Sustainability: how the flathead stocks rate MELBOURNE
Ross Winstanley
During 2019, teams of fisheries scientists around Australia conducted the fifth in a series of assessments of major Australian fish stocks. Among the 148 species covered were four flathead species taken by commercial and recreational fishers in two or more states: • Bluespotted flathead Platycephalus caeruleopunctatus • Dusky flathead Platycephalus fuscus
in the past, the bluespotted flathead in NSW waters is not considered to be depleted to the point where recruitment, or spawning success, is impaired. On this basis, the species is classified as a ‘sustainable’ stock. Note: the bluespotted flathead should not be confused with the southern bluespotted or yank flathead, Platycephalus speculator, which occurs in inshore waters, bays and inlets across southern Australia. DUSKY FLATHEAD Dusky flathead occur and are fished commercially
Duskies offer the lot – sport, a feed and a trophy photo. • Southern sand flathead Platycephalus bassensis • Tiger flathead Platycephalus richardsoni BLUESPOTTED FLATHEAD Bluespotted flathead were assessed at the level of the biological stock, which extends from southern Queensland to eastern Victoria, eastern Bass Strait, and Tasmania’s north coast. Almost all the information of use in assessing this stock comes from NSW, with commercial catch data since 1947/48. In the 10 years to 2019, annual catches there averaged 120 tonnes. Estimates of recreational catches are hampered by much of the data being for mixed ‘other ocean sand flatheads’. After being heavily fished
and recreationally throughout East Coast estuaries and inshore waters, from northern Queensland to southern NSW; they are also a popular angling species in eastern Victoria. In the absence of genetic information, dusky flathead are regarded as a single stock with at least some limited movement between estuaries. The 2019 assessments were conducted on the basis of the separate Queensland, NSW and Victorian management jurisdictions. Queensland In the Moreton Bay region, the dusky flathead ‘spawning biomass’ was estimated to be reduced to 36-39% of the unfished stock. The estimated Maximum Sustainable Yield of 104-112 tonnes/year matches the
current combined commercial and recreational catches from this region. Fishing pressure was much lower in the Fraser Island region, where the spawning biomass was estimated to be 70% of the unfished stock there. Government buy-outs of commercial licences had effectively reduced commercial net fishing to an all-time low in 2019, and the most recent estimate of recreational fishing effort showed a decline since 2001. Taking into account the reductions in fishing pressure, the dusky flathead in Queensland waters is not considered to be depleted to the point where recruitment is impaired. On this basis, the species is classified as a ‘sustainable’ stock. New South Wales In recent years, commercial landings of dusky flathead fluctuated between 116 and 172 tonnes, mainly taken in mesh nets. The recreational retained catch in 2017/18 was estimated to be 190 tonnes, although as many as 55% of the total numbers caught were released, due to a combination of catchand-release fishing and the daily catch limit specifying only one larger than 70cm. Survival rates of duskies released by anglers have been shown to be very high, and recent compulsory changes to commercial nets have reduced the incidence of releases and associated mortality rates. Thus, the overall impacts of fishing on this popular species have been contained. On the available evidence, dusky flathead are classified as a ‘sustainable’ stock in NSW waters. Victoria Through the 2000s, commercial fishing was removed from Mallacoota Inlet, Tamboon Inlet and Lake Tyers through a series of licence buy-outs. Despite this, angler catch rates have not recovered to former levels, believed to have been driven by strong recruitment events. Anglers have readily accepted tightened catch limits as part of their commitment to rebuilding dusky flathead numbers. The last Victorian commercial inlet fishing licences – for the Gippsland Lakes – ceased in 2020, followed in 2021 by the release
DAILY RECREATIONAL CATCH LIMITS Current daily recreational catch limits for flathead species around Australia. Note: additional fishing restrictions also apply in some states. State Species Size limit/slot Daily bag limit QLD Dusky flathead 40-75cm 5 Other flatheads combined 30cm 5 NSW Dusky flathead 36-70cm 10 (1>70cm) Bluespotted and tiger, combined 33cm 10 VIC Dusky 30-55cm 5 Others, combined 27cm 20 TAS Sand and tiger, combined 32cm 20 Southern bluespotted and rock, combined 40-60cm 5 (1>60cm) SA Flatheads, combined 30 cm 10 WA Flatheads, combined 30 cm 8 54
OCTOBER 2021
