Ballot's Saucer Scallop (2018)

Ylistrum balloti

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

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WA is home to four stocks of Ballot’s Saucer Scallop, all of which are sustainable. The one stock in QlLD is classified as depleted.

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Stock Status Overview

Stock status determination
Jurisdiction Stock Fisheries Stock status Indicators
Queensland East Coast Otter Trawl Fishery ECOTF Depleted Estimated biomass, abundance survey, CPUE, catch, effort
East Coast Otter Trawl Fishery (QLD)
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Stock Structure

Ballot’s Saucer Scallop in Australian waters are now classified as Ylistrum balloti (formerly Amusium balloti) following a recent revision of the genus Amusium [Mynhardt et al. 2014]. This species is distributed from Israelite Bay in Western Australia, across the tropics, to the southern coast of New South Wales. Ballot’s Saucer Scallop 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 separate management units have been established in this jurisdiction for those areas where Ballot's Saucer Scallop occur in commercial quantities.

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 (Western Australia); and East Coast Otter Trawl Fishery (Queensland).

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Stock Status

East Coast Otter Trawl Fishery

In Queensland, the annual catch of Ballot's Saucer Scallop has been declining since 2001, and from 2014–17 was less than 546 t meat weight (2 730 t whole weight) per year, near the lowest MSY estimate across a range of productivity scenarios for the stock [Campbell et al. 2012]. The most recent stock assessment [Yang et al. 2016] estimated that spawning biomass of the East Coast biological stock in 2015 may have been as low as five to six per cent of the 1977unfished level. Results of the 2017 fishery independent survey of abundance also showed relatively low densities of pre-recruits and scallops older than one year old.

At 134 t annual meat weight (670 t whole weight) in 2017, landings of Ballot’s Saucer Scallop by the East Coast Otter Trawl Fishery were at a historical low [QDAF 2018]. This is likely due in part to recent management intervention, including total closure of high abundance scallop replenishment areas since November 2016 and prohibition on harvesting during the May-October spawning season. However, the annual catch rate in 2017 also decreased to the lowest level seen since 1997, when recruitment failed [QDAF 2018]. Average monthly catch rates in late 2017 were about 40 per cent higher than the historic lows of January 2015-April 2016 [QDAF 2018]; providing some evidence of stock rebuilding, at least in the southern-most part of the fishery. The above evidence indicates that the biomass of this stock is likely to be depleted and that recruitment is likely to be impaired.

A long-term decline in the annual number of scallop harvesting days has been evident since 1997, when the stock was first considered to be overfished, and effort in 2017 was at a historically low level [QDAF 2018]. However, a shift in fleet composition towards more efficient vessels has increased fishing power since 2000 [Campbell et al. 2012]. Results from a recent fishery-independent survey reinforce concerns about low scallop abundance. Mean scallop densities in 14 out of 15 strata were lower in 2017 than mean densities from comparable strata in long-term (1997–2006) scallop abundance surveys [A. Courtney, personal communication]. Spatial and temporal closures introduced in late 2016 to reduce fishing pressure and total closure of the fishery from May-October have probably also reduced annual effort. The above evidence indicates that current fishing mortality is constrained by management to a level that should allow the stock to recover from its recruitment impaired state; however measurable improvements are yet to be detected.

On the basis of the evidence provided above, the East Coast Otter Trawl Fishery (Queensland) management unit is classified as a depleted stock.

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Ballot’s Saucer Scallop biology [Dredge 1981, Heald 1978, Joll 1989, Orensanz et al. 2006, Williams and Dredge 1981]

Species Longevity / Maximum Size Maturity (50 per cent)
Ballot's Saucer Scallop Maximum of 4 years and 140 mm SH  At 4 year of age and 85–90 mm SH 
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Commercial catch of Ballot’s Saucer Scallop - note confidential catch not shown

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Fishing methods
Otter Trawl
Management methods
Method Queensland
Limited entry
Seasonal closures
Size limit
Spatial closures
Vessel restrictions
Commercial 133.60t in ECOTF
Indigenous No catch
Recreational No catch
East Coast Otter Trawl Fishery (QLD)

Queensland – Indigenous (Management Methods). In Queensland, under the Fisheries Act 1994 (Qld), Indigenous fishers are able to use prescribed traditional and non-commercial fishing apparatus in waters open to fishing. Size and bag limits and seasonal closures do not apply to Indigenous fishers. Further exemptions to fishery regulations can be obtained through permits.

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Catch Chart

Commercial catch of Ballot’s Saucer Scallop - note confidential catch not shown

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  1. Campbell, AB, O’Neill, MF, Leigh GM, Wang Y-G & Jebreen, EJ 2012, Reference points for the Queensland scallop fishery, final report to the Fisheries Research and Development Corporation, project 2009/089, Queensland Department of Employment, Economic Development and Innovation.
  2. Caputi, N, de Lestang, S, Hart, A, Kangas, M, Johnston, D and Penn, J 2014a, 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.
  3. Caputi, N, Feng, M, Pearce, A, Benthuysen, J, Denham, A, Hetzel, Y, Matear, R, Jackson, G, Molony, B, Joll, L and Chandrapavan, A 2014b, 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.
  4. 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.
  5. 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.
  6. Gaughan, DJ and Santoro K (eds) 2018, State of the fisheries and aquatic resources report 2016/17, Department of Primary Industries and Regional Development, Western Australia.
  7. Heald, D 1978, A successful marking method for the saucer scallop Amusium balloti (Bernardi), Australian Journal of Marine and Freshwater Research, 29: 845–851.
  8. 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.
  9. 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.
  10. 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.
  11. 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.
  12. 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..
  13. Orensanz, JM, Parma, AM, Turk, T and Valero, J 2006, Dynamics, assessment and management of exploited natural populations, in SE Shumway and GJ Parson (eds), Scallops: biology, ecology and aquaculture, Developments in aquaculture and fisheries science, 35: 765–868.
  14. Queensland Department of Agriculture and Fisheries 2018, Queensland Stock Status Assessment Workshop Proceedings 2018. Species Summaries. 19-20 June 2018, Brisbane.
  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. 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.

Downloadable reports

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