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Ballot's Saucer Scallop

Ylistrum balloti

  • Mervi Kangas (Department of Fisheries, Western Australia)
  • Brad Zeller (Department of Agriculture and Fisheries, Queensland)

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Stock Status Overview

Stock status determination
Jurisdiction Stock Fisheries Stock status Indicators
Western Australia Abrohlos Island and Mid-West Trawl managed Fishery AIMWTMF Environmentally limited Recruitment surveys, catch rate, catch
Western Australia Shark Bay Scallop Managed Fishery SBSCMF Transitional-recovering Recruitment surveys, catch
Western Australia South Coast Trawl Fishery SCTF Sustainable Catch
Western Australia South West Trawl Managed Fishery SWTMF Sustainable Catch
AIMWTMF
Abrolhos Islands and Mid West Trawl Managed Fishery (WA)
SBSCMF
Shark Bay Scallop Managed Fishery (WA)
SCTF
South Coast Trawl Fishery (Condition) (WA)
SWTMF
South West Trawl Managed Fishery (WA)
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Stock Structure

Ballot’s Saucer Scallops in Australian waters are now classified as Ylistrum balloti (formerly Amusium balloti) following a recent revision of the genus Amusium1. This species is distributed from Esperance in Western Australia, across the tropics, to the southern coast of New South Wales. Ballot’s Saucer Scallops occur along most of the coast of Western Australia, but given the vast length of this coastline and the potential for regional differences in recruitment, four functionally independent management units have been established in this jurisdiction.

The eastern Australian stock stretches from Innisfail in Queensland to Jervis Bay in New South Wales. No fishery for Ballot’s Saucer Scallop exists in New South Wales waters. The stock classification presented here is based on information from the commercial fishery in central and southern Queensland (latitude 22°–27° south).

Here, assessment of stock status is presented at the management unit level—Shark Bay Scallop Managed Fishery, Abrolhos Islands and Mid-West Trawl Managed Fishery, South West Trawl Managed Fishery and South Coast Trawl Fishery for Western Australia; and East Coast Otter Trawl Fishery for Queensland.

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Stock Status

Shark Bay Scallop Managed Fishery

The Shark Bay Scallop Managed Fishery (Western Australia) management unit is currently in a recovery phase. A trial quota system with a conservative total allowable commercial catch (TACC) and target ranges for resumption of fishing was implemented in 2015 to provide protection for the breeding stock and aid in recovery. Management measures in 2015 included a ban on Ballot’s Saucer Scallop harvest from northern Shark Bay (to provide full protection for the breeding stock) and a conservative 100 tonnes (t) (meat weight) TACC in Denham Sound2 (which is regarded as a separate stock from that in the northern Shark Bay). In 2015, a total of 57.6 t meat weight (288 t whole weight) was landed.

Fishery-independent recruitment surveys are conducted each year on this management unit, using well-established methodology3–5. Catch predictions for 2015 for the two separate stocks are derived from the correlation of the annual landed catch (meat weight) and the mean catch rate (number per nautical mile trawled) of recruit (0+) and residual (1+) scallops for standard survey sites for each area sampled in November 2014. The predictions were very low for northern Shark Bay (40 t meat weight, below the target of 100 t) and moderate for Denham Sound (175 t meat weight, above the 50 t target). The estimated spawning biomass in northern Shark Bay remains at record low levels, but recruitment of 0+ Ballot’s Saucer Scallops has increased.

Prior to implementation of these management measures, the stock biomass within this management unit had fallen to a level where there was a significant risk of recruitment failure. The stock has fully recovered in Denham Sound and appears to be recovering slowly in northern Shark Bay. The current low stock biomass seems to be the result of a series of poor recruitment events associated with protracted unfavourable environmental conditions dating back to a marine heat wave that began in late 20106,7. Fisheries management has responded to this environmentally driven decline in productivity with a complete cessation of fishing (for 3 years) until fishery-independent surveys have indicated potential for a modest harvest.

