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Southern Sand Flathead (2020)

Platycephalus bassensis

  • Jeff Norriss (Department of Primary Industries and Regional Development, Western Australia)
  • Nils Krueck (Institute for Marine and Antarctic Studies, University of Tasmania)
  • Paul Rogers (SARDI Aquatic Sciences, South Australia)
  • Victorian Fisheries Authority (Victorian Fisheries Authority)

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Summary

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

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Stock Status Overview

Stock status determination
Jurisdiction Stock Stock status Indicators
Victoria Port Phillip Bay Recovering Catch, CPUE, survey biomass estimates, survey pre-recruit estimates, age/ length compositions
Victoria Victoria Other Sustainable Catch, CPUE
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Stock Structure

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, Hirst et al. 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 per cent smaller than fish from Bass Strait and 20 per cent 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.

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Stock Status

Port Phillip Bay

Historically large commercial catches (~200–300 t pa) were taken from Port Phillip Bay (PPB)[Koopman et al. 2009], but since the 1980s  have declined to negligible levels (< 1 t pa) due to removal of commercial effort by license buy-back schemes and lack of targeting by the remaining operators. Catch from PPB is now entirely recreational, accounting for 80% of all flathead species taken [Hirst et al. 2014]. Although recent estimates of recreational catch are unavailable, estimates in the late 1980s indicated 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 pa [Hirst et al. 2014, Ryan et al. 2009].

Standardised CPUE from creel surveys has remained relatively low since the mid-2000s and in 2018/19 was about midway between minimum (i.e. 2013/14) and average values [Conron et al. 2020]. Creel CPUE indicates that availability of legal-sized sand flathead has stabilised since 2008 with signs of an increase from the lowest point in 2013 [Conron et al. 2020]. Consistent with creel CPUE, diary angler CPUE showed historic declines, but since 2011 its increasing trend is more pronounced than for creel CPUE and is now above the average [Conron et al. 2020]. Unlike creel CPUE, diary angler CPUE  represents catch rates of fish both above and below the LML, and the recent increasing trend is influenced by increased abundance of pre-recruit sand flathead below the LML since 2011 [Conron et al. 2020] that do not contribute to the creel survey catch rates. 

Long-line CPUE [Conron et al. 2020] is not considered indicative of stock status since 2015 due to the exceptionally low reported catches but is analysed nevertheless  for context along with mature biomass inferred from otter trawls (ceased in 2011) [Conron et al. 2020]. These two indicators of mature biomass show a period of higher biomass from the mid-1990’s to the early 2000’s [Conron et al. 2020]). Ongoing small beam trawl CPUE for mature fish (>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 diary angler data [Conron et al. 2020]. Again, this increasing trend is influenced by fish less than the LML being included in the beam trawl survey. Overall, various CPUE indices suggest abundance is slowly increasing from an historic low during the late 2000’s, with the current increases in abundance due to recent recruitment to a population now dominated by small fish just below the LML. 

Pre-recruit abundance indicates high biomass during the mid-1990s to early 2000s was due to strong recruitment during the late 1980’s to mid-1990’s [Conron et al. 2020] . 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. 2009, 2013) have been important in stemming ongoing decline, and driving some increase in biomass. The 2018 recruitment is expected to contribute to the stability of the stock and may be sufficient to support continuation of a slowly increasing trend. 

On balance, the PPB population has been stable over the last decade at lower levels of abundance than during the 1990s. Recent recruitment is sufficient to balance natural mortality and fishing impacts so that overfishing is unlikely to be occurring. Despite recent signs of slow recovery in recreational CPUE, ongoing recovery in stock biomass will remain slow due to ongoing low recruitment. While stock biomass is still considered depleted relative to levels observed in the 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.

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 Corner Inlet-Nooramunga and Port Phillip Bay is low, averaging about 1.5 t per year since 2000. Recreational catch is not known. Information on recreational catch rates from creel surveys in Western Port have shown variable catch rates from 1998 until 2018/19, but unlike Port Phillip Bay, there is no evidence of a long-term declining trend during the 2000s, and Southern Sand Flathead is not a priority target species [Conron et al. 2016b].

