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Stock Status Overview
|South Australia||Gulf St. Vincent||MSF||Sustainable||Catch, CPUE, age structures, biomass|
|South Australia||Spencer Gulf/West Coast||MSF||Transitional-depleting||Catch, CPUE, age structures, biomass|
|South Australia||Western Victoria||MSF||Sustainable||Catch, CPUE , pre-recruit surveys, age and length composition|
- Marine Scalefish Fishery (SA)
Snapper has a wide distribution in Australia, from the Gascoyne region on the west coast of Western Australia, around the south of the continent, and up to northern Queensland, around Hinchinbrook Island1. Within this broad distribution, the biological stock structure is complex.
Snapper on the east coast of Australia, from Proserpine in north Queensland to around Wilsons Promontory (Victoria), show little genetic differentiation and are considered to represent a single genetic stock2. Similarly, in Victoria, little genetic variation has been found for Snapper3. However, tagging and otolith chemistry data have indicated some separation between Snapper to the east of Wilsons Promontory (the East coast biological stock) and to the west, including Port Phillip Bay and Western Port (Western Victorian biological stock) and extending across western Victoria to near the Murray mouth in South Australia4–6.
Despite the separation of the Eastern and Western stocks in Victorian waters, Snapper are managed at a state-wide level in Victoria, with management arrangements that govern commercial fishing in specific regions such as bays and inlets, and offshore waters. Bag and size limits for the recreational sector are the same for the Western and Eastern stocks in Victorian waters. Recent changes to commercial fishing in Port Phillip Bay (Western stock) have resulted in removal of most of the fishing effort by net methods, and capping of catches for the remaining hook method operators. The Eastern stock, from Victoria to Queensland, is managed at a state level.
Further research has been undertaken to inform the level of stock sharing between Victoria and South Australia.
The South Australian fishery was originally divided into six management units, due to uncertainty about the extent of the movement of fish between different regional populations7. However, a recent study evaluated the stock structure and adult movement between regional populations of South Australia and western Victoria8 based on inter-regional comparisons of otolith chemistry and increment widths, as well as demographic features. The study differentiated three stocks. The Western Victorian stock extends from Wilsons Promontory westward into south-eastern South Australia. This stock depends on recruitment into, and subsequent emigration from, Port Phillip Bay in Victoria. As such, this is a cross-jurisdictional stock, although the components from the two states are still assessed and managed independently. The two further stocks are wholly located within South Australia. The Spencer Gulf/West Coast stock depends on recruitment into Northern Spencer Gulf from where fish emigrate to replenish the populations of Southern Spencer Gulf and the west coast of Eyre Peninsula. The third stock is the Gulf St. Vincent stock, which relies on recruitment into, and subsequent emigration from, Northern Gulf St. Vincent.
In Western Australia, Snapper is divided into six management units, some at small geographic scales (for example, there are three separate biological stocks located inside Shark Bay) and others that cover greater areas of oceanic waters in the Gascoyne, west and south coast regions9–13. The inshore Shark Bay biological stocks in the inner gulfs are predominantly fished by the recreational and charter sectors.
Here, assessment of stock status is presented at the biological stock level—Shark Bay inshore–Eastern Gulf, Shark Bay inshore–Denham Sound, Shark Bay inshore–Freycinet Estuary (Western Australia); East coast, Western Victorian, Spencer Gulf West Coast (South Australia) and Gulf St Vincent Fishery (South Australia); and the management unit level—South coast, Shark Bay oceanic and West coast (Western Australia).
The main indicators used for assessment of the Western Victorian biological stock are catch per unit effort (CPUE) from the commercial and recreational sectors, fishery-independent annual surveys of pre-recruit (young-of-the-year) catch rates in Port Phillip Bay (the main spawning and nursery area for the Western stock)4, and age and length composition of catches taken by the recreational and commercial sectors.
The most recent stock assessment was in 201625. This assessment indicated that the stock was in good condition. Commercial longline catch rates of adult Snapper in the main fishery of Port Phillip Bay have declined since the recent peak in 2011–12, but remain well above the long-term average since 1978. The recent decline in the longline catch rate was consistent with a decline in recreational catch rate evident in creel survey and diary angler data. This decline was expected as the two dominant year classes in the adult component of the fishery (birth years 2001 and 2004) are now depleted beyond their peak biomass. The catch rates in the haul seine fishery, which catches sub-adults, had a recent peak in 2011–14, consistent with recruitment of the three moderate year classes detected by the 2008, 2009 and 2010 Port Phillip Bay pre-recruit surveys. These sub-adults will enter the fishery over the next 3 years, which is expected to increase catch rates. Effort has remained relatively stable for both longline and haul seine gear types, which account for most of the commercial catch. Recent pre-recruit surveys in Port Phillip Bay have shown above-average (24-year time series) recruitment for the 2013 and 2014 year classes, but very poor recruitment for 2015 and 2016.
