Western King Prawn
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Stock Status Overview
|South Australia||Gulf St. Vincent Prawn Fishery||GSVPF||Transitional-depleting||Survey catch rates, catch effort|
|South Australia||Spencer Gulf Prawn Fishery||SGPF||Sustainable||Survey catch rates, catch|
|South Australia||West Coast Prawn Fishery||WCPF||Sustainable||Survey catch rates, catch|
- Gulf St Vincent Prawn Fishery (SA)
- Spencer Gulf Prawn Fishery (SA)
- West Coast Prawn Fishery (SA)
Western King Prawn is distributed throughout the Indo–West Pacific1. No research has been conducted into Western King Prawn biological stock structure in Western Australia or Queensland, and status in those states is therefore reported at the management unit level. In South Australia, one study of the genetic structure of Western King Prawn found no differences between the three fisheries2; however, each fishery functions as an independent population at time scales relevant to management, with distinct adult and juvenile habitats and independent variations in recruitment and abundance. Each fishery in South Australia is therefore assessed and managed as a separate management unit.
Here, assessment of stock status is presented at the management unit level—Shark Bay Prawn Managed Fishery, Exmouth Gulf Prawn Managed Fishery, North Coast Prawn Managed Fisheries, South West Trawl Managed Fishery (Western Australia); East Coast Otter Trawl Fishery (Queensland); Spencer Gulf Prawn Fishery, Gulf St. Vincent Prawn Fishery and West Coast Prawn Fishery (South Australia).
Spencer Gulf Prawn Fishery
While time series and spatial distribution of commercial catches are presented by calendar year, the stock status for South Australia’s Spencer Gulf Prawn Fishery and Gulf St Vincent Prawn Fishery management units refer to the 2014–15 financial year as it more closely aligns with the fishing seasons for those fisheries (October–June or September).
The primary measure for stock status in Spencer Gulf is the weighted average catch rate of adult prawns (defined as 20 or fewer prawns per pound), used as an index of relative biomass, obtained during fishery-independent surveys conducted yearly in November, February and April16. This index is evaluated against limit and trigger reference points of 48 and 68 kg per hour, respectively, where the trigger reference point is considered to be the minimum catch rate at which future recruitment to the fishery will be adequate (that is, the level that delineates a stock status classification of sustainable from transitional).
Mean catch rates of adult prawns for surveys in November 2014 and February and April 2015 were 85, 78 and 104 kg per hour, respectively, while those for ‘newly-recruited’ prawns (more than 20 prawns per pound) were 26, 57 and 67 kg per hour, respectively. The weighted average catch rate of 91 kg per hour for adult prawns was above the limit and trigger reference points. The above evidence indicates that the biomass of this stock is unlikely to be recruitment overfished.
The fishery has shown a long history of stable recruitment and commercial catch (generally between 1600 and 2400 t). In 2015, the total catch of 1616 t was below the long-term (2006–14) average (1908 t), while effort, at 1972 vessel nights was virtually the same as the long-term average (1973 vessel nights). The above evidence indicates that the current level of fishing mortality is unlikely to cause the management unit to become recruitment overfished.
On the basis of the evidence provided above, the Spencer Gulf Prawn Fishery (South Australia) management unit is classified as a sustainable stock.
Gulf St. Vincent Prawn Fishery
The Gulf St. Vincent Prawn Fishery has undergone considerable management changes in the past decade. Two significant changes were implemented in the fishery during the 2011–12 season: 1) the number of surveys conducted during the fishing season were reduced from four–two (in April and May); and 2) from March 2012, all trawl nets used for commercial fishing were required to have T90-mesh codends and grids to facilitate the escapement of small prawns and reduce the level of non-prawn bycatch. The fishery was closed in 2012–13 and 2013–14, primarily due to consecutive years of poor financial returns, so no survey results were available for 2013. Along with low mean survey catch rates in 2012, consecutive declines in annual catch to the lowest since the fishery was closed in 1991–92 and 1992–93 indicated that, while the biomass was not considered to be recruitment overfished, fishing pressure was moving the stock in the direction of becoming recruitment overfished. In May 2014 a spatially reduced survey was conducted. The fishery was subsequently re-opened under an interim management framework including individually transferable effort in the form of transferable fishing nights.
