King George Whiting (2023)
Sillaginodes punctatus
Date Published: June 2023
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Summary
King George Whiting is a sustainable species found in WA, VIC and SA waters. It is the premium species in SA and attracts the highest price per unit weight for commercial fishers.
Stock Status Overview
Jurisdiction | Stock | Stock status | Indicators |
---|---|---|---|
South Australia | Gulf St. Vincent | Sustainable | Catch, CPUE, age structure, biomass |
South Australia | Spencer Gulf | Sustainable | Catch, CPUE, age structure, biomass |
South Australia | West Coast Eyre Peninsula | Sustainable | Catch, CPUE, age structure, biomass |
Stock Structure
Research on King George Whiting stock structure in southern Australia using genetic and otolith chemistry approaches indicates that separate stocks occur in each state jurisdiction (Western Australia, Victoria and South Australia), but with some genetic mixing between Victorian and South Australian populations [Jenkins et al. 2015]. King George Whiting sampled from northern Tasmania appear genetically different from those in the mainland states. Furthermore, two genetically distinct stocks have been identified in north-west and north-east Tasmania [Jenkins et al. 2015].
The South Australian population of King George Whiting is thought to be comprised of three biological stocks—Gulf St Vincent, Spencer Gulf and the West Coast-Eyre Peninsula. This delineation has been determined based on understanding of the life history, including movement patterns of adult fish, knowledge of the location of spawning grounds and nursery areas [Fowler et al. 2000a; Fowler et al. 2002], and understanding of larval advection pathways and distances based on early life history and hydrodynamic modelling [Fowler et al. 2000b]. Recently, this stock structure has been called into question based on results from a detailed study of the early life history that included consideration of the larval movement processes. This involved studies that considered the microstructure and chemistry of otoliths from larvae and post-settlement juveniles [Rogers et al. 2019a, b], as well as biophysical oceanographic modelling [Rogers et al. 2020]. The complex findings from this study indicated that there was potential for movement of larvae between the putative stocks. Nevertheless, given the lack of empirical evidence about the extent of such movement, it is considered preferable here to retain the original model of stock structure until further information becomes available. The Gulf St Vincent biological stock occurs throughout Gulf St Vincent, Investigator Strait and around Kangaroo Island. The Spencer Gulf biological stock occurs throughout the waters of Spencer Gulf and adjacent coastal waters from western Kangaroo Island to the Eyre Peninsula. The West Coast-Eyre Peninsula biological stock extends throughout all the bays and offshore areas of the west coast of Eyre Peninsula.
Further subdivision in biological stock structure is uncertain for Western Australian and Victorian populations. In Western Australia, King George Whiting occurs in the West Coast Bioregion (WCB) and South Coast Bioregion (SCB). Juveniles occur in inshore waters of both bioregions, but adults appear to be restricted to offshore waters of the WCB [Hyndes et al. 1998; Sulin 2012; Brown et al. 2013]. On this basis there is assumed to be a single biological stock in Western Australia, with the spawning component of the stock residing in the WCB. Similarly, there is assumed to be a single biological stock in Victorian waters, with juveniles occurring mostly in bays and estuaries and adults in coastal waters [Jenkins et al. 2015].
The spatial scale of assessment of South Australia’s three biological King George Whiting stocks has changed as a result of the regionalisation component of the Marine Scalefish Fishery (MSF) reform in 2021. The three biological stocks of Gulf St Vincent, Spencer Gulf, and West Coast-Eyre Peninsula are now assessed at different spatial scales and are now considered as fishery management units rather than biological stocks. Here, assessment of stock status is presented at the jurisdictional level for Western Australia and Victoria and at the management unit level for Spencer Gulf, Gulf St Vincent / Kangaroo Island and West Coast-Eyre Peninsula (South Australia).
