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Sustainability of estuary species

Sustainability of popular estuary 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 those 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 inshore and estuary species: • Luderick Girella tricuspidata • Mulloway Argyrosomus japonicus • Southern Garfish Hyporhamphus melanochir • Yelloweye Mullet Aldrichetta forsteri

These four species are among a large range of species Australian is sustainable.

Luderick are taken by state-managed fisheries, and are assessed at that level.

QUEENSLAND

Commercial catches are confined to southern latitudes where they have fallen from an average of 12 tonnes annually, to four tonnes in 2019. While the lack of data on recreational catches makes classification difficult, there are no concerns about the stock in Queensland waters.

NEW SOUTH WALES

Successive periods of fishing effort reduction have led to commercial catches falling from the 1989 peak of nearly 800 tonnes, to under 400 tonnes in 2004, and ‘stabilising’ at around the 2019 level, 268 tonnes. Most of the catch comes from the estuaries and is taken by gillnets and haul seines. The recreational catch was estimated at about 50,000 and declined from 41 tonnes in 2007, to three tonnes in 2019. The recreational catch is unknown. Because of difficulties in interpreting catch rate trends, it is not possible to classify the stock status in Victoria. It is doubtful that fishing pressure had significant or lasting impacts on the adult stock. TASMANIA

With luderick being a low-level byproduct of net fishing, Tasmania’s negligible commercial and recreational catches suggest that neither stock size nor spawning success have suffered from fishing.

Across the four eastern states, with 97% of the combined commercial and recreational catches taken in NSW, all the evidence indicates that, at current levels of fishing, this stock is sustainable. MULLOWAY

Mulloway occur in tonnes in that year.

With the commercial fishery based largely on juveniles, and average sizes declining, remedial action was taken in 2013. To restore the heavily-fished stock, these measures included an increase in the minimum size, to 70 cm (the average length at maturity for females), and tighter catch limits for both sectors. Imposing these measures is expected to reduce fishing pressure sufficiently to “allow the stock to recover from its recruitment impaired state”. The available evidence points to mulloway in NSW waters being a depleted stock. South Australia

SA’s 2018/19 commercial catch, 117 tonnes, was the third highest ever recorded there. Most (93%) was taken from the Lakes and Coorong fishery which accounts for most of the landings each year. The state’s recreational catch was estimated at 60 tonnes in 2013/14.

In the Coorong, the presence of 2-8 year old juveniles in 2019/20 reflected years of successful recruitment, with mulloway spawned in 2015/16 and 2016/17 the most abundant. The lack of older fish is attributed to their movement into adjacent coastal waters, plus the effects of fishing.

In 2019/20, mulloway sampled from commercial and recreational catches in coastal waters, ranged in age from five to 24 years, although the species can live to 41 years in SA waters. The lack of older fish was attributed to the impacts of the Millennium Drought on recruitment, and on the effects of fishing.

On the basis of the recent evidence relating to stock size, recruitment and fishing pressure, mulloway in SA waters are classified as a sustainable stock. WESTERN AUSTRALIA

Over the past decade, about 70-80% of WA’s annual mulloway catch has been taken by commercial fishers. Reductions in commercial fishing effort in the West Coast and Gascoyne demersal fisheries have seen catches decrease, to settle at 11-28 tonnes since 2007/08; the state-wide catch totalled 13 tonnes in 2019.

Boat-based recreational and charter catches have remained low, at <10 tonnes annually, coming mainly from the same regions. In 2017/18, these combined catches totalled four tonnes.

The available evidence indicates that the stock is “unlikely to be depleted” or “recruitment impaired”. Hence, mulloway in WA are classified as a sustainable stock. SOUTHERN GARFISH

Ranging between Lancelin, WA, to Eden, NSW, of the 10 recognised temperate garfish stocks, six are rated as sustainable, two as depleted and two as recovering. Victoria

Past estimates of the combined recreational catch of ‘garfish species’ in Victoria were 25 tonnes in 2000-01 and 21 tonnes in 2005/06. However, there are no recent or specific estimates of recreational catches of southern garfish.

The recent closures of commercial net fishing in Port Phillip Bay and the Gippsland Lakes leave Corner Inlet as the last significant commercial fishery for garfish in the State. In 2020/21, all but one of the 33 tonnes of southern garfish reported statewide, were taken in Corner Inlet. They are taken mainly by seine nets, with some also taken in gillnets.

