Southern Garfish has a wide distribution in Australia, extending from Lancelin in Western Australia along the southern coast of mainland Australia and up the east coast to Eden in southern New South Wales, as well as the surrounding waters of Tasmania1.
A multidisciplinary otolith-based study (otolith chemistry and morphometrics) identified at least five biological stocks in South Australia: west coast, northern Spencer Gulf, southern Spencer Gulf, northern Gulf St Vincent and southern Gulf St Vincent2. Given the level of spatial separation of Southern Garfish observed within the gulfs, it was assumed that Southern Garfish from the south-east also comprised a distinct biological stock. From recent stock assessments, most of the biomass exists in the northern gulfs: northern Spencer Gulf and northern Gulf St Vincent. The remaining biological stocks have generally produced relatively low catches. For South Australia, status is reported at the level of the six individual biological stocks.
Differences in size and age composition between the north and east coasts of Tasmania suggest that there may be multiple biological stocks; however, no firm evidence exists at present, and current stock assessments assume a single statewide biological stock3. Status for Southern Garfish in Tasmania is reported at the level of this assumed single biological stock.
There has been no research into the stock structure for Western Australian populations of Southern Garfish. However, given the limited dispersal capabilities of Southern Garfish, and the large spatial separation between the west and south coasts of Western Australia, it is likely that the west and south coast host separate biological stocks of this species. Furthermore, the majority of west coast landings are from Cockburn Sound, and the majority of south coast landings are from Wilson Inlet. Garfish spawn within Wilson Inlet, thus maintaining a self-sustaining population within this estuary, which is usually separated from the ocean by a sand bar. Hence, status is reported at the level of the west and south coast biological stocks.
There has been no research into the stock structure for Victorian populations of Southern Garfish. Therefore, Southern Garfish in Victoria is assessed at the jurisdictional level.
West coast (South Australia) biological stock
A negligible amount of Southern Garfish is landed by the commercial sector on the west coast of South Australia, with the contribution to the statewide catch rarely exceeding 2 per cent. Consequently, there is insufficient information available to confidently classify the status of this stock.
On the basis of the evidence provided above, the biological stock is classified as an undefined stock.
Southern Spencer Gulf (South Australia) biological stock
Large areas of southern Spencer Gulf have been closed to commercial hauling-net fishing, with the most recent closure implemented in 2005. Consequently, the hauling-net sector has been effectively removed from this region, which is now mainly fished by commercial dab netters. The relative contribution of this region to the statewide catch has decreased to less than 5 per cent. Fishing effort has also substantially decreased (47 per cent) in the dab net sector over the past 4 years. Given the relatively small size of this regional fishery, it is difficult to access meaningful quantities of Southern Garfish to ascertain trends in the local population demography. Hence, there is insufficient information available to confidently classify the status of this stock.
On the basis of the evidence provided above, the biological stock is classified as an undefined stock.
Northern Spencer Gulf (South Australia) biological stock
The northern Spencer Gulf biological stock has been the most productive for Southern Garfish in South Australia since 1983, typically contributing to more than half of the statewide catch. This stock is exclusively commercially fished by the hauling-net sector. The most recent assessment4 assessed three types of performance indicators: commercial catch rates; age-length frequency distributions; and model-based assessments of exploitation rate, egg production and fishable biomass. Catch rates have trended upwards since 1999. The composition of the commercial harvest is dominated by 1 year old plus and 2 year old plus Southern Garfish, indicating that the population structure has remained severely truncated as a result of sustained levels of high exploitation (higher than 65 per cent). Despite this, both fishable biomass and egg production remained relatively stable at moderate levels from 2003 to 2011. Consequently, the stock is not yet considered to be in a recruitment overfished state. However, the current level of fishing pressure has the potential to cause the stock to become recruitment overfished. New statewide harvest strategies have recently (2012) been implemented to promote the recovery of the stock, by reducing the harvest fraction and increasing egg production through a combination of effort (spatial closures) and gear-based (increased hauling-net mesh size) restrictions. It is too early to assess the flow-on effects of these strategies. Proportional strategies are currently being developed for the recreational sector.
On the basis of the evidence provided above, the biological stock is classified as a transitional–depleting stock.
Southern Gulf St Vincent (South Australia) biological stock
Before 1993, the commercial catch of Southern Garfish from southern Gulf St Vincent was equally shared among the hauling-net and dab-net sectors. Since then, the hauling-net sector has declined, with a steady reduction in fishing effort, and, by 2006, dab nets had become the dominant gear type. This dominance was accelerated by the implementation of a voluntary net buy-back scheme and spatial netting closures in 2005. Before this management restructure, the commercial Southern Garfish catch from the region rarely exceeded 10 per cent of the statewide harvest; after its implementation, catch decreased to less than 5 per cent. Like southern Spencer Gulf, little is known about the size and age structures of the commercial catch of Southern Garfish in southern Gulf St Vincent, as it is difficult to access adequate biological samples from this relatively small regional fishery. Hence, there is insufficient information available to confidently classify the status of this stock.