Stock Status
Gulf St. Vincent
The most recent stock assessment was completed in 2023, which considered data collected up until the end of June 2022 [Smart et al. 2023]. For that assessment the primary fishery performance indicators were: total catch, targeted handline effort and targeted handline CPUE; and population age structures determined from fishery-dependent market sampling. All datasets pertaining to the fishery were integrated in a computer stock assessment model WhitEst that produced time-series of annual estimates of output parameters that included fishable biomass, recruitment, harvest fraction and egg production. Such comprehensive stock assessments are done on a biennial basis and stock status is determined using a weight-of-evidence approach. However, for the year between stock assessments, stock status has also been determined for the Marine Scalefish Fishery statistics report based on commercial fishery statistics [Smart et al. 2023]. As part of the MSF reform implemented in 2021, this management unit is now managed under a total allowable commercial catch (TACC) and with individual transferable quota units (ITQs) for fishers catching King George Whiting.
Annual commercial catches and effort for this stock peaked during the early 1990s and have subsequently undergone continual long-term decline. These declines reflect the decreases in the numbers of fishers participating in the fishery and targeting this species [Smart et al. 2023]. In particular, there were considerable declines in commercial catch and effort between 2009–10 and 2013–14. Furthermore, whilst the CPUE had shown a long-term increasing trend between 1983–84 and 2006–07, there was a six-year period of consistent decline between 2006–07 and 2011–12 during which it fell by around 25%. In response, the model-derived estimates of biomass for the period from 2008–09 to 2013–14 showed considerable decline, associated with declining recruitment [Fowler et al. 2014]. Based on these fishery performance indicators, the fishery was classified as transitional depleting [Fowler et al. 2014]. This led to an extensive review of management arrangements throughout 2016 that culminated in significant changes that were implemented in December 2016. These were: increase in the legal minimum length from 310 to 320 mm total length (TL); reduction of recreational bag and boat limits; and implementation of a month-long spatial spawning closure in Investigator Strait and southern Spencer Gulf. The latter was subsequently removed in 2018 as the result of this stock being assessed as sustainable in the same year.
Since 2017–18, trends in fishery-derived catch, effort, and CPUE have all been positive, with decreasing levels of fish harvested and fishing effort resulting in some of the highest values of CPUE recorded for this stock. Furthermore, since 2011–12, trends in standardised target handline CPUE have also increased. In 2021–22 this stock had the lowest catch (27 t) and effort (1,304 fisher days) on record, with only 59% of the 46 t TACC harvested but the highest targeted handline CPUE on record at 15.9 kg.fisher-day-1 [Smart et al. 2023]. Furthermore, the model-derived estimates of biomass have increased over the past several years, which was supported by stable recruitment and continual decreasing harvest fraction. Recreational catch from this stock continued to be high, with an estimate of 76 t from the 2021–22 recreational fishing survey [Beckmann et al. 2023]. The Charter Boat Fishery reported taking 10,879 fish in 2020–21, which represented 26.7% of all fish harvested in this management zone [Durante et al. 2022].
The above evidence indicates that the biomass of the Gulf St Vincent/Kangaroo Island management unit is unlikely to be depleted and that recruitment is unlikely to be impaired. The current level of fishing mortality is unlikely to cause the management unit to become recruitment impaired.
On the basis of the evidence provided above, the Gulf St Vincent/Kangaroo Island management unit is classified as a sustainablestock.
Spencer Gulf
The most recent stock assessment was completed in 2023, which considered data collected up until the end of June 2022 [Smart et al. 23]. The assessment methods were the same as those applied for the Gulf St. Vincent/Kangaroo Island stock. Stock assessments for this stock are conducted on a biennial cycle, with stock status determined between assessments based only on commercial fishery statistics [Smart et al. 2023]. As part of the Marine Scalefish Fishery reform implemented in 2021, this stock is now managed under a total allowable commercial catch (TACC) and with individual transferable quota units (ITQ's) for fishers harvesting King George Whiting. The spatial scale of assessment has changed for this management unit, which now includes the south-west region of Eyre Peninsula [Smart et al. 2023].