The productivity of the Western Victorian biological stock has declined since the peak in 2011–12, and may decline further over the coming 1–2 years until the 2008, 2009 and 2010 year classes fully recruit to the adult fishery. Recent strong year classes observed in pre-recruit surveys in 2013 and 2014 will further bolster the fishery in 6–7 years’ time. Commercial catches by Victorian licensed operators will, however, decline from 2016 onwards due to removal of most netting effort from Port Phillip Bay and capping of the catches by remaining longline operators. Nonetheless, continued above-average catch rates of both sub-adult and adult Snapper, particularly in the Port Phillip Bay Fishery, and the recent strong recruitment of juvenile Snapper suggests that the Western Victorian biological stock is not recruitment overfished and 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 Western Victorian biological stock is classified as a sustainable stock.
Spencer Gulf/West Coast
The Spencer Gulf/West Coast (South Australia) (SG/WC) stock involves three regions that were previously described as management units: Northern Spencer Gulf (NSG), Southern Spencer Gulf (SSG) and the west coast of Eyre Peninsula (WC)8. The NSG supports the primary nursery area for the stock and is a self-replenishing region. Replenishment of the other two regions depends, to some extent, on emigration of fish from NSG. The 32-year time series of annual commercial fishery statistics from 1984–2015 provide significant fishery performance indicators for each of the three regional populations. The recent fisheries in each region are characterised by declining trends in total catch, targeted effort and targeted CPUE for the two primary gear types of handlines and longlines26. For NSG, the performance indicators all declined considerably in 2012, and have subsequently remained low. In SSG, total catch, targeted effort and CPUE have all shown declining trends since 2007. For the WC, the trends in commercial statistics have been downward, particularly between 2009 and 2015. Such decreasing trends across the component regional populations of the stock are consistent with declining biomass across the broad spatial scale.
South Australian Snapper populations are characterised by high inter-annual variability in recruitment, which results in strong and weak year classes that are manifested in the population age structures over numerous years7. The recent age structures from NSG show the lack of strong year classes since 199926, indicating that recruitment has been below average throughout the 2000s. This is particularly evident in SSG which relies on emigration of fish from strong year classes from NSG. As recruitment has been relatively low in the north, such emigration has been minimal, which is evident as weak year classes in the age structures throughout the 2000s.
While there is evidence that the biomass of the SG/WC stock is declining, it is not clear that the stock is recruitment overfished, even though recruitment has been below average through the 2000s. Low recent fishing effort in the three regions since 2012 indicates that exploitation rates have declined. Significant management changes were implemented for the recreational (including charter) and commercial sectors fisheries between 2012 and 20137 that were focussed on reducing commercial catch and increasing reproductive output and recruitment. They included: introduction of a daily commercial catch limit; a further restriction to the number of hooks that can be used on set lines; extension of the state-wide closed season for a further 2 weeks into mid-December; implementation of four spatial spawning closures throughout SG to protect key spawning aggregation sites. Benefits from these changes may take some time to be realised.
On the basis of the evidence provided above, the Spencer Gulf/West Coast (South Australia) biological stock is classified as a transitional–depleting stock.
Gulf St. Vincent
The Gulf St. Vincent Fishery (South Australia) biological stock involves two regions previously described as management units: Northern Gulf St. Vincent (NGSV) and Southern Gulf St. Vincent (SGSV). NGSV includes an important nursery area and supports a self-replenishing population8. SGSV has recently supported a much lower biomass than NGSV. This may reflect that it is at the boundary of the three South Australian stocks, and occasionally receives some emigration from those stocks, although apparently at relatively low levels.
In recent years, NGSV has provided the highest catches ever recorded from any regional Snapper population of South Australia26. Total catch increased from 66–417 t between 2007 and 2010 and has subsequently remained at record high levels. This related particularly to expansion of the commercial longline sector. Targeted effort, catch and CPUE increased to record levels to 2010, and have subsequently remained at these high levels. These results indicate that there has been a considerable increase in biomass since the early-2000s. There has also been adoption of new longline technology that increased the efficiency of the fishing activity. For SGSV, increasing trends in total catch and longline data were also evident, but the annual catch was an order of magnitude less than for NGSV (38 t in 2010) and the trends were not persistent. As such, there appears to have been a temporary increase in biomass in the region between 2009 and 2012.