The primary measures for stock status in Gulf St. Vincent are the average catch rates obtained during fishery-independent surveys and catch rates from fishery-dependent data. This assessment is based on data from the 2014–15 season, which extended from 1 November 2014–31 July 201517.
Fishing was conducted over 294 vessel nights in 2014–15 with 50 vessel nights fished during the early spawning period (November–December)—the latter representing a substantial increase in effort compared to the 24 vessel nights fished in 2011–12. The total commercial catch of 249.4 t in 2014–15 was almost double that in 2011–12 (125.0 t) and among the highest in recent years. Harvest during the early spawning period (November–December) was 57.1 t in 2014–15; this represented 22.6 per cent of the total annual catch and was the largest catch during early spawning since 2002–03 (64 t).
The most recent survey was conducted in May 2015, where the mean nominal catch rate was 60.4 kg per hour. This represented a significant increase compared to before the fishery closure following the May 2012 survey (43.5 kg per hour), but remained below levels seen from 2006–07 to 2009–10 (range 71.1–83.3 kg per hour). The annual nominal commercial CPUE in 2014–15 was 85.9 kg per hour. This was 67 per cent higher than 2011–12 (51.5 kg per hour) and the highest since 2009–10 (95.5 kg per hour). In contrast, the recruitment index (recruits per hour, estimated from a 7 kg subsample per shot) declined by 55 per cent from 681 recruits per hour in 2012 to 306 recruits per hour in 2015. This was the lowest value on record, but above the recruitment limit reference point (250 recruits per hour). The management response to low recruitment values during the May 2015 survey was to reduce the number of nights available for fishing during November and December 2015 to 30 vessel nights, which aims to protect the spawning biomass and future recruitment into the fishery. The above evidence indicates that the biomass of this stock is unlikely to be recruitment overfished, but that recruitment appears to be declining.
This evidence indicates that the current level of fishing pressure may cause the stock to become recruitment overfished.
On the basis of the evidence provided above, the Gulf St. Vincent Prawn Fishery (South Australia) management unit is classified as a transitional–depleting stock.
West Coast Prawn Fishery
The West Coast Prawn Fishery (South Australia) harvests from an oceanic stock that shows large fluctuations in recruitment, thought to be environmentally-driven, and consequently in commercial catch. The primary measures for stock status on the west coast are the total commercial catch and the annual average catch rate from fishery-independent surveys (conducted annually in March, June and November), which are used as an indicator of relative biomass.
The fishery appeared to experience a prolonged period of stock depletion from 2002 until it was closed in 2006. During this period, survey catch rates remained below 30 kg per hour and annual commercial catch below 42 t. However, both commercial catch and survey catch rates indicate that the stock has rebuilt and the fishery has been in a relatively strong position since 201118. During the 2015 season (calendar year), the commercial catch of 191 t was 31 per cent greater than 2014 and the highest catch since 1996 (216 t). The annual commercial catch rate was 102 kg per hour in 2015 and this was the highest on record. The mean survey catch rate in 2015 of 85 kg per hour was 26 per cent higher than 2014 and the highest on record. The above evidence indicates that the biomass is unlikely to be recruitment overfished and that the current level of fishing pressure is unlikely to cause the management unit to become recruitment overfished.
On the basis of the evidence provided above, the West Coast Prawn Fishery (South Australia) management unit is classified as a sustainable stock.
