extension and a duct like process which runs from the ventral surface to the urogenital opening.