Throughout the 1980s and 1990s, estimates of total catch and effort for this stock were higher than the levels that were recorded through the 2000s and 2010s [Smart et al. 2023]. There have been continual declines in catch and effort from the early 1990s until 2020–21. Targeted handline CPUE has varied cyclically over time but demonstrated a long-term increasing trend [Smart et al. 2023]. However, between 2006–07 and 2013–14, catch, effort and CPUE all declined, which resulted in declining estimates of biomass from WhitEst [Steer et al. 2018a]. These declining trends were associated with a significant decline in recruitment. Based on these fishery performance indicators in 2014, this stock was classified as transitional depleting [Fowler et al. 2014]. The management strategy implemented were the same as those applied for the Gulf St. Vincent/Kangaroo Island stock.
Between 2013–14 and 2017–18, there were notable increases in the fishery performance indicators that relate to commercial fishery statistics. Over this period, handline effort, total catch, and targeted handline CPUE all showed positive trends which led to this stock being assessed as sustainable in 2018 [Steer et al. 2018b]. The change in stock status supported the removal of the spatial spawning closures that were implemented for one month in 2017 and 2018. Since 2017–18, fishery statistics have all followed positive trajectories, with catch and effort decreasing and targeted handline CPUE continuing to increase [Smart et al. 2023]. King George Whiting harvest continues to decrease was the lowest and second lowest on record over recent years and was 71 t in 2021–22. At the same time, fishing effort has continued to decrease and was 2,753 fisher days in 2021–22, which was also the lowest on record [Smart et al. 2023]. In 2021–22 targeted handline CPUE was the highest on record at 21.9 kg.fisher-day-1 as a result of moderate catches from historic low levels of targeted effort. The standardised CPUE showed a relatively stable trend over the past 15 years and for 2021–22 remained amongst the highest recorded [Smart et al. 2023]. Estimates of recreational catch continue to be high and were estimated to be 161 t in Spencer Gulf from the 2021–22 recreational fishing survey [Beckmann et al. 2023]. The Charter Boat Fishery reported taking 19,547 fish in 2020–21, which represented 70.7% of all fish harvested by this sector within this management unit [Durante et al. 2022]. Model-derived estimates of biomass have shown a slow (22%) decline over the last six years, with an estimate of biomass of > 280mm TL fish of 1,228 t for 2021–22 [Smart et al. 2023]. This continued slow decline in model-estimated biomass was the result of smaller than average recruitment events since 2013. As such, the model-derived estimates of biomass and recruitment are not directly comparable to previous assessments. However, consecutive years of declines in estimates of biomass and recruitment are of concern and are being monitored.
The above evidence indicates that the biomass of this stock is unlikely to be depleted and that recruitment is unlikely to be impaired. Furthermore, the evidence indicates that the current level of fishing mortality is unlikely to cause the stock to become recruitment impaired.
On the basis of the evidence provided above, the Spencer Gulf (South Australia) Management Unit is classified as a sustainable stock.
West Coast Eyre Peninsula
The most recent stock assessment, which considered data collected up until the end of June 2022, was completed in 2023 [Smart et al. 2023]. Assessment methods were the same as applied for the Gulf St Vincent/Kangaroo Island and Spencer Gulf management units. Stock assessments for this stock are conducted on a biennial cycle, with stock status determined between assessments based only on commercial fishery statistics [Smart et al. 2023]. As part of the MSF reform implemented in 2021, this stock is now managed under a total allowable commercial catch (TACC) which was set at 473 t in 2021–22. Commercial fishers do not have ITQ for harvesting King George Whiting in this management unit but were restricted in harvest by the implemented TACC for 2021–22. The spatial scale of assessment has also changed with the south-west region of Eyre Peninsula removed from the West Coast South Australian stock [Smart et al. 2023].
