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Gemfish

Rexea solandri

  • Andy Moore (Australian Bureau of Agricultural and Resource Economics and Sciences)
  • Geoff Liggins (Department of Primary Industries, New South Wales)
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Stock Status Overview

Stock status determination
Jurisdiction Stock Fisheries Stock status Indicators
Commonwealth, New South Wales Eastern SESSF (CTS), SESSF (GHTS), OTF, OTLF Overfished Biomass, fishing mortality
Commonwealth Western SESSF (CTS), SESSF (GABTS), SESSF (GHTS) Sustainable Biomass, fishing mortality
OTF
Ocean Trawl Fishery (NSW)
OTLF
Ocean Trap and Line (NSW)
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)
SESSF (GHTS)
Southern and Eastern Scalefish and Shark Fishery (Gillnet Hook and Trap Sector) (CTH)
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Stock Structure

There is genetic evidence for two biologically distinct stocks of Gemfish in Australia—an Eastern and a Western biological stock—separated by a boundary at the western end of Bass Strait1,2. Studies suggest that there are no genetic differences between Gemfish in eastern Australia and New Zealand2. For the purposes of management and assessment, the eastern Australian population is treated as a single biological stock, independent of the New Zealand population.

Given the evidence of two genetically distinct stocks in Australian waters, stock status is reported accordingly.

Here, assessment of stock status is presented at the biological stock level—Eastern and Western.

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Stock Status

Eastern

Historically high catches of Gemfish from the Eastern biological stock through the 1970s and 1980s substantially reduced the biomass of Eastern Gemfish by the 1990s3. The biological stock has remained at a depressed level, with limited recruitment over this period4. The most recent assessment4 estimated that biomass in 2010 was 15.6 per cent of the unfished (1968) level. Based on this evidence, the stock is considered to be recruitment overfished5.

A recent study suggests that the spawning biomass in the Eastern stock has fewer effective genetically successful contributors between generations than expected1. Smaller effective population size was not detected in the Western Gemfish stock. Hybridisation between east and west populations was detected, but there was no evidence of introgression of genetic material between either population, suggesting all hybrids are sterile. The decreased effective population size in Eastern Gemfish may be related to wasted reproductive effort in producing sterile hybrids, in combination with an overfished stock.

A spawning potential ratio analysis6 indicated high fishing mortality rates on Eastern Gemfish until the late-1990s, but much lower rates since 2002. Because fishing mortality rates have substantially decreased, assessment model projections indicate that the stock should reach 20 per cent of unfished biomass by 20254, which is less than the one generation time plus 10 years required under the Commonwealth Fisheries Harvest Strategy Policy7.

This rebuilding projection, however, is based on future recruitments determined from the stock recruitment relationship and total removals being limited to the 100 tonnes (t) incidental catch allowance (no targeting is allowed). If these assumptions are not met, the time required to rebuild the stock may be underestimated.

Discards were estimated at 131 t in 2013, which was around double the catch in that year. The combined mortality of 183 t is in excess of the 100 t incidental bycatch level that would allow rebuilding. Discarding decreased to 33 t in 2014, with a combined total catch of 70 t8. Total landed catch in 2015–16 was 30 t, however discard estimates are not available for this period and therefore total removals cannot be determined. It is uncertain whether current fishing pressure has been reduced by management to a level that should allow the stock to recover from its recruitment overfished state.

Anecdotal evidence indicates that some recreational anglers target Gemfish, however, a survey of recreational catch in New South Wales during 2013–14 detected no Gemfish captures9.

On the basis of the evidence provided above, the Eastern biological stock is classified as an overfished stock.

Western

The catch from the Western Australian component of this stock has been negligible, averaging a little over 5 kg per year between 2004 and 2014, with no reported catch in 2015. In view of these low catches, status determination for this stock is based on evidence for the Commonwealth fisheries.