On the basis of the evidence provided above, the biological stock is classified as an undefined stock.
Northern Gulf St Vincent (South Australia) biological stock
Northern Gulf St Vincent has historically been the second most productive region in the state, accounting for an average of 35 per cent of South Australia’s annual Southern Garfish catch. The most recent assessment4 used three types of performance indicators: commercial catch rates; age-length frequency distributions; and model-based assessments of exploitation rate, egg production and fishable biomass. Like the adjacent Northern Spencer Gulf biological stock, the Southern Garfish population in northern Gulf St Vincent is severely truncated as a result of sustained levels of exploitation (higher than 60 per cent). The recent trends in fishable biomass and egg production have remained relatively stable over the past decade, indicating that the stock is not yet considered to be recruitment overfished. However, this continued level of fishing pressure has the potential to cause the stock to become recruitment overfished. New statewide harvest strategies have recently (2012) been implemented to promote the recovery of the stock, by reducing the harvest fraction and increasing egg production through a combination of effort (spatial closures) and gear-based (increased hauling-net mesh size) restrictions. It is too early to assess the flow-on effects of these strategies. Proportional strategies are currently being developed for the recreational sector.
On the basis of the evidence provided above, the biological stock is classified as a transitional–depleting stock.
South-east (South Australia) biological stock
Very few Southern Garfish are landed by the commercial sector in the south-east; the statewide contribution rarely exceeds 0.3 per cent. Consequently, there is insufficient information available to confidently classify the status of this stock.
On the basis of the evidence provided above, the biological stock is classified as an undefined stock.
West coast (Western Australia) biological stock
From 2009 to 2013, 87 per cent of west coast commercial landings of Southern Garfish were from Cockburn Sound. This represented 47 per cent of total Western Australian commercial landings of this species. The Southern Garfish catch and catch per unit effort (CPUE) in Cockburn Sound followed a declining trend from 2002 to 2013. Both catch and CPUE reached a historically low level in 2013 (that is, the lowest since the early 1970s, when the fishery commenced). Catch and CPUE indicators suggest that stock abundance is currently relatively low in Cockburn Sound. A new assessment, based on age-structure information, is under way to provide a better understanding of the status of this stock. Currently, insufficient information is available to confidently classify the status of this stock.
On the basis of the evidence provided above, the biological stock is classified as an undefined stock.
South coast (Western Australia) biological stock
From 2009 to 2013, 58 per cent of south coast commercial landings of Southern Garfish were from Wilson Inlet. This represented 27 per cent of total Western Australian commercial landings of this species. Over this period, the catch in this estuary ranged from 3 to 10 tonnes (t) per year. The remainder of south coast landings each year comprised multiple small catches from other estuarine and coastal fisheries. From 2002 to 2013, the annual catch in Wilson Inlet followed an increasing trend, suggesting that the biomass has remained stable and that this stock is unlikely to be recruitment overfished. However, insufficient information is available to confidently classify the status of this stock.
On the basis of the evidence provided above, the biological stock is classified as an undefined stock.
Victoria
The commercial catch rate for Southern Garfish in Victoria has been relatively stable for the past 35 years. The majority (58 t) of the commercial catch of Southern Garfish comes from Corner Inlet, where catch rates vary annually but have been relatively stable since the early 1990s5. The majority of the recreational catch of Southern Garfish comes from Port Phillip Bay. In 2000–01, it was estimated that 25 t was taken by the Victorian recreational fishery, constituting 3.4 per cent of the statewide recreational catch in marine waters6. Recreational catch rates of Southern Garfish by avid and non‐avid anglers in Port Phillip Bay have declined slightly since 20045. Available fishery and scientific data indicate that the fishery is performing within its historical range, based on total annual catch and catch rate. The above evidence indicates that the biomass of this stock is unlikely to be recruitment overfished and the current level of fishing pressure is unlikely to cause the stock to become recruitment overfished.
On the basis of the evidence provided above, Southern Garfish in Victoria is classified as a sustainable stock.
Scalefish Fishery (Tasmania) biological stock
From 1995–96 to 2005–06, commercial catches in the Scalefish Fishery (Tasmania) were stable and typically between 80 and 100 t. They have generally been less than 60 t in the past 6 years3. This coincides with a decline in average size and truncation of age classes of the catch, which may have resulted from heavy fishing pressure and/or a period of poor recruitment3. As a result, seasonal closures were introduced in 2009 to protect spawning fish. Since then, there has been an increase in the size of Southern Garfish captured, a greater variety of age classes present in the catch and increasing CPUE. This provides some evidence that the stock is recovering. At present, however, insufficient information is available to confidently classify the status of this stock.
On the basis of the evidence provided above, the biological stock is classified as an undefined stock.
Figure 2: Commercial catch of Southern Garfish in Australian waters, 2003 to 2013 (calendar years)
Note: Western Australian data were not provided at the level of the individual stocks reported in the Southern Garfish chapter. To protect commercial confidentiality of data, the catch in the OF (Victoria) cannot be reported because there are fewer than five licence holders.