On the basis of the evidence provided above, Denham Sound has fully recovered and northern Shark Bay is in transitional recovery; therefore, the Shark Bay Scallop Managed Fishery (Western Australia) management unit is classified as a transitional–recovering stock.

Abrohlos Island and Mid-West Trawl managed Fishery

The Abrolhos Islands and Mid-West Trawl Managed Fishery (Western Australia) management unit is managed under an escapement policy. The impact on the spawning biomass is limited by fishing after the peak spawning period; setting the duration of fishing according to catch predictions (based on pre-season surveys); closing the fishery at a minimum catch rate threshold (250 kg meat weight per day); and by not opening sections of the fishery if Ballot’s Saucer Scallop abundance is considered too low (below a specified target)2.

Annual pre-season surveys have shown very low recruitment since 2011, and the fishery has been closed since 2012. The predicted catch for 2015 was below the target range (95 t meat weight), with minimal recovery in the southern part of the fishery, and the fishery remained closed. It may take several years of favourable conditions for the stock to recover. Research to assess the feasibility of supplementation measures such as translocation and/or the release of hatchery-produced spat (to aid in rebuilding the spawning biomass) continues.

Stock biomass within this management unit has fallen to a level where there is a significant risk of recruitment failure. Research surveys in 2015 indicated low Ballot’s Saucer Scallop abundance, with catch predictions below the target level for resumption of fishing. The current low stock biomass is not due to overfishing or lack of appropriate fisheries management; it is the result of a series of poor recruitment events associated with sustained unfavourable environmental conditions dating back to the marine heat wave that began in late 20106,7. The fishery has now been closed for five years to provide maximum protection to all remaining stock. Fisheries management has responded appropriately to the environmental change in productivity with a complete cessation of fishing since June 2011.

On the basis of the evidence provided above, the Abrolhos Islands and Mid-West Trawl Managed Fishery (Western Australia) management unit is classified as an environmentally limited stock.

South West Trawl Managed Fishery

The South West Trawl Managed Fishery (Western Australia) (SWTMF) management unit is a comparatively small, low-activity fishery in which effort has been related to either the abundance of Western King Prawn or Ballot’s Saucer Scallop in any given year, which can be highly variable due to sporadic scallop recruitment. Only two to four vessels have operated in the fishery since 2005, and they have only covered approximately one to three per cent of the allowable fishery area2. Since 2005, an average of 168 boat days have been recorded annually, with a catch range of between 1 and 217 t whole weight, compared to 490 boat days on average the previous 10 years (1995–2004), with a catch range of between 3–23 t whole weight. The level of fishing pressure is unlikely to adversely impact the spawning biomass of Ballot’s Saucer Scallop. No vessels fished in the SWTMF in 2015. The above evidence indicates that the fishing pressure is unlikely to cause the stock to become recruitment overfished. It also indicates that the biomass of this stock is unlikely to be recruitment overfished.

On the basis of the evidence provided above, the South West Trawl Managed Fishery (Western Australia) management unit is classified as a sustainable stock.

South Coast Trawl Fishery

The South Coast Trawl Fishery (Western Australia) management unit is a low-activity fishery in which effort is related to the abundance of Ballot’s Saucer Scallop in any given year, which can be highly variable (due to sporadic recruitment). The few vessels (up to four) that operate in the fishery only fish over one to three per cent of the allowable fishery area. In 2015, a total of 315 t whole weight was landed for 222 boat days. The mean catch rate in 2015 was 1419 kg whole weight per boat day compared with a mean of 1168 kg per boat day (range 669–1643 kg per boat day) for the previous 5 years. The above evidence indicates that the biomass of this stock is unlikely to be recruitment overfished2. It also 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 South Coast Trawl Fishery (Western Australia) management unit is classified as a sustainable stock.

