East coast biological stock
Components of this biological stock in both Queensland and New South Wales have been heavily fished for many years, under different management arrangements. However, the status of the biological stock has never been assessed on a whole-stock basis; rather, the state components have been assessed using different methodologies. These assessments have arrived at
different outcomes.
Queensland assessed the part of the biological stock based on a sex, age and length stock analysis model. The assessment in 200914 indicated that exploitable biomass was approximately 35 per cent of unfished biomass and would continue to decline if fishing pressures remained unchanged. Updated mortality estimates in 2010, combined with decreasing commercial catch and no increase in catch rate, indicated that biological stock status had not improved. Based on this information, Queensland considered Snapper in Queensland waters to be recruitment overfished.
The assessment undertaken in New South Wales was largely based on attempting to maximise the yield per recruit in a fishery that was known to have been heavily exploited for a very long time (>50 years), and had been shown to be in a state best described as 'growth overfished'15. Management to address this problem was instigated in 2001, when the minimum legal length for Snapper was increased from 28 to 30 cm total length. Since then, increases in commercial catch and catch rate of Snapper in New South Wales, together with increases in the proportion of fish aged more than 5 years in landings, indicate that the biomass is unlikely to be recruitment overfished. However, the size composition data from detailed monitoring of the fishery show that the New South Wales portion of the biological stock continues to be heavily fished, and the status has remained at 'growth overfished' in all recent assessments.
An assessment of the status of the eastern biological stock of Snapper in waters adjacent to Victoria was undertaken in 201116. The assessment found that insufficient data were available to adequately assess the status of Snapper in these waters. The catch of Snapper for this part of the state is much less than for the western biological stocks; for commercial fishers, the eastern biological stock of Snapper has historically been considered a byproduct species.
Because of conflicting signals and the fact that no stock assessment has been conducted on the biological stock as a whole, the east coast biological stock is classified as an undefined stock.
A formal cross-jurisdictional stock assessment of this biological stock is needed as a matter of priority. New South Wales and Queensland have data sets that can be used in a future joint stock assessment. The undefined classification will not be resolved until this combined biological stock assessment has been completed.
Western Victorian biological stock
The most recent stock assessment for Snapper in Victoria was undertaken in 201116. It assessed commercial and recreational catch rates, fishery-independent pre-recruitment catch rates and age– length frequency distributions for the western biological stock. Commercial catch rates have shown an increasing trend since the late 1990s. Effort for all gear types in Victoria has decreased since 1999, as a result of a reduction in the number of licensed fishers in Victorian waters, and is at historically low levels.
Catch rate indicators for the western Victorian biological stock are in 'good condition' for 7 of the
10 indicators used to assess the status of the biological stock16, indicating that the biomass of the biological stock is unlikely to be recruitment overfished. Despite low recruitments in 2005–06 and 2010–11, the recent series of moderate recruitment years (2007–08, 2008–09, 2009–10) is expected to generate average abundance over the coming few years. These fluctuations are probably the result of environmental conditions affecting spawning success and/or recruitment to the fishery.
Based on the analyses outlined above, the current level of fishing mortality is unlikely to cause the biological stock to become recruitment overfished. The recent shift in the targeting of Snapper by Commonwealth- or state-licensed trawlers may pose a significant risk of overfishing the biological stock. Before 2005, Snapper taken as bycatch by Commonwealth-licensed trawlers was usually less than 20 tonnes (t) per year; landings by Victorian-licensed trawl fishers have generally been between zero and about 1.7 t per year, but increased to about 34 t in 2011. Fisheries managers are currently working with the commercial fishing industry to ensure that this risk is managed.
On the basis of the evidence provided above, the biological stock is classified as a sustainable stock.
South East Fishery (South Australia) biological stock
The South Australian South East Fishery biological stock has traditionally provided much lower catches than the three gulf-based biological stocks described below. Catches rose considerably through the mid–late 2000s, as a result of substantial increases in longline fishing effort, reflecting the uptake of the new longline fishing technology. Since 2003–04, commercial longline catch per unit effort (CPUE) has increased, indicating an increase in fishable biomass. No estimates of size
and age structures are available for this biological stock, indicating a lack of indicators of year-class strength and recruitment history.
