Blacklip Abalone Haliotis rubra

Craig Mundy^a, Stephen Mayfield^b, Harry Gorfine^c and Duncan Worthington^d

Table 1: Stock status determination for Blacklip Abalone

Jurisdiction	Tasmania	Victoria			South Australia	New South Wales
Stock	Tasmania^e(BSZF, CWZF, EZF [TAS], NZF, WZF [TAS])	WZF [VIC]^f	CZF [VIC]^g	EZF [VIC]	South Australia (CZF [SA], SZF, WZF [SA])	New South Wales^h (AF)
Stock status						↑
Stock status	Sustainable	Undefined	Sustainable	Sustainable	Sustainable	Transitional– recovering
Indicators	Catch, CPUE, catch size structure by reporting unit, fisher knowledge	Survey, catch, CPUE, catch size structure by reporting unit, fisher knowledge	Survey, catch, CPUE, catch size structure by reporting unit, fisher knowledge	Survey, catch, CPUE, catch size structure by reporting unit, fisher knowledge	Catch, CPUE, catch size structure by reporting unit, fisher knowledge	Catch, CPUE, catch size structure by reporting unit, fisher knowledge

AF = Abalone Fishery (New South Wales); BSZF = Bass Strait Zone Fishery (Tasmania); CPUE = catch per unit effort; CWZF = Central Western Zone Fishery (Tasmania); CZF [SA] = Central Zone Fishery (South Australia); CZF [VIC] = Central Zone Fishery (Victoria); EZF [VIC] = Eastern Zone Fishery (Victoria); EZF [TAS] = Eastern Zone Fishery (Tasmania); NZF = Northern Zone Fishery (Tasmania); SZF = Southern Zone Fishery (South Australia); WZF [SA] = Western Zone Fishery (South Australia); WZF [TAS] = Western Zone Fishery (Tasmania); WZF [VIC] = Western Zone Fishery (Victoria);

Stock Structure

Empirical field studies¹ and molecular techniques^2–3 both strongly suggest that Blacklip Abalone (Haliotis rubra) fisheries comprise a large number of small, independent populations. Each biological stock may extend over only a few hundred metres, and each Blacklip Abalone fishery is likely to consist of an indeterminate number of these small biological stocks. The number of biological stocks (hundreds or many thousands) may vary among fishing zones. Given the large number of biological stocks, it is not practical to assess each biological stock separately. Where all management units within a jurisdiction have the same status, a single classification is given for the jurisdiction. Where the separate management units within a jurisdiction are assessed as having a different status, the classification for each management unit is reported separately.

Stock Status

All states rely on empirical performance measures—specifically, catch, catch per unit effort (CPUE) (as kilograms of abalone harvested per hour) and commercial catch size structure. The annual catch in Blacklip Abalone fisheries is generally equivalent to the total allowable commercial catch (TACC), with negligible overcatch or undercatch of the TACC.

Tasmania

Status and TACCs are determined by annual fishery assessments and a process involving multiple workshops (four each year). Annual assessments of the Tasmanian fishery zones rely heavily on fishery-dependent data⁴. There are no direct or derived estimates of biomass or fishing mortality. Mean CPUE and CPUE frequency distribution are key performance measures. Catch, catch rates, commercial catch size structure and diver observations are reviewed, leading to an expert opinion that is based on the weight of evidence. Each TACC is set at a level considered sustainable and to minimise the potential for biological stocks becoming recruitment overfished.

In the Eastern Zone Fishery (Tasmania) management unit, a legal minimum length of 13.8 cm provides two years of spawning before Blacklip Abalone are recruited to the fishery. Relative stock biomass in this fishery (estimated using CPUE as a proxy) has varied substantially since 1995, with evidence of an approximate eight-year cycle. Based on declining CPUE between 2000 and 2003, the TACC was reduced from 1190 tonnes (t) to 857 t in 2002, and to 770 t in 2004. Based on recent increasing CPUE and increasing median length of the commercial catch, the TACC was increased by 5 per cent in 2008, 2009 and 2010, resulting in a TACC of 896 t by 2010. Geometric mean catch rate (CPUE) across the zone was lowest in 2002 at 46 kg/hour, and highest in 2009 at 83 kg/hour, but declined to 63 kg/hour in 2010.

This evidence indicates that biological stocks in the Eastern Zone Fishery management unit are unlikely to be recruitment overfished, and that the current level of fishing mortality is unlikely to cause these biological stocks to become recruitment overfished.