Commercial catch and effort have continued to decline since 1983–84. Total catch (78 t) and targeted handline effort (3,221 fisher days) were both the lowest on record in 2021–22, with only 17% of the TACC being harvested for that year [Smart et al. 2023]. Nevertheless, despite these declines in catch and effort, CPUE has continued to slowly increase through time and in 2021–22 attained the fourth highest rate of 24.2 kg.fisherday-1[Smart et al. 2023]. The continued reductions in catch and effort primarily relate to the decline in the numbers of fishers both targeting and taking King George Whiting in this management unit. The reported recreational catch from in the 2021–22 fishery survey was estimated to be 59 t for the West Coast zone. The Charter Boat Fishery reported taking 1,092 King George Whiting in 2020-21, which represented 23.2% of all fish caught onboard charter fishing vessels in this management zone [Durante et al. 2022].
Since 2016–17, the model-derived estimates of fishable biomass have been increasing and in 2021–22 was the second highest on record at 2,718 t. The general increasing trend in biomass reflects long-term trends in increasing recruitment and declining exploitation rate. The latter was associated with the declining fishing effort that relates to declining numbers of commercial fishers.
The above evidence indicates that the biomass of this stock is unlikely to be depleted and that recruitment is unlikely to be impaired. Furthermore, the evidence indicates that the current level of fishing mortality is unlikely to cause the stock to become recruitment impaired.
On the basis of the evidence provided above, the South Australia West Coast Eyre PeninsulaManagement Unit is classified as a sustainable stock.
Biology
King George Whiting biology [Hyndes et al. 1998; Fowler et al. 2000a; Hamer et al. 2004; Sulin 2012]
Species | Longevity / Maximum Size | Maturity (50 per cent) |
---|---|---|
King George Whiting | South Australia 22 years, 590 mm TL Western Australia at least 14 years, 620 mm TL Victoria at least 11 years, 600 mm TL | South Australia 3–4 years, 300–350 mm TL Western Australia 3–4 years, 410 mm TL Victoria unknown |
Tables
South Australia | |
---|---|
Commercial | |
Gillnet | |
Unspecified | |
Seine Nets | |
Handline | |
Indigenous | |
Spearfishing | |
Recreational | |
Spearfishing | |
Hook and Line | |
Charter | |
Rod and reel |
Method | South Australia |
---|---|
Commercial | |
Gear restrictions | |
License | |
Limited entry | |
Size limit | |
Spatial closures | |
Spatial restrictions | |
Indigenous | |
Bag and boat limits | |
Size limit | |
Recreational | |
Bag and boat limits | |
Size limit | |
Spatial closures |
South Australia | |
---|---|
Commercial | 170.85t |
Indigenous | Unknown |
Recreational | 305 t (2021–22) |
Western Australia – Recreational (Management Methods). In Western Australia a recreational fishing licence is only required for fishing from a boat.
Victoria – Recreational (Management Methods). Boat limits do not apply in Victoria. In Victoria a recreational fishing licence is required for all forms or recreational fishing, unless exempt.
Victoria – Indigenous (Management Methods). A person who identifies as Aboriginal or Torres Strait Islander is exempt from the need to obtain a Victorian recreational fishing licence, provided they comply with all other rules that apply to recreational fishers, including rules on equipment, catch limits, size limits and restricted areas. Traditional (non-commercial) fishing activities that are carried out by members of a traditional owner group entity under an agreement pursuant to Victoria’s Traditional Owner Settlement Act 2010 are also exempt from the need to hold a recreational fishing licence, subject to any conditions outlined in the agreement. Native title holders are also exempt from the need to obtain a recreational fishing licence under the provisions of the Commonwealth’s Native Title Act 1993.
South Australia - Recreational (Catch). Beckmann et al. [2023].
Catch Chart
References
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- Durante, LM, Smart, JJ, Tsolos, A 2022, South Australian Charter Boat Fishery 2020/21 data summary, Report to PIRSA Fisheries and Aquaculture. South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2011/000438-4. SARDI Research Report Series No. 1159. 124pp.
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