An updated integrated stock assessment was conducted for the Western biological stock of Gemfish in the Commonwealth Trawl Sector and Great Australian Bight Trawl Sector (Commonwealth) in 201310. The most recent assessment10 estimates that biomass in 2013 was 74 per cent of the unfished (1985) level. The stock is not considered to be recruitment overfished5.

A catch-rate analysis11 for the Commonwealth Trawl Sector estimated that catch rates were above the Commonwealth limit but below the target catch rate (based on a historical reference catch period).

The total allowable catch for the Southern and Eastern Scalefish and Shark Fishery (Commonwealth) for the 2015–16 fishing season was 199 t. Landed catch of Western Gemfish from this fishery in the 2015–16 fishing season was 84 t. Discards in 2013 were estimated at 69 per cent of the catch, dropping to 24 per cent of the catch in 2014. Discard estimated for 2015 were not available at the time of writing. However, total catch and discarding have remained at, or below, the total allowable catch in recent years and are not expected to exceed it in 2015. This level of fishing pressure is unlikely to cause the stock to become recruitment overfished.

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

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Biology

Biology
Species Longevity / Maximum Size Maturity (50 per cent)
Gemfish Males 13 years; up to 1 060 mm TL , 15 kg Females 17 years; up to 1 160 mm TL, > 15 kg Males 4–5 years; 600 – 660 mm TL Females 5–6 years; 710 – 740 mm TL 

Gemfish biology12–14

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Distributions

Distribution of reported commercial catch of Gemfish

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Tables

Fishing methods
Commonwealth New South Wales
Commercial
Demersal Longline
Dropline
Danish Seine
Otter Trawl
Midwater Trawl
Hand Line, Hand Reel or Powered Reels
Setline
Indigenous
Hand Line, Hand Reel or Powered Reels
Recreational
Hand Line, Hand Reel or Powered Reels
Management methods
Method Commonwealth New South Wales
Commercial
Gear restrictions
Limited entry
Spatial closures
Total allowable catch (incidental)
Trip limits
Indigenous
Aboriginal cultural fishing authority
Bag limits
Gear restrictions
Spatial closures
Recreational
Bag limits
Gear restrictions
Spatial closures
Active vessels
Commonwealth New South Wales
42 in SESSF (CTS), 3 in SESSF (GABTS), 6 in SESSF (GHTS) 11 in OTF, 20 in OTLF
OTF
Ocean Trawl Fishery (NSW)
OTLF
Ocean Trap and Line (NSW)
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)
SESSF (GHTS)
Southern and Eastern Scalefish and Shark Fishery (Gillnet Hook and Trap Sector) (CTH)
Catch
Commonwealth New South Wales
Commercial 103.14t in SESSF (CTS), 2.70t in SESSF (GABTS), 8.05t in SESSF (GHTS) 283.64kg in OTF, 5.89t in OTLF
Indigenous Unknown
Recreational Unknown
OTF
Ocean Trawl Fishery (NSW)
OTLF
Ocean Trap and Line (NSW)
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)
SESSF (GHTS)
Southern and Eastern Scalefish and Shark Fishery (Gillnet Hook and Trap Sector) (CTH)

Commonwealtha New South Wales a Recreationalb Indigenousc,d,e

 

 

a Data for the Commonwealth align with the Commonwealth Southern and Eastern Scalefish and Shark Fishery
2015–16 fishing season (1 May 2015–30 April 2016). Data for New South Wales align with the 2015 calendar year.

b 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.

c 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.

d The Aboriginal Cultural Fishing Interim Access Arrangement allows an Indigenous fisher in New South Wales to take in excess of a recreational bag limit in certain circumstances—for example, if they are doing so to provide fish to other community members who cannot harvest themselves.

e The Aboriginal cultural fishing authority is the authority that Indigenous persons can apply to take catches outside the recreational limits under the Fisheries Management Act 1994 (NSW), Section 37 (1)(c1), Aboriginal cultural fishing authority.

f  New South Wales – Indigenous (catch) A survey of recreational fishing in NSW and the ACT during 2013–149 did not detect the capture of any Gemfish. However, recreational catch of Gemfish is known to occur. Hence, the magnitude of recreational catch is listed as “0 t”, indicated an unknown but relatively small catch.