The population age structures for NGSV help explain the substantial increase in biomass26. Numerous strong year classes recruited to this region throughout the 2000s, augmenting several strong year classes from the late-1990s. The high recent biomass relates to successful recruitment throughout the 2000s, indicating a differentiation from the Spencer Gulf/West Coast stock. Recent management changes implemented in 2012–13 for the recreational and commercial sectors are expected to control fishing pressure, to the extent that average recruitment levels in this region are maintained into the future. The evidence above indicates that the biomass of this stock is unlikely to be recruitment overfished and that the current level of fishing mortality is unlikely to cause the biomass to become recruitment overfished.
On the basis of the evidence provided above, the Gulf St. Vincent (South Australia) biological stock is classified as a sustainable stock.
|Species||Longevity / Maximum Size||Maturity (50 per cent)|
|Snapper||30–40 years; 1300 mm TL||2–7 years; 220–560 mm TL|
Distribution of reported commercial catch of Snapper
|Hand Line, Hand Reel or Powered Reels|
|Hand Line, Hand Reel or Powered Reels|
|Hand Line, Hand Reel or Powered Reels|
|187 in MSF|
- Marine Scalefish Fishery (SA)
|Commercial||505.78t in MSF|
|Recreational||332 t (2013–14)|
- Marine Scalefish Fishery (SA)
a Victoria – Indigenous In Victoria, regulations for managing recreational fishing are also applied to fishing activities by Indigenous people. Recognised Traditional Owners (groups that hold native title or have agreements under the Traditional Owner Settlement Act 2010 [Vic]) are exempt (subject to conditions) from the requirement to hold a recreational fishing licence, and can apply for permits under the Fisheries Act 1995 (Vic) that authorise customary fishing (for example, different catch and size limits, or equipment). The Indigenous category in Table 3 refers to customary fishing undertaken by recognised Traditional Owners. In 2012–13, there were no applications for customary permits to access Snapper.
b Queensland – Indigenous Under the Fisheries Act 1994 (Qld), Indigenous fishers in Queensland are entitled to use prescribed traditional and non-commercial fishing apparatus in waters open to fishing. Size and possession limits, and seasonal closures do not apply to Indigenous fishers. Further exemptions to fishery regulations may be applied for through permits.
c Western Australia – Recreational (management methods) In Western Australia, total recreational catch limits (that is, maximum catch limits) have been applied to stocks of Snapper in inner Shark Bay and the west coast, to aid recovery of stocks.
d New South Wales – Indigenous (management methods) Aboriginal fishing interim compliance policy (increased bag limits) – allows an Indigenous fisher in New South Wales to take in excess of a recreational bag limit in certain circumstances, for example, if they are doing so to provide fish to other community members who cannot harvest themselves.
e New South Wales – Indigenous (management methods) Aboriginal cultural fishing authority - the authority that Indigenous persons can apply to take catches outside the recreational limits under the Fisheries Management Act 1994 (NSW), Section 37 (1)(c1), Aboriginal cultural fishing authority.
Commercial catch of Snapper
Effects of fishing on the marine environment
- Most of the fisheries that target adult Snapper use hook and line fishing techniques, which are likely to have little direct impact on benthic habitats. To date, limited research on the effects of fish traps on the benthic environment in New South Wales suggests only a minor influence (unpublished data, Department of Primary Industries, New South Wales).
- Snapper are generalist feeders and normally just one of a number of such species inhabiting continental shelf waters. Effects on the food chain from fishing for Snapper are considered to be low risk. This is supported by a recent study which found no evidence of material changes in finfish community structure over the past 30 years in the three Western Australian Bioregions where Snapper are captured32.
Environmental effects on Snapper
- A recent Fisheries Research and Development Corporation project identified two potential significant effects of climate change on Snapper populations33. First, there is an optimal temperature range of 18–22°C for the production and survivorship of Snapper larvae. Furthermore, peak spawning times vary with latitude, resulting in peak production corresponding to the optimal temperature range. Warmer projected sea surface temperature regimes in the future will alter the timing and/or length of these optimal conditions for spawning and larval survivorship in different regions. This might restrict opportunities for successful spawning and recruitment in the northern fisheries, but provide enhanced opportunities for some southern fisheries, and the opportunity for establishing new populations and fisheries further south. Such environmental changes might also affect spawning and recruitment for the populations in South Australia’s gulfs and Port Phillip Bay, Victoria.