Western King Prawn biology8,19,20
|Species||Longevity / Maximum Size||Maturity (50 per cent)|
|Western King Prawn||2–3 years, maximum 4 years South Australia: males 46 mm CL, females 57 mm CL Western Australia: males 45 mm CL, females 60 mm CL||6–7 months; 25 mm CL|
Distribution of reported commercial catch of Western King Prawn
|10 in GSVPF, 39 in SGPF, 3 in WCPF|
- Gulf St Vincent Prawn Fishery (SA)
- Spencer Gulf Prawn Fishery (SA)
- West Coast Prawn Fishery (SA)
|Commercial||212.42t in GSVPF, 1.62Kt in SGPF|
- Gulf St Vincent Prawn Fishery (SA)
- Spencer Gulf Prawn Fishery (SA)
a Queensland - Indigenous In Queensland, under the Fisheries Act 1994 (Qld), Indigenous fishers in Queensland are able 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.
Commercial catch of Western King Prawn
Effects of fishing on the marine environment
- In 2011, the Spencer Gulf Prawn Fishery (South Australia) became the first prawn fishery in the South Pacific to become accredited by the Marine Stewardship Council (MSC). Accreditation by the MSC has been maintained since. The Shark Bay and Exmouth Gulf prawn fisheries (Western Australia) were both accredited by MSC in October 2015.
- Fishing for Western King Prawns in Western Australia, Queensland and South Australia is considered to be of low risk to the trophic structures in the ecosystems in which the fisheries operate. Although harvest rates may be relatively high, Western King Prawn have very high natural mortality rates and make up only a small proportion of the total biomass on the trawl grounds. Predators of prawns need to be opportunistic because of the natural variations in prawn populations. Consequently, given the small areas and short periods now fished, it is considered unlikely that the commercial take of prawns impacts significantly on other trophic levels4,8,12. An assessment of trawl-related risk to trophic structures was not explicitly assessed for the East Coast Otter Trawl Fishery (Queensland) (ECOTF), but in the Great Barrier Reef Marine Park (GBRMP). It found that there is no more than an intermediate risk of overfishing species assemblages exposed to trawling14.
- Although trawling can impact on habitats, these effects are managed in the Western King Prawn fisheries in Western Australia, Queensland and South Australia. In Western Australia, extensive permanent and temporary closures result in the fleet operating in only seven per cent of the Shark Bay fishery region and 17 per cent of inner Shark Bay, generally less than 30 per cent of the Exmouth Gulf, and less than three per cent of the north coast region. Fishing operations are restricted to areas of sand and mud, where trawling has minimal long-term physical impact4,8,12,21,22. In Queensland, the GBRMP occupies 63 per cent of the ECOTF23, 34 per cent of which is open to trawling24, but effort is highly aggregated, occurring within only a small fraction of the open area. South of the GBRMP, the fishery operates in only 10 per cent of the area open to trawling25. In South Australia, trawl effort has decreased by more than 60 per cent from its historical peaks in all fisheries. Since the inception of the South Australian fisheries, permanent closures have included all waters less than 10 m to ensure protection of seagrass habitats16.
- Although the incidental capture of by-product and bycatch species by trawling can lead to a range of indirect ecosystem effects26, studies in Western Australia, Queensland and South Australia found no significant difference in biodiversity or overall distribution patterns of seabed biota between trawled and non-trawled areas15,21,22,27. The spatial contraction and/or temporal reduction in effort in all three jurisdictions are likely to have mitigated somewhat the ecosystem impacts of trawling.
- The use of bycatch reduction devices (BRDs) in prawn trawling can significantly reduce bycatch—by more than 50 per cent by weight in some fisheries28,29. All prawn trawlers operating in Western Australia must use BRDs, including turtle excluder devices (TEDs), secondary fish exclusion devices and hoppers to increase survival of returned fish. The introduction of TEDs in the Western Australian prawn trawl fisheries in 2003 reduced turtle bycatch by at least 95 per cent30. In the ECOTF, the use of BRDs became mandatory in 1999, and the introduction of TEDs in 2001 largely eliminated capture of most large bycatch species, including turtles, sharks and rays31. More recently, commitment to continuous improvement in bycatch mitigation has facilitated increased use of best practice TEDs and BRDs in the ECOTF. Reduced impact of trawling and a general absence of high risk of overfishing bycatch species have been acknowledged in recent ecological risk assessments of the fishery14. In South Australia, all vessels use crab bags, and 49 of the 52 vessels use hopper systems to ensure rapid return of bycatch to the water. The Spencer Gulf, Shark Bay Prawn Managed Fishery and the Exmouth Gulf Prawn Managed Fishery MSC certifications include the assessment of broad environmental impacts and are important evidence for low risk of trawling impacts. In the Gulf St. Vincent Prawn Fishery (South Australia), all 10 vessels use T90-mesh codends with rigid grids that substantially reduce bycatch volumes32.
