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Deepwater Flathead (2018)

Platycephalus conatus

  • Andy Moore (Australian Bureau of Agricultural and Resource Economics and Sciences)
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Summary

Caught only in the Great Australian Bight, in Commonwealth waters, Deepwater Flathead is a sustainable stock.

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Stock Status Overview

Stock status determination
Jurisdiction Stock Fisheries Stock status Indicators
Commonwealth Great Australian Bight SESSF (CTS), SESSF (GABTS) Sustainable Spawning stock biomass, fishing mortality
SESSF (CTS)
Southern and Eastern Scalefish and Shark Fishery (Commonwealth Trawl Sector) (CTH)
SESSF (GABTS)
Southern and Eastern Scalefish and Shark Fishery (Great Australian Bight Trawl Sector) (CTH)
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Stock Structure

The biological stock structure of Deepwater Flathead is unknown; however, it is treated as a single biological stock or management purposes in the Southern and Eastern Scalefish and Shark Fishery (SESSF). Stock assessments for Deepwater Flathead have only been completed for the Great Australian Bight part of the biological stock [Haddon 2016].

Here, assessment of stock status is presented at the biological stock level—Great Australian Bight.

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Stock Status

Great Australian Bight

The most recent quantitative assessment [Haddon 2016] estimated that the spawning biomass at the start of the 2016–17 fishing season was 45 per cent of the unfished (1978) level. This assessment was generally consistent with previous assessments and fishery-independent surveys [Knuckey et al. 2009 and 2011], however the 2015 fishery-independent survey suggested a 45 per cent decrease in Deepwater Flathead catch rates compared to previous surveys [Knuckey et al. 2015]. There were uncertainties around the outputs of the survey due to seismic testing and unintentional changes to the trawl net used. The 2018 fishery-independent survey suggested a decrease in relative biomass of 33 per cent compared to 2015 and 63 per cent compared to 2011 [Knuckey et al. 2018]. This trend is concerning and an updated assessment is warranted.

Previous quantitative stock assessments estimated that the spawning biomass was progressively fished-down in the mid-2000s, but the biological stock had recovered to above the maximum economic yield target of 43 per cent by the start of 2010 [Klaer 2013, Haddon 2016]. The recovery was likely a result of lower fishing pressure, combined with at least one substantial recruitment event. As indicated above, the 2016 stock assessment suggests spawning biomass at the start of 2016–17 to be 45 per cent of the unexploited biomass. The stock is not considered to be recruitment impaired [Moore and Mobsby 2018].

The biologically-derived [Haddon 2016] recommended biological catch (RBC) was used to set a total allowable catch (TAC) for the SESSF Great Australian Bight Trawl Sector (Commonwealth) for the 2017–18 fishing season at 1 128 tonnes (t). Landed catch of Deepwater Flathead from this fishery in the 2017–18 fishing season was 548 t [Moore and Mobsby 2018]. The SESSF Commonwealth Trawl Sector also landed 67 t, leading to a combined catch that was below the RBC. The level of discards for this species was low in 2017 [Castillo-Jordan et al. 2018]. This level of fishing mortality is unlikely to cause the stock to become recruitment impaired [Moore and Mobsby 2018].

On the basis of the evidence provided above, the Great Australian Bight biological stock is classified as a sustainable stock.

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Biology

Deepwater Flathead biology [Kailola et al. 1993, Stokie and Krusic-Golub 2005, Stokie and Talman 2003]

Biology
Species Longevity / Maximum Size Maturity (50 per cent)
Deepwater Flathead Females ~26 years, 820 mm TL Males ~19 years, 590 mm TL Females 5–6 years, 430 mm TL Males 4–5 years, 430 mm TL
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Distributions