With recent catch rates stable, and recruitment apparently healthy, and major bay/inlet fisheries closed, all indications point to southern garfish in Victorian waters as a sustainable stock. Tasmania

Following a sharp decline in commercial catches, a seasonal closure was introduced in 2009 to protect spawning fish. By 2012, increased numbers of size classes and of larger fish indicated a stock recovery, with catches totalling 40-60 tonnes. However, catches

Luderick have a strong following among anglers in the

eastern states. Photo courtesy of Geoff Wilson.

taken in inshore, bay and inlet waters around southern Australia. Several other species (eg. snapper) and species groups (eg. bream, trevally, and whiting) also taken in these waters, have been described in previous articles. A number of others are of more localised interest, including eastern sea garfish, greenback flounder, and sea mullet. Details for many of these and other species are available at https://www.fish. gov.au/reports LUDERICK

Occurring in estuaries and shallow coastal waters, luderick range from southern Queensland, around to South Australia, including northern Tasmania. Tagging studies show that they can travel between estuaries via coastal waters. While the stock structure is unknown, luderick are believed to belong to a single stock. Fishery statistics show that, overall, the stock off eastern fish or 30 tonnes in 2017/18, down from about 100,000 fish in 2013/14, during a period of high abundance. Because of the combination of recreational catch limits, reduced commercial fishing pressure, and their high level of post-release survival, the NSW part of the stock is unlikely to face reduced spawning success. VICTORIA

Since the assessments shown in the SAFS 2020 report, commercial net fishing has ceased in the Gippsland Lakes where luderick were a by-product in the black bream fishery. Commercial net fishing ceased in Port Phillip Bay in March 2022. As a result, commercial landings of luderick in Victoria are now reduced to by-catch in the one remaining estuary net fishery, in Corner Inlet. In the previous 20 years, Victoria’s main luderick catches came from the Gippsland Lakes, sub-tropical and temperate coastal and estuary waters in every mainland state. Based on separate assessments of the fisheries in each state, the status of the mulloway stock is sustainable in WA and SA, depleted in NSW and undefined in Queensland. Queensland

Recreational fishers account for most of the mulloway catch from Queensland inshore and inlet waters. The 2013/14 catch was estimated to be 98 tonnes, while the state-wide commercial catch was nine tonnes in 2019. New South Wales

After peaking at 400 tonnes in the mid-70s, the commercial estuary (net) and coastal (line) catches of mulloway have been less than 100 tonnes since the mid-90s; the 2019 catch was 48 tonnes. In 2017/18, the estimated recreational catch was 90 tonnes, compared to the commercial catch of 72 Mulloway are the largest popular fish in inshore and estuary

waters around Australia. Photo courtesy of Geoff Wilson.

Queensland

• garfish – 50 • luderick 30cm 10 • mullet – 50 • mulloway 75cm 1

NSW

• luderick 27cm 10 • mulloway 70cm 1

Victoria

• garfish – 40 • luderick 23cm 10 • mulloway 60cm 5 • mullet (all species) – 40

Tasmania

• garfish 25cm 15 • mullet 25cm 15

SA

• mullet 21cm 60 • mulloway 46cm Coorong 46-82cm 10 Other waters, 2 • southern garfish 23cm 30 Note: additional fishing restrictions apply in some states. Mullet species are not commonly targeted by anglers and are not rated highly commercially.

subsequently declined, reaching seven tonnes in 2028/19 – the lowest ever recorded in the State.

Record low catches, despite the closure, suggest that the stock cannot support current fishing pressure, and that “recruitment is likely to be impaired”. All indications support the classification of southern garfish in Tasmania as a depleted stock. South Australia

Southern garfish are rated as a “primary species” in SA’s commercial multispecies, multi-method Marine Scale Fishery. Of the six stocks recognised in SA waters, four are classified as sustainable, one as recovering and one as depleted.

The statewide recreational catch was last estimated at 79 tonnes, in 2013/14. Gulf St Vincent

Separate stocks occur in the northern and southern Gulf St Vincent.

From a peak of 221 tonnes in 2000, the annual commercial catch from the northern stock declined, reaching 73 tonnes in 2018. Following management action taken to reduce fishing pressure during the peak winter season, targeted catch rates by haul nets have increased since 2015. Biomass and egg production estimates suggest that the stock is depleted and that recruitment is impaired.

The evidence points to southern garfish here being a depleted stock.

In contrast, in the much smaller commercial fishery based on the southern stock, hauling nets were removed in 2005, and the remaining fishing effort declined to the lowest levels recorded, in the past three years.

Under low fishing pressure, and with catch rates remaining high, this garfish species in the southern Gulf St Vincent is rated as a sustainable stock. Northern Spencer Gulf

Separate stocks also occur in the northern and southern Spencer Gulf.