Environmental effects on Western King Prawn
- Major extreme weather events associated with the recent protracted La Niña episode33 are thought to have influenced recent recruitment patterns and depressed catches of a number of oceanic fishery species in Queensland, including Western King Prawn in 2011. Management of Western King Prawn and other species in the East Coast Otter Trawl Fishery (Queensland) management unit will benefit from knowledge gained from current research into the interrelationships among physical oceanographic features (for example, sea surface temperature anomalies), catch rates, biological parameters, and the spatial distribution of Saucer Scallop, a co-occurring species in Queensland and Western Australian trawl fisheries.
- Water temperature has been shown to effect the recruitment of Western King Prawns in Western Australia, with elevated water temperatures in Exmouth Gulf since 2011 contributing to lower than average recruitment levels11.
- In South Australia, there is some evidence to suggest that strong El Niño conditions result in unfavorable upwelling in critical spawning grounds, which may result in recruitment failure, particularly in the West Coast Prawn Fishery (South Australia) management unit34.
- 1 Grey, DL, Dall, W and Baker, A 1983, A Guide to the Australian Penaeid Prawns, Northern Territory Department of Primary Production, Darwin.
- 2 Carrick, NA 2003, Spencer Gulf Prawn (Melicertus latisulcatus) Fishery, Fishery Assessment Report to Primary Industries and Regions South Australia Fisheries, South Australian Research and Development Institute publication RD03/0079-2, SARDI Research Report Series 161, SARDI, Adelaide.
- 3 Wise, BS, ST John, J and Lenanton, R 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. Report to the FRDC on Project No. 2003/052. Fisheries Research Report No. 163. Department of Fisheries, WA, 130 pp.
- 4 Fletcher, WJ (ed.) 2016, State of the Fisheries and Aquatic Resources Report 2016/15, Western Australian Department of Fisheries, Perth.
- 5 Penn, JW 1984, The behaviour and catchability of some commercially exploited penaeids and their relationship to stock and recruitment, in: Gulland, JA and Rothschild, BJ (eds.), Penaeid shrimps – their biology and management, Fishing News Books Ltd, Farnham, pp. 173-186.
- 6 Penn, JW and Caputi, N 1986, Spawning stock-recruitment relationships and environmental influences on the brown tiger prawn (Penaeus esculentus) fishery in Exmouth Gulf, Western Australia. Australian Journal of Marine and Freshwater Research 37: 491-505.
- 7 Caputi, N, Penn, JW, Joll, LM and Chubb, CF 1998, Stock-recruitment-environment relationships for invertebrate species of Western Australia. Can. Spec. Publ. Fish. Aquat. Sci. 125: 247-255.
- 8 Kangas, MI, Sporer, EC, Hesp, SA, Travaille, KL, Brand-Gardner, SJ, Cavalli, P and Harry, AV 2015, Shark Bay Prawn Managed Fishery, Western Australian Marine Stewardship Council Report Series 2: 294 pp.
- 9 Caputi , N, de Lestang, S, Hart, A, Kangas, M, Johnston, D, and Penn, J 2014, Catch predictions in stock assessment and management of invertebrate fisheries using pre-recruit abundance—case studies from Western Australia, Reviews in Fisheries Science and Aquaculture, 22:1, 36-54.
- 10 DoF 2014, Shark Bay Prawn Managed Fishery Harvest Strategy 2014 – 2019. Fisheries Management Paper No. 267. Department of Fisheries, WA.
