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Southern Sand Flathead is popular with recreational fishers. It is found in shallow waters around southern Australia. In VIC, one stock is sustainable and one is recovering. The TAS stock is depleted, the SA stock is undefined and the WA stock is negligible.  

Southern Sand Flathead (Platycephalus bassensis) is endemic to Australia and inhabits bays, inlets, estuaries, and shallow coastal waters to a depth of around 100 m from the central New South Wales coast, around Tasmania to South Australia and southern Western Australia [Gomon et al. 2008]. There is some evidence of regional sub-populations with differences in physical characteristics, recruitment dynamics and growth rates. Information from tagging, larval sampling and growth rate studies [Brown 1977; Hamer et al. 2010, 2014], indicate that Southern Sand Flathead in Port Phillip Bay, Victoria, comprise a distinct biological stock that has slower growth, and asymptotic length that is 30% smaller than fish from Bass Strait and 20% smaller than fish from south-east Tasmania [Hirst et al. 2014; Koopman et al. 2009]. However, biological stock structure has not been studied in detail in other areas and each of the State jurisdictions have different management arrangements for Southern Sand Flathead.

Here, assessment of stock status is presented at the biological stock level—Port Phillip Bay (Victoria); at the management unit level—Corner Inlet and Victoria Other (Victoria); and at the jurisdictional level—Western Australia, Tasmania, and South Australia.

Port Phillip Bay

Historically large commercial catches (approximately 200–300 t per year) were taken from Port Phillip Bay (PPB) [Koopman et al. 2009], but since the 1980s, catches have declined, reaching negligible (less than 1 t per year) since 2010 due to removal of commercial effort by license buy-back schemes and a lack of targeting by remaining operators. Catch from PPB is now entirely recreational, with Southern Sand Flathead accounting for 80% of flathead landings [Hirst et al. 2014]. Although a recent estimate of recreational catch is unavailable, estimates in the late 1980s indicated recreational catches of flathead species from PPB were about 450 t per year [MacDonald and Hall 1987] and by the mid-2000s had dropped to approximately 110 t per year [Hirst et al. 2014; Ryan et al. 2009].

Standardised catch per unit effort (CPUE) from creel surveys has remained relatively low since the mid-2000s but has stabilised with signs of an increase from the lowest point in 2013 through until 2020–21, however in 2021–22 CPUE declined reaching a historic low [Bell et al. 2023]. Consistent with creel CPUE, diary angler CPUE showed historic declines, but since 2004 showed and increasing trend in both under- and over-legal minimum fish [Bell et al. 2023]. The catch rate of legal size fish has declined since 2019–20, similar to creel catch rates.

Since 2015, long-line CPUE is no longer considered indicative of stock status due to the exceptionally low reported catches, and likely discarding, but is considered nevertheless for context along with mature biomass inferred from otter trawls (ceased in 2011) [Bell et al. 2023]. These two indicators of mature biomass show a period of higher biomass from the mid-1990’s to the early 2000s [Bell et al. 2023]. Ongoing fishery independent small beam trawl CPUE for mature fish (greater than 25 cm TL) indicates a similar drop in biomass from 2004 to 2006 as per long-line and trawl biomass, but an increasing trend since 2012 consistent with recreational catch rates [Bell et al. 2023]. Overall, various CPUE and fishery independent indices suggest abundance is slowly increasing from an historic low during the late 2000s, with the current increases in abundance due to recent recruitment to a population now dominated by fish below the legal minimum length. A large proportion of these fish are mature, and therefore contributing to recruitment.  

Pre-recruit abundance suggests that the high biomass during the mid-1990s to early 2000s was due to strong recruitment during the late 1980’s to mid-1990’s [Bell et al. 2023]. Recruitment levels since 2000 have been much lower, driving the biomass declines observed during the 2000s. The stock has now stabilised at a lower biomass under this lower recruitment regime, and recruitment has been sufficient to balance natural and fishing mortality at this lower level. Recent recruitment events (i.e., 2004, 2009 and 2013) have been important in stemming ongoing decline and driving the abovementioned increase in biomass. The relatively high 2018 and 2021 recruitment events are expected to contribute to the stability of the stock and should be sufficient to support continuation of the slowly increasing trend.  

