King George whiting

The King George whiting's distinctive body shape and mouth placement is an adaptation to bottom feeding, which is the predominant method of feeding for all whiting species. All larger whiting feed by using their protrusile jaws and tube-like mouths to suck up various types of prey from in, on or above the ocean substrate.[9] There is a large body of evidence that shows whiting do not rely on visual cues when feeding, instead using a system based on the vibrations emitted by their prey.[10]

Studies of gut content have shown that the primary food items of King George whiting are amphipods, copepods and polychaete worms.[11] Unlike any of its relatives, the King George whiting does not appear to feed on molluscs, which is unusual because in many parts of Southern Australia, the main bait used by recreational fishers to catch whiting is the cockle; a mollusc, but then, it has been deshelled. An excellent bait for catching King George Whiting is raw king prawn, such as banana prawn. They are better bought in the shell and peeled shortly before using, as this keeps the bait fresh. Also rare in the diet are echinoderms, which are frequent prey for other species of Sillago. This may be a function of niche partitioning, as in many areas the King George whiting's habitat overlaps with other species of the genus Sillago.[9] Other minor components of the diet include crustaceans such as carids, leptostracans, stomatopods, crabs, tanaids, cumaceans and isopods as well as other fish and benthic algae.

As previously mentioned, younger fish tend to school when foraging, and have been known to forage in groups with other species such as silver trevally, tarwhine and other species of whiting.[6] Larger fish tend to occupy areas with larger species such as Australasian snapper, blue morwong and larger trevally.

King George whiting, especially juveniles, are known to be common prey for a number of larger inshore fishes and wading birds. The most prominent inshore predators are Australian salmon, members of the flathead family, the barracouta (a snake mackerel), snook as well as various species of sharks and rays.[12] Various species of diving birds, particularly the pied cormorant are also common predators of the species,[13] as are marine mammals such as bottlenose and common dolphins.[14]

King George whiting reach sexual maturity at three to four years of age, with males reaching 30 cm in length and females 34 cm. These lengths are used as guides when setting minimum legal lengths for the species, allowing adequate time for an individual to reproduce before being taken.[15] Spawning occurs in a range of areas, depending on the geographic locality of the individual; some spawning in deeper water up to 9 m deep, others in estuaries.[16] May and June are the most common times for spawning, with some spawning events recorded as early as February and as late as July.[3] Juvenile fish are recruited to areas by ocean currents, with studies showing the species is too weak a swimmer to be able to undertake long distance journeys.[17] The location of spawning also has implications for the location of the juveniles, as with some estuary breeding individuals.

The main commercial King George whiting fishery is centred on South Australia from Ceduna in the west to Gulf St Vincent in the east. Smaller fisheries are present in Victoria and south west Western Australia. Common catching practices include haul seine nets, gill nets as well as longline and handline methods. This fishery is one of the most important in the country, reportedly worth five million Australian dollars a year,[4] as King George whiting fetch premium price in markets. This single species alone was reported as comprising 60% of the total annual catch in South Australia during the late 1980s.[18] The fish are sold either whole or as fillets and are generally rated as one of the very best quality Australian fish for the table, and are ubiquitous in Fish and chips shops.

In Southern Australia, the King George whiting is often the sole target for fishermen who seek it for its high quality eating.[1] A number of coastal towns rely heavily on the species as a tourism drawcard for anglers seeking a range of fish and crustacean species, but King George whiting is often the most desired catch.[19] They are a relatively easy species to catch, with no special baits, rigs or techniques required and are often caught from jetties, beaches and rocks; meaning a boat is not necessary. Simple rigs such varieties of running ball sinker or paternoster rigs are commonly used, with a fixed sinker employed in area of high tidal movement.[20] As mentioned previously, molluscs, particularly the Goolwa cockle are common bait, with varieties of worms, gents, squid, cuttlefish, fish pieces and especially raw king prawn are commonly successful. The larger fish inhabiting deep reefs are often caught on whole pilchards while fishing for snapper and morwong.[20]

The King George whiting has differing size and bag limits for anglers in different states. In Victoria, there is a minimum size limit of 27 cm and a bag limit of 20 per person.[21] South Australia is divided into two zones concerning the taking of this species, with fish caught east of longitude 136° restricted to a minimum length of 32 cm and fish caught to the west of longitude 136° having a minimum length of 30 cm. In both divisions, the bag limit is 10 fish per person.[22] Western Australia has set a minimum legal limit of 28 cm and a bag limit of 8 per person.[23]

Due to the King George whitings’ popularity as a food fish, extensive investigations into the viability of the species as an aquaculture species have occurred, with most initial investigations indicating the long larval cycle is a major barrier to the successful farming of the fish. Other problems have arisen in a parasite previously unknown in the species only affecting the fish in captivity. Thyroid growth hormones may be used in the future to hasten growth of larvae and make such ventures more feasible.[24]