*

Gemfish (2020)

Rexea solandri

  • Timothy Emery (Australian Bureau of Agricultural and Resource Economics and Sciences)
  • James Woodhams (Australian Bureau of Agricultural and Resource Economics and Sciences)
  • Andy Moore (Australian Bureau of Agricultural and Resource Economics and Sciences)
  • Geoffrey Liggins (New South Wales Department of Primary Industries)
  • David Fairclough (Department of Primary Industries and Regional Development, Western Australia)

Date Published: June 2021

You are currently viewing a report filtered by jurisdiction. View the full report.

Toggle content

Summary

Gemfish is found throughout southern Australia. There are two genetically distinct national stocks. The western stock, harvested in WA and Commonwealth waters, is sustainable. The eastern stock, harvested in NSW and Commonwealth waters, is depleted.

Toggle content

Stock Status Overview

Stock status determination
Jurisdiction Stock Stock status Indicators
New South Wales Eastern Depleted

Biomass, fishing mortality

Toggle content

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 Strait [Colgan and Paxton 1997, Moore et al. 2016]. Studies suggest that there are no genetic differences between Gemfish in eastern Australia and New Zealand [Colgan and Paxton 1997]. For the purposes of management and assessment, the Eastern Australia 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.

Toggle content

Stock Status

Eastern

Eastern Gemfish in Commonwealth fisheries was managed as a Tier 1 stock under the Southern and Eastern Scalefish and Shark (SESSF) Harvest Strategy Framework [AFMA, 2019] but is currently managed under a rebuilding strategy [AFMA 2015] with an incidental catch allowance of 100 tonnes (t). In 2009, the species was listed as conservation dependent under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act).

The last quantitative stock assessment for Eastern Gemfish was published in 2010, using data up to 2009 [Little & Rowling 2010]. The base-case model estimated that the spawning stock biomass in 2009 was 16 per cent of the unfished level. That assessment [Little & Rowling 2010] included projections of Eastern Gemfish biomass that were based on 2 scenarios: zero and 100 t (retained catch) each year. The projections for catches of zero and 100 t (retained catch) indicated that the spawning stock biomass may reach the limit reference point of 0.2SB0 (20 per cent of unfished levels) by 2017 and 2025, respectively, assuming average recruitment. A preliminary update of the 2010 assessment in 2016 [Little 2016], while not accepted by SERAG, indicated that the spawning stock biomass in 2015 had decreased to 8 per cent (0.08SB0), due to a prolonged period of below-average recruitment [AFMA 2016; Little 2016].

In 2008, a rebuilding strategy was implemented for Eastern Gemfish (subsequently revised in 2015) with the goal of rebuilding stocks to, or above, the limit reference point by or before 2027 (1 mean generation time plus 10 years) [AFMA 2015]. Projections to support this time frame from the 2010 assessment [Little & Rowling 2010] assume that total removals are limited to the incidental catch allowance (currently set at 100 t) and rely on at least average levels of recruitment [Morison et al. 2013]. 

Recent research suggests that the spawning biomass in the eastern stock has fewer effective genetically successful contributors between generations [Moore et al. 2016; Ovenden et al. 2020]. Smaller effective population size was not detected in the Western Gemfish stock. The decreased effective population size in Eastern Gemfish may be related to few effective parents contributing to spawning each year or differential selection against recruits [Ovenden et al. 2020].

The above evidence indicates that the Eastern biological stock is depleted and that recruitment is likely to have been impaired. 

Commercial landings in NSW have declined over the past decade from 20.6 t in 2009–10 to 3.0 t during 2018–19, with nearly all catch coming from the Ocean Trap and Line fishery. NSW landings represent a small proportion of annual fishing mortality. Anecdotal evidence, including photographs and reports on social media websites, indicates that Gemfish are targeted and captured by recreational anglers. However, surveys of recreational catch in New South Wales during 2013–14 [West et al. 2015] and 2017–18 [Murphy et al. 2020] detected no Gemfish captures. It is therefore concluded that recreational catch is negligible, relative to commercial catch.

Catch landed by the Commonwealth Trawl and Scalefish Hook sectors of the SESSF was 70 t in the 2019–20 fishing season (39.1 t in 2018–19 fishing season), based on catch disposal records. Discards have been estimated to be 45.3 t based on the weighted average of the previous four calendar years (2015 to 2018) [Burch et al., 2019]. While an assessment update is understood to be scheduled for 2021, there are currently no reliable indicators to determine if this level of fishing mortality will allow the stock to rebuild to above the limit reference point within a biologically reasonable time frame.

On the basis of the evidence provided above, the Eastern biological stock is classified as a depleted stock.