- 11 Caputi, N, Feng, M, Pearce, A, Benthuysen, J, Denham, A, Hetzel, Y, Matear, R, Jackson, G, Molony, B, Joll, L and Chandrapavan, A 2014, Management implications of climate change effect on fisheries in Western Australia: Part 1, final report, Fisheries Research and Development Corporation, project 2010/535, Fisheries Research Report, Western Australian Department of Fisheries.
- 12 Kangas, MI, Sporer, EC, Hesp, SA, Travaille, KL, Moore, N, Cavalli, P and Fisher, EA 2015, Exmouth Gulf Prawn Managed Fishery, Western Australian Marine Stewardship Council Report Series 1: 273 pp.
- 13 DoF. 2014, Exmouth Gulf Prawn Managed Fishery Harvest Strategy 2014 – 2019. Fisheries Management Paper No. 265. Department of Fisheries.
- 14 Pears, RJ, Morison, AK, Jebreen, EJ, Dunning, MC, Pitcher, CR, Courtney, AJ, Houlden, B and Jacobsen, IP 2012, Ecological risk assessment of the East Coast Otter Trawl Fishery in the Great Barrier Reef Marine Park: technical report, Great Barrier Reef Marine Park Authority, Townsville.
- 15 Pitcher, CR, Doherty, P, Arnold, P, Hooper, J, Gribble, N, Bartlett, C, Browne, M, Campbell, N, Cannard, T, Cappo, M, Carini, G, Chalmers, S, Cheers, S, Chetwynd, D, Colefax, A, Coles, R, Cook, S, Davie, P, De’ath, G, Devereux, D, Done, B, Donovan, T, Ehrke, B, Ellis, N, Ericson, G, Fellegara, I, Forcey, K, Furey, M, Gledhill, D, Good, N, Gordon, S, Haywood, M, Jacobsen, I, Johnson, J, Jones, M, Kinninmoth, S, Kistle, S, Last, P, Leite, A, Marks, S, McLeod, I, Oczkowicz, S, Rose, C, Seabright, D, Sheils, J, Sherlock, M, Skelton, P, Smith, D, Smith, G, Speare, P, Stowar, M, Strickland, C, Sutcliffe, P, Van der Geest, C, Venables, W, Walsh, C, Wassenberg, T, Welna, A and Yearsley, G 2007, Seabed biodiversity on the continental shelf of the Great Barrier Reef World Heritage Area, Australian Institute of Marine Science, CSIRO, Queensland Museum, Queensland Department of Primary Industries and CRC Reef Research Centre, task final report, CSIRO Marine and Atmospheric Research.
- 16 PIRSA 2014, Management Plan for the South Australian Commercial Spencer Gulf Prawn Fishery, South Australian Fisheries Management Series, no. 67, Primary Industries and Regions South Australia, Adelaide.
- 17 Beckmann, CL, Noell, CJ and Hooper, GE 2015, Status of the Gulf St Vincent Prawn Penaeus (Melicertus) latisulcatus Fishery in 2014/15. Fishery Status Report to PIRSA Fisheries and Aquaculture. South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2007/00174-4. SARDI Research Report Series No. 870. 25pp.
- 18 Beckmann, CL and Hooper, GE 2016, Status of the West Coast Prawn Penaeus (Melicertus) latisulcatus Fishery in 2015. Fishery Status Report to PIRSA Fisheries and Aquaculture. South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2007/000772-8. SARDI Research Report Series No. 906. 33pp.
- 19 Penn, JW 1980, Spawning and fecundity of the western king prawn, Penaeus latisulcatus, Kishinouye, in Western Australian waters, Australian Journal of Marine and Freshwater Research 31: 21-35.
- 20 Noell, CJ and Hooper, 2015, Spencer Gulf Prawn Penaeus (Melicertus) latisulcatus Fishery 2013/14, Fishery Assessment Report to PIRSA Fisheries and Aquaculture, South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2007/000770-8. SARDI Research Report Series No. 843. 68pp.