The Western Zone Fishery (Tasmania) management unit has a legal minimum length of 14 cm in the south and south-west, and 13.6 cm in the north-west, to provide two years of spawning before Blacklip Abalone are recruited to the fishery. The Western Zone Fishery was split into two zones—western and central western—in 2007; the two zones are considered here as a single zone for continuity during the period 2000–10. The TACC in this management unit was reduced in 2008 from 1400 t to 1228 t, in association with a zonal restructure and a downturn in CPUE. The TACC reduction reflects a management action to redistribute effort from the south of the western zone to the under-utilised north. The CPUE has declined gradually from 138 kg/hour in 2000 to 106 kg/hour in 2010. However, the 2010 CPUE is high relative to other regions and also to the CPUE observed in this zone over the previous two decades.

This evidence indicates that the biological stocks in the Western Zone Fishery management unit are unlikely to be recruitment overfished, and that the current level of fishing mortality is unlikely to cause the biological stocks to become recruitment overfished.

The Northern Zone Fishery (Tasmania) and the Bass Strait Zone Fishery (Tasmania) were separated in 2003 but are discussed together here to provide continuity in the stock data. The legal minimum length varies between fishing blocks across this region between 11 cm, 12.7 cm and 13.2 cm, to provide two years of spawning before Blacklip Abalone are recruited to the fishery. Catch and catch rates have varied between 2000 and 2010 as a function of changing market preference and adaptive management (effort redistribution and change in legal minimum length). The combined TACC for the Northern Zone Fishery and the Bass Strait Zone Fishery reached a high of 402.5 t in 2008. Geometric mean CPUE peaked at 81 kg/hour in 2008, and peaked again in 2010 at a comparatively high TACC of 332.5 t⁴, suggesting that catch levels are sustainable.

This evidence indicates that the biological stocks in the Northern Zone Fishery management unit are unlikely to be recruitment overfished, and that the current level of fishing mortality is unlikely to cause the biological stocks to become recruitment overfished.

On the basis of the evidence provided above, Blacklip Abalone in Tasmania is classified as a sustainable stock.

Western Zone Fishery (Victoria) management unit

The Victorian fisheries for Blacklip Abalone are managed as three different management units: western zone, central zone and eastern zone, each with independent TACCs and annual fishery assessments. Legal minimum length is set independently of the fishing zones, along gradients in biological growth rates. Industry has requested progressive increases in legal minimum lengths at localised scales, based on size-at-maturity and growth data, where available. In the western zone, higher legal minimum lengths were adopted to mitigate potentially adverse impacts from the resumption of harvesting in areas that were previously affected by the abalone viral ganglioneuritis (AVG) disease.

Annual assessments of the Western Zone Fishery (Victoria) management unit rely heavily on fishery-dependent data. There are no direct or derived estimates of biomass or fishing mortality. Mean CPUE is a key performance measure. Catch and CPUE in this management unit were stable between 2000 and 2005⁵, until the appearance of AVG in the wild abalone fishery. The effect of AVG on western zone biological stocks was significant⁶, resulting in managed catch reductions from around 280 t in 2000 to around 50 t by 2010. Normal fishing has not resumed in this management unit. A structured fishing program commenced in 2009, allowing limited catch (200 kg) to be taken at strategic locations.

Insufficient information is available to confidently classify the status of this management unit. Because of the lack of evidence, the Western Zone Fishery management unit is classified as an undefined stock.

Central Zone Fishery (Victoria) management unit

Annual assessments of this management unit rely heavily on fishery-dependent data. There are no direct or derived estimates of biomass or fishing mortality. Mean CPUE is a key performance measure. Catch and CPUE in this management unit were stable between 2000 and 2005⁵.
The spread of AVG into the western end of the Central Zone Fishery affected production from approximately 8.5 per cent of fishing area from 2008. Managed catch reductions were implemented, reducing the TACC from around 620 t in 2007 to 429 t in 2010. CPUE declined to a 10-year low of 74 kg/hour in 2010. However, CPUE in this management unit in 2010 remains high relative to 1980–95, when CPUE averaged 64 kg/hour.

Using CPUE as a proxy for stock biomass, this evidence indicates that biological stocks in the Central Zone Fishery management unit are unlikely to be recruitment overfished, and that the current level of fishing mortality is unlikely to cause these biological stocks to become recruitment overfished.

On the basis of the evidence provided above, the Central Zone Fishery management unit is classified as a sustainable stock.

Eastern Zone Fishery (Victoria) management unit

Annual assessments of this management unit rely heavily on fishery-dependent data. There are no direct or derived estimates of biomass or fishing mortality. Mean CPUE is a key performance measure. Catch in the eastern zone has been relatively stable between 2000 and 2010; it was 460 t in 2000, 490 t in 2008 and 460 t in 2010. CPUE has been stable at a 20-year historical high between 2004 and 2010⁵, with an average CPUE in 2010 of 112 kg/hour⁵.

