Gemfish Rexea solandri

Lee Georgesona, Andy Moorea and Geoffrey Ligginsb
Gemfish

Table 1: Stock status determination for Gemfish

Jurisdiction

Commonwealth, New South Wales

Commonwealth

Stock

Eastern

(CTS, GHaT, OTF, OTLF)

Western

(CTS, GHaT, GABTS)

Stock status

   

Overfished

Sustainable

Indicators

Biomass, fishing mortality

Biomass, fishing mortality


CTS = Commonwealth Trawl Sector; GABTS = Great Australian Bight Trawl Sector (Commonwealth); GHaT = Gillnet Hook and Trap Sector (Commonwealth); OTF = Ocean Trawl Fishery (New South Wales); OTLF = Ocean Trap and Line Fishery (New South Wales)


Stock Structure

There are considered to be 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. Studies suggest that there are no genetic differences between Gemfish in eastern Australia and New Zealand 1. For the purposes of management and assessment, the eastern Australian population is treated as a single biological stock, independent of the New Zealand population.


Stock Status

Eastern biological stock 

Historically high catches of Gemfish from the eastern biological stock through the 1970s and 1980s substantially reduced the biomass of eastern Gemfish by the 1990s2. The biological stock has remained at a depressed level, with limited recruitment over this period3. The most recent (2010) estimate of spawning stock biomass was 15.6 per cent of the unfished (1968) level3. The biological stock is considered to be recruitment overfished4.

A spawning potential ratio analysis5 suggested high fishing mortality rates for eastern Gemfish until the late 1990s, but much lower rates since 2002. Because fishing mortality rates have substantially decreased, assessment model projections indicate that, with average recruitment, the stock should reach 20 per cent of unfished biomass in 20256, which is less than the one generation time plus 10 years required under the Commonwealth Fisheries Harvest Strategy Policy7. However, this rebuilding projection is based on average levels of recruitment, and total removals being limited to the 100 tonnes (t) incidental catch allowance (no targeting is allowed), assumptions that may underestimate the time that it will take to rebuild the stock. Total landed catch in 2013 was 161 t, and discard estimates were 28 t in 2012 (unknown for 2013). Recruitment has remained low in recent years5. There is a lack of evidence on recreational fishing catch. The above evidence indicates that it is uncertain whether current fishing pressure is constrained by management to a level that will allow the stock to recover from its recruitment overfished state4. Measurable improvements in biomass are yet to be detected. The Australian Fisheries Management Authority is reviewing the rebuilding timeframe as part of the 2014 review of the rebuilding strategy.

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

Western biological stock 

An updated integrated stock assessment model was developed for the western biological stock of Gemfish in the Commonwealth Trawl Sector and Great Australian Bight Trawl Sector (Commonwealth) in 20138. The updated assessment gave a spawning biomass estimate of 74 per cent of unfished biomass, which was similar to the estimate from the 2011 assessment (69 per cent). A catch-rate analysis9 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 biological stock is not considered to be recruitment overfished4.

The total allowable catch for the Southern and Eastern Scalefish and Shark Fishery (Commonwealth) for the 2013–14 fishing season was 199 t. Landed catch of western Gemfish from this fishery in the 2013–14 fishing season was 72 t. This level of fishing mortality is unlikely to cause the biological stock to become recruitment overfished4.

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


Table 2: Gemfish biology10–12

Longevity and maximum size

10–15 years; up to 1100 mm TL, 15 kg

Maturity (50%)

Males 3–5 years, females 4–6 years; 500 mm TL


TL = total length


Figure 1: Distribution of reported commercial catch of Gemfish in Australian waters, 2013 (calendar year)
Figure 1: Distribution of reported commercial catch of Gemfish in Australian waters, 2013 (calendar year)



Table 3: Main features and statistics for Gemfish fisheries in Australia, 2013

Jurisdiction

New South Walesa

Commonwealtha

Fishing methods

Commercial

Otter trawl

✓

✓

Hand line

✓

Dropline

✓

✓

Setline (demersal)

✓

✓

Recreationalb

Rod and line

✓

Electric (automatic) reel

✓

Indigenousc

Rod and line

✓

Management methods

Commercial

Limited entry

✓

✓

Total allowable catch (incidental)

✓

Trip limits

✓

✓

Spatial closures

✓

✓

Gear restrictions

✓

✓

Recreationalb

Bag limits

✓

Spatial closures

✓

Gear restrictions

✓

Indigenousc,d,e

Bag limits

✓

Spatial closures

✓

Gear restrictions

✓

Aboriginal cultural fishing authority

✓

Active vessels

 

6 in OTF

22 in OTLF

34 in CTS

6 in GABTS

7 in GHaT

Catch

Commercial

<1 t in OTF

10 t in OTLF

106 t in CTS

26 t in GABTS

18 t in GHaT

Recreationalb

Unknown

Indigenousc

Unknown

Markets

Domestic

✓

✓

Export


CTS = Commonwealth Trawl Sector; GABTS = Great Australian Bight Trawl Sector (Commonwealth); GHaT = Gillnet Hook and Trap Sector (Commonwealth); OTF = Ocean Trawl Fishery (New South Wales); OTLF = Ocean Trap and Line Fishery (New South Wales)

a Data for New South Wales align with the 2013 calendar year. Data for the Commonwealth align with the Commonwealth Southern and Eastern Scalefish and Shark Fishery 2013–14 fishing season (1 May 2013 – 30 April 2014).

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 noncommercial Indigenous fishing in Commonwealth waters, with the exception of the Torres Strait. In general, noncommercial Indigenous fishing in Commonwealth waters is managed by the state or territory immediately adjacent to those waters.

d The Aboriginal Fishing Interim Compliance Policy 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 to take catches outside the recreational limits under the New South Wales Fisheries Management Act 1994 (NSW), section 37(1)(c1) (Aboriginal cultural fishing authority).


Figure 2: Commercial catch of Gemfish in Australian waters, 1968 to 2013 (calendar years)
Figure 2: Commercial catch of Gemfish in Australian waters, 1968 to 2013 (calendar years)



Effects of fishing on the marine environment

  • There can be a substantial level of bycatch in the fish trawl sector. In 2006, mandatory requirements for otter trawls to use 90 mm square-mesh codend panels were introduced to reduce the catch of small species and juvenile fish13.

  • 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 Authority14 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 generally15. 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 gear15.

  • In 2011, AFMA mandated individual vessel seabird management plans16. The seabird action plans are used in the Commonwealth Trawl Sector to mitigate the impacts of trawling on seabirds. Seabird mitigation measures include warp deflectors (‘pinkys’), bird bafflers (a system of ropes and PVC piping that protects the warp cable) and seal excluder devices.

  • 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 Commonwealth Trawl Sector and Great Australian Bight Trawl Sector fisheries.

  • The eastern biological stock of Gemfish is listed as ‘Conservation Dependent’ under the EPBC Act17 and is subject to a stock rebuilding strategy6.


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 recruitment12.

a Australian Bureau of Agricultural and Resource Economics and Sciences
b Department of Primary Industries, New South Wales