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Biology

Biology
Species Longevity / Maximum Size Maturity (50 per cent)
Ballot's Saucer Scallop Maximum of 4 years and 140 mm SH  At 1 year of age and 85–90 mm SH

Ballot’s Saucer Scallop biology12–15

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Distributions

Distribution of reported commercial catch of Ballot’s Saucer Scallop

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Tables

Fishing methods
Western Australia
Commercial
Otter Trawl
Unspecified
Various
Management methods
Method Western Australia
Commercial
Catch limits
Effort limits
Limited entry
Spatial closures
Active vessels
Western Australia
0 in AIMWTMF, 22 in SBSCMF, 4 in SCTF, 0 in SWTMF
AIMWTMF
Abrolhos Islands and Mid West Trawl Managed Fishery (WA)
SBSCMF
Shark Bay Scallop Managed Fishery (WA)
SCTF
South Coast Trawl Fishery (Condition) (WA)
SWTMF
South West Trawl Managed Fishery (WA)
Catch
Western Australia
Commercial 287.87t in SBSCMF, 314.94t in SCTF
Indigenous No catch
Recreational No catch
SBSCMF
Shark Bay Scallop Managed Fishery (WA)
SCTF
South Coast Trawl Fishery (Condition) (WA)

AIMWTMF = Abrolhos Islands and Mid-West Trawl Managed Fishery (Western Australia), ECOTF = East Coast Otter Trawl Fishery (Queensland), SBSMF = Shark Bay Scallop Managed Fishery (Western Australia), SCTF = South Coast Trawl Fishery (Western Australia), SWTMF = South West Trawl Managed Fishery (Western Australia)

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Catch Chart

Commercial catch of Ballot’s Saucer Scallop

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Effects of fishing on the marine environment

  • Habitat effects of Western Australian and Queensland Ballot’s Saucer Scallop fisheries are considered low risk, with trawl vessels generally sweeping a small proportion of the designated trawl area (six per cent in the Great Barrier Reef Marine Park [GBRMP])16. Furthermore, the physical impact of this gear on the sandy habitat that supports scallops is negligible within Western Australian Scallop fisheries17, and intermediate to low in the Queensland East Coast Otter Trawl Fishery (ECOTF) within the GBRMP16, where an estimated 45 per cent of the stock biomass and its associated benthic biota are protected from fishing impacts through permanent closures16,18. Rotational and temporal closures in the ECOTF also play a role in alleviating fishing pressure on the maturing stock and maintaining benthic assemblages.
  • Food chain effects of Western Australian Ballot’s Saucer Scallop fisheries are deemed low risk, with the total biomass taken by these operations being small. The high natural recruitment variability and therefore Ballot’s Saucer Scallop stock abundance2 also means that few predators will have become highly dependent on this species19. Trawl-related risks to ecological processes within GBRMP are low18.
  • Bycatch reduction devices (grids) are mandatory mitigation measures to minimise fishing impacts in the Shark Bay Scallop Managed Fishery and the Abrolhos Islands and Mid-West Trawl Managed Fishery, as are turtle excluder devices in the East Coast Trawl Fishery. These gear modifications are effective in limiting bycatch of larger species such as turtles, sharks, rays and sea snakes20,21. Square mesh codends decrease bycatch of smaller aquatic organisms22 and their use was mandated in 2015 for vessels towing scallop gear in the ECOTF. Compliance monitoring of bycatch reduction devices and vessel activities (through vessel monitoring systems) occurs in each management area.
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Environmental effects on Ballot's Saucer Scallop

