How sustainable are whiting stocks?

Part I: How sustainable are whiting 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 148 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 six whiting species: • eastern school or silver whiting (Sillago flindersi) • King George whiting (Sillaginodes punctatus) • sand whiting (Sillago ciliate) • stout or robust whiting (Sillago robusta) • trumpeter or winter whiting (Sillago maculate) • yellowfin whiting (Sillago schomburgkii)

Part one of this article describes the status of eastern school whiting and King George whiting. Part two will address the other four species. EASTERN

SCHOOL WHITING

This species is viewed as a single stock, occurring from southern Queensland to western Victoria and eastern Tasmania. Its status has been assessed under two ‘management units’: Southern Australia and New South Wales. Historically, the NSW-managed fishery took about 60% of the commercial catch, with most of the balance taken by the Commonwealthmanaged South East (trawl) Fishery. Marketed to anglers as silver whiting, the species After years of tag-recapture and genetic research, the range, movements and recruitment patterns of King George whiting are now well known.

Nothing puts a smile on an angler’s face like a good catch of KGs.

has become popular as a bait for snapper, sharks and squid.

Unlike other whiting species, much of the 1,700 tonne commercial catch of school whiting is exported, mainly to Japan.

New South Wales

The estimated NSW recreational catch of school whiting in 2017/18 was 1.5 tonnes.

Since 2019, the statemanaged trawl fishery for whiting has operated under a combined Total Allowable Catch for school whiting and stout whiting. Between 2017 and 2019, the combined commercial catches for the school whiting stock exceeded recommended limits. In 2020, the stock was estimated to be at just 35% of the unfished level. After the NSW TAC for 2020/21 was reduced by 25%, the whole stock was projected to increase significantly, allowing for easing of future catch limits.

Southern Australia

In 2012/13, the recreational school whiting catch from Tasmania was two tonnes.

The total commercial catch from this southern management unit in 2018/19 was 584 tonnes, comprising 538 tonnes from the South East Fishery, and 41 tonnes from Tasmania’s and less than five tonnes from Victoria’s state-managed fisheries.

Based on the overall evidence from both management units, the eastern school whiting is classified as a “sustainable stock”. KING

GEORGE WHITING

The King George whiting fishery is exceptional: this is the top-priced scalefish in southern seafood markets, keenly sought by commercial and amateur fishers. But uniquely among such closely managed species, most of those caught and retained are immature fish. During the past decade, total commercial landings have fallen from about 500 tonnes to 350 tonnes.

While the species occurs across southern Australia, from New South Wales to Western Australia, including Tasmania, the SAFS 2020 report addresses King George whiting from just three Victoria

While King George whiting may live for 20 years, most of those caught in Victoria’s bays and inlets are 2-4 year old juveniles. The numbers recruiting each year are strongly influenced by environmental factors, notably the strength of winter westerlies that drive postlarval movements around the coast and into sheltered bays. The combination of year-toyear variations in weather patterns, with a fishery based on juvenile fish, results in highly variable numbers and catches over short time frames. The 150-year history shows that the Victorian fishery for these juveniles continues to allow enough to progress to adulthood in open coastal waters where fishing pressure is low.

During the past 20 years, Victoria’s whiting fisheries have proved to be sustainable, while fluctuating in response to yearly recruitment fluctuations. Over the same period, commercial fisher numbers have been reduced by a series of licence buy-outs. As a result, from 2022, the only remaining commercial net fishery will be in Corner is no recent estimate of the recreational catch.

On the basis of the available evidence, the Victorian King George whiting is classified as a “sustainable stock”. South Australia

In SA waters, the separation of this species into three stocks is based largely on understanding of key elements of the life history”: adult movement patterns, spawning and nursery areas, and larval dispersal. The statewide commercial catch was recently reported as 230tonnes and the recreational catch was estimated to be 367 tonnes in 2013/14.

Gulf St Vincent stock

This biological stock occurs throughout Gulf St Vincent, the Investigator Strait and around Kangaroo Island.

From the 1990s, the commercial fishery catch and effort declined in step with reduced fisher numbers, while catch rates increased until 2007. Then, between 2008 and 2012, the estimated stock biomass fell, associated with low recruitment or spawning success. In 2016, the resulting review of management

states. While genetic studies suggest the existence of separate stocks in Victoria, South Australia and Western Australia, assessments are presented separately at the jurisdictional level for Victoria and WA. When combined with knowledge of differences in life history, there is enough certainty for the results to be presented for three separate SA biological stocks. There is some genetic mixing between whiting off Victoria and SA, but those occurring off Tasmania appear to be genetically distinct. Inlet, leaving recreational fishing as the main source of pressure on this stock statewide. In 2018/19, the Corner Inlet fishery landed 94 tonnes of whiting. So, after 40 years, when the Victorian commercial catches ranged from 100 to 200 tonnes, future totals are unlikely to exceed 100 tonnes.

Creel surveys showed exceptional catch rates in the bays in 2018/19, reflecting strong recruitment from 2016 to 2019. This strong recruitment is expected to support high catch rates over the next few years. There arrangements led to the legal size increase to 32cm, a reduced recreational bag limit, and a one-month closed season for the Investigator Strait and southern Spencer Gulf.

From 2013, the commercial catch rates increased, with indications that the stock size had stabilised. Based on all recent indications of stock size and recruitment, the Gulf St. Vincent biological stock is classified as a “sustainable stock”.

Spencer Gulf stock

This biological stock occurs throughout Spencer

Gulf and nearby coastal waters, from western Kangaroo Island to the Eyre Peninsula.

Estimates of commercial catch and effort through the 2000s have been lower than those recorded during the previous 20 years. While varying over time, catch rates showed “a long-term increasing trend”, indicating a healthy stock size to present times. The exception was from 2007 to 2013 when the stock size fell, along with a decline in recruitment. The post-2013 recovery in recruitment led to the highest biomass estimates recorded for this stock.

The mid-2000s declines in stocks in both gulfs led to the extensive management review mentioned above, followed in 2016 by tightened controls including the spawning closure for the Investigator Strait and southern Spencer Gulf.

On the basis of the most recent assessment, the Spencer Gulf biological stock is classified as a “sustainable” stock.

West Coast Eyre Peninsula stock

This biological stock extends through SA’s inshore and offshore coastal waters west of the Eyre Peninsula.

Stock size estimates have increased since 1984, reflecting increasing recruitment and decreasing commercial fisher numbers and fishing effort. On this basis, the West Coast biological stock is classified as a “sustainable stock”.

Western Australia

In what is considered to be a single WA stock, juvenile King George whiting occur in inshore waters of both

Most of the eastern school whiting are caught by trawlers and Danish seiners for export markets. School whiting, sold as silver whiting, are a popular bait species among anglers.

the West Coast and South Coast bioregions. The adult spawning component of this biological stock appears to be restricted to offshore waters of the West Coast Bioregion. Since 2000, annual commercial catches have been about 20-40 tonnes, following decades of wide fluctuations reaching as high as 150 tonnes. A 2013 assessment found that fishing pressure was “moderate” in the inshore areas frequented by juvenile whiting, and “low” where the adults occur, offshore. Fishing mortality estimates indicate that recruitment is secure at current catch levels. Recently, combined commercial and recreational catches have suggesting a stable stock size.

On the basis of all available evidence, King George whiting in WA 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.