There’s nothing sophisticated about flatty fishing. of 45,000 dusky flathead fingerlings into the Lakes, plus 5000 into the Bemm River. Despite the removal of all commercial inlet fishing and the introduction of tight recreational catch limits, dusky flathead are best classified as an ‘undefined’ stock in Victorian waters. SOUTHERN SAND FLATHEAD For more than a century, the southern sand flathead has been a popular ‘breadand-butter’ favourite with recreational fishers. While particularly popular in Victoria and Tasmania, sand flathead occur in bays and inlets, and in shallow coastal waters from central NSW, around the south coast, to southern Western Australia. Tagging, growth rate and larval studies suggest that sand flathead in Port Phillip Bay form a distinct biological stock, growing more slowly and to smaller maximum sizes than the sand flathead stock occurring in other southern waters. The SAFS assessment examined southern sand flathead at a biological stock level in Port Phillip Bay; at a management unit level for other Victorian waters; and at jurisdictional levels for Tasmania, South Australia and Western Australia. Victoria Port Phillip Bay After a century of catches of up to 300 tonnes annually, the commercial fishery tapered off to less than 10 tonnes after 1997, and will effectively be zero when the last commercial net fishing ends in 2022. During the post-1990 period, when sand flathead numbers declined by almost 90%, two estimates put the recreational catch at 322 tonnes (in 2000) and 110 tonnes (2006). After reaching historically low levels since about 2008, catch rate information suggests that flathead numbers are stable, and possibly increasing. At a time of reduced overall fishing pressure, this has been aided by moderate recruitment in 2009 and 2013. On balance, southern sand flathead in Port Phillip Bay were rated as a
‘recovering’ stock. More recently, monitoring in 2021 found that the Bay stock experienced the largest annual recruitment seen in 25 years, improving recreational fishing prospects in years to come. Victoria Other waters Commercial catches of southern sand flathead from ‘other’ Victorian waters – except Corner Inlet – have averaged less than two tonnes since 2000; there is no estimate of the recreational catch. Long term commercial catches from Corner Inlet averaged 11 tonnes until 2000. Since then, they have averaged less than two tonnes, probably as the result of licence buy-outs. There are no estimates of the recreational catch and, on the basis of the limited available evidence, southern sand flathead in ‘Victorian other’ waters are classified as ‘sustainable’. Tasmania During the past 25 years, southern sand flathead have moved closer to being a recreational-only species. Over this period, annual commercial catches – by various hook and net methods – have declined from 10-15 tonnes to less than five tonnes. The recreational catch was estimated as 184 tonnes in 2017/18. Annual surveys over the past decade indicated low numbers of legal-sized fish. While reductions in recreational size and bag limits in 2015 may be beneficial to flathead numbers, current fishing pressure “remain above recommended levels”. Based on the 2019 assessment, southern sand flathead is classified as “depleting” in Tasmania. South Australia Over the ten years to 2019, the commercial catch of all eight flathead species, combined, taken commercially in SA’s coastal waters, by hook and net fishing, averaged two tonnes annually. The recreational catch of all flathead species was estimated at eight tonnes
in 2013/14. In the absence of assessments of fishing for southern sand flathead, or estimates of recruitment or biomass, the species is classified as an undefined stock in SA waters. Western Australia Having never been targeted, caught and reported in appreciable numbers, the stock status of this species is regarded as “Negligible” in WA. TIGER FLATHEAD Occurring off NSW, eastern Victoria and Tasmania, tiger flathead has historically been a target species for the offshore trawl fishery, these days managed by the Commonwealth Government as the Southern and Eastern Scalefish and Shark Fishery (SESSF). It is also the flathead species most commonly targeted by anglers in offshore waters. Regularly reviewed, the ‘global’ catch limit makes allowances for smaller statemanaged inshore commercial and recreational fisheries off these southern states. As well as the retained catches by all of these sectors, the rigorous stock assessment and catchsetting processes take account of mortalities of released and discarded flathead, aiming to maintain the adult stock at 40% of the unfished level. Thus, while the recommended upper ‘fishing mortality’ limit set for all fishing was 2826 tonnes for 2019/20, the Total Allowable Catch (TAC) was set at 2468 tonnes. Recent assessments have shown the spawning stock to be at 32% of the unfished stock in 2018, that is, below the target level. As a result, TACs have been set aimed at rebuilding the stock while also compensating for recent below-average spawning successes. In 2018/19, the total commercial tiger flathead catch of 2167 tonnes comprised 2057 tonnes in the SESSF, 91 tonnes in NSW, 17 tonnes in Tasmania and 2 tonnes in Victoria. In 2017/18, the estimated recreational catch of tiger flathead off NSW totalled 49,000 fish, of which 25,000 were retained by anglers. While ‘flathead’ form the most popular target species group for Tasmanian anglers, accounting for 70% of all finfish, tiger flathead make up just 3% or about 30,000 of the 1.7 million flathead caught in 2017/18. All the available evidence points to tiger flathead being a “sustainable” stock off southeastern Australia. NATIONAL REPORTING Definitions of ‘sustainability’ and quoted passages in this article are taken from the Status of Australian Fish Stocks 2020 Reports. Details can be found at www.fish.gov.au/reports