This evidence indicates that the biological stocks in the Eastern Zone Fishery management unit are unlikely to be recruitment overfished, and that the current level of fishing mortality is unlikely to cause these biological stocks to become recruitment overfished.

On the basis of the evidence provided above, the Eastern Zone Fishery (Victoria) management unit is classified as a sustainable stock.

South Australia

In the South Australian fisheries, assessments of Blacklip Abalone rely heavily on fishery-dependent data. There are no direct or derived estimates of biomass or fishing mortality. CPUE is a key performance indicator.

In the Western Zone Fishery (South Australia) management unit, a minimum legal length of 13 cm is in place for Blacklip Abalone, which allows spawning to occur before Blacklip Abalone are recruited to the fishery. Total catch was stable between 2000 and 2009, declining by 6 per cent in 2010⁷. The CPUE for Blacklip Abalone in the western zone was high between 2001 and 2008 (mean of 75 kg/ hour), most likely due to increased recruitment in the late 1990s⁷. CPUE has since declined and, in 2010, was 68 kg/hour, which is similar to the long-term mean between 1980 and 2010 (65 kg/hour). This evidence indicates that biological stocks in the Western Zone Fishery management unit are unlikely to be recruitment overfished, and that the current level of fishing mortality is unlikely to cause these biological stocks to become recruitment overfished.

In the Central Zone Fishery (South Australia) management unit, a minimum legal length of 13 cm is in place to allow spawning to occur before Blacklip Abalone are recruited to the fishery. Total catches between 2006 and 2010 (24 t/year) were substantially lower than those from 2000 to 2005 (mean of 37 t/year), as a result of TACC reductions. CPUE was stable between 2000 and 2010 (range: 61–75 kg/hour; mean: 68 kg/hour). This evidence indicates that biological stocks in the Central Zone Fishery management unit are unlikely to be recruitment overfished, and that the current level of fishing mortality is unlikely to cause these biological stocks to become recruitment overfished.

In the Southern Zone Fishery (South Australia) management unit, a minimum legal length of 12.5 cm applies across most of the fishery, which allows spawning to occur before Blacklip Abalone are recruited to the fishery. About 30 per cent of the catch has been harvested from so-called 'fish-down' areas, where the minimum legal length is 11 cm; Blacklip Abalone in these areas reach sexual maturity at a smaller shell length than those elsewhere in the fishery⁸. Total catch has been stable between 2000 and 2010, with CPUE in both non-fish-down and fish-down areas at near record high levels⁹. This evidence indicates that the biological stocks in the Southern Zone Fishery management unit are unlikely to be recruitment overfished, and that the current level of fishing mortality is unlikely to cause the biological stocks to become recruitment overfished. Fine-scale spatial assessment and management are currently being implemented in this fishery.

On the basis of the evidence provided above, Blacklip Abalone in South Australia is classified as a sustainable stock.

New South Wales

The Abalone Fishery (New South Wales) is managed as a single management unit with a single TACC. Annual assessments of this management unit rely heavily on fishery-dependent data. The fishery is reviewed by an independent total allowable catch committee, which also determines the annual TACC. There are no direct or derived estimates of biomass or fishing mortality. Mean CPUE and catch are key performance measures. A legal minimum length of 11.7 cm allows spawning to occur before Blacklip Abalone are recruited to the fishery.

This management unit was stable at a TACC of 333 t through the late 1980s and 1990s. Following mortality of abalone associated with infection with Perkinsus (a disease that affects shellfish10), biological stocks declined sharply in the south between 2002 and 2005. Large reductions in TACC were made, from 333 t in 1999 to 75 t in 2008. The TACC was held at 75 t in 2009 and 2010.

After the significant reductions in TACC which occurred during the early 2000s, there has been a strong recovery in CPUE since 2005, particularly in the southern areas that support the majority of the current catch. Northern areas of the state remain impacted by mortality of abalone associated with Perkinsus. Although CPUE is increasing in a similar fashion to the more productive southern New South Wales regions, catch remains very low¹¹. For the period 2005–10, a number of regions have supported the majority (~90 per cent) of the New South Wales TACC. CPUE in these regions has increased from 10–15 kg/hour in 2005 to 30–40 kg/hour in 2010¹¹. Doubling of CPUE in these regions, associated with reductions in TACC, suggests that current fishery management will facilitate biological stock recovery. This evidence indicates that the current level of fishing mortality should allow these biological stocks to recover from their recruitment overfished state.

On the basis of the evidence provided above, Blacklip Abalone in New South Wales is classified as a transitional–recovering stock.

