Blacklip Abalone (2020)
Haliotis rubra rubra
Date Published: June 2021
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Blacklip Abalone is harvested in NSW, SA, TAS and VIC, with twelve management zones. Stocks are sustainable in six zones, depleting in two zones, depleted in two zones, undefined in one zone and negligible in one zone.
Stock Status Overview
|Victoria||Victoria Central Zone Fishery||Depleting||Catch, CPUE, fishery independent surveys|
|Victoria||Victoria Eastern Zone Fishery||Depleting||Catch, CPUE, fishery independent surveys|
|Victoria||Victoria Western Zone Fishery||Sustainable||Catch, CPUE, fishery independent surveys|
There are substantial difficulties in applying classical stock assessment models to abalone resources, given the possibly large number of stocks in each fishery, and that stock structure in abalone depart substantially from dynamic pool assumptions required by integrated models. In some regions Haliotis rubra rubra also displays spatially variable growth rates and maturity curves. All jurisdictions therefore rely on indicators and empirical performance measures. Primarily these are commercial catch and catch per unit effort (CPUE; as kg of abalone harvested per hour). but they can also include commercial catch per area searched (CPUA), and metrics derived from fishery independent surveys, and commercial and fishery-independent size composition. CPUE and similar indicators from individual fishing events are relevant locally but are not indicative of status broadly [Parma et al. 2003], and status of the many populations within a management unit cannot be assumed to be trending in the same direction. Thus, it is only the average CPUE across each spatial reporting unit that provides the broader perspective for fishery assessment. Fishery assessment is usually based on a combination of indicators, and some jurisdictions combine the indicators to give a combined score for stock status. The annual catch by Blacklip Abalone fisheries is generally close to the established total allowable commercial catches (TACCs), with little over-catch or under-catch of the TACC.
Victoria Central Zone Fishery
Commercial catch per unit effort (CPUE) doubled from about 50 kg per hour in the early 1980s to around 100 kg per hour in the early 2000s, a pattern consistent throughout the state. The increase is thought to be at least partly due to changes in fishing practices that improved fishing efficiency [VFA 2017a]. Similar patterns have been observed during the same period in the other Australian Blacklip Abalone jurisdictions, and have been partially attributed to increased exploitable biomass. The introduction of a total allowable commercial catch (TACC) in the Victoria Central Zone in 1988 was expected to improve biomass and contribute to CPUE increases to some extent. The TACC was stable for more than a decade prior to the introduction of marine parks which reduced the available fishing grounds, probably because catch quotas were not linked to biomass trends at that time [Victorian Department of Natural Resources and Environment 1996].
Since the peak in the early 2000s CPUE has shown a declining trend, and by 2017–18 was almost one quarter lower at 74 kg per hour. Some of the smaller short-term fluctuations in CPUE during the past decade may be attributable to increases and decreases in abalone size limits. The abalone viral ganglioneuritis (AVG) outbreak west of Cape Otway contributed to a 50 t decline in catches and probably reduced catch rates to some extent. The TACC was reduced substantially from 620 t in 2006–07 to 285 t in 2010–11, following which it fluctuated between years by up to 8 per cent. The TACC has been set most recently at 252.6 t, which is a reduction of 18 per cent since 2015 [Dixon and Dichmont 2019a]. Trends in abundance estimated from fishery-independent survey (FIS) data were consistent with observed declines in CPUE, showing a major decline since 2003 of approximately 50–60 per cent in the relative abundance of sub-legal sized (pre-recruit) and legal-sized (recruit) abalone. Both of these FIS indices [A1] [Anon2] have been relatively stable since 2010. Although there are no prescribed reference points for these fishery-independent indicators of stock status, a draft harvest strategy specifies CPUE reference points with limits ranging from 40–50 kg per hour, thresholds from 60–70 kg per hour, and targets from 70–130 kg per hour among 11 of the 12 defined spatial management units (SMU) for which the Central Zone fishery is regulated [Dixon and Dichmont 2019a]. In the absence of recent catches, the Port Phillip Bay SMU was excluded. Current CPUE values in 2019 were