  • Strong La Niña events that are typically associated with strong Leeuwin Currents and warm sea surface temperatures often result in below-average Ballot’s Saucer Scallop recruitment and may necessitate the closure of the Shark Bay Scallop Managed Fishery and/or the Abrolhos Islands and Mid-West Trawl Managed Fishery23–26. Between 2012–15, fishery closures in these two fisheries occurred due to a marine heat wave event in 2010–11 (associated with a strong La Niña) that resulted in mortality of breeding stock and subsequent very poor recruitment for a number of years6,7,27,28. Further research continues into understanding recruitment variation (including the collapse) of Ballot’s Saucer Scallop stocks in Western Australia.
  • Environmental variables affecting the Queensland east coast Ballot’s Saucer Scallop stock productivity have also been the subject of recent research. Highly significant correlations were found between November catch rates and several oceanographic variables, including chlorophyll densities and seabed temperature anomalies in the preceding June and August, respectively11. While the precise causal mechanisms of these associations remain uncertain, concerns have arisen that current stock assessment procedures may not adequately account for these and other environmental factors11.
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References

  1. 1 Mynhardt, G, Alejandrino, A, Puslednik, L, Corrales, J and Serb, JM 2014, Shell shape convergence masks biological diversity in gliding scallops: description of Ylistrum n. gen. (Pectinidae) from the Indo-Pacific Ocean, Journal of Molluscan Studies, 80: 400–411.
    .
  2. 2 Fletcher, WJ and Santoro, K (ed.s) unpublished, State of the fisheries and aquatic resources report 2015/16, Western Australian Department of Fisheries, Perth.
  3. 3 Joll, LM and Caputi, N 1995, Environmental influences on recruitment in the Saucer Scallop (Amusium balloti) Fishery of Shark Bay, Western Australia, ICES Journal of Marine Sciences Symposium, 199: 47–53.
  4. 4 Kangas, M, Sporer, E, Brown, S, Shanks, M, Chandrapavan, A and Thomson, A 2011, Stock assessment for the Shark Bay Scallop Fishery, Fisheries research report 226, Western Australian Department of Fisheries, Perth.
  5. 5 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 & Aquaculture, 22: 36–54.
  6. 6 Caputi, N, Kangas, M, Hetzel, Y, Denham, A, Pearce, A and Chandrapavan, A 2016, Management adaptation of invertebrate fisheries to an extreme marine heat wave event at a global warming hotspot, Ecology and Evolution, 6: 3583–3593.
  7. 7 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, Fisheries research report, Fisheries Research and Development Corporation project 2010/535, Western Australian Department of Fisheries, Perth.
  8. 8 Yang, WH, Wortmann, J, Robins, JB, Courtney AJ, O’Neill, MF and Campbell, MJ 2016, Quantitative assessment of the Queensland Saucer Scallop (Amusium balloti) Fishery, The University of Queensland Centre for Applications in Natural Resource Mathematics and the Queensland Department of Agriculture and Fisheries.
  9. 9 Queensland Department of Agriculture and Fisheries unpublished, Queensland Stock Status Assessment Workshop, 14–15 June 2016, Brisbane, Species Summary Pages, Queensland DAF, Brisbane.
  10. 10 Welch, DJ, Saunders, T, Robins, J, Harry, A, Johnson, J, Maynard, J, Saunders, R, Pecl, G, Sawynok, B and Tobin, A 2014, Implications of climate change on fisheries resources of northern Australia. Part 1: vulnerability assessment and adaptation options, Fisheries Research and Development Corporation project 2010/565, March 2014, James Cook University.
  11. 11 Courtney, AJ, Spillman, CM, Lemos, R, Thomas, J, Leigh GM and Campbell, AB 2015, Physical oceanographic influences on Queensland reef fish and scallops, final report FRDC 2013/020, Department of Agriculture and Fisheries, Queensland, Centre of Australian Weather and Climate Research, Australian Government Bureau of Meteorology, Centre for Applications in Natural Resource Mathematics, School of Mathematics and Physics, University of Queensland.
