Greenback Flounder (2020)
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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
Stock Status Overview
Greenback Flounder has a wide distribution in Australia, from Jervis Bay on the central coast of New South Wales, around the south of the continent including Tasmania, and up to Mandurah on the south-eastern 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 , 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.
Although not generally reported at the species level, Greenback Flounder are assumed to constitute the majority of the commercial catch of flounder in Tasmania. Flounder landings have declined steadily from recorded peak annual catches >30 t in the mid-1990s to a historical low of 1 t in 2015–16. Catches over the last two years were slightly higher, amounting to 3.9 t in 2017–18 and 2.2 t in 2018–19 [Krueck et al. 2020]. Greenback Flounder are a relatively important recreational species, and in recent years, recreational landings have matched or exceeded those of the commercial sector [Lyle et al. 2019]. Similar to commercial catches, recreational catches appear to have declined progressively over the years, with an estimated peak of 15.2 t in 2000–01 and a low of 3.8 t in 2017–18 [Lyle et al 2019]. Possible explanations for declining catches of flounder include a ban on overnight gillnetting and reduced market demand. However, the potential role of overfishing and population depletion cannot confidently be assessed due to insufficient data. The data available are inadequate to estimate biomass or exploitation rates. There is little knowledge on recruitment or harvestable biomass. 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, Greenback Flounder in Tasmania is classified as an undefined stock.
[Sutton et al. 2010; Earl 2014]
|Species||Longevity / Maximum Size||Maturity (50 per cent)|
10 years; 500 mm TL
198 mm TL for females; 211 mm TL for males (SA)
Distribution of reported commercial catch of Greenback Flounder.
|Hook and Line|
|Hand held- Implements|
|Bag and possession limits|
|Recreational||3.8 t (in 2017–18)|
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.
- Conron S, Green C, Hamer P, Giri K and Hall K (2016). Corner Inlet-Nooramunga Fishery Assessment 2016. Fisheries Victoria Science Report Series No. 11.
- Earl, J 2014, Population biology and ecology of the greenback flounder (Rhombosolea tapirina) in the Coorong estuary, South Australia, PhD Thesis. School of Biological Sciences, Flinders University, Adelaide, Australia.
- Earl, J 2020, Assessment of the South Australian Lakes and Coorong Fishery in 2018/19. Report to PIRSA Fisheries and Aquaculture. South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2020/000208-01. SARDI Research Report Series No. 1059. 81pp.
- 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.
- 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.
- Giri, K, Hall, K 2015, South Australian Recreational Fishing Survey. Fisheries Victoria Internal Report Series No. 62.
- 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.
- Krueck N, Hartmann, K and Lyle J 2020, Tasmanian Scalefish Fishery Assessment 2018/19. Institute for Marine and Antarctic Studies, University of Tasmania.
- Kurth, D 1957, An investigation of the greenback flounder, Rhombosolea tapirina Günther. PhD thesis Thesis, University of Tasmania, Hobart.
- 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.
- Sutton, CP, MacGibbon, DJ, 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.
- 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.
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