between 53–103 kg per hour among the SMU, all above the limit reference points but with six below their respective thresholds and only one minor SMU above its target, in this instance of only 70 kg per hour [Dixon and Dichmont 2019a]. The stable, but relatively low, abundances observed in FIS indices indicate that the decline in biomass observed over two decades may have stabilised, but there is no evidence of recovery and commercial CPUE has decreased by 14 per cent during the past decade [VFA 2017a]. However, pre-recruit abundance levels are similar to those for recruits, implying that reasonable recruitment has been occurring at recent stock levels. The current challenge facing the fishery is ensuring that the spatial distribution of catch is aligned with catch targets that reflect the biological productivity of the resource and enable stocks to rebuild. The most recent assessment concluded that maintaining the TACC at current levels was likely to meet objectives for stabilising the biomass at its current level but unlikely to recover stocks to previous levels. The above evidence indicates that the biomass of this stock is unlikely to be depleted and that recruitment is unlikely to be impaired. For the period 2009–2019 the biomass declined, but the stock is not yet considered to be recruitment impaired. Evidence based on the pre-recruit abundance index indicates that reasonable recruitment has been occurring at recent stock levels. [Dixon and Dichmont 2019a].
On the basis of the evidence provided above, the Victoria Central Zone Fishery management unit is classified as a depleting stock.
Victoria Eastern Zone Fishery
The Eastern Zone management unit was not affected by abalone viral ganglioneuritis (AVG) but has experienced impacts from environmental and ecosystem changes such as increasing abundance of the Longspined Sea Urchin (Centrostephanus rodgersii). These urchins denude reefs of macro-algae, turning them into ‘barrens’ that are unsuitable for abalone, with significant areas of reef in the Eastern Zone having been affected by urchins in this manner over the past 20 years [Gorfine et al. 2012]. It is also likely that reproductive capacity has been reduced by habitat loss caused directly by the increased density of urchins [Bell 2020]. Industry has a history of stewardship and working with fishery managers to sustain the fishery, including active control of urchins at reefs near Mallacoota for the last eight years. The urchin range extension has led to an increased concentration of fishing effort on urchin-free reef areas, with an increased associated risk of localised depletion.
In common with other jurisdictions, improvements in fishing methods have also occurred in this management unit and are thought to have contributed to fishing efficiency-related increases in catch per unit effort (CPUE) from the mid-1990s to early 2000s. The introduction of a total allowable commercial catch (TACC) in the Victoria Eastern Zone in 1988 was expected to improve biomass and contribute to CPUE increases to some extent. The TACC was stable for more than a decade prior to the introduction of marine parks which reduced the available fishing grounds, probably because catch quotas were not linked to biomass trends at that time [Victorian Department of Natural Resources and Environment 1996].
The Eastern Zone catch was relatively stable from 1992 to 2002, ranging from 431 to 445 t per quota year before increasing to 480 t in 2003. Catch was maintained at this level until 2008 and has slowly declined thereafter. The 2018–19 catch quota (TACC) of 346.5 t was the lowest on record. Since 2012, there have been sequential reductions in the total catch harvested from the Eastern Zone. Standardised CPUE significantly increased from 1992 to 2011, before significantly declining over five years from 2011 to 2016, then increasing again from 2016 to 2019. The rate of increase among the seven defined spatial management units (SMU) for which the Eastern Zone fishery is regulated ranged from 6–19 per cent during this 4-year period [Dixon and Dichmont 2019b]. Current CPUE values in 2019 were 89–126 kg per hour among the SMU, well above the limit reference point of 50 kg per hour specified throughout the Eastern Zone, as well as SMU threshold and target reference points specified in a draft harvest strategy, that vary respectively between 70–80 kg per hour and 100–130 kg per hour [Dixon and Dichmont 2019b]. The increases in CPUE are likely to have resulted, at least in part, from ongoing reductions in catch since 2012, as well as from decreases in legal minimum length (LML) in some SMUs in recent years [Dixon and Dichmont 2019b].