Historically, this biological stock has provided only incidental catches and low catch rates. However, from 2007–08, the catch and catch rates increased exponentially to record levels. There is recent evidence for at least one very strong recruitment event, which suggests that the population is not recruitment overfished8.
Given the fact that the biological stock has not previously been heavily exploited, combined with a lack of information on biomass and fish movement, the biological stock is classified as an undefined stock.
Gulf St Vincent Fishery (South Australia) biological stock
Commercial catches and catch rates for this biological stock have historically been consistently low. However, since 2008–09, there have been exponential increases in catch, effort and CPUE, to unprecedented levels. This is consistent with a substantial recent increase in biomass. Population age structures indicate that this relates to the recent recruitment of several strong year-classes to the population. As a consequence, the recent stock assessment suggests that, between 2000
and 2009, the stock biomass nearly doubled, to more than 2900 t8. Therefore, the biomass of this biological stock is unlikely to be recruitment overfished.
As a result of the estimated increasing biomass, catch and effort have increased substantially. The current CPUE is at historically high levels and has been increasing since 2007. The catch in
2010 was 454 t, which is approximately 16 per cent of the estimated biomass. This level of catch is unlikely to cause the biological stock to become recruitment overfished.
On the basis of the evidence provided above, the biological stock is classified as a sustainable stock.
Southern Spencer Gulf Fishery (South Australia) biological stock
From 2004–05, there was a substantial increase in commercial longline fishing effort for this biological stock, which related to the uptake of new longline fishing technology8. This resulted in a substantial increase in the effectiveness of fishers, culminating in dramatic increases in catches and CPUE. However, from 2008–09, CPUE declined dramatically, suggesting that the fishable biomass had become depleted8. This evidence indicates that the current level of fishing mortality is likely to cause the biological stock to become recruitment overfished.
Age-structure data indicate that no strong year-class has recruited to this biological stock since
1999. The stock assessment integrated these data and suggested that, between 2004 and 2009, biomass fell from 4200 to 3600 t8. Since recruitment for Snapper in South Australia is known to
be highly variable and environmentally driven8, it is unclear if the poor recent recruitment is related to overfishing.
On the basis of the evidence provided above, the biological stock is classified as a transitional–depleting stock.
Northern Spencer Gulf Fishery (South Australia) biological stock
The Northern Spencer Gulf Fishery (South Australia) biological stock was traditionally the most important of the South Australian biological stocks, generally providing more than 50 per cent of the state's total catch. However, during the mid–late 2000s, its contribution declined to approximately
20 per cent. These lower catches reflect declines in fishing effort, which are consistent with a decline in biomass. The high levels of CPUE associated with these lower levels of catch and effort are thought to relate to hyperstability, reflecting the aggregative behaviour of Snapper and the experience of the fishers in this region17.
The suggestion of a decline in biomass relative to the 1990s is supported by the lack of recruitment of any strong year-classes to the population since 1999. It is not clear whether this lack of recruitment reflects the biological stock being recruitment overfished or an absence of environmental conditions conducive to spawning. In the absence of further recruitment, fishing mortality is likely to deplete the biological stock even further.
On the basis of the evidence provided above, the biological stock is classified as a transitional–depleting stock.
West Coast Fishery (South Australia) biological stock
The South Australian West Coast Fishery biological stock has traditionally provided much lower catches than the three gulf-based biological stocks described above. Catches rose considerably through the mid–late 2000s, as a result of substantial increases in longline fishing effort, reflecting the uptake of the new longline fishing technology. However, since 2003–04, commercial longline CPUE has declined, indicating a possible decline in fishable biomass. No estimates of size and age structures are available for this biological stock, indicating a lack of indicators of year-class strength and recruitment history.
