East coast biological stock
The cross-jurisdictional east coast biological stock has components in New South Wales, Queensland and Victoria. Each jurisdiction assesses and manages the part of the biological stock that occurs in its waters. The status presented here for the entire biological stock has been established using evidence from the three jurisdictions.
The New South Wales part of the biological stock is assessed annually in terms of commercial landings, catch rates and size composition. Periodic sampling of age compositions are used to generate mortality estimates. Snapper are currently assessed as being ‘growth overfished’ in New South Wales waters, despite an increase in minimum legal length from 28 to 30 cm in 2001. Since that time, commercial median catch rates (kilograms per day trapping) have nearly tripled, from approximately 9 kg/day to an average of more than 25 kg/day, between 2008 and 2013. The size compositions of Snapper in commercial landings have remained remarkably stable, with the average size being approximately 31–32 cm fork length each year since 2004. The most recent commercial age-composition samples in 2007–08 and 2010–11 showed that the fishery continues to be dominated by fish aged between 2 and 5 years, but with a slight increase in the proportion of fish aged more than 5 years in commercial landings. The above evidence indicates that the biomass of this part of the stock is unlikely to be recruitment overfished.
Commercial landings in the New South Wales part of the biological stock in 2013 (approximately 216 tonnes [t]) were the lowest since 2003 (noting that the catch records for 2013 may be incomplete at this time). The reported number of fisher-days per year in the trap fishery has approximately halved since 2001, from approximately 10 000 to 5000 days. Typical size compositions in 2013 suggest no large changes to the fishery. The above evidence indicates that the current level of fishing pressure is unlikely to cause this part of the stock to become recruitment overfished.
Queensland assessed its jurisdictional component of the east coast biological stock in 2009 using a sex-, age- and length-based stock analysis model 14. The assessment indicated that exploitable biomass was approximately 35 per cent of unfished biomass and would continue to decline if fishing pressures remained unchanged. Based on this assessment, the Queensland Department of Agriculture, Fisheries and Forestry classified Snapper as an ‘overfished’ stock in 2009. Commercial and charter sector catches15 have declined since this stock assessment was completed, along with the commercial catch per unit effort (CPUE). Although there was a small improvement in commercial CPUE in 2013, measurable improvements in biomass are yet to be detected, and it is likely that the biomass of the Queensland part of the stock is still recruitment overfished. The number of commercial and charter licences accessing the fishery has declined, while fishing mortality estimates remain high, exceeding natural mortality for the 2013 fishing year. The current level of fishing pressure is constrained by management to a level that should allow the stock to recover from its recruitment overfished state, but measurable improvements are yet to be detected.
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 Victorian part of the east coast biological stock. The catch of Snapper for this part of the state is much less than for Victoria’s western biological stocks; for commercial fishers, Snapper in the Victorian part of the east coast biological stock has historically been considered a byproduct species.
A cross-jurisdictional east coast Snapper stock assessment is planned that should resolve the stock status classification for this stock in the future. However, conflicting signals and the fact that no stock assessment has been conducted on the biological stock as a whole, result in the east coast biological stock being classified as an undefined stock.
Western Victorian biological stock
The main indicators used for assessment of the western Victorian biological stock are CPUE from both the commercial and recreational sectors, fishery-independent annual surveys of pre-recruit (young-of-year) catch rates in Port Phillip Bay (the main spawning and nursery area for the western stock)4, and age–length composition of catches taken by both the recreational and commercial sectors.
The most recent stock assessment was in 201116. This assessment indicated that the stock was in good condition. More recent review of commercial longline catch rates shows they have remained relatively stable since the 2011 assessment, after increasing from the late 1990s through to 2008. It appears that catch rates have stabilised after the full recruitment of the strong 2001, 2004 and 2005 year-classes to the adult fishery. The catch rates in the haul-seine fishery, which catches subadults, have also been stable since the 2011 assessment, consistent with recruitment of the three moderate year-classes detected by the 2008, 2009 and 2010 Port Phillip Bay pre-recruit surveys. Effort has remained relatively stable for both the longline (slight increase since 2011) and the haul-seine gear types, which account for most of the commercial catch. Recreational catch-rate data are consistent with the trends observed in the commercial data. Recent pre-recruit surveys in Port Phillip Bay have shown above-average (22-year time series) recruitment for the 2013 and 2014 year-classes.
The current high productivity of the Victorian western stock fishery may decline slightly over the coming 2–5 years as a result of the very poor juvenile recruitments in 2011 and 2012, but will increase again when the 2013 and 2014 strong year-classes enter the adult fishery in 6–7 years’ time. The continued high catch rates of both subadult and adult Snapper, particularly in the Port Phillip Bay Fishery, and the recent strong recruitments of juvenile Snapper suggest that the western Victorian biological stock is not recruitment overfished.
The previous Status of key Australian fish stocks reports addressed the risk for the western Victorian biological stock associated with increasing catches from coastal waters. Recent data on fishery catches from both Commonwealth and state fisheries operating in offshore waters indicate that recent management measures have been successful in limiting catches. Based on this and the other evidence provided above, the current level of fishing pressure is unlikely to cause the stock to become recruitment overfished.