In contrast with the CPUE trends, the fishery-independent survey indices showed that in 2015, pre-recruit abundance had declined by almost 70 per cent from historically high levels in 1995. From 1995–2015, the survey index of recruit abundance declined by 50 per cent and has since remained relatively steady [VFA 2017b].
For the periods 1995 to 2015 and 2012 to 2017, fishery independent and dependent performance measures respectively indicated that the biomass was declining, but not to the extent that the stock could be considered to have become depleted or recruitment impaired. In the last two years, both CPUE and recruit abundance have increased. Pre-recruit abundance has continued to decline and remains of concern, however it is reasonable to conclude that the status of the resource has stabilised and the likelihood of depletion to a level causing recruitment impairment in the near to medium term is low at the current precautionary TACC of 337.5 t [Dixon and Dichmont 2019b].
On the basis of the evidence provided above, the Victoria Eastern Zone Fishery management unit is classified as a depleting stock.
Victoria Western Zone Fishery
The Western Zone management unit has undergone significant changes over its recent history. Most notable was the impact of an outbreak of abalone viral ganglioneuritis (AVG) in 2006. Industry has worked with fishery managers since that time to respond to the disease outbreak, including development of a harvest strategy for the fishery that has been applied since 2016 (Sainsbury et al. 2019). Abalone mortalities due to the disease severely reduced the biomass and resulted in a major reduction in total allowable commercial catch (TACC) for this zone from 280 t in 2001–02 to 20 t in 2008–09. While some fishing occurred on uninfected reefs for a period immediately after the disease was first recognised, by 2008 most areas in the Western Zone had been impacted and were closed to fishing. These events complicate comparisons between recent and historical fishery-dependent and independent data.
Progression of the disease through the fishery had abated by 2009. This enabled fishers and researchers to conduct a structured fishing program [Mayfield et al. 2011], where divers were assigned precise fishing locations to gather information and assess the capacity of remaining stocks to support a viable commercial fishery. Since SAFS 2016, and in line with the Western Zone harvest strategy based on simulation modelling by Helidoniotis and Haddon , the TACC has been increased to 70 t reflecting increases in estimates of exploitable biomass of Blacklip Abalone with shell lengths larger than a conservative legal minimum length (LML) of 130–135 mm. Recent TACCs have been set at around 10 per cent of the estimated biomass of legal-sized abalone [WADA 2020] to facilitate continued rebuilding.
Commercial catch per unit effort (CPUE) for the management unit increased by 73 per cent from 1979–2001. These increases likely reflect changes in the sophistication of management strategies, change in fishing practice and adoption of improved technology, which led to increased efficiency of the fleet. The introduction of a TACC in the Victoria Western Zone in 1988 was anticipated to improve biomass and is likely to have contributed to the CPUE increases to some extent. The TACC was stable for more than a decade prior to the introduction of marine parks, probably because catch quotas were not linked to biomass trends at that time [Victorian Department of Natural Resources and Environment 1996]. The CPUE from 2001–06 declined slightly, until the 2006 AVG outbreak caused substantial declines in catch and catch rate. In 2007, the highest average annual CPUE on record occurred, most likely due to fishing becoming restricted to disease-free areas [Gorfine et al. 2018] and some divers reverting to fishing at the LML of 120 mm prior to AVG spreading to reefs in the Portland region of the Western Zone. After normal fishing practices resumed in 2011 and divers were free to choose where to fish, CPUE increased rapidly until 2013. This increase was likely to have arisen from divers being able to target the more productive reefs again after structured fishing ended. Catch-per-unit-effort during the past two years has been 77 kg per hour, the same as the pre-disease average for the period 1992–93 to 2003–04, and comparable with the other two management units [Dixon and Dichmont 2019 a,b], despite the conservative LML of 130–135 mm.