- 21 Kangas, M, Morrison, S, Unsworth, P, Lai, E, Wright, I and Thomson, A 2007, Development of biodiversity and habitat monitoring systems for key trawl fisheries in Western Australia, final report, Fisheries Research and Development Corporation, project 2002/038, Fisheries Research Report 160, Fisheries Western Australia, North Beach.
- 22 Kangas, M, and Morrison, S 2013, Trawl impacts and biodiversity management in Shark Bay, Western Australia, Marine and Freshwater Research, 64: 1135–1155.
- 23 Huber, D 2003, Audit of the management of the Queensland East Coast Trawl Fishery in the Great Barrier Reef Marine Park, Great Barrier Reef Marine Park Authority, Townsville, www.gbrmpa.gov.au/__data/assets/pdf_file/0012/4080/Huber-2003.pdf.
- 24 Queensland Department of Agriculture, Fisheries and Forestry 2014, Queensland Stock Status Assessment Workshop 2014, 5–6 June 2014, Brisbane, Queensland DAFF, Brisbane.
- 25 Coles, R, Grech, A, Dew, K, Zeller, B and McKenzie, L 2008, A preliminary report on the adequacy of protection provided to species and benthic habitats in the East Coast Otter Trawl Fishery by the current system of closures, Queensland Department of Primary Industries and Fisheries, Brisbane.
- 26 Dayton, PK, Thrush, SF, Agardy, MT and Hofman, RJ 1995, Environmental effects of fishing, Aquatic Conservation: Marine and Freshwater Ecosystems, 5: 205–232.
- 27 Currie, DR, Dixon, CD, Roberts, SD, Hooper, GE, Sorokin, SJ and Ward, TM 2009, Fishery-independent by-catch survey to inform risk assessment of the Spencer Gulf Prawn Trawl Fishery, report to Primary Industries and Regions (Fisheries), South Australian Research and Development Institute (Aquatic Sciences), Adelaide.
- 28 Brewer, D, Rawlinson, N, Eayrs, S and Burridge, C, 1998, An assessment of bycatch reduction devices in a tropical Australian prawn trawl fishery, Fisheries Research, 36:195–215.
- 29 Kennelly, SJ and Broadhurst, MK 2014, Mitigating the bycatch of giant cuttlefish Sepia apama and blue swimmer crabs Portunus armatus in an Australian penaeid-trawl fishery, Endangered Species Research, 26:161–166.
- 30 Kangas, MI and Thomson, A 2004, Implementation and assessment of bycatch reduction devices in the Shark Bay and Exmouth Gulf trawl fisheries, final report, Fisheries Research and Development Corporation, project 2000/189, Western Australian Department of Fisheries, Perth. .
- 31 Roy, D and Jebreen, E 2011, Extension of Fisheries Research and Development Corporation funded research results on improved bycatch reduction devices to the Queensland East Coast Otter Trawl Fishery, final report to the Fisheries Research and Development Corporation, project 2008/101, FRDC, Canberra, .
- 32 Dixon, C, Raptis, J, Gorman, D, Roberts, S, Hooper, G, Bicknell, N, Sorokin, S, Newman, R, Noell, C, Benediktsson, T, Saint, J and Hill, W 2013, A collaborative approach to novel by-catch research for rapid development, extension and adoption into a commercial trawl fishery, final report to the Fisheries Research and Development Corporation, project 2009/069, South Australian Research and Development Institute (Aquatic Sciences) publication F2012/000250-1, SARDI research report series 643, SARDI, Adelaide.
- 33 Bureau of Meteorology 2012, Record-breaking La Nĩna events. An analysis of the La Nĩna life cycle and the impacts and significance of the 2010–11 and 2011–12 La Nĩna events in Australia, Bureau of Meteorology, Melbourne.
- 34 Carrick, N 2008, Determining the impact of environmental variability on the sustainability, fishery dynamics and economic performance of the West Coast Prawn Fishery, final report, Fisheries Research and Development Corporation project 2005/082, FRDC and Fisheries and Environmental Consulting Services, Canberra.