Insufficient information is available to confidently classify the status of this biological stock; as a result, the biological stock is classified as an undefined stock.
South coast biological stock
This biological stock has not been formally assessed; hence, insufficient information is available to confidently classify its status. The biological stock is classified as an undefined stock.
Shark Bay oceanic biological stock
The most recent model-based stock assessment (Department of Fisheriesa 2011, unpublished) indicated that spawning biomass in 2010 was approximately 30 per cent of the unfished level, which is also the minimum threshold level for this biological stock. The biomass is estimated to have been increasing since a historical low of around 20 per cent in 2003 and is expected to reach the management target level (40 per cent of the unfished level) by 2014, suggesting a recovering biological stock.
The total allowable commercial catch (TACC) was reduced in 2007 (it had initially been reduced by
40 per cent in 2004) to 277 t to further assist biological stock recovery, with the aim of achieving the target level of 40 per cent of the unfished level by 2014. Since 263 t was caught in 2010, this level of fishing mortality should allow continued recovery of the biological stock.
On the basis of the evidence provided above, the biological stock is classified as a transitional–recovering stock.
Shark Bay inshore—eastern gulf biological stock
The most recent model-based stock assessment (Department of Fisheries 2011, unpublished) indicated that spawning biomass was approximately 60 per cent of the unfished level, which is well above the management target (40 per cent of unfished biomass) and the minimum threshold level (30 per cent of unfished biomass). The biological stock is not considered to be recruitment overfished.
There was no commercial catch of Snapper in the eastern gulf biological stock in 2010. As well, recreational catch was minor (4 t) and within the target catch range (0–12 t). This level of fishing mortality is unlikely to cause this biological stock to become recruitment overfished.
On the basis of the evidence provided above, the biological stock is classified as a sustainable stock.
Shark Bay inshore—Denham Sound biological stock
The most recent model-based stock assessment (Department of Fisheries 2011, unpublished)
indicated that spawning biomass was approximately 42 per cent of the unfished level,
which is above the management target (40 per cent of unfished biomass) and the minimum threshold level (30 per cent of unfished biomass). The biological stock is not considered to be recruitment overfished.
The total commercial catch of Snapper in the Denham Sound biological stock was less than 0.5 t in
2010. As well, recreational catch was minor (7 t) and within the target catch range (0–12 t). This level of fishing mortality is unlikely to cause this biological stock to become recruitment overfished.
On the basis of the evidence provided above, the biological stock is classified as a sustainable stock.
Shark Bay inshore—Freycinet Estuary biological stock
The most recent model-based stock assessment (Department of Fisheries 2011, unpublished) indicated that spawning biomass was approximately 22 per cent of the unfished level. This level of biomass is below both the management target level (40 per cent of unfished biomass) and the minimum threshold level (30 per cent of unfished biomass). Modelled estimates indicate that the biological stock will continue to rebuild very slowly to around 25 per cent of unfished biomass
by 2015. The biological stock is considered recruitment overfished (according to the 30 per cent threshold level in Western Australia). However, biomass has been increasing in recent years, suggesting a recovering biological stock.
There was no commercial catch of Snapper from the Freycinet Estuary biological stock in 2010. As well, recreational catch was minor (1 t) and within the target catch range (0–3.8 t). This level of fishing mortality should allow the biological stock to recover from its recruitment overfished state.
On the basis of the evidence provided above, the biological stock is classified as a transitional–recovering stock.
West coast biological stock
Assessments completed in 2007 and 2009 showed that the fishing mortality on this biological
stock exceeded the limit reference point of 1.5 times natural mortality18–19. Based on agreed decision rules, to decrease fishing mortality to a level that would allow the biological stock to recover, the total catch had to be reduced by 50 per cent, from levels near to or above 400 t. New management arrangements to achieve the required catch reductions have been successfully implemented for all commercial and recreational sectors, and the current catch in this region has been at acceptable levels (<200 t) since 2009–10.
On the basis of the evidence provided above, the biological stock is classified as a transititional–recovering stock.