On balance, the PPB population has been slowly rebuilding over the last decade but remains at a lower biomass than during the 1990s. Recent recruitment has been sufficient to balance natural mortality and fishing impacts, and indeed enabled some rebuilding, so that overfishing is unlikely to be occurring. Despite recent signs of slow recovery, ongoing recovery in stock biomass will remain slow due to modest recruitment compared to that observed in the 1990s. While the stock biomass is still considered depleted relative to levels observed in the 1990s and early 2000s, the level of fishing mortality should allow the stock to recover from its recruitment impaired state and there is evidence that this is occurring, particularly for sub-legal sized fish, many of which are mature and contributing to recruitment.

On the basis of the evidence provided above, Southern Sand Flathead in Port Phillip Bay (Victoria) is classified as a recovering stock.

Victoria Other

Victorian commercial catch of Southern Sand Flathead from coastal waters and other bays and inlets besides Port Phillip Bay is relatively low, below 5 t per year since 2000, noting that historical landings from Corner Inlet-Nooramunga were largely misidentified Southern Bluespotted Flathead. Recreational landings are not known. 

Southern Sand Flathead are a by-product of several commercial fisheries, principally the Inshore Trawl fishery that operates in coastal waters and the Corner Inlet-Nooramunga fishery [Bell et al. 2023]. However, the lack of targeting, low landings, and the abovementioned misidentification issues mean historical data are too few, or unreliable, to enable meaningful analysis.

Some information exists on recreational Southern Sand Flathead catch rates from creel surveys in Western Port and Corner Inlet-Nooramunga, and from anglers fishing in Bass Strait but landing inside Victorian bays and inlets [Bell et al. 2023]. However, these data are too scarce to be used as a meaningful proxy for biomass because Southern Sand Flathead do not represent a popular target species (Western Port and Corner Inlet-Nooramunga), the time series is to short to establish temporal trends (Corner Inlet-Nooramunga) and, in general, few anglers leave the bays and inlets where creel surveys are undertaken meaning that although they are a popular target in Bass Strait, few creel survey interviews encounter these anglers.

In addition to the above, there is no knowledge on recruitment or harvestable biomass, and there are no defined target or limit reference levels. This prevents assessment of current stock size or fishing pressure. Consequently, there is insufficient information available to confidently classify the status of this stock. 

On the basis of the evidence provided above, Southern Sand Flathead in the “Victorian Other” management unit is classified as an undefined stock.

Southern Sand Flathead biology [Bani and Moltschaniwskyj 2008; Brown 1977; Jordan 1998; Koopman et al. 2004]

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 fishinglicence under the provisions of the Commonwealth’s Native Title Act 1993.

Tasmania – Commercial (Catches). Catches reported for the Tasmanian Scalefish Fishery are for the period 1 July to 30 June the following year. The most recent assessment available is for 2021–22.

Tasmania – Recreational (Management methods). In Tasmania, a recreational licence is required for fishers using dropline or longline gear, along with nets, such as gillnet or beach seine. Due to a recent change in stock status, fishery regulations for the species are currently under review. Until 31 October 2023, the species is subject to a minimum size limit of 350 mm, a bag limit of 10 fish and a possession limit of 30 fish for recreational fishers.

Tasmania – Indigenous (Management methods). In Tasmania, Indigenous persons engaged in traditional fishing activities in marine waters are exempt from holding recreational fishing licences, but must comply with all other fisheries rules as if they were licensed. For details, see the policy document 'Recognition of Aboriginal Fishing Activities” (https://dpipwe.tas.gov.au/Documents/Policy%20for%20Aboriginal%20tags%20and%20alloting%20an%20UIC.pdf).