Historically, SA’s most productive commercial southern garfish region in the northern gulf, annual catches have declined from 271 tonnes in 1990, to an all-time low, averaging 86 tonnes from 2016 to 2018. While estimates of biomass and annual egg production indicate a depleted stock size, with depressed recruitment, there have been improvements in catch rates and stock size since the mid-2000s.

The evidence points to southern garfish in the northern Spencer Gulf being a recovering stock.

With much of the southern Spencer Gulf closed to haul nets since 2005, the fishery is now largely based on dip nets. This has seen the catch fall from 71 tonnes in 1998, to less than 15 tonnes since 2009. As catch rates by targeted fishing remain stable, the indications point to southern garfish in the southern Spencer Gulf being a sustainable stock. Other SA Regions

Between them, commercial fisheries of the West Coast and South East Coast stocks are lightly fished, producing less than 10 tonnes annually. All evidence points to southern garfish in both regions being sustainable stocks. YELLOWEYE MULLET

Occurring in inshore waters, bays and inlets, from southern WA to southern NSW, it is uncertain whether yelloweye mullet form more than a single stock. Assessed at state levels, yelloweye mullet stocks are classified as “sustainable” in Tasmanian, SA and WA waters, and “recovering” in Victorian waters. Victoria

While there are no estimates of the recreational catch, yelloweye mullet are rarely targeted by anglers. Taken across bay and inlet commercial fisheries, catch rate data from recent decades indicated stock depletion of yelloweye mullet. However, as the result of net fishing restrictions, closures of commercial inlet fisheries and focussing on highervalue species, both fishing pressure and commercial catches have declined from a peak in the 1980s to 13 tonnes in 2020/21.

On the basis of recent evidence indicating improvements to both biomass and recruitment, the yelloweye mullet in Victorian waters is rated as a recovering stock. Tasmania

Using gillnets and beach seines permitted in Tasmania, recreational fishers target yelloweye mullet in inshore waters. The estimated recreational catch in 2016/17 was 4.6 tonnes, down from the peak of 30 tonnes in 2000/01. Netting restrictions

FISHING NEWS

in inlets affords considerable protection to the stock, and commercial catches have declined to negligible levels in recent years. South Australia

With 70% of yelloweye mullet taken by recreational fishers, on lines and in gillnets, the total retained catch from SA was estimated at 18 tonnes in 2013/14.

Since 2007, about 90% of the commercial catch has come from the Lakes and Coorong Fishery. After peaking at 519 tonnes in 1989/90, commercial catches declined as the result of licence buy-backs and low market prices. Since the 2000s, with increased targeted gillnet fishing and high catch rates, catches have stabilised, with 301 tonnes recorded in 2018/19. Western Australia Fishing pressure on yelloweye mullet is so low that there is no estimate of the recreational catch. After exceeding 500 tonnes annually in the 1970s and 1980s, low market demand has resulted in recent commercial catches varying between 10 and 30 tonnes. 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 – https://www.fish.gov. au/reports

Snapper beating barotrauma

Snapper are one of the most popular oceanic sport and table fish in Australia, however, many fishos now choose to release larger reddies to give the breeding stock a helping hand.

Up until fairly recently, it was assumed that snapper weren’t a particularly good catch and release option as they can display symptoms of barotrauma when caught from water over 10m. However, research by NSW DPI and other Fisheries agencies around Australia has revealed that snapper are actually very resilient to barotrauma impacts, provided they can get back to depth.

If you wish to give your released snapper the best chances of survival, ensure you release the fish ASAP to minimise barotrauma effects. If the fish is displaying significant barotrauma symptoms (such as an inflated abdomen, distended intestines and even the stomach pushed outside the mouth) and is clearly unable to submerge by itself, a release weight should be used to re-pressurise the fish back to depth. A release weight is essentially a large sinker attached to a barbless hook, which pulls fish down to the depths when they can’t get down there by themselves. To see a video on how a release weight works, go to YouTube and search for ‘maximising snapper survival’.

Venting snapper – ie, piercing the fish to release trapped gas – is not recommended as a normal response to barotrauma symptoms, due to the inherent risk of further injury or infection. Also, please note that slowing down the retrieval of fish to the surface has been found to not help with the severity of barotrauma.

Keeping fish in live wells after they have been caught from deep water can increase the effects of barotrauma. As detailed above, it is best to release the fish as quickly as possible after being caught, particularly from water over 10m deep.

To find out more about best practice catch and release fishing, barotrauma info, and to find out how to make your own release weight, Google ‘DPI release weight’.

If you love fishing for reds, do your bit to help ensure that those fish you release have the best chance of survival - carry a release weight on your boat and get to know those catch and release tips! – NSW DPI

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