Toggle content

Biology

Gemfish biology [Hutchins and Swainston 1986, Rowling 1999]

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
Toggle content

Distributions

Distribution of reported commercial catch of Gemfish

Toggle content

Tables

Fishing methods
New South Wales
Commercial
Line
Various
Charter
Hook and Line
Rod and reel
Indigenous
Hook and Line
Rod and reel
Recreational
Hook and Line
Rod and reel
Management methods
Method New South Wales
Charter
Bag/boat limits
Bag/possession limits
Gear restrictions
Licence
Marine park closures
Commercial
Catch limits
Gear restrictions
Limited entry
Marine park closures
Mesh size regulations
Spatial closures
Vessel restrictions
Indigenous
Customary fishing management arrangements
Recreational
Bag/boat limits
Bag/possession limits
Gear restrictions
Licence
Marine park closures
Catch
New South Wales
Commercial 3.01t
Indigenous Negligible (2017-18)
Recreational Negligible (2017-18)

Commonwealth – Commercial (Management Methods/Catch) Data provided for the Commonwealth align with the Commonwealth Southern and Eastern Scalefish and Shark Fishery for the 2018-19 financial year. 

Commonwealth – Recreational The Commonwealth 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 Torres Strait. In general, non-commercial Indigenous fishing in Commonwealth waters is managed by the state or territory immediately adjacent to those waters

New South Wales – Data for New South Wales is the 2018–19 financial year.

New South Wales – Indigenous (Management Methods) Customary Fishing Management Arrangements. See https://www.dpi.nsw.gov.au/fishing/aboriginal-fishing 

New South Wales Indigenous and Recreational catch estimates of “Negligible” are based zero catches of Gemfish recorded during the 2017-18 suvey of recreational catch by 1-3 year recreational licence holders in NSW [Murphy et al. 2020]

Toggle content

Catch Chart

Commercial catch of Gemfish - note confidential catch not shown

Toggle content

References

  1. AFMA 2016, Stock rebuilding strategies annual reviews. Eastern gemfish stock rebuilding strategy - annual review, South East Resource Assessment Group (SERAG) meeting 2016, Australian Fisheries Management Authority, Canberra.
  2. AFMA 2019, Harvest strategy framework for the Southern and Eastern Scalefish and Shark Fishery 2009 (amended 2019), Australian Fisheries Management Authority, Canberra.
  3. Australian Fisheries Management Authority 2015, Eastern gemfish (Rexea solandri) stock rebuilding strategy, AFMA, Canberra.
  4. Burch, P, Althaus, F and Thomson, R 2019, Southern and Eastern Scalefish and Shark Fishery (SESSF) catches and discards for TAC purposes using data until 2018, Prepared for the SERAG Meeting, 3-4 December 2019, Hobart, CSIRO Oceans and Atmosphere, Hobart, Tasmania.
  5. 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.
  6. Hutchins, B, and Swainston, R, 1986 Sea fishes of southern Australia, Swainston Publishing, Perth.
  7. Kailola, PJ, Williams, M, Stewart, PC, Reichelt, R, McNee, A, and Grieve, C 1993, Australian fisheries resources, Bureau of Resource Sciences, Canberra.
  8. Little, R & Rowling, K 2010, 2010 update of the eastern gemfish (Rexea solandri) stock assessment, CSIRO Marine and Atmospheric Research and NSW Fisheries, Hobart, Tasmania.
  9. Little, R 2016, Preliminary 2016 update of the eastern gemfish (Rexea solandri) stock assessment, CSIRO Oceans and Atmosphere, Hobart, Tasmania.
  10. 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.
  11. Morison, AK, Knuckey, I, Simpfendorfer, CA & Buckworth, RC 2013, Southern and Eastern Scalefish and Shark Fishery (SESSF): draft 2012 stock assessment summaries for species assessed by GABRAG, ShelfRAG and Slope/DeepRAG, Canberra.
  12. Murphy, JJ, Ochwada-Doyle, FA, West, LD, Stark, KE and Hughes, JM, 2020, The NSW Recreational Fisheries Monitoring Program - Survey of recreational fishing, 2017/18. NSW DPI - Fisheries Final Report Series No. 158.
  13. Ovenden, J, Davenport, D & Moore, A, 2020, 'A perfect storm of genetic drift and divergence may prevent the rebuilding of the gemfish (Rexea solandri) stock on the east Australian coast'. Fisheries Research, 230, 105645.
  14. Rowling, K 1999, The fisheries biology and population dynamics of Gemfish Rexea solandri, PhD thesis, University of New South Wales, Sydney.
  15. Sporcic, M. 2019, Tier 4 Assessment for Western Gemfish (data to 2018), CSIRO Oceans and Atmosphere, Hobart.
  16. 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.

Downloadable reports

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