Date Published: June 2021
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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.
Stock Status Overview
CPUE, fishing mortality
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.
Western Gemfish is primarily caught by the Commonwealth managed Southern and Eastern Scalefish and Shark Fishery (SESSF) and the Great Australian Bight Trawl Sector (GABTS), with small catches from Western Australia. Stock status classification reported here is based on the standardised catch per unit effort (CPUE) analyses conducted for the Commonwealth fishery.
Catches of the Western biological stock of Gemfish by Western Australian state commercial and recreational fisheries remains very small (≤ 0.1 t in each year between 2008 and 2019). This species is caught as byproduct by fishers targeting demersal species.
Western Gemfish in Commonwealth fisheries is managed as a Tier 4 stock under the SESSF Harvest Strategy Framework [AFMA, 2019]. The latest standardised CPUE analysis was undertaken in 2019 [Sporcic 2019] using data solely from the Commonwealth Trawl Sector (CTS) (zone 50) up to 2018. The analysis estimated that the 4-year average CPUE (2015 to 2018), including discards, was above the target reference point. This led to a Recommended Biological Catch (RBC) of 423 t.
However, the most recent stock structure research suggests zone 50 is an overlap zone between the eastern and western biological stocks (Ovenden et al. 2020) and that the western stock occurs west of Portland through the Great Australian Bight. As a result, the Tier 4 may not adequately assess the western stock. Future assessments should consider both zone 50 and the western biological stock.
Catch landed by the Commonwealth Trawl and Scalefish Hook sectors of the SESSF was 96.2 t in the 2019–20 fishing season (78.5 t in 2018–19 fishing season). Discards have been estimated to be 41.7 t based on the weighted average of the previous four calendar years (2015 to 2018) [Burch et al., 2019], which, when combined with negligible State catch and Commonwealth landings, is below the RBC of 423 t calculated in the 2019 analysis.
The above evidence suggests that the biomass of this stock is unlikely to be depleted and that recruitment is unlikely to be impaired. On the basis of the evidence provided above, the Western biological stock is classified as a sustainable stock.
Gemfish biology [Hutchins and Swainston 1986, Rowling 1999]
|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|
Distribution of reported commercial catch of Gemfish
|Hand Line, Hand Reel or Powered Reels|
|Hook and Line|
|Rod and reel|
|Rod and reel|
|Bag and possession limits|
|Marine park closures|
|Marine park closures|
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]
Commercial catch of Gemfish - note confidential catch not shown
- 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.
- AFMA 2019, Harvest strategy framework for the Southern and Eastern Scalefish and Shark Fishery 2009 (amended 2019), Australian Fisheries Management Authority, Canberra.
- Australian Fisheries Management Authority 2015, Eastern gemfish (Rexea solandri) stock rebuilding strategy, AFMA, Canberra.
- 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.
- 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.
- Hutchins, B, and Swainston, R, 1986 Sea fishes of southern Australia, Swainston Publishing, Perth.
- Kailola, PJ, Williams, M, Stewart, PC, Reichelt, R, McNee, A, and Grieve, C 1993, Australian fisheries resources, Bureau of Resource Sciences, Canberra.
- 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.
- Little, R 2016, Preliminary 2016 update of the eastern gemfish (Rexea solandri) stock assessment, CSIRO Oceans and Atmosphere, Hobart, Tasmania.
- 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.
- 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.
- 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.
- 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.
- Rowling, K 1999, The fisheries biology and population dynamics of Gemfish Rexea solandri, PhD thesis, University of New South Wales, Sydney.
- Sporcic, M. 2019, Tier 4 Assessment for Western Gemfish (data to 2018), CSIRO Oceans and Atmosphere, Hobart.
- 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.