King George Whiting Sillaginodes punctata

Jodie Kemp^a, Anthony Fowler^b and Kim Smith^c

Table 1: Stock status determination for King George Whiting

Jurisdiction	South Australia			Western Australia	Victoria
Stock	Gulf St Vincent (MSF)	Spencer Gulf (MSF, NZRLF)	West coast–Eyre Peninsula (MSF, NZRLF)	Western Australia (SCEMF, WCEMF)	Victoria (CIF, GLF, OF, PPBF)
Stock status
Stock status	Sustainabe	Sustainable	Sustainable	Undefined	Sustainable
Indicators	Biomass, CPUE, age–length composition, exploitation rate, recruitment	Biomass, CPUE, age–length composition, exploitation rate, recruitment	Biomass, CPUE, age–length composition, exploitation rate, recruitment	na	CPUE (commercial and recreational), fishery- independent pre-recruit CPUE, age–length composition

CIF = Corner Inlet Fishery (Victoria); CPUE = catch per unit effort; GLF = Gippsland Lakes Fishery (Victoria); MSF = Marine Scalefish Fishery (South Australia); na = not applicable; OF = Ocean Fishery (Victoria); PPBF = Port Phillip Bay Fishery (Victoria); NZRLF = Northern Zone Rock Lobster Fishery (South Australia); SCEMF = South Coast Estuarine Managed Fishery (Western Australia); WCEMF = West Coast Estuarine Managed Fishery (Western Australia)

Stock Structure

Three separate King George Whiting biological stocks have been identified in South Australian waters^1–2. Hence, for South Australia, reporting is undertaken at the biological stock level. The biological stock structure of King George Whiting in Victoria and Western Australia is not known, but they are assumed to be separate stocks for management purposes. Status for Victoria and Western Australia is therefore reported at the jurisdictional level.

Stock Status

Gulf St Vincent biological stock

The most recent assessment of the Gulf St Vincent biological stock of King George Whiting² assessed three types of performance indicators: commercial catch rates; age–length frequency distributions; and model-based estimates of exploitation rate, recruitment and fishable biomass. Despite a gradual increase in the exploitation rate of the Gulf St Vincent biological stock since 2001, recruitment has been stable for about 10 years (up to 2010), and the fishable biomass has increased since 2004. This evidence indicates that the biomass of this biological stock is unlikely to be recruitment overfished.

Changes in management arrangements, including increased size limits, licence buy-backs, changes in gear type and reduced effort across the South Australian King George Whiting fishery, have led to reduced commercial catches since record highs in the 1990s. Commercial catch has been consistent at 300–350 tonnes (t) per year between 2004 and 2010. Although targeted commercial catch and effort have been relatively low in Gulf St Vincent, catch per unit effort (CPUE) has increased, particularly since 2001². This evidence indicates that the current level of fishing mortality is unlikely to cause the biological stock to become recruitment overfished.

On the basis of the evidence provided above, the biological stock is classified as a sustainable stock.

Spencer Gulf biological stock

The most recent assessment of the Spencer Gulf biological stock of King George Whiting² assessed three types of performance indicators: commercial catch rates; age–length frequency distributions; and model-based estimates of exploitation rate, recruitment and fishable biomass. The exploitation rate of the Spencer Gulf biological stock has shown a long-term decline since 1992; recruitment has been stable for about 10 years (up to 2010); and the fishable biomass has increased since 2004². This evidence indicates that the biomass of this biological stock is unlikely to be recruitment overfished.

Commercial catch and effort in the southern Spencer Gulf declined from record highs in 1992 until 2004. Since then, both commercial catch and effort have stabilised and marginally increased in recent years. CPUE in this area increased steadily from 1984, with a significant increase from 2003 to 2007. After a slight decline in 2008, CPUE has been stable and remains at historically high levels. In the northern Spencer Gulf, trends in commercial catch and effort are similar to those in the southern Spencer Gulf; however, no increase has been observed in more recent years. CPUE in this area increased between 1984 and 2005. Although there has been a decline in recent years, CPUE remains at a level that was observed in 2002, and above levels observed before 1996². This evidence indicates that the current level of fishing mortality is unlikely to cause the biological stock to become recruitment overfished.

On the basis of the evidence provided above, the biological stock is classified as a sustainable stock.

West coast–Eyre Peninsula biological stock

The most recent assessment of the west coast–Eyre Peninsula biological stock of King George Whiting² assessed three types of performance indicators: commercial catch rates; age–length frequency distributions; and model-based estimates of exploitation rate, recruitment and fishable biomass. Recruitment has increased since 2002, and the fishable biomass of the west coast–Eyre Peninsula biological stock increased from 2004 onwards². This evidence indicates that the biomass of this biological stock is unlikely to be recruitment overfished.

Commercial catch and effort have declined on the far west coast since the early 2000s; however, CPUE has been increasing during this time. There was a small reduction in CPUE in 2010, following a record high in 2009. On the mid-west coast, commercial catch and effort declined until about 2002, but has increased since then. Additionally, CPUE in this area has increased since 2000. Record CPUE levels were recorded in 2009, falling to the third highest level on record in 2010. This evidence indicates that the current level of fishing mortality is unlikely to cause the biological stock to become recruitment overfished.

On the basis of the evidence provided above, the biological stock is classified as a sustainable stock.

Western Australia

No formal stock assessments have been undertaken in Western Australia. Two projects are currently under way to determine the status of King George Whiting in south-western Western Australia and develop methods for ongoing monitoring of this stock. Currently, insufficient information is available to confidently classify the status of Western Australian King George Whiting³.

On the basis of the evidence provided above, King George Whiting in Western Australia is classified as an undefined stock.