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Catch Chart

Commercial catch of Gemfish

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Effects of fishing on the marine environment

  • There is bycatch in the fish trawl sector. In 2006, mandatory requirements for otter trawls to use 90 mm square-mesh codend panels were introduced in an effort to reduce the catch of small species and juvenile fish15.
  • Interactions also occur with animals protected under the Environment Protection and Biodiversity Conservation Act 1999, including marine mammals (dolphins, seals and sea lions), seabirds, some shark species and seahorses and pipefish (syngnathids). These interactions are reported quarterly by the Australian Fisheries Management Authority (AFMA)16 and on-board observer programs are used to validate the reporting in commercial logbooks.
  • In 2007, the South East Trawl Fishing Industry Association released an industry code of practice that aims to minimise interactions with fur seals, as well as addressing the environmental impacts of the fishery more generally17. Operators have developed other mitigation protocols that have further reduced seal mortalities, including using breakaway ties that keep the net closed until it is below depths that seals regularly inhabit, adopting techniques to close the trawl opening during recovery to minimise opportunities for seals to enter the net, switching off gantry lights that are not required during night trawling to avoid attracting bait species and seals, and dumping offal only when the boat is not engaged in deploying or hauling gear17.
  • The AFMA mandated individual vessel seabird management plans18. The seabird action plans are used in the Southern and Eastern Scalefish and Shark Fishery (Commonwealth Trawl Sector) (SESSF [CTS]) to mitigate the impacts of trawling on seabirds. From 1 May 2017, all vessels in the SESSF(CTS) and Southern and Eastern Scalefish and Shark Fishery (Great Australian Bight Trawl Sector) (Commonwealth) (SESSF [GABTS]) fisheries must use one of the following mitigation devices: sprayers; bird bafflers; or pinkies with zero discharge fish waste19.
  • The effects of trawl fishing on the marine environment are assessed through an environmental risk assessment and risk management framework and mitigated through spatial closures, and the implementation of bycatch and discard workplans in the SESSF (CTS) and SESSF (GABTS) fisheries20,21.
  • The Eastern biological stock of Gemfish is listed as ‘Conservation Dependent’ under the Environment Protection and Biodiversity Conservation Act 199922 and is subject to a stock rebuilding strategy23.
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Environmental effects on Gemfish

  • The abundance of Gemfish is likely to be affected by environmental conditions, including ocean currents and temperatures, which may influence habitat suitability, food availability and recruitment24.
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References

