Table 1: Stock status determination for Bigeye Tuna
Jurisdiction |
Commonwealth |
Stock |
Indian Ocean
(WTBF, IOTCb ) |
Pacific Ocean
(ETBF, WCPFCb) |
Stock status |
|
|
Sustainable |
Overfished |
Indicators |
Spawning stock biomass, fishing mortality |
Spawning stock biomass, fishing mortality |
ETBF = Eastern Tuna and Billfish Fishery (Commonwealth); IOTC = Indian Ocean Tuna Commission; WCPFC = Western and Central Pacific Fisheries Commission; WTBF = Western Tuna and Billfish Fishery (Commonwealth)
b The Indian Ocean Tuna Commission (www.iotc.org) and the Western and Central Pacific Fisheries Commission (www.wcpfc.int) are intergovernmental organisations established to manage a number of highly migratory fish species.
Bigeye Tuna in the Indian Ocean and Pacific Ocean are considered to be two distinct biological stocks and are managed by separate regional fisheries management organisations. In the Indian Ocean, tagging and genetic studies have indicated a single biological stock1,2. Genetic studies have also indicated a single biological stock across the Pacific Ocean3. The Indian Ocean biological stock is under the jurisdiction of the Indian Ocean Tuna Commission. The Pacific Ocean stock is under the jurisdiction of the Western and Central Pacific Fisheries Commission.
The data used to determine stock status differ, depending on the assessment, because of delays in reporting catch data to the Indian Ocean Tuna Commission, and the Western and Central Pacific Fisheries Commission. Data for the Indian Ocean assessment were from 1952 to 2011, or 1952 to 20123 (several assessments were undertaken). Data for the Pacific Ocean assessment were from 1952 to 20124.
Indian Ocean biological stock
The Indian Ocean biological stock is fished by Australian fishers endorsed to fish in the Western Tuna and Billfish Fishery (Commonwealth), and numerous international jurisdictions. The assessments undertaken by the Indian Ocean Tuna Commission take into account information from all jurisdictions.
In the Indian Ocean, the 2013 stock assessment1 estimated (over the plausible models investigated) that the spawning biomass of the Bigeye Tuna biological stock in 2012 was 40 per cent of the initial unfished biomass and above the level that would produce maximum sustainable yield (MSY) in the long term. The biological stock is therefore not considered to be recruitment overfished5. This assessment also estimated that the current (2012) fishing mortality was below the level associated with MSY (42 per cent of mortality at MSY). This level of fishing mortality is unlikely to cause the biological stock to become recruitment overfished5.
On the basis of the evidence provided above, the biological stock is classified as a sustainable stock.
Pacific Ocean biological stock
The Pacific Ocean biological stock is fished by Australian fishers endorsed to fish in the Eastern Tuna and Billfish Fishery (Commonwealth), and numerous international jurisdictions. The assessments undertaken for the Western and Central Pacific Fisheries Commission take into account information from all jurisdictions.
In the Pacific Ocean, the stock assessment4 estimated (over the plausible models investigated) that the 2012 spawning biomass of the Bigeye Tuna biological stock was 16 per cent of the levels predicted in the absence of fishing and below the level that would support MSY. The biological stock is therefore considered to be recruitment overfished6. This assessment also estimated that current fishing mortality was well above the level associated with MSY (127–196 per cent of mortality at MSY). This level of fishing mortality is expected to prevent the stock recovering from a recruitment overfished state6.
On the basis of the evidence provided above, the biological stock is classified as an overfished stock6.
Table 2: Bigeye Tuna biology7,8
Longevity and maximum size |
~16 years; 2000 mm FL |
Maturity (50%) |
~3 years; ~1000 mm FL |
FL = fork length
Figure 1: Distribution of reported commercial catch of Bigeye Tuna in Australian Fisheries, 2013 (calendar year)
Table 3: Main features and statistics for Bigeye Tuna fisheries in Australia, 2013 (calendar year)
Jurisdiction |
Commonwealth (Indian Ocean) |
Commonwealth (Pacific Ocean) |
Fishing methods |
Commercial |
Pelagic longline |
✓ |
✓ |
Minor lines (e.g. hand line, troll, rod and reel) |
✓ |
✓ |
Purse seine |
✓ |
|
Recreationala,b |
Rod and line |
✓ |
✓ |
Spearfishing |
|
✓ |
Indigenousb,c |
|
Unknown |
Unknown |
Management methods |
Commercial |
Limited entry |
✓ |
✓ |
Gear restrictions |
✓ |
✓ |
Area restrictions |
✓ |
|
Catch limits |
✓ |
✓ |
Individual transferable quotas |
✓ |
✓ |
Recreationala,b |
Bag limits |
✓ |
✓ |
Indigenousb,c |
|
None |
None |
Active vessels |
|
5 in WTBF
Unknown in IOTC |
40 in ETBF
Unknown in WCPFC |
Catchd |
Commercial |
91 t in WTBF
115 794 t in IOTC (2012) |
553 t in ETBF
161 561 t in WCPFC (2012) |
Recreationala,b |
Unknown |
Unknown |
Indigenousb,c |
Unknown |
Unknown |
Markets |
Domestic |
✓ |
✓ |
Export |
✓ |
✓ |
ETBF = Eastern Tuna and Billfish Fishery (Commonwealth); IOTC = Indian Ocean Tuna Commission; WCPFC = Western and Central Pacific Fisheries Commission; WTBF = Western Tuna and Billfish Fishery (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 Recreational and Indigenous fishing sectors in the Indian Ocean are Western Australia, South Australia and Victoria; recreational sectors in the Pacific Ocean are Queensland, New South Wales and Tasmania. A tick indicates that a measure exists in one of these jurisdictions.
c 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.
d Catches reported for the IOTC and WCPFC are for 2012 (the most recent year available).
Figure 2: Commercial catch of Bigeye Tuna in the Western and Central Pacific Fisheries Commission, and Indian Ocean Tuna Commission areas, 1970 to 2012 (calendar years)
Following completion of environmental risk assessments (levels 1–3) in the Western Tuna and Billfish Fishery (Commonwealth), no species were identified as high risk9. In the Eastern Tuna and Billfish Fishery (Commonwealth), nine species were identified as high risk or precautionary high risk. This is the priority list of species for attention under the Eastern Tuna and Billfish Fishery ecological risk management strategy; it includes two species of sunfish, four species of shark, two species of cetacean and one species of marine turtle10,11.
No target species, ecological communities or habitats were assessed to be at high risk from the effects of fishing in the Eastern Tuna and Billfish Fishery (Commonwealth) or the Western Tuna and Billfish Fishery (Commonwealth).
Australia implements regulations to minimise the environmental impact of fisheries for tuna and tuna-like species on pelagic ecosystems, specifically on seabirds, sea turtles and sharks. Both the Indian Ocean Tuna Commission and the Western and Central Pacific Fisheries Commission have passed conservation and management measures that are broadly consistent with each other and with Australia’s domestic requirements.
Australia has prohibited shark finning in longline fisheries managed by the Commonwealth and has also prohibited the use of wire leaders 12 in these fisheries, to reduce fishery impacts on sharks.
- The distribution and abundance of tuna can be affected by environmental factors13,14. For example, seasonal changes in the abundance of Bigeye and Yellowfin Tuna on the east coast of Australia are linked to the expansion and contraction of the East Australian Current15.
a Australian Bureau of Agricultural and Resource Economics and Sciences