  12. 12 Orensanz, JM, Parma, AM, Turk, T and Valero, J 2006, Dynamics, assessment and management of exploited natural populations, in SE Shumway and GJ Parson (ed.s), Scallops: biology, ecology and aquaculture, Developments in aquaculture and fisheries science, 35: 765–868.
  13. 13 Heald, D 1978, A successful marking method for the saucer scallop Amusium balloti (Bernardi), Australian Journal of Marine and Freshwater Research, 29: 845–851.
  14. 14 Joll, LM 1989, History, biology and management of Western Australian stocks of the saucer scallop Amusium balloti, in MLC Dredge, WF Zacharin and LM Joll (ed.s), Proceedings of the Australasian scallop workshop, Hobart, Tasmania, pp 30–40.
  15. 15 Williams, ML and Dredge, MCL 1981, Growth of the saucer scallop, Amusium japonicum balloti Habe, in central eastern Queensland, Australian Journal of Marine and Freshwater Research, 32: 657–666.
  16. 16 Dredge, MCL 1981, Reproductive biology of the saucer scallop Amusium japonicum balloti (Bernardi) in central Queensland waters, Australian Journal of Marine and Freshwater Research 32: 775–787.
  17. 17 Pears RJ, Morison, AK, Jebreen, EJ, Dunning, M, 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: data report, Great Barrier Reef Marine Park Authority, Townsville
  18. 18 Laurenson, LJB, Unsworth, P, Penn, JW and Lenanton, RCJ 1993, The impact of trawling for saucer scallops and western king prawns on the benthic communities in coastal waters off south western Australia, Fisheries research report No. 100, Department of Fisheries, Western Australia, 93 pp.
  19. 19 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.
  20. 20 Kangas, M, McCrea, J, Fletcher, W, Sporer, E and Weir, V 2006, Shark Bay Scallop Fishery, ESD report series 2, Western Australian Department of Fisheries, Perth.
  21. 21 Kangas, M and Thomson, A 2004, Implementation and assessment of bycatch reduction devices in the Shark Bay and Exmouth Gulf trawl fisheries, FRDC Project No. 2000/189, Department of Fisheries, Government of Western Australia, North Beach.
  22. 22 Courtney, AJ, Campbell, MJ, Roy, DP, Tonks, ML, Chilcott, KE and Kyne, PM 2008, Round scallops and square-meshes: a comparison of four codend types on the catch rates of target species and bycatch in the Queensland (Australia) Saucer Scallop (Amusium balloti) Trawl Fishery, Marine and Freshwater Research 59: 849–864.
  23. 23 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.
  24. 24 Joll, LM and Caputi, N 1995, Geographic variation in the reproductive cycle of the Saucer Scallop, Amusium balloti (Bernardi, 1861) (Mollusca: Pectinidae), along the Western Australian coast, Marine and Freshwater Research, 46: 779–792.
  25. 25 Caputi, N, Penn, JW, Joll, LM and Chubb, CF 1998, Stock–recruitment–environment relationships for invertebrate species of Western Australia, in GS Jamieson and A Campbell (ed.s) Proceedings of the North Pacific Symposium on Invertebrate Stock Assessment and Management, Canadian Special Publication of Fisheries and Aquatic Sciences, 125: 247–255.
  26. 26 Lenanton, RC, Caputi, N, Kangas, M and Craine, M 2009, The ongoing influence of the Leeuwin Current on economically important fish and invertebrates off temperate Western Australia—has it changed? Journal of the Royal Society of Western Australia, 92(2): 111–127.
  27. 27 Pearce, A, Lenanton, R, Jackson, G, Moore, J, Feng, M and Gaughan, D 2011, The “marine heat wave” off Western Australia during the summer of 2010/11, Fisheries Research Report 222, Western Australian Department of Fisheries, Perth.
  28. 28 Caputi, N, Feng, M, Pearce, A, Benthuysen, J, Denham, A, Hetzel, Y, Matear, R, Jackson, G, Molony, B, Joll, L and Chandrapavan, A 2015, Management implications of climate change effect on fisheries in Western Australia, part 2: case studies, FRDC Project No. 2010/535, Fisheries Research Report No. 261, Department of Fisheries, Western Australia.

Archived reports

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