Victoria

The 2010 assessment of King George Whiting in Victoria⁴ used a weight-of-evidence assessment of commercial and recreational catch rates, fishery-independent pre-recruit catch rates and age–length frequency distributions. Commercial catch and catch rates in Victoria follow a clear 8–10-year cyclic trend. Fluctuations in the indicators are likely to be the result of environmental conditions affecting spawning success and/or recruitment to the fishery.

Commercial catch rates have shown an increasing trend since 1984–85 and peaked at 23 kg/day in 2007–08 (coinciding with the peak of the cyclic trend). Effort for all gear types in Victoria has decreased since 1999 as a result of a reduction in the number of licensed fishers in Victorian waters, and is at historically low levels. This evidence indicates that the biomass of Victorian King George Whiting is not recruitment overfished, and that the current level of fishing mortality is unlikely to cause King George Whiting in Victoria to become recruitment overfished.

On the basis of the evidence provided above, King George Whiting in Victoria is classified as a sustainable stock.

Table 2: King George Whiting biology^1,5–7

Longevity and maximum size	Western Australia: 14 years; 62 cm TL South Australia: 22 years; 54 cm TL
Maturity (50%)	Western Australia: 3–4 years; 41 cm TL South Australia: 3–4 years; 30–35 cm TL

TL = total length

Figure 1: Distribution of reported commercial catch of King George Whiting in Australian waters, 2010

Main features and statistics for King George Whiting stocks/fisheries in Australia in 2010

Commercial catch of King George Whiting is taken using a range of gear, including fish haul nets, gillnets, and rod and line. Recreationally, they are harvested using rod and reel.
A range of input and output management controls are in place across jurisdictions:
- Input controls include limited entry licensing, restrictions on fishing equipment and methods, and spatial and temporal closures.
- Output controls include legal minimum size limits and daily bag limits. Recreational fishers in Western Australia (boat based only) and Victoria (boat and shore based) are required to hold a recreational fishing licence.
In 2010, commercial King George Whiting catch was reported from 95 vessels in Gulf St Vincent, 147 vessels in Spencer Gulf, 84 vessels in the west coast–Eyre Peninsula, 51 vessels in Western Australia and 94 vessels in Victoria (the figure for Victoria is for the 2010–11 financial year).
Total commercial catch of King George Whiting across Australia in 2010 was 513 t, comprising 147 t from Gulf St Vincent, 105 t from Spencer Gulf, 75 t from the west coast–Eyre Peninsula, 13 t from Western Australia and 173 t from Victoria (the figure for Victoria is for the 2010–11 financial year).
The estimated total recreational harvest of King George Whiting in 2010 was 123 t from Gulf St Vincent, 172 t from Spencer Gulf and 76 t from the west coast–Eyre Peninsula. The total amount of King George Whiting harvested by charter operations in 2010 was 9 t from Gulf St Vincent, 9 t from Spencer Gulf and 1 t from the west coast–Eyre Peninsula. For 2000–01, it was estimated that the annual recreational harvest of King George Whiting from Western Australia was 105 t and from Victorian waters 214 t⁸. Ryan et al.⁹ estimated that, in 2006–07, approximately 155 t was caught recreationally in Victoria. The Indigenous catch of King George Whiting is unknown.

Figure 2: Commercial catch of King George Whiting in Australian waters, 2000–10 (calendar year)
Note: Victorian catch is reported by financial year (e.g. 2010 refers to 2010–11).

Catch Explanation

For the South Australian biological stocks, there was a considerable decline in commercial catch in 2000–01 compared with previous years, predominantly in Spencer Gulf and Gulf St Vincent. However, since then, regional commercial catches and other indicators have stabilised. Reduced commercial catches in South Australia can be attributed to management changes that reduced the total effort in the fishery. The South Australian biological stocks showed marginal increases in biomass through the 2000s, with the highest increase apparent for the west coast–Eyre Peninsula biological stock. In Western Australia, King George Whiting is a minor component (by weight) of the total commercial catch; commercial catches have remained relatively stable over the past decade. In Victoria, commercial catches have remained stable over the past decade (within an 8–10-year cyclic trend, which peaked in 2007–08).

Effects of fishing on the marine environment

Some bycatch may be expected from nets used to harvest King George Whiting. However, as a result of targeted fishing and the nature of the methods used, the effects of fishing on the marine environment are considered to be minor.

Environmental effects on King George Whiting

Commercial catch and catch rates in Victoria follow a clear 8–10-year cyclic trend. Fluctuations in the indicators are likely to be the result of environmental conditions affecting spawning success and/or recruitment to the fishery. The abundance of post-larval King George Whiting has been low since 2006, indicating that both recreational and commercial catches will be lower than average for the next few years. The next peak season for King George Whiting in Victorian waters is expected to occur between 2015–16 and 2017–18⁴.
A significant relationship has been found between the abundance of post-larvae in Port Phillip Bay in Victoria and the strength of zonal westerly winds in south-eastern Australia¹⁰. The zonal westerly wind index has shown a long-term downward trend since about 1970, suggesting that the strength of the westerly wind flow over Victoria has decreased over the past 40 years. This is consistent with the prediction that westerly winds will weaken in southern Australia as a result of climate change, due to a southward migration of the high-latitude westerly windbelt south of Australia¹¹. This could ultimately have a significant impact on the abundance of larvae that enter Victoria's bays and inlets, and could negatively influence the long-term commercial catch of King George Whiting (G Jenkins, pers. comm. 2012).

^a Department of Primary Industries, Victoria
^b South Australian Research and Development Institute
^c Department of Fisheries, Western Australia