Table 1: Stock status determination for Deepwater Flathead
Jurisdiction |
Commonwealth |
Stock |
Great Australian Bight
(CTS, GABTS) |
Stock status |
|
Sustainable |
Indicators |
Biomass, fishing mortality
|
CTS = Commonwealth Trawl Sector; GABTS = Great Australian Bight Trawl Sector (Commonwealth)
The biological stock structure of Deepwater Flathead is unknown; however, it is considered a single biological stock in the Southern and Eastern Scalefish and Shark Fishery for management purposes. Hence, stock status is reported at the level of the individual biological stock. Stock assessments for Deepwater Flathead have been completed only for the Great Australian Bight part of the biological stock1. Because the Great Australian Bight Trawl Sector (Commonwealth) accounts for the majority of catch taken from this biological stock, the stock status for the entire biological stock is based on assessments and catch from this area.
Great Australian Bight (Commonwealth) biological stock
The most recent quantitative assessment1 estimated the spawning biomass at the start of 2014–15 to be 45 per cent of the unfished (1978) level. This assessment is generally consistent with previous assessments and fishery-independent surveys2,3. The assessment estimated that the spawning biomass was progressively fished-down in the mid-2000s, but the biological stock had recovered by the start of 2010. This was most likely a result of lower fishing pressure in recent years, combined with at least one substantial recruitment event. The biological stock is not considered to be recruitment overfished4.
The biologically derived total allowable catch for the Great Australian Bight Trawl Sector (Commonwealth) for the 2013–14 fishing season was 1150 tonnes (t), which was adjusted to 1301 t to account for undercatch and overcatch. Landed catch of Deepwater Flathead from this fishery in the 2013–14 fishing season was 985 t. The Commonwealth Trawl Sector also landed 71 t, leading to a combined catch that was below the total allowable catch. The level of discards for this species is low1. This level of fishing mortality is unlikely to cause the biological stock to become recruitment overfished 4.
On the basis of the evidence provided above, the biological stock is classified as a sustainable stock.
Table 2: Deepwater Flathead biology3, 5–8
Longevity and maximum size |
Females: ~26 years; 820 mm TL
Males: ~19 years; 590 mm TL |
Maturity (50%) |
Females: 5–6 years; 430 mm TL
Males: 4–5 years; 430 mm TL |
TL = total length
Figure 1 Distribution of reported commercial catch of Deepwater Flathead in Australian waters, 2013–14 (calendar year)
Table 3: Main features and statistics for Deepwater Flathead fisheries in Australia, 2013 (calendar year)
Jurisdiction |
Commonwealth |
Fishing methods |
Commercial |
Demersal otter trawl |
✓ |
Danish-seine |
✓ |
Recreationala |
|
|
Indigenousb |
|
|
Management methods |
Commercial |
Limited entry |
✓ |
Gear restrictions |
✓ |
Spatial closures |
✓ |
Total allowable catch |
✓ |
Recreationala |
|
|
Indigenousb |
|
|
Active vessels |
|
15 in CTS
6 in GABTS |
Catch |
Commercial |
71 t in CTS
975 t in GABTS |
Recreationala |
|
Indigenousb |
|
Markets |
Domestic |
✓ |
Export |
|
CTS = Commonwealth Trawl Sector; GABTS = Great Australian Bight Trawl Sector (Commonwealth)
a The Australian Government does not manage recreational fishing in Commonwealth waters. Recreational fishing in Commonwealth waters is managed by the state or territory immediately adjacent to those waters, under its management regulations.
b The Australian Government does not manage noncommercial Indigenous fishing in Commonwealth waters, with the exception of the Torres Strait. In general, noncommercial Indigenous fishing in Commonwealth waters is managed by the state or territory immediately adjacent to those waters.
Figure 2 Commercial catch of Deepwater Flathead in Australian waters, 1986 to 2013 (calendar years)
- The Great Australian Bight Trawl Sector (Commonwealth) encounters nontarget species (bycatch). These fisheries have bycatch and discarding workplans or bycatch triggers in place to reduce interactions with nontarget species and minimise environmental impacts9–11. Management and voluntary measures undertaken by the Great Australian Bight Trawl Sector (Commonwealth) to reduce impacts on the environment include spatial closures, use of T-90 square mesh net panels to reduce bycatch and implementation of seabird management plans.
- Changes in ecosystem structure and function associated with changes in the climate may affect larval recruitment of Deepwater Flathead12.
a Australian Bureau of Agricultural and Resource Economics and Sciences