Table 1: Stock status determination for Tiger Flathead
Jurisdiction Commonwealth, New South Wales, Tasmania, Victoria |
Stock |
Southern Australia (CTS, ITF, OTF, SF) |
Stock status |
|
Sustainable |
| Indicators |
Spawning stock biomass, fishing mortality |
CTS = Commonwealth Trawl Sector; ITF = Inshore Trawl Fishery (Victoria); OTF = Ocean Trawl Fishery (New South Wales); SF = Scalefish Fishery (Tasmania)
Tiger Flathead is endemic to Australia and distributed from northern New South Wales to western Victoria, including Tasmanian waters. There is some evidence of regional differences in physical characteristics, growth rates and spawning periods for Tiger Flathead, but biological stock structure has not been studied using genetic techniques. A single biological stock structure is assumed for management purposes. Status is reported at the level of the individual biological stock.
Southern Australia biological stock
The most recent assessment1 estimated spawning stock biomass in 2010 to be 9713 tonnes (t) or 44 per cent of the unfished (1915) level. The spawning biomass that supports maximum sustainable yield of Tiger Flathead was estimated to be 30 per cent of the unfished biomass. The biological stock is not considered to be recruitment overfished.
Commercial catch levels are constrained by a total allowable commercial catch (TACC) in the Commonwealth Trawl Sector, and catches from state fisheries are not increasing. Total commercial catch for the biological stock in recent years has approached the estimated long-term sustainable catch of about 2500 t1. The fishing mortality required to take this catch is unlikely to cause the biological stock to become recruitment overfished.
On the basis of the evidence provided above, the biological stock is classified as a sustainable stock.
Table 2: Tiger Flathead biology1
Longevity and maximum size |
20 years; males 50 cm SL, females 60 cm SL |
Maturity (50%) |
3 years; 30 cm SL |
SL = standard length
Figure 1: Distribution of reported commercial catch of Tiger Flathead in Australian waters, 2010
- Commercial catch of Tiger Flathead is predominantly taken using Danish-seine and fish otter trawl methods. Recreational fishers typically use rod and reel.
- A range of input and output controls are in place across jurisdictions:
- Input controls include limited entry to the fisheries and gear restrictions.
- Output controls include TACCs in some jurisdictions and size limits in the commercial sector. Size limits and bag or possession limits also apply to recreational fishers in New South Wales, Victoria and Tasmania.
- In 2010, commercial catch was reported from 15 Danish-seine and 29 trawl vessels in the Commonwealth Trawl Sector, 4 Danish-seine vessels in the Scalefish Fishery (Tasmania), 65 trawl vessels in the Ocean Trawl Fishery (New South Wales) and 5 vessels in the Inshore Trawl Fishery (Victoria) (these boats also fished in the Commonwealth Trawl Sector).
- Total commercial catch of Tiger Flathead in 2010–11 was 2911 t, comprising 2675.5 t in the Commonwealth Trawl Sector, 180 t in the Ocean Trawl Fishery (New South Wales), 54 t in the Scalefish Fishery (Tasmania) and 1.5 t in the Inshore Trawl Fishery (Victoria). Tiger Flathead is an important target species for the New South Wales recreational fishing sector, where the annual catch is estimated to be 20–60 t2. Tiger Flathead is a minor component of flathead catch by anglers in Victoria and Tasmania3. There is no reliable estimate of Indigenous catch.
a)
b)
Figure 2: a) Commercial catch of Tiger Flathead in southern Australia, 1915–2010 (calendar year);
b) percentage of unfished spawning biomass of Tiger Flathead, 1915–2010
The commercial fishery has experienced boom-and-bust cycles during its history, since the start of commercial trawling in 1915, with catch peaking at almost 4000 t in 1929 and again in 19634. These peaks in catch may indicate high abundance of Tiger Flathead due to favourable environmental conditions and strong recruitment of young fish. Since 2000, the annual Tiger Flathead commercial catch has been reduced from levels above 3000 t per season through TACC reductions, and is now close to the estimated long-term sustainable yield.
- Trawling and Danish-seining methods have the potential for interactions with threatened, endangered and protected species, particularly seals, seabirds, and seahorses and pipefishes (syngnathids). Fishery management agencies and the trawling industry are investigating methods for reducing these interactions—for example, seal excluder devices in trawl and Danish-seine nets, and bird-scaring devices to deter warp strikes. Observer programs and reporting requirements ensure that interactions with protected species are managed.
- Otter trawl methods of fishing can potentially have detrimental impacts on benthic habitats.
- Discarding of quota species catch can be significant in some parts of the Commonwealth Trawl Sector. However, discard rates for Tiger Flathead are low (less than 10 per cent), and trawl and Danish-seine fishers are now using nets with large meshes to reduce capture of undersized fish.
- There is some speculation that past peaks in abundance of Tiger Flathead may have been linked to favourable, but undetermined, environmental conditions5. Recent strong recruitment of small flathead may have a similar environmental basis. However, the effect of long-term shifts in the marine environment, such as those associated with global climate change, cannot yet be predicted for the Tiger Flathead biological stock.
a Australian Bureau of Agricultural and Resource Economics and Sciences
b Institute for Marine and Antarctic Studies, Tasmania
c Department of Primary Industries, New South Wales