- The second possible effect of climate change on Snapper populations is greater variation in recruitment of fish aged 0+ years33. Such variable recruitment already accounts for the population dynamics and variation in fishery productivity for a number of Australia’s southern Snapper fisheries. Variation in recruitment is driven by the survivorship of the larvae. Larval survivorship depends on the overlap of the optimal temperature window with periods of high larval prey concentrations. The latter depends on nutrient input to marine environments. The effects of climate change on the dynamics of nutrient supply in Snapper spawning areas are difficult to predict because the sources of such nutrients vary from place to place. Furthermore, current understanding of nutrient supply and the dynamics of planktonic food chains is limited.
- 1 Kailola, PJ, Williams, MJ, Stewart, PC, Reichelt, RE, McNee, A and Grieve, C 1993, Australian fisheries resources, Bureau of Resource Sciences, Department of Primary Industries and Energy and Fisheries Research and Development Corporation, Canberra.
- 2 Sumpton, WD, Ovenden, JR, Keenan CP and Street, R 2008, Evidence for a stock discontinuity of Snapper (Pagrus auratus) on the east coast of Australia, Fisheries Research, 94(1): 92–98.
- 3 Meggs, LB and Austin CM 2003, Low allozyme variation in Snapper, Pagrus auratus, in Victoria, Australia, Fisheries Management and Ecology, 10: 155–162.
- 4 Donnellan, SC and McGlennon D 1996, Stock identification and discrimination in Snapper (Pagrus auratus) in southern Australia, final report to the Fisheries Research and Development Corporation, project 94/168, South Australian Research and Development Institute, Adelaide.
- 5 Hamer, PA, Acevedo, S, Jenkins, GP and Newman, A 2011, Connectivity of a large embayment and coastal fishery: spawning aggregations in one bay source local and broad-scale fishery replenishment, Journal of Fish Biology, 78: 1090–1109.
- 6 Sanders, MJ 1974, Tagging study indicates two stocks of Snapper (Chrysophrys auratus) off south east Australia, Australian Journal of Marine and Freshwater Research, 8: 371–374.
- 7 Fowler, AJ, McGarvey, R, Burch, P, Feenstra, JE, Jackson, WB and Lloyd MT 2013, Snapper (Chrysophrys auratus) fishery, Fishery assessment report to Primary Industries and Regions South Australia (Fisheries and Aquaculture), South Australian Research and Development Institute (Aquatic Sciences) publication F2007/000523-3, SARDI research report series 713, SARDI, Adelaide.
- 8 Fowler, AJ 2016, The influence of fish movement on regional fishery production and stock structure for South Australia’s Snapper (Chrysophrys auratus) fishery. Final Report to FRDC (Project No. 2012/020). 181 pp.
- 9 Edmonds, JS, Steckis, RA, Moran, MJ, Caputi, N and Morita, M 1999, Stock delineation of Pink Snapper Pagrus auratus and Tailor Pomatomus saltatrix from Western Australia by analysis of stable isotope and strontium/calcium ratios in otolith carbonate, Journal of Fish Biology, 55: 243–259.
- 10 Jackson G 2007, Fisheries biology and management of Pink Snapper, Pagrus auratus, in the inner gulfs of Shark Bay, Western Australia, PhD thesis, Murdoch University, Perth.
- 11 Johnson, MS, Creagh, S and Moran, M 1986, Genetic subdivision of stocks of Snapper, Chrysophrys unicolor, in Shark Bay, Western Australia, Australian Journal of Marine and Freshwater Research, 37: 337–345.
- 12 Lenanton, R, St John, J, Keay, I, Wakefield, C, Jackson, G, Wise, B and Gaughan, D (eds) 2009, Spatial scales of exploitation among populations of demersal scalefish: implications for management, part 2, Stock structure and biology of two indicator species, West Australian Dhufish (Glaucosoma hebraicum) and Pink Snapper (Pagrus auratus), in the West Coast Bioregion, Fisheries research report 174, Western Australian Department of Fisheries, Perth.
- 13 Moran, M, Burton, C and Jenke, J 2003, Long-term movement patterns of continental shelf and inner gulf Snapper (Pagrus auratus, Sparidae) from tagging in the Shark Bay region of Western Australia, Marine and Freshwater Research, 54: 913–922.
- 14 Fairclough, D, Johnson C and Lai, E 2009, West Coast Demersal Scalefish Fishery, in WJ Fletcher and K Santoro (eds) 2009, State of the fisheries report 2008/09, Western Australian Department of Fisheries, Perth.
- 15 Fairclough, DV, Molony, BW, Crisafulli, BM, Keay, IS, Hesp, SA and Marriott, RJ 2014, Status of demersal finfish stocks on the west coast of Australia, Fisheries research report 253, Western Australian Department of Fisheries, Perth.
