Table 1: Stock status determination for Swordfish
Jurisdiction |
Commonwealthb |
Stock |
Indian Ocean
(WTBF, IOTCb ) |
South Pacific Ocean
(ETBF, WCPFCb) |
Stock status |
|
|
Sustainable |
Undefined |
Indicators |
Spawning stock biomas, 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.
Swordfish in the Indian and Pacific Oceans are considered to be two distinct biological stocks and are managed under separate regional fisheries management organisations. In the Indian Ocean, genetic research has indicated the presence of a single biological stock1. In the Pacific Ocean, genetic studies have suggested the presence of several semi-independent biological stocks2, although the degree of genetic variation among these stocks is generally low3. In addition, electronic tagging has indicated that Swordfish in the Coral/Tasman seas in Australia may be distinct from the larger south-west Pacific population4. Two stocks are assessed in the Pacific Ocean: the south-west Pacific stock and the north Pacific stock. Only the south-west Pacific stock is relevant to Australia, and status is reported at the management unit level (that is, for the south-west Pacific Ocean). The Indian Ocean biological stock is under the jurisdiction of the Indian Ocean Tuna Commission. The Pacific Ocean management unit is under the jurisdiction of the Western and Central Pacific Fisheries Commission.
The data used to determine 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 assessments were from 1952 to 20094; data for the Pacific Ocean assessment were from 1952 to 20112.
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 other international jurisdictions. The assessments undertaken by the Indian Ocean Tuna Commission take into account information from all jurisdictions.
In the Indian Ocean, the most recent stock assessments5 estimated (over the plausible models investigated) that spawning biomass of the Swordfish stock in 2009 was 30–53 per cent of initial unfished biomass, and above the level that would produce maximum sustainable yield (MSY) (107–159 per cent of MSY). The biological stock is therefore not considered to be recruitment overfished6. This assessment also estimated that fishing mortality in 2009 was below the level associated with MSY (50–63 per cent of mortality at MSY). This level of fishing mortality is unlikely to cause the biological stock to become recruitment overfished6.
On the basis of the evidence provided above, the biological stock is classified as a sustainable stock.
South-west Pacific Ocean management unit
The south-west Pacific Ocean management unit is fished by Australian fishers endorsed to fish in the Eastern Tuna and Billfish Fishery (Commonwealth), and numerous other international jurisdictions. The assessments undertaken for the Western and Central Pacific Fisheries Commission take into account information from all jurisdictions.
In the south-west Pacific Ocean, the most recent assessment2 used two different growth and maturity schedules (Hawaiian and Australian). The key models selected across both schedules estimated that current (2007 to 2010) spawning stock biomass of the Swordfish management unit ranged from 27 to 55 per cent of initial unfished biomass and was above the biomass that would produce MSY (115–353 per cent of MSY)7. The management unit is therefore not considered to be recruitment overfished8.
However, the assessment found that the two growth schedules produced different estimates of fishing mortality. The Hawaiian schedule estimated that fishing mortality was below the level associated with MSY (40–70 per cent MSY), while the Australian schedule estimated that fishing mortality was above the level associated with MSY (106–177 per cent MSY). The Western and Central Pacific Fisheries Commission Scientific Committee was unable to determine which growth schedule was more reliable. The assessment of the current level of fishing pressure is therefore considered to be too uncertain to use for status determination8.
On the basis of the evidence provided above, the management unit is classified as an undefined stock.
Table 2: Swordfish biology9,10
Longevity and maximum size |
30+ years; 4550 mm FL |
Maturity (50%) |
Females: 6–7 years; ~1700 mm FL
Males: 1–3 years; ~1200 mm FL |
FL = fork length (measured from the lower jaw for Swordfish)
Figure 1: Distribution of reported commercial catch of Swordfish in Australian fisheries, 2013 (calendar year)
Table 3: Main features and statistics for Swordfish fisheries in Australia, 2013 (calendar year)
Jurisdiction |
Commonwealth (Indian Ocean) |
Commonwealth (south-west Pacific Ocean) |
Fishing methods |
Commercial |
Pelagic longlines |
✓ |
✓ |
Minor lines (e.g. hand line, troll, rod and reel) |
✓ |
✓ |
Purse seine |
✓ |
|
Recreationala,b |
Rod and reel |
✓ |
✓ |
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 |
|
4 in WTBF
Unknown in IOTC |
41 in ETBF
Unknown in WCPFC |
Catchd,e |
Commercial |
204 t in WTBF
26 187 t in IOTC (2012) |
1064 t in ETBF
22 202 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 South Australia, Victoria and Western Australia. Recreational sectors in the Pacific Ocean are New South Wales, Queensland and Tasmania. A tick indicates that a measure exists in at least 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.
e WCPFC catches are for the entire south Pacific Ocean (south of the equator).
Figure 2: : Commercial catch of Swordfish in the Western and Central Pacific Fisheries Commission and Indian Ocean Tuna Commission areas, 1970 to 2012 (calendar years)
Following completion of ecological risk assessments (levels 1–3) in the Western Tuna and Billfish Fishery (Commonwealth), no species were identified as high risk11. In the Eastern Tuna and Billfish Fishery (Commonwealth), a combined total of nine species were identified as being at 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 turtle12,13.
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.
To reduce fishery impacts on sharks, Australia has prohibited the practice of shark finning and the use of wire leaders14 in longline fisheries managed by the Commonwealth.
- The distribution and abundance of tuna, and possibly billfish, can be affected by environmental factors15,16. For example, seasonal changes in the abundance of Bigeye Tuna and Yellowfin Tuna on the east coast of Australia are linked to the expansion and contraction of the East Australian Current17.
a Australian Bureau of Agricultural and Resource Economics and Sciences