Table 2: Blacklip Abalone biology^2,12

Longevity and maximum size	25 years; 20 cm shell length
Maturity (50%)	5 years; 7.5–14 cm shell length

Figure 1: Distribution of reported commercial catch of Blacklip Abalone in Australian waters, 2010 Main features and statistics for Blacklip Abalone fisheries in Australia in 2010

Main features and statistics for Blacklip Abalone stocks/fisheries in Australia in 2010

Blacklip Abalone are hand harvested by divers, who typically operate from small, trailable or tender vessels using low-pressure surface–air supply equipment (hookah). Abalone are removed from the reef using a tool known as an abalone iron.
A range of input and output controls are applied to Blacklip Abalone stocks across all states:
- Input controls include limited entry and spatial closures.
- Output controls include commercial and recreational total allowable catches and size limits.
In 2010, 229 commercial vessels harvested Blacklip Abalone in Australian waters: 121 in Tasmania, 48 in Victoria, 35 in South Australia and 25 in New South Wales.
The total commercial catch in 2010 was 3825 t, comprising 2484 t in Tasmania, 798 t in Victoria, 447 t in South Australia and 96 t in New South Wales. In all states, recreational and Indigenous harvests are small, probably less than 5 per cent of the commercial catch¹³.
Illegal fishing occurs, but its magnitude is poorly estimated and thus seldom factored into stock assessments.

Figure 2: Commercial catch of Blacklip Abalone in Australian waters, 2000–10 (calendar year)

Catch Explanation

Total Blacklip Abalone catches have been relatively stable over the past decade in Tasmania and South Australia. Catch in Victoria has declined sharply as a result of significant mortality associated with the entry of AVG into Victorian state waters in late 2005¹⁴. New South Wales catch declined through longer term consequences of infection with Perkinsus¹⁰ and a delay in reduction of the TACC to allow stock rebuilding. The maximum Blacklip Abalone harvest between 2000 and 2010 was reported in 2000 (4851 t) and the lowest in 2010 (3825 t). This temporal trend largely reflects the progression of AVG eastwards along the Victorian coastline and subsequent impacts on abalone fishery productivity in affected areas.

Illegal, unreported and unregulated (IUU) fishing is difficult to quantify, because small (but valuable) catches can be taken easily with minimal equipment. One aspect that constrains the IUU fishery in Australia is that the major market is international. Since the challenges of exporting IUU product are significant, the primary market for Australian IUU catch is the small domestic market.

Significant protection is provided by the island status of the Tasmanian Abalone fisheries (producing ~50 per cent of the Australian catch), which facilitates detection of IUU catch during distribution. TACC setting in all states acknowledges that recreational, Indigenous and IUU fishing occurs at a very low rate compared with legal commercial fishing. There is no information from state compliance organisations to indicate that IUU catch is increasing.

Effects of fishing on the marine environment

Since Blacklip Abalone are hand selected by divers operating from vessels that seldom anchor, the fishery has limited direct physical impact on the environment. There is also substantial evidence that the ecosystem effects of removing abalone are minimal^15–17.

Environmental effects on Blacklip Abalone

AVG was detected as a disease in the wild fishery in 2005, folowing detection also of AVG in two land-based abalone aquaculture farms and two offshore experimental farms adjacet to the wild fishery¹⁴.
AVG is highly pathogenic, resulting in estimated mortalities of 60–95 per cent in infected wild populations.
Southward and westward strengthening of the relatively oligotrophic East Australian Current into the inshore waters of eastern Victoria and Tasmania is thought to have triggered changes in near-shore community structure over the past two decades, primarily through range expansion of species such as the Hollow-spined Sea Urchin (Centrostephanus rodgersii) from New South Wales to Tasmania and Victoria, and significant reduction in the biomass of Giant Kelp (Macrocystis porifera)18–20. This has resulted in localised depletions of abalone populations and a reduction in the habitat available for abalone^21–22.
Above-average warm-water events were assumed to have resulted in minor mortalities of abalone in Tasmania in February 2010 (Tasmanian Abalone Divers, pers. comm.), although the spatial extent and magnitude of the mortalities were not quantified. These events are expected to increase under most climate change scenarios.

^aInstitute for Marine and Antarctic Studies, Tasmania
^b South Australian Research and Development Institute
^c Department of Primary Industries, Victoria
^d Ambrad Consulting
^e Total allowable commercial catches were reduced in 2011 and 2012 in the Tasmanian Eastern Zone fishery to address declining catch rates and the risk of recruitment overfishing.
^f Abalone viral ganglioneuritis (AVG) has not been sighted in the Western Zone Fishery (Victoria) in 2012.
^g AVG persists in the Central Zone Fishery (Victoria), but its spread has slowed through 2011 and 2012, and may have halted. Catch reductions in the Victorian Central Zone Fishery continued in 2011 and 2012.
^h Significant rebuilding is apparent in the southern region of New South Wales in 2011; in 2012, the total allowable commercial catch was increased from 96 t to120 t.