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Stock Status Overview
|Commonwealth||Bass Strait Central Zone Scallop Fishery||BSCZSF||Undefined||Biomass surveys, size composition, catch, effort|
- Bass Strait Central Zone Scallop Fishery (CTH)
There are several Commercial Scallop beds fished commercially in Commonwealth, Victorian and Tasmanian waters. These beds often contain different age classes of scallop and most have been fished at some stage in the past. Commercial Scallops in Port Phillip Bay (Victoria) are genetically distinct from those in the D’Entrecasteaux Channel (Tasmania), and also differ from conspecifics in most other locations in south eastern Australia1,2. The genetic structure of Commercial Scallops in Bass Strait is complex and unclear2,3.
Here, assessment of stock status is reported at the management unit level—Bass Strait Central Zone Scallop Fishery (Commonwealth), Ocean Scallop Fishery (Victoria), Port Phillip Bay Dive Scallop Fishery (Victoria) and Tasmanian Scallop Fishery.
Many scallop fisheries have experienced repeated ‘boom and bust’ phases, with declines often resulting in prolonged fishery closures. Management arrangements for the three jurisdictions that harvest Commercial Scallop in Australian waters all include a minimum size limit (to allow adult scallops to spawn several times before harvest) and some means of capping fishing effort (through spatial and/or temporal closures) and overall catch (through a total allowable catch [TAC]). Estimating Commercial Scallop biomass by means of surveys is complicated by unpredictable and highly variable recruitment, which can result in scallops declining in one area and reappearing in another4.
Bass Strait Central Zone Scallop Fishery
Commercial Scallops in the Bass Strait Central Zone Scallop Fishery were considered recruitment overfished until 2007. Following 3 years of closure due to low scallop abundance and concerns about overfishing, the Bass Strait Central Zone Scallop Fishery (Commonwealth) was reopened in 2009, under a new harvest strategy5. Commercial Scallops experienced die-offs in 2