Given the low commercial harvest of only 1 t in 2018/19 and lack of declining trend in recreational catch rates in Western Port, the current level of fishing mortality of Southern Sand Flathead in the “Victorian Other” management unit is unlikely to cause the stock to become recruitment impaired.

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

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Biology

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

Biology
Species Longevity / Maximum Size Maturity (50 per cent)
Southern Sand Flathead 23 years (both sexes) Males 370 mm TL Females 480 mm TL Males 2.5–3.5 years, 210 mm TL Females 2.6–5.2 years, 235 mm TL
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Distributions

Distribution of reported commercial catch of Southern Sand Flathead
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Tables

Fishing methods
Victoria
Commercial
Hook and Line
Net
Recreational
Spearfishing
Hook and Line
Management methods
Method Victoria
Charter
Bag limits
License
Marine park closures
Size limit
Commercial
Gear restrictions
Licence
Limited entry
Size limit
Spatial closures
Recreational
Bag limits
Gear restrictions
Licence
Size limit
Spatial closures
Catch
Victoria
Commercial 1.01t
Indigenous Unknown (No catch under permit) 
Recreational Unknown

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.

TasmaniaCommercial (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 2016–17

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. The species is subject to a minimum size limit of 320 mm. A bag limit of 20 fish and a possession limit of 30 fish (Sand and Tiger Flathead) is in place 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).

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Catch Chart

Commercial catch of Southern Sand Flathead - note confidential catch not shown
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References

  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. Brown, IW 1977, Ecology of three sympatric flatheads (Platycephalidae) in Port Phillip Bay, Victoria. PhD thesis, Monash University, Victoria.
  3. 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.
  4. Conron, S, Hamer, P and Jenkins, G 2016, Western Port Fishery Assessment 2015, Recreational Fishing Grants Program Research Report, Fisheries Victoria, Department of Economic Development, Jobs, Transport and Resources.
  5. Conron, SD, Bell, JD, Ingram, BA and Gorfine, HK 2020, Review of key Victorian fish stocks — 2019, Victorian Fisheries Authority Science Report Series No. 15, First Edition, November 2020. VFA: Queenscliff. 176pp.
  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. Giri, K and Hall, K 2015, South Australian Recreational Fishing Survey, Fisheries Victoria Internal Report Series No. 62.
  8. Gomon, M, Bray, D and Kuiter, R (ed) 2008, Fishes of Australia's southern coast, Sydney: Reed New Holland.
  9. Hamer, P, Conron, S, Hirst, A and Kemp, J 2016, Sand Flathead Stock Assessment 2015, Fisheries Victoria Science Report Series No. 13, Fisheries Victoria, Queenscliff.
  10. 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.
  11. Henry, GW and Lyle, JM 2003, The National Recreational and Indigenous Fishing Survey, Fisheries Research and Development Corporation project 99/158, Australian Government Department of Agriculture, Fisheries and Forestry, Canberra.
  12. 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.
  13. Jordan, AR 1998, The life‐history ecology of Platycephalus bassensis and Nemadactylus macropterus. PhD thesis, University of Tasmania.
  14. 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.
  15. Koopman, MT, Morrison, AK and Coutin, PC (eds) 2009, Sand Flathead 2000, Fisheries Victoria internal report 10, Victorian Department of Primary Industries, Queenscliff.
  16. Krueck N, Hartmann, K and Lyle J 2020, Tasmanian Scalefish Fishery Assessment 2018/19. Institute for Marine and Antarctic Studies, University of Tasmania.
  17. 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.
  18. 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.
  19. 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.
  20. Southern Sand Flathead–Port Phillip Bay stock status indicators update 2018.
  21. Steer, MA, Fowler, AJ, Rogers, PJ, Bailleul, F, Earl, J, Matthews, C, Drew, M, and Tsolos, A 2020, Assessment of the South Australian Marine Scalefish Fishery in 2018, Report to PIRSA Fisheries and Aquaculture. South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2017/000427-3. SARDI Research Report Series No. 1049. 213pp.
  22. Victorian Fisheries Authority 2020, Review of key Victorian fish stocks — 2019. VFA Internal Report Series, May 2020.
  23. Victorian Fisheries Authority, 2017, Review of key Victorian fish stocks—2017, Victorian Fisheries Authority Science Report Series No. 1.

Downloadable reports

Click the links below to view reports from other years for this fish.