On the basis of the evidence provided above, the western Victorian biological stock is classified as a sustainable stock.
South East Fishery (South Australia) management unit
The South East Fishery (South Australia) management unit has traditionally provided much lower catches than the gulf-based management units (Figure 2). Catches rose considerably through the mid- to late 2000s, as a result of substantial increases in longline fishing effort, reflecting the uptake of new longline fishing technology. This culminated in the region producing 25 per cent of South Australia’s catch in 20108. Furthermore, from 2003 to 2004, commercial longline CPUE increased, indicating an increase in biomass. This was related to recruitment of two strong year-classes in 2001 and 2004, evident in the population age structures8. Nevertheless, after 2010, both catch and CPUE decreased considerably, which is consistent with decreasing biomass due to depletion of the two strong year-classes. The biomass of this stock is not likely to be recruitment overfished, but the current level of fishing pressure is likely to cause the stock to become recruitment overfished.
Significant changes were made to management arrangements in 2012 and 2013, including an extension to the closed season and introduction of daily commercial catch limits. The influence of these changes will take some time to manifest. Currently, given the decreasing levels of catch and CPUE, based on depletion of only a few strong year-classes in the age composition, this management unit is classified as a transitional–depleting stock.
Southern Gulf St Vincent Fishery (South Australia) management unit
The Southern Gulf St Vincent management unit has also traditionally provided lower catches than the other gulf-based management units (Figure 2). Nevertheless, longline catches and CPUE increased from 2008 to 2010, consistent with an increase in biomass8. This was associated with recruitment of two strong year-classes in 2001 and 2004, which are evident in the population age structures. However, catch and CPUE then decreased in 2011 and 2012, suggesting a decrease in biomass due to depletion of the two strong year-classes. The biomass of this stock is not likely to be recruitment overfished, but the current level of fishing pressure is likely to cause the stock to become recruitment overfished.
Significant changes were made to management arrangements in 2012 and 2013, including an extension to the closed season, introduction of daily commercial catch limits and a further restriction on the number of commercial hooks that can be used on set lines. The influence of these changes will take some time to manifest. Currently, given the declining levels of catch and CPUE, based on depletion of only a few strong year-classes in the age composition, the management unit is classified as a transitional–depleting stock.
Northern Gulf St Vincent Fishery (South Australia) management unit
Since 2008, there has been a significant shift to new longline technology in the Northern Gulf St Vincent Fishery, which has become the dominant gear type in this management unit. As a result of this shift, dramatic increases in longline catch, effort and CPUE have culminated in this regional fishery becoming the dominant contributor to the state’s Snapper catches8. The age structures show numerous strong year-classes recruiting to the population through the 2000s. As a consequence, the estimated fishable biomass increased by 80 per cent between 2000 and 2012. From 2008, catch, effort and CPUE all increased in response to the increase in fishable biomass. The above evidence indicates that the biomass of this stock is unlikely to be recruitment overfished and that the current level of fishing pressure is unlikely to cause the stock to become recruitment overfished.
Significant changes were made to management arrangements in 2012 and 2013, including an extension to the closed season, introduction of a spatial closure to protect key spawning aggregation sites, introduction of daily commercial catch limits and a further restriction on the number of commercial hooks that can be used on set lines. The influence of these changes will take some time to manifest.
On the basis of the evidence provided above, the management unit is classified as a sustainable stock.
Southern Spencer Gulf Fishery (South Australia) management unit
From 2005, there was a substantial increase in commercial longline fishing effort for the regional Southern Spencer Gulf Fishery, which related to the uptake of new longline fishing technology8. This increased the effectiveness of fishers, culminating in dramatic increases in catches and CPUE. However, from 2009, CPUE declined dramatically, suggesting that the fishable biomass had become depleted. Age-composition data indicate that no strong year-classes have recruited to this region since 1999. The stock assessment integrated these data and suggested that fishable biomass had fallen each year between 2005 and 2012, by a total of 27 per cent8. Because recruitment for Snapper is highly variable and environmentally driven, the extent to which poor recent recruitment is related to overfishing is uncertain. The biomass of this stock is not likely to be recruitment overfished, but the current level of fishing pressure is likely to cause the stock to become recruitment overfished.
Significant changes were made to management arrangements in 2012 and 2013, including an extension to the closed season, introduction of daily commercial catch limits and a further restriction on the number of commercial hooks that can be used on set lines. The influence of these changes will take some time to manifest.
On the basis of evidence provided above, the management unit is classified as a transitional–depleting stock.