- 16 Wise, BS, St John, J and Lenanton, RC (eds) 2007, Spatial scales of exploitation among populations of demersal scalefish: implications for management, part 1, Stock status of the key indicator species for the demersal scalefish fishery in the West Coast Bioregion, Fisheries research report 163, Western Australian Department of Fisheries, Perth.
- 17 Norriss, JV, Fisher, EA, Hesp, SA, Jackson, G, Coulson, PG, Leary, T and Thomson AW (in press) Status of inshore demersal scalefish stocks on the South Coast of Western Australia Fisheries Research Report, Western Australian Department of Fisheries, Perth.
- 18 Stewart, J, Hegarty, A, Young, C, Fowler, AM and Craig, J 2015, Status of Fisheries Resources in NSW 2013-14, NSW Department of Primary Industries, Mosman: 391pp.
- 19 West, L.D, Stark, KE, Murphy, JJ, Lyle JM and Doyle, FA 2015, Survey of recreational fishing in New South Wales and the ACT, 2013/14. Fisheries Final Report Series
- 20 Campbell, AB, O’Neill, MF, Sumpton, W, Kirkwood, J and Wesche, S 2009, Stock assessment summary of the Queensland Snapper fishery (Australia) and management strategies for improving sustainability, Queensland Department of Employment, Economic Development and Innovation, Brisbane.
- 21 Henry, GW and Lyle, JM 2003, The National Recreational and Indigenous Fishing Survey, Fisheries Research and Development Corporation project 99/158, Australian Government Department of Agriculture, Fisheries and Forestry, Canberra.
- 22 Queensland Department of Agriculture, Fisheries and Forestry 2016, Queensland Stock Status Assessment Workshop 2016, 14–15 June 2016, Brisbane, Queensland DAF, Brisbane.
- 23 Taylor, S, Webley, J and McInnes, K 2012, 2010-11 Statewide Recreational Fishing Survey, Queensland Department of Agriculture, Fisheries and Forestry, Brisbane.
- 24 Webley, J, McInnes, K, Teixeira, D, Lawson, A and Quinn, R 2015, 2013-14 Statewide Recreational Fishing Survey, Queensland Department of Agriculture and Fisheries, Brisbane.
- 25 Hamer, P and Conron, S 2016, Snapper stock assessment 2016, Fisheries Victoria Science Report Series 10, Fisheries Victoria, Queenscliff.
- 26 Fowler, AJ, McGarvey, R, Carroll, J, Feenstra, JE, Jackson, WB and Lloyd MT 2016, Snapper (Chrysophrys auratus) fishery, Fishery assessment report to Primary Industries and Regions South Australia (Fisheries and Aquaculture), South Australian Research and Development Institute (Aquatic Sciences) in preparation.
- 27 Coutin, PC, Cashmore, S and Sivakumuran, KP 2003, Assessment of the Snapper fishery in Victoria, Fisheries Research and Development Corporation final report, project 97/128, Victorian Department of Primary Industries, Melbourne.
- 28 Stewart, J, Rowling, K, Hegarty, AM and Nuttall, A 2010, Size and age at sexual maturity of Snapper (Pagrus auratus) in New South Wales 2008/09, Fisheries research report series 27, Industry and Investment New South Wales, Cronulla.
- 29 Wakefield, CB 2006, Latitudinal and temporal comparisons of the reproductive biology and growth of Snapper, Pagrus auratus, in Western Australia, PhD thesis, Murdoch University, Perth.
- 30 Ryan, KL, Morison, AK and Conron, S 2009, Evaluating methods of obtaining total catch estimates for individual Victorian bay and inlet recreational fisheries, Fisheries Research and Development Corporation final report 2003/047, Department of Primary Industries, Victoria
- 31 Giri, K, and Hall, K, 2015, South Australian Recreational Fishing Survey. Fisheries Victoria Internal report Series No. 62.
- 32 Hall, NG and Wise, BS 2011, Development of an ecosystem approach to the monitoring and management of Western Australian fisheries, Fisheries Research and Development Corporation report 2005/063, Fisheries research report 215, Western Australian Department of Fisheries, Perth.
- 33 Pecl, G, Ward, T, Briceno, F, Fowler, A, Frusher, S, Gardner, C, Hamer, P, Hartmann, K, Hartog, J, Hobday, A, Hoshino, E, Jennings, S, Le Bouhellec, B, Linnane, A, Marzloff, M, Mayfield, S, Mundy, C, Ogier, E, Sullivan, A, Tracey, S, Tuck, G and Wayte, S 2014, Preparing fisheries for climate change: identifying adaptation options for four key fisheries in south eastern Australia, draft final report to the Fisheries Research and Development Corporation, project 2011/039.