Sustainable outer-shelf stocks

Sustainability of popular outer-shelf fish stocks

MELBOURNE Ross Winstanley

During 2019, teams of fisheries scientists around the country conducted the fifth in a series of assessments of major Australian fish stocks.

Among the species covered in the Status of Australian Fish Stocks 2020 report were species taken by commercial and recreational fishers in two or more states. These included assessments of popular line-fishing species of the outer continental shelf: • bastard trumpeter Latridopsis forsteri

In NSW, recreational surveys in 20013/14 and 2017/18 reported catches of 208 and 508 trumpeter, respectively. Commercial catches were low, historically, and averaged less than three tonnes between 2014 and 2019.

Similarly, trumpeter have not been targeted commercially or recreationally in Victoria and SA. The stock status off NSW, Victoria and SA is reported as ‘negligible’. Tasmania

In contrast to those three states, trumpeter are targeted by Tasmanian recreational and commercial fishers on coastal reefs and kelp beds, wharves, and as adults by recreational fishing on Tasmanian inshore reefs. Further interest comes from the high regard Victorian anglers hold for this species, from both sport and eating qualities, when it is not so well regarded as a marketable species.

There are two separate stocks of blue warehou: one occurs from southern NSW to southern Tasmania, and the other from western Tasmania to the Great Australian Bight. After peaking at almost 2500 tonnes in 1991, the catch from the combined Commonwealth-managed fisheries declined to below 500 tonnes through the 2000s.

Classified as ‘overfished’ since 1999, both stocks have been subject to a rebuilding strategy since 2008. The annual cap of 118 tonnes, applied across both stocks, aims to prevent targeted fishing and to limit bycatch. Under tight controls. total commercial catches hit their lowest level, 10 tonnes, in 2016 and have risen slowly since then. Landings from Commonwealth fisheries totalled 52 tonnes in 2019/20. Eastern stock

Since 2000, NSW commercial catches have been below 2.5 tonnes; blue warehou have not been identified in recreational catch surveys. Recent annual commercial catches from Victoria have not exceeded two tonnes.

In Tasmania, since peaking at 318 tonnes in 1991, commercial catches have fallen to 1.5 tonnes in 2018/19. Taken mainly in gillnets, recreational catches have also shown a declining trend: 33 tonnes (2010), 15 tonnes (2012) and one tonne (2017). Two thirds of Tasmanian catches come from the eastern stock.

Despite recent years of low catches, under ‘remedial’ catch limits, there are no signs of stock recovery. All the evidence supports the classification of Eastern blue warehou as a ‘depleted stock’. Western stock

Recreational fishers target juvenile warehou (referred to as ‘haddock’) seasonally, from piers and wharves in Geelong, Apollo Bay and Portland. Warehou are not identified in SA’s commercial fisheries records or in the 2013/14 recreational fishing survey.

Blue and other warehou species are not identified in SA commercial fisheries landings and the catch from this stock from Tasmania’s state fisheries is included in the 1.5 tonnes reported in 2018/19

Taken overall, the evidence points to classification of the Western blue warehou as a ‘depleted stock’.

OCEAN JACKETS

Extending around southern Australia, from southern Queensland to North West Cape, WA, ocean jackets occur across and beyond the continental shelf. Juveniles occur in estuaries and bays before ranging across a variety of habitats out to depths of 250m.

In the absence of information on stock structure, the assessments are conducted at the management and jurisdictional levels. Ocean jackets are a by-product species in the Commonwealth-managed Great Australian Bight and Southeast Scalefish and Shark fisheries.

While catches have declined, catch rates have stayed ‘relatively stable’ in recent years and ocean jackets in both fisheries are classified as ‘sustainable stocks’.

New South Wales

Ocean jackets are an important part of the combined leatherjacket catches by recreational and charter fishing. Mainly hook-caught, the NSW recreational combined catch totalled 53,000 fish or 23 tonnes in 2017/18, down from 246,000 fish in 2000.

Over the past century, the commercial trawl and trap catches have gone through ‘boom and bust’ cycles. Since peaking in 2012, annual catches declined to 235 tonnes in 2018/19. However overall, the evidence indicates that the stock and its reproductive capacity are sound.

On this basis, the NSW ocean jackets are classified as a ‘sustainable stock’. Victoria

Commercial and recreational catches of leatherjackets are small and records do not distinguish between species. The 2019 commercial catch was 17 tonnes and there are no records of the recreational catch. In the absence of adequate information, the ocean jacket is classified as an ‘undefined stock’. Tasmania

Commercial and recreational leatherjacket catch records combine species and there is no sign that ocean jackets have been targeted or form a part of these fisheries. The 2017/18 recreational catch of leatherjackets, combined, was five tonnes, and annual commercial catches during the past decade have not exceeded five tonnes.

The 2019 assessment concluded that ‘the stock status for Ocean Jacket in Tasmania is assumed to be ‘negligible’.

South Australia

Ocean jackets are a minor commercial species and are ‘not heavily targeted’ by recreational and charter-boat fishers. The 2013/14 recreational fishing survey showed that the catch of all leatherjacket species, combined, totalled 75,787 fish.

SA’s commercial offshore trap fishery for ocean jackets began in 1984, peaked at 972 tonnes in the early 1990s, and has since followed an up-anddown pattern similar to that seen off NSW. In 2018, the commercial ocean jacket catch was 95 tonnes.