Distribution of reported commercial catch of Deepwater Flathead

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Tables

Fishing methods
Commonwealth
Commercial
Danish Seine
Otter Trawl
Management methods
Method Commonwealth
Commercial
Gear restrictions
Limited entry
Spatial closures
Total allowable catch
Active vessels
Commonwealth
11 in SESSF (CTS), 4 in SESSF (GABTS)
SESSF (CTS)
Southern and Eastern Scalefish and Shark Fishery (Commonwealth Trawl Sector) (CTH)
SESSF (GABTS)
Southern and Eastern Scalefish and Shark Fishery (Great Australian Bight Trawl Sector) (CTH)
Catch
Commonwealth
Commercial 66.92t in SESSF (CTS), 547.59t in SESSF (GABTS)
Indigenous Unknown
Recreational Unknown
SESSF (CTS)
Southern and Eastern Scalefish and Shark Fishery (Commonwealth Trawl Sector) (CTH)
SESSF (GABTS)
Southern and Eastern Scalefish and Shark Fishery (Great Australian Bight Trawl Sector) (CTH)

Commonwealth – Recreational The Australian Government does not manage recreational fishing in Commonwealth waters. Recreational fishing in Commonwealth waters is managed by the state or territory immediately adjacent to those waters, under its management regulations.

Commonwealth – Indigenous The Australian Government does not manage non-commercial Indigenous fishing in Commonwealth waters, with the exception of the Torres Strait. In general, non-commercial Indigenous fishing in Commonwealth waters is managed by the state or territory immediately adjacent to those waters.

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Catch Chart

Commercial catch of Deepwater Flathead — note confidential catch not shown

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References

  1. Castillo-Jordan, C, Althaus, F, Burch, P, Thomson, R, 2018 SESSF catches and discards for TAC purposes, 2018 CSIRO, Hobart
  2. Haddon, 2016, Deepwater flathead (Platycephalus conatus) stock assessment using data to 2015/16, draft report, CSIRO Oceans and Atmosphere, Hobart.
  3. Kailola, PJ, Williams, MJ, Stewart, PC, Reichelt, RE, McNee, A and Grieve, C 1993, Australian Fisheries Resources, Bureau of Resource Sciences and Fisheries Research and Development Corporation, Canberra.
  4. Klaer, N, 2013 Deepwater flathead (Neoplatycephalus conatus) stock assessment based on data up to 2012/13 in GN Tuck (ed.), Stock assessment for the Southern and eastern Scxalefish and Shark Fishery 2013, part 1, CSIRO, Hobart.
  5. Knuckey, I, Koopman, M and Hudson, R 2009, Resource survey of the Great Australian Bight Trawl Fishery—2009, AFMA Project 2008/848, Report to the Australian Fisheries Management Authority, Canberra.
  6. Knuckey, I, Koopman, M and Hudson, R 2011, Resource survey of the Great Australian Bight Trawl Fishery—2011, Report to the Australian Fisheries Management Authority, Canberra.
  7. Knuckey, I, Koopman, M and Hudson, R 2015, Resource Survey of the Great Australian Bight Trawl Sector—2015, Australian Fisheries Management Authority Project 2014/0809, Fishwell Consulting.
  8. Knuckey, I, Koopman, M and Hudson, R 2018, Resource Survey of the Great Australian Bight Trawl Sector – 2018. AFMA Project 2017/0807. Fishwell Consulting 39pp.
  9. Moore, A and Mobsby 2018, Great Australian Bight Trawl Sector, in H Patterson, Larcombe, J, Nicol, S and Curtotti, R (eds), 8, Australian Bureau of Agricultural and Resource Economics and Sciences, Canberra.
  10. Stokie, T and Krusic-Golub, K 2005, Age estimation of Bight Redfish and Deepwater Flathead in the Great Australian Bight Trawl Fishery, 2004–05, Australian Fisheries Management Authority, Canberra.
  11. Stokie, T and Talman, S 2003, Age estimation of Deepwater Flathead (Neoplatycephalus conatus), Report to the Australian Fisheries Management Authority, Canberra.

Archived reports

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