Greenlip Abalone is distributed across southern Australia. Its biological stock structure is currently being examined (Fisheries Research and Development Corporation, Project 2010/013). However, genetic evidence has confirmed that Blacklip Abalone comprises numerous independent biological stocks1, and a similar, but spatially broader, biological stock structure is anticipated for Greenlip Abalone. It is estimated that there are many biological stocks across Tasmania, Victoria, South Australia and Western Australia. Given the large number of biological stocks, it is not practical to assess each separately. Instead, status for Greenlip Abalone is reported at the jurisdictional level.
South Australia
Greenlip Abalone is caught in three fisheries in South Australia: the Western Zone Fishery, the Central Zone Fishery and the Southern Zone Fishery.
In the Western Zone Fishery, substantial fishery-dependent and fishery-independent data are available for Greenlip Abalone stock assessment. However, there are no direct estimates of biomass or fishing mortality. Catch per unit effort (CPUE; as kilograms of abalone harvested per hour) is a key performance indicator. A minimum legal length of 14.5 cm is in place for Greenlip Abalone in this fishery. This exceeds estimates of the shell length at which 50 per cent of Greenlip Abalone are sexually mature, allowing spawning to occur before Greenlip Abalone are recruited to the fishery. Total commercial catch has been stable since 1989. The CPUE for Greenlip Abalone in the Western Zone Fishery was high between 2002 and 2008 (mean of 72 kg/hour; Figure 2b), most likely due to increased recruitment in the late 1990s2. CPUE has since declined and, in 2010, was 62 kg/hour, which is similar to the long-term mean between 1979 and 2010 (59 kg/hour). This evidence indicates that Greenlip Abalone biological stocks in the Western Zone Fishery 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, substantial fishery-dependent and fishery-independent data are used for the Greenlip Abalone stock assessment. CPUE is a key performance indicator for the fishery. A minimum legal length of 13 cm is in place to allow spawning to occur before Greenlip Abalone are recruited to the fishery. Total commercial catch has been stable since 1994; more than 70 per cent of the Greenlip Abalone are harvested from Tiparra Reef3. CPUE in the Central Zone Fishery increased substantially between 1999 (65 kg/hour) and 2000 (84 kg/hour), and has since steadily declined (Figure 2b). In 2010, CPUE was 72 kg/hour, which was around 10 per cent greater than the long-term mean between 1979 and 2010 (59 kg/hour). A length-structured model was used to assess the Greenlip Abalone biological stocks at Tiparra Reef3, providing additional key performance indicators—spawning biomass and exploitation rate—for this fishing ground. Model estimates of spawning biomass and exploitation rate in 2009 were around 50 per cent of unfished (1968) levels and 36 per cent, respectively (Figure 2c). Although information for assessment of other fishing grounds is limited, this evidence indicates that Greenlip Abalone biological stocks in the Central Zone Fishery 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, Greenlip Abalone comprises a small component (<5 per cent) of the commercial abalone catch in this zone (Blacklip Abalone makes up the majority of catch) and less than 5 per cent of the total commercial abalone catch in South Australia. Consequently, there are limited data to classify the status of Greenlip Abalone in this zone. However, given the small commercial catch of Greenlip Abalone in this zone (~7 t/year), the catch is unlikely to affect the overall status classification of Greenlip Abalone in South Australia.
On the basis of the evidence provided above, Greenlip Abalone in South Australia is classified as a sustainable stock.
Western Australia
In the Commercial Abalone Fishery (Western Australia), substantial fishery-dependent and fishery-independent data are available for Greenlip Abalone. However, there are no direct estimates of biomass or fishing mortality. The fishery is divided into eight management areas, and Greenlip Abalone is taken in areas 1, 2 and 3. A minimum legal length of 14 cm is in place in Western Australia, which allows spawning to occur before recruitment to the fishery. Total commercial catch has been stable since 1970. Standardised CPUE is a key performance indicator. Standardised CPUE in areas 2 and 3 has fluctuated from year to year; in 2010, it was 14.6 and 13.3 kg/hour, respectively, similar to the long-term means from 1992 to 2010 (13.1 and 13.4 kg/hour, respectively) (Figure 2d). This evidence indicates that Greenlip Abalone biological stocks in the Commercial Abalone Fishery (Western Australia) 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, Greenlip Abalone in Western Australia is classified as a sustainable stock.
Tasmania
The availability of limited data on Greenlip Abalone in Tasmania makes formal status assessment difficult. Consequently, high reliance is placed on diver observations and commercial catch history. There is insufficient information to confidently classify status.
Because of the lack of evidence, Greenlip Abalone in Tasmania is classified as an undefined stock.
Victoria
Greenlip Abalone comprises less than 2 per cent of the Victorian commercial abalone catch. The availability of limited data on Greenlip Abalone in Victoria makes formal status assessment difficult. Consequently, high reliance is placed on diver observations and commercial catch history. Most of the commercial catch is harvested from the Western Zone, following reduction in catches of Blacklip Abalone due to the impact of the disease abalone viral ganglioneuritis. Total allowable commercial catches (TACCs) have recently been reduced by 50 per cent. There is insufficient information to confidently classify status.
Figure 1: Distribution of reported commercial catch of Greenlip Abalone in Australian waters, 2010
Figure 2: a) Commercial catch of Greenlip Abalone in Australian waters, 1970–2010 (calendar year); b) catch per unit effort in the Central Zone Fishery (South Australia) and Western Zone Fishery (South Australia); c) spawning biomass and exploitation rate for Tiparra Reef, South Australia; d) standardised catch per unit effort in Western Australia areas 2 and 3
Substantial numbers of Greenlip Abalone are harvested commercially in South Australia, Western Australia and Tasmania, and smaller quantities are caught in the Victorian commercial abalone fisheries (Figure 2a). In 2010, the proportion of the commercial Greenlip Abalone catch harvested from these states was 54 per cent, 24 per cent, 19 per cent and 3 per cent, respectively.
Total commercial Greenlip Abalone catches were high before the implementation of TACCs across fishing zones and states (between 1985 and 1990). Since then, commercial catch has been relatively stable, with no long-term trends evident (Figure 2a). The maximum commercial catch was reported in 1978 (1244 t) and the lowest in 1993 (629 t).
