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Greenback Flounder occur around Australia's southern coastline (including TAS), from Jervis Bay in NSW to Mandurah in WA. The species is also found in New Zealand. While there is evidence of population structuring in TAS Greenback Flounder, biological stock structure on the mainland coast in unknown, and assessments are consequently presented here at the jurisdictional level. Greenback Flounder are classified as negligible in WA, sustainable in VIC, undefined in TAS, and depleted in SA.

Photo: CSIRO Australian National Fish Collection

Greenback Flounder has a wide distribution in Australia, from Jervis Bay on the south coast of New South Wales, around the south of the continent including Tasmania, and up to Mandurah on the south-western coast of Western Australia [Kailola et al. 1993]. They also occur in New Zealand [Sutton et al. 2010]. 

The broad distribution of Greenback Flounder in Australia is thought to be divisible into a number of separate biological stocks. Genetic studies have demonstrated that the most significant division occurs between Australian and New Zealand populations [van den Enden et al. 2000]. Within Australia, there is strong evidence that populations in western Tasmania are genetically isolated from populations in Victoria, and northern and south-eastern Tasmania. These results are consistent with those of Kurth [1957], who identified distinct western and eastern Tasmania populations on the basis of morphometrics. Biological stock structure along the southern mainland coasts of Australia is not known.  

Here, assessment of stock status for Greenback Flounder is presented at the jurisdictional level—Western Australia, Victoria, Tasmania and South Australia.

Victoria

Commercial catches of Greenback Flounder in Victoria have averaged 11 t annually over the past two decades, and generally ranged between approximately 9–20 t.  

Since the closure of most commercial Bay and Inlet fisheries, Greenback Flounder are mostly taken commercially by haul/ring seine, and to a lesser extent mesh nets, from Corner Inlet-Nooramunga. Greenback flounder are also targeted by recreational fishers in bays and inlets, predominantly by wading at night with a submersible light and hand spear but there is no recent information on landings.

In Corner Inlet-Nooramunga, haul/ring seine catch rates have shown an increasing trend through time since historic lows in the late 1980s and early 1990s, but have been highly variable over time with peaks in the raw data in 1978–79, 1984–85, 1997–98, 2004–05, 2011–12 and 2021–22 [Bell et al. 2023]. In contrast, the trend for mesh net catch rate follows a consistently negative trajectory, leveling out at close to zero after the mid-2000s [Bell et al. 2023]. While this results in conflicting information about stock status, it is important to note that Greenback Flounder were historically targeted using specifically designed mesh nets set over shallow sand, whereas in recent years, fishers in Corner Inlet have predominantly targeted rock flathead with mesh nets set over seagrass and taken flounder as by-product. Consequently, the low landings of flounder by mesh net during the past two decades should not be interpreted as a reduction in biomass, but rather a change in targeting by the commercial sector [Bell et al. 2023]. Thus, given the low selectivity of haul/ring seines, the CPUE of this gear is considered a more reliable indicator of biomass for Greenback Flounder in Victoria, showing and increasing trend through time. In addition, the closure of all other Victorian Bay and Inlet commercial fisheries means fishing mortality has decreased through time so there is no reason to believe Greenback Flounder abundance has declined.  

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 above 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 provide above, Greenback Flounder in Victoria is classified as a sustainable stock.

[Sutton et al. 2010; Earl et al. 2014]

Distribution of reported commercial catch of Greenback Flounder.

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 - 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://fishing.tas.gov.au/Documents/Policy%20for%20Aboriginal%20tags%20and%20alloting%20an%20UIC.pdf

Commercial catch of Greenback Flounder - note confidential catch not shown.

1. 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 and Livestock Sciences), Adelaide. SARDI Publication No. F2022/000385-1. SARDI Research Report Series No. 1161. 185pp.
2. 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. 141pp
3. Earl, J 2023, Assessment of the South Australian Lakes and Coorong Fishery in 2021-22. Report to PIRSA Fisheries and Aquaculture. South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2020/000208-04. SARDI Research Report Series No. 1176. 94pp.
4. Earl, J and Ye, Q 2016, Greenback Flounder (Rhombosolea tapirina) Stock Assessment Report 2014/15. Report to PIRSA Fisheries and Aquaculture. South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2007/000315-2. SARDI Research Report Series No. 889. 40pp.
5. Earl, J, Fowler, AJ, Ye, Q and Dittmann, S 2014, Age validation, growth and population characteristics of greenback flounder (Rhombosolea tapirina) in a large temperate estuary. New Zealand Journal of Marine and Freshwater Research 48(2), 229-244.
6. Earl, J, Fowler, AJ, Ye, Q and Dittmann, S 2017, Complex movement patterns of greenback flounder (Rhombosolea tapirina) in the Murray River estuary and Coorong, Australia. Journal of Sea Research 122, 1-10.
7. Kailola, PJ, Williams, MJ, Stewart, PC, Reichelt, RE, McNee, A and Grieve, C 1993, Australian fisheries resources, Bureau of Resource Sciences, Department of Primary Industries and Energy and Fisheries Research and Development Corporation, Canberra.
8. Kurth, D 1957, An investigation of the greenback flounder, Rhombosolea tapirina Günther. PhD thesis Thesis, University of Tasmania, Hobart.
9. 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.
10. Sharples, R, Cresswell, K, Hartmann, K and Krueck, N 2023, Tasmanian Scalefish Fishery Assessment 2021/22. Institute for Marine and Antarctic Studies, University of Tasmania.
11. Sutton, CP, MacGibbon, DJ and Stevens, DW 2010, Age and growth of greenback flounder (Rhombosolea tapirina) from southern New Zealand. New Zealand Fisheries Assessment Report 2010/48. Ministry of Fisheries, Wellington. 16pp.
12. van den Enden, T, White, RW and Elliott, NG 2000, Genetic variation in the greenback flounder Rhombosolea tapirina Günther (Teleostei, Pleuronectidae) and the implications for aquaculture. Marine and Freshwater Research 51(1), 23-33.