Table 1: Stock status determination for School Shark
Jurisdiction |
Commonwealth, New South Wales, South Australia, Tasmania, Victoria, Western Australia |
Stock |
Southern Australian
(CIF, JASDGDLF, LACF, MSF, OF, OTF, OTLF, PPBF, SESSF, SF, WCDGDLF) |
Stock status |
|
Overfished |
Indicators |
Estimate of biomass—relative pup production |
CIF = Corner Inlet Fishery (Victoria); JASDGDLF = Joint Authority Southern Demersal Gillnet and Demersal Longline Managed Fishery; LACF = Lakes and Coorong Fishery (South Australia); MSF = Marine Scalefish Fishery (South Australia); OF = Ocean Fishery (Victoria); OTF = Ocean Trawl Fishery (New South Wales); OTLF = Ocean Trap and Line Fishery (New South Wales); PPBF = Port Phillip Bay Fishery (Victoria); SESSF = Southern and Eastern Scalefish and Shark Fishery (Commonwealth); SF = Scalefish Fishery (Tasmania); WCDGDLF = West Coast Demersal Gillnet and Demersal Longline Managed Fishery (Western Australia)
School Shark has a broad distribution throughout temperate waters of the eastern North Atlantic, western South Atlantic, north-eastern and south-eastern Pacific, off South Africa, New Zealand
and southern Australia. A single genetic stock exists in Australian waters, and a spatially structured fishery assessment model is applied to this biological stock1.
Southern Australian biological stock
Assessments since 1991 have consistently estimated that the School Shark biological stock is
less than 20 per cent of the unfished biomass. The most recent integrated stock assessment was published in 20092. Some uncertainty remains regarding the accuracy of the model estimates
of productivity, but current estimates of very low intrinsic productivity (2 per cent)2 result in slow recovery projections. There is also concern regarding the use of commercial catch per unit effort (CPUE) as an index of abundance: total allowable catch reductions since 2002 may have resulted in most fishers avoiding School Shark, causing CPUE to be an unreliable index of abundance.
The most recent assessment estimates that biomass in 2009 was 8–17 per cent of the unfished (1927) level. This range is below the Commonwealth Fisheries Harvest Strategy Policy3 proxy limit reference point (20 per cent of the unfished level). Most stock assessment sensitivity analyses suggest that the adult biomass has stabilised and may even be recovering at present commercial catch levels, but some indicate that it is still in decline. Because of insufficient monitoring data, it is not possible to determine at this stage whether rebuilding has commenced. The biological stock is considered to be recruitment overfished.
This biological stock is subject to a recovery strategy, adopted in 2008, that requires the biological stock to be rebuilt to 20 per cent of the unfished level within 32 years (one mean generation time plus 10 years). Acknowledging that the low intrinsic productivity estimate for School Shark is uncertain, the assessment indicates that an annual commercial catch of 26 tonnes (t) or less per
year would be required to return the biological stock to 20 per cent of unfished levels within 32 years. The most recent stock assessment report1 indicates that the current level of fishing mortality is expected to prevent the biological stock from recovering from its recruitment overfished state within the timeframe specified by the recovery strategy.
On the basis of the evidence provided above, the biological stock is classified as an overfished stock.
Table 2: School Shark biology4–7
Longevity and maximum size |
50 years; ~175 cm TL, 32.5 kg |
Maturity (50%) |
12–16 years; mean length at female maturity and pupping are 124 and 142 cm, respectively |
TL = total length
Figure 1: Distribution of reported commercial catch of School Shark in Australian waters, 2010
- Fishing is primarily undertaken using demersal gillnets or demersal longlines.
- Management of this biological stock is undertaken by the Australian Government under Offshore Constitutional Settlement arrangements between the Australian Government and Tasmania, South Australia and Victoria. Some byproduct may also be landed in the Western Australian and New South Wales fisheries. Since 2001, School Shark has not been subject to targeted fishing in Commonwealth fisheries because of its stock status. A range of management controls have been implemented across the fisheries that take incidental catch (bycatch) from the biological stock:
- Output controls include total incidental catch allowances (i.e. byproduct allowances). Size and bag limits apply in all states.
- Input controls include gear restrictions, and spatial and temporal closures.
- The numbers of commercial vessels that caught School Shark incidentally in 2010 were 103 vessels in the Commonwealth fisheries, 1 vessel in Queensland and 17 vessels in Victoria. It is not known how many vessels caught School Shark incidentally in New South Wales, Western Australia, Tasmania or South Australia, because incidental catch of the species is presumably not reported or not landed.
- The total amount of School Shark caught commercially in Australia in 2010 was approximately 197 t1. Total recreational and Indigenous catch of School Shark in Australian waters is unknown.
Figure 2: Commercial catch of School Shark in Australian waters, 1970–2010 (calendar year)
Note: Records of School Shark catch are unavailable for Victoria, New South Wales or Queensland.
Commercial catch of School Shark peaked at around 2500 t per year in the early 1970s, before rapidly declining and then rising to another peak of around 2000 t per year in the late 1980s. The initial reduction in catch was partly caused by a ban on the sale of large School Shark in Victoria during 1972–1985 because the mercury content of the meat was thought to exceed health standards. However, when gillnets replaced longlines as the preferred fishing method in the early 1970s, catches rose steadily. In 2001, the Shark Resource Assessment Group (SharkRAG) recommended a step-down, over five years, of the 350 t total allowable catch (TAC) to a level estimated to be the unavoidable incidental catch in the Gummy Shark fishery (240 t). In the 2011 season, the Australian Fisheries Management Authority (AFMA) implemented a 20 per cent rule that limited School Shark catch by operators to 20 per cent of their Gummy Shark catch. The TAC has been reduced further in recent years, and was set at 150 t for the 2012–13 fishing season.
- Interactions with marine mammals (Australian Sea Lions, Australian Fur Seals, New Zealand Fur Seals and dolphins) in some gillnet fisheries continue to be a major issue. Mitigation actions that have been implemented include spatial closures, increased monitoring and implementation of the Australian Sea Lion Management Strategy8.
- Offal management strategies, introduced in April 2011, include requirements for gillnet operators to remove any biological materials from nets before they are set. This has been effective in reducing seabird interactions in other fisheries8.
- Dolphin interactions in the Commonwealth gillnet sector have recently been identified as an issue, based on the increased monitoring associated with Australian Sea Lions8. AFMA has closed the area where most interaction has occurred and increased observer coverage to
100 per cent in adjacent areas.
- Sea level rise and changes in sea temperature associated with climate change are of potential concern to the School Shark biological stock, since the habitats they use as nursery and feeding grounds are potentially prone to the effects of climate change9.
a Australian Bureau of Agricultural and Resource Economics and Sciences
b South Australian Research and Development Institute
c Institute for Marine and Antarctic Studies, Tasmania
d Department of Fisheries, Western Australia
e Department of Primary Industries, Victoria