Northern Spencer Gulf Fishery (South Australia) management unit
The regional Northern Spencer Gulf Fishery was traditionally the most significant in South Australia; up to 2004, it provided approximately 50 per cent of the state’s total catch of Snapper8. However, since the mid-2000s, fishing effort has declined considerably, resulting in lower catches. By 2012, the fishery produced less than 10 per cent of the state’s total catch. Although such results are consistent with declining fishable biomass, this was initially inconsistent with very high levels of CPUE. However, there was a dramatic decline in CPUE in 2012, which suggests that the earlier high values were artificially high as a consequence of hyperstability, reflecting the aggregative behaviour of Snapper and the experience of fishers in the region 17. The suggestion of declining biomass through the mid- to late 2000s is consistent with the lack of recruitment of any strong year-classes to the population since 1999, as evident from population age structures. It is not clear whether the poor recent recruitment reflects recruitment overfishing or poor environmental conditions for recruitment. If recruitment remains poor, fishing mortality would cause further depletion of biomass. The biomass of this stock is not likely to be recruitment overfished, but the current level of fishing pressure is likely to cause the stock to become recruitment overfished.
Significant changes were made to management arrangements in 2012 and 2013, including an extension to the closed season, introduction of several spatial closures to protect key spawning aggregation sites, introduction of daily commercial catch limits and a further restriction on the number of commercial hooks that can be used on set lines. The influence of these changes will take some time to manifest.
On the basis of evidence provided above, the management unit is classified as a transitional–depleting stock.
West Coast Fishery (South Australia) management unit
The West Coast regional fishery has traditionally provided much lower catches than the gulf-based management units described above. Catches were relatively high through the mid- to late 2000s, as a result of substantial increases in longline fishing effort, reflecting the uptake of new longline fishing technology8. However, since 2003–04, longline CPUE has declined, indicating possible declining fishable biomass. However, no size and age data are available for this region, which limits understanding of recruitment patterns that could otherwise confirm a trend of declining biomass. Significant changes were made to management arrangements in 2012 and 2013, including an extension to the closed season and introduction of daily commercial catch limits. The influence of these changes will take some time to manifest. There is currently insufficient information available to confidently classify the status of this stock.
On the basis of the evidence provided above, the management unit is classified as an undefined stock.
South coast management unit (Western Australia)
With a total annual catch (all sectors) of only approximately 30–40 t taken from such a large geographic area, the stock is very unlikely to be recruitment overfished. However, the south coast management unit has not been formally assessed, and insufficient information is available to confidently classify its status.
On the basis of the evidence provided above, the management unit is classified as an undefined stock.
Shark Bay oceanic management unit (Western Australia)
The most recent model-based stock assessment (unpublished data from the Western Australian Department of Fisheries, 2014) indicated that spawning biomass in 2013 was just below 40 per cent of the unfished level, which is also the target level for this management unit. 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 by 2015–16. The above evidence indicates that the biomass of this stock is unlikely to be recruitment overfished.
The total allowable commercial catch was reduced in 2007 to 277 t to further assist stock rebuilding to the target level of 40 per cent of the unfished level.
Approximately 235 t of Snapper was caught in 2013, and the level of fishing mortality is likely to be promoting rebuilding of this stock. The above evidence indicates that the current level of fishing pressure is unlikely to cause the stock to become recruitment overfished.
On the basis of the evidence provided above, the management unit is classified as a sustainable stock.
Shark Bay inshore—eastern gulf biological stock (Western Australia)
The most recent model-based stock assessment (unpublished data from the Western Australian Department of Fisheries, 2011) 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 2013. As well, the recreational catch was likely to have been minor and within the target catch range (0–12 t). This level of fishing mortality 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.
Shark Bay inshore—Denham Sound biological stock (Western Australia)
The most recent model-based stock assessment (unpublished data from the Western Australian Department of Fisheries, 2011) 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 2013. The recreational catch was likely to have been minor and within the target catch range (0–12 t). This level of fishing mortality 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.
Shark Bay inshore—Freycinet Estuary biological stock (Western Australia)
The most recent model-based stock assessment (unpublished data from the Western Australian Department of Fisheries, 2011) 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 stock will continue to very slowly rebuild to around 25 per cent of the unfished biomass by 2015. The biological stock is considered to be recruitment overfished, based on the 30 per cent threshold.
There was no commercial catch of Snapper from the Freycinet Estuary biological stock in 2013. The recreational catch was assumed to have been within the target catch range (0–3.8 t) because of the conservative management regime that has been in place since 2003. This level of fishing mortality should allow the 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 management unit (Western Australia)
Assessments completed in 2007, 2009 and 2013 showed that the fishing mortality in the west coast management unit of Western Australia exceeded the limit reference point of 1.5 times natural mortality18–20. However, the most recent assessment indicated that fishing mortality had decreased, following the introduction of significant management changes, which provides evidence that recovery has begun. Based on agreed decision rules to decrease fishing mortality to a level that would allow the stock to recover, the total catch of Snapper by all sectors had to be reduced by at least 50 per cent—that is, to no more than 163 t. New management arrangements to achieve the required catch reductions have been successfully implemented for the commercial and recreational sectors. Although the current catch of Snapper by the West Coast Demersal Scalefish Interim Managed Fishery in this region has recently increased above the acceptable level of 120 t for the fishery, management action has been taken to reduce catch in 2015 to allow recovery to continue. The above evidence indicates that the stock is considered to be recruitment overfished but that the current level of fishing mortality should allow the stock to recover from its recruitment overfished state.
On the basis of the evidence provided above, the management unit is classified as a transitional–recovering stock.