Based on the available evidence, SA’s ocean jackets are classified as a ‘sustainable stock’.

Note: While ocean jackets occur off WA, the SAFS assessments did not examine the stock there. WA’s 2017/18 survey of recreational fishing showed that fishers retained 1145 leatherjackets, all

Juvenile blue warehou or ‘haddock’ are commonly taken around southern harbour

structures. Photo courtesy of Steve Cooper.

• blue warehou Seriolella brama • ocean jackets Nelusetta ayraudi • redfish Centroberyx affinis • bight redfish Centroberyx gerrardi BASTARD TRUMPETER

Bastard or silver trumpeter occur as juveniles on inshore reefs, and as adults to depths of at least 60m, from New South Wales to South Australia.

Popular among spearfishers, most trumpeter are taken from state-managed fisheries where current and historic catches are reported as ‘negligible’. The exception is Tasmania, where the species is also a popular target species taken in amateur graballs or gillnets. As little is known of the stock status, and management varies from state to state, the assessments were conducted at the jurisdictional level.

NSW, Victoria and SA principally by gillnetting. Catches by both sectors are almost entirely of juvenile fish, and the legal minimum length (38cm) is below the size at first maturity (>45cm).

It is hardly surprising, then, that commercial catch records show a decline from about 60 tonnes in the mid-1990s, to three tonnes in 2018/19. Despite tightened catch limits, estimates of the recreational catch reflect such a decline: from 7.5 tonnes in 2013/14 to 3.4 tonnes in 2017/18.

All the evidence leads to the classification of bastard trumpeter in Tasmania as a ‘depleted stock’. BLUE WAREHOU

Blue warehou have been subject to targeted commercial fishing, mainly by trawling, on the outer continental shelf and upper slope. Interestingly, after a pelagic larval stage, they are targeted – as juveniles – by Victorian anglers fishing from piers and Geelong’s Cunningham Pier is a hot spot when the

‘haddock’ are on. Photo courtesy of the Geelong Advertiser.

species combined. REDFISH

OR NANNYGAI

Despite regional variations in growth and other characteristics, redfish are regarded – and assessed - as a single stock, occurring on the continental shelf off the east coast, from northern NSW to Tasmania.

Redfish feature prominently as a coastal and offshore target species for NSW anglers, with 4.4 tonnes, or 17,018 fish, retained in 2018/19. At 14% of the catch, charter fishing records showed this to be ‘the most abundant species’ caught during spring months. While this species does not appear among catches recorded in surveys in the more southern states, the related Bight redfish is popular among anglers in SA and WA (see below).

Redfish are subject to commercial fishing off NSW and, sporadically, off Tasmania. After peaking at around 2000 tonnes in the early 1980s, total annual catches from this stock have fallen to 36 tonnes in 2018/19. Catches by the NSW-managed fishery have declined from 30 tonnes in 2009 to four tonnes in 2018/19.

Since 1992, the redfish stock has been assessed as ‘depleted’ and is subject to a ‘stock rebuilding strategy’. The Total Allowable Catch for the Commonwealthmanaged trawl fishery is set at a minimum level of 50 tonnes, to allow for incidental, but not targeted catches. This fishery landed 29 tonnes of redfish in 2019/20.

With the adult stock severely depleted, and spawning capacity depressed, the redfish is classified as a ‘depleted stock’.

BIGHT REDFISH

Bight redfish occur as a single stock where it is fished by recreational and commercial fishers, from western Bass Strait to southern WA. Just to confuse things, they too are popularly known as nannygai.

Catches of 19 tonnes (2013/14) and 16 tonnes (2017/18) indicate the popularity of Bight redfish among anglers in SA and WA, respectively.

After peaking at 1407 tonnes in 2007/08, catches from the Great Australian Bight Trawl Fishery have come down to between 120 and 320 tonnes since 2008/09. Ageing of fish sampled from WA’s commercial and recreational fisheries show most Bight redfish caught there to be between 40 and 70 years old. WA’s commercial fishery recorded 58 tonnes in 2018/19, taken mainly by line fishing. SA’s multi-method commercial fisheries reported a total catch of 17 tonnes.

At current levels of fishing, the Bight redfish is classified as a ‘sustainable stock’. NATIONAL REPORTING

The Status of Australian Fish Stock Reports are a series of assessments of the biological sustainability of a broad range of wildcaught fish stocks against a nationally agreed reporting framework. The two-yearly reports examine whether the abundance of fish and the level of harvest from each stock is sustainable. Definitions of ‘sustainability’ and quoted passages in this article are taken from the SAFS 2020 Reports.

More details about the status of Australian fish stocks are available at – www.fish.gov.au/reports.

Bastard trumpeter are a favourite target for spearfishers.

SPECIES LIMITS State/Species

NSW

Leatherjacket species

Victoria

leatherjacket species warehou species

Size limit Bag limit

– 20 combined

20 combined 20 combined

Tasmania

Bastard trumpeter Blue warehou Leatherjacket species 38cm 25cm 20cm

SA

Bight redfish, redfish and swallowtail 30cm 5 10 10 combined

10 each

WA

Leatherjacket species Redfish species 25 cm

8 combined refer to rules.fish.wa.gov.au/

Current daily recreational catch limits around southern Australia. Note 1: additional fishing restrictions, apply in some states.

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