The fishery-independent survey (FIS) data from 2003 onwards clearly show the impact of the AVG mortalities. Survey abundance indices for both pre-recruits and recruits showed 32 per cent and eight per cent less abundance respectively in 2018, compared with the pre-disease averages during 1995–2006 [VFA 2017c]. Since 2010 pre-recruit abundance has increased more than three-fold and recruit abundance has increased by 75 per cent since 2008 [VFA 2017c]. Despite the signs of recovery, the current mature biomass remains below the 2020 target reference point, but above the limit reference point, in the harvest strategy for the fishery but has declined for the last 3 years. Mature biomass is dominated by abalone below the LML, and so is also likely to be influenced by variation in year-class strength. Recent declines in mature biomass follow a large increase in the biomass of under-sized abalone to 2016 and are more closely related to declines in legal-sized biomass in recent years whereby mature, but undersize abalone biomass remains more stable [WADA 2020].
The above evidence indicates that the biomass of the stock is unlikely to be depleted, and that recruitment is unlikely to be impaired. Abalone viral ganglioneuritis did not disrupt the fundamental breeding and juvenile recruitment processes.
Fishery-dependent and independent information indicate that the management unit has been stable since 2011, although at a lower biomass than pre-AVG. The recent stability of commercial CPUE under the higher LML of 130–135 mm, combined with stability of the fishery-independent pre-recruit and recruit survey indices, and biomass estimates derived from them, indicate that the current management arrangements are constraining fishing pressure sufficiently to avert declines in the productivity of the stock. Signs are now evident of an increase in pre-recruit abundance, indicating that the stock has been rebuilding despite progressive increases in TACC [VFA 2017c].
The harvest strategy details criteria on which to base SAFS assessments of the fishery during the rebuilding phase following AVG. These include provisions for both mature biomass, estimated from the fishery independent surveys, and harvest fractions of the available biomass. The mature biomass is currently above the performance indicator of 20 per cent of the unfished biomass and the harvest fraction has remained below 15 per cent, with both reference points from Helidoniotis and Haddon , implying that the stock is unlikely to become recruitment impaired. Although the stock is not expected to be able to support pre-AVG catch levels in the short to medium term, the above evidence indicates that the current level of fishing mortality is unlikely to cause the stock to become recruitment impaired.
On the basis of the evidence provided above, the Victoria Western Zone Fishery management unit is classified as a sustainable stock.
Blacklip Abalone biology [Shepherd 1973, Officer 1999, Tarbath et al. 2001, Tarbath and Officer 2003]
|Species||Longevity / Maximum Size||Maturity (50 per cent)|
|Blacklip Abalone||20–50 years, 150–220 mm SL||~ 5 years, 80–130 mm SL|
Distribution of reported commercial catch of Blacklip Abalone
|Total allowable catch|
New South Wales – Indigenous (Management Methods) https://www.dpi.nsw.gov.au/fishing/aboriginal-fishing
Victoria – Indigenous (Management Methods) A person who identifies as Aboriginal or Torres Strait Islander is exempt from the need to obtain a Victorian recreational fishing licence, provided they comply with all other rules that apply to recreational fishers, including rules on equipment, catch limits, size limits and restricted areas. Traditional (non-commercial) fishing activities that are carried out by members of a traditional owner group entity under an agreement pursuant to Victoria’s Traditional Owner Settlement Act 2010 are also exempt from the need to hold a recreational fishing licence, subject to any conditions outlined in the agreement. Native title holders are also exempt from the need to obtain a recreational fishing licence under the provisions of the Commonwealth’s Native Title Act 1993.
Commercial catch of Blacklip Abalone - note confidential catch not shown
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