  1. 1 Moore, A, Ovenden, J and Bustamante, C 2016, Research to underpin better understanding and management of western Gemfish stocks in the Great Australian Bight, FRDC project No. 2013/014, FRDC, Canberra.
  2. 2 Colgan, DJ and Paxton, JR 1997, Biochemical genetics and recognition of a western stock of the common Gemfish, Rexea solandri (Scombroidea: Gempylidae), in Australia, Marine and Freshwater Research, 48(2): 103–118.
  3. 3 Kailola, PJ, Williams, M, Stewart, PC, Reichelt, R, McNee, A and Grieve, C 1993, Australian fisheries resources, Bureau of Resource Sciences, Canberra.
  4. 4 Little, R and Rowling, K 2011, 2010 update of the Eastern Gemfish (Rexea solandri) stock assessment, in GN Tuck (ed) Stock Assessment for the Southern and Eastern Scalefish and Shark Fishery: 2010, Part 1, Australian Fisheries Management Authority and CSIRO Marine and Atmospheric Research, Hobart.
  5. 5 Georgeson, L, Nicol, S, Moore, A and Green, R 2016, Commonwealth Trawl and Scalefish Hook sectors, in H Patterson, R Noriega, L Georgeson, I Stobutzki and R Curtotti (ed.s), Fishery status reports 2016, Australian Bureau of Agricultural and Resource Economics and Sciences, Canberra, pp 135–230.
  6. 6 Little, R 2011, A summary of the spawning potential ratio (SPR), its calculation and use in determining over-fishing in the SESSF: an example with eastern gemfish, in GN Tuck (ed) Stock Assessment for the Southern and Eastern Scalefish and Shark Fishery: 2010, Part 1, Australian Fisheries Management Authority and CSIRO Marine and Atmospheric Research, Hobart.
  7. 7 Australian Government Department of Agriculture, Fisheries and Forestry 2007, Commonwealth Fisheries Harvest Strategy: policy and guidelines, DAFF, Canberra.
  8. 8 Upston, J and Thomson, R 2015, Integrated Scientific Monitoring Program for the Southern and Eastern Scalefish and Shark Fishery—discard estimation 2014, Australian Fisheries Management Authority and CSIRO Marine Resources and Industries, Hobart.
  9. 9 West, LD, Stark, KE, Murphy JJ, Lyle JM and Ochwada-Doyle, FA 2015, Survey of recreational fishing in New South Wales and the ACT, 2013/14, Fisheries Final Report Series No. 149. NSW Department of Primary Industries, Wollongong.
  10. 10 Chambers, M, Moore, A and Barnes, B 2014, Quantitative assessment of the western gemfish stock, Australian Bureau of Agricultural and Resource Economics and Sciences research report, ABARES, Canberra.
  11. 11 Haddon, M 2015, Tier 4 analyses in the SESSF, including deep water species: data from 1986–2014, CSIRO Marine and Atmospheric Research, Hobart.
  12. 12 Australian Government Department of the Environment, no date, Rexea solandri (eastern Australian population) (Gemfish) listing advice, advice to the Minister for the Environment, Heritage and the Arts from the Threatened Species Scientific Committee on Amendments to the list of Threatened Species under the Environment Protection and Biodiversity Conservation Act 1999.
  13. 13 Hutchins, B and Swainston, R 1986, Sea fishes of southern Australia, Swainston Publishing, Perth.
  14. 14 Rowling, K 1999, The fisheries biology and population dynamics of Gemfish Rexea solandri, PhD thesis, University of New South Wales, Sydney.
  15. 15 Australian Fisheries Management Authority 2005, SESSF direction no. 05: gear requirements for the Commonwealth Trawl Sector, AFMA, Canberra.
  16. 16 Australian Fisheries Management Authority, Protected species interaction reports, AFMA, Canberra.
    http://www.afma.gov.au/sustainability-environment/protected-species-management/protected-species-interaction-reports/
  17. 17 South East Trawl Fishing Industry Association 2007, Industry code of practice to minimise interactions with seals, SETFIA, Shearwater, Tasmania.
  18. 18 Australian Fisheries Management Authority, Seabirds, AFMA, Canberra. 
  19. 19 AFMA 2016, AFMA moves to strengthen seabird safety, AFMA media release 15 July 2016. http://www.afma.gov.au/afma-moves-strengthen-seabird-safety/
  20. 20 Australian Fisheries Management Authority 2014, Commonwealth Trawl Sector (Otter Board Trawl and Danish Seine) bycatch and discarding workplan 2014–2016, AFMA, Canberra.
  21. 21 Australian Fisheries Management Authority 2014, Great Australian Bight Trawl Sector bycatch and discarding workplan 2014–2016, AFMA, Canberra.
  22. 22 Department of the Environment and Energy, Rexea solandri (eastern population)—Eastern Gemfish, EPBC listing.
  23. 23 Australian Fisheries Management Authority 2015, Eastern gemfish (Rexea solandri) stock rebuilding strategy, AFMA, Canberra.
  24. 24 Hobday, AJ, Poloczanska, ES and Matear, RT (ed.s) 2008, Implications of climate change for Australian fisheries and aquaculture: a preliminary assessment, report to the Australian Government Department of Climate Change, Canberra.

Archived reports

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