1. Bani, A and Moltschaniwskyj, NA 2008, Spatio-temporal variability in reproductive ecology of Sand Flathead, Platycephalus bassensis, in three Tasmanian inshore habitats: potential implications for management. Journal of Applied Icthyology ,24: 555–561.
2. Beckmann, CL, Durante, LM, Graba-Landry, A, Stark, KE and Tracey, SR 2023, Survey of recreational fishing in South Australia 2021–22, Report to PIRSA Fisheries and Aquaculture. South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2022/000385-1. SARDI Research Report Series No. 1161. 185pp.
3. Bell, JD, Ingram, BA, Gorfine, HK and Conron, SD 2023, Review of key Victorian fish stocks — 2022, Victorian Fisheries Authority Science Report Series No. 38, First Edition, June 2023. VFA: Queenscliff. 40pp.
4. Brown, IW 1977, Ecology of three sympatric flatheads (Platycephalidae) in Port Phillip Bay, Victoria. PhD thesis, Monash University, Victoria.
5. Cresswell K, Sharples R, Hartmann K, Krueck N 2023, Tasmanian Scalefish Fishery Assessment 2021/22. Institute for Marine and Antarctic Studies, University of Tasmania.
6. Ewing, GP, Lyle, JM and Mapstone, A 2014, Developing a low-cost monitoring regime to assess relative abundance and population characteristics of sand flathead, Institute for Marine and Antarctic Studies, University of Tasmania, Hobart.
7. Fraser, K, Hartmann, K, Haddy, J and Krueck, N 2022, Tasmanian Scalefish Fishery Assessment 2020/21. Institute for Marine and Antarctic Studies, University of Tasmania.
8. Gomon, M, Bray, D and Kuiter, R (ed) 2008, Fishes of Australia's southern coast, Sydney: Reed New Holland.
9. Hamer, P, Kemp, J and Kent, J 2010, Analysis of existing data on sand flathead larval and juvenile recruitment in Port Phillip Bay, Fisheries Victoria Research Report Series No. 50.
10. Hirst, A, Rees, C, Hamer, PA, Kemp, JE and Conron, SD 2014, The decline of Sand Flathead stocks in Port Phillip Bay: magnitude, causes and future prospects, Recreational Fishing Grant Program Research Report, Fisheries Victoria, Queenscliff.
11. Jordan, AR 1998, The life‐history ecology of Platycephalus bassensis and Nemadactylus macropterus. PhD thesis, University of Tasmania.
12. Koopman, M, Morison, AK and Troynikov, V 2004, Population dynamics and assessment of sand and rock flathead in Victorian waters, Final Report, Fisheries Research and Development Corporation project 2000/120, Primary Industries Research Victoria, Department of Primary Industries, Queenscliff.
13. Koopman, MT, Morrison, AK and Coutin, PC (eds) 2009, Sand Flathead 2000, Fisheries Victoria internal report 10, Victorian Department of Primary Industries, Queenscliff.
14. Krueck N, Hartmann, K and Lyle, J 2020, Tasmanian Scalefish Fishery Assessment 2018/19. Institute for Marine and Antarctic Studies, University of Tasmania.
15. Lyle, JM, Stark, KE, Ewing, GP and Tracey, SR 2019, 2017-18 Survey of recreational fishing in Tasmania. Institute for Marine and Antarctic Studies, Hobart, Tasmania.
16. MacDonald, CM and Hall, DN 1987, A survey of recreational fishing in Port Phillip Bay, Victoria, Marine Fisheries Report No. 11, Department of Conservation Forests and Lands.
17. Ryan, KL, Morison, AK and Conron, S 2009, Evaluating methods of obtaining total catch estimates for individual Victorian bay and inlet recreational fisheries, Final report, FRDC project 2003/047.
18. Smart, JJ, McGarvey, R, Feenstra, J, Drew, MJ, Earl, J, Durante, L, Beckmann, CL, Matthews, D, Matthews, JM, Mark, K, Bussell, J, Davey, J, Tsolos, A, Noell, C 2023, Assessment of the South Australian Marine Scalefish Fishery in 2021–22, Report to PIRSA Fisheries and Aquaculture. South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2017/000427-6. SARDI Research Report Series No. 1184. 259pp.
19. VFA unpublished, Southern Sand Flathead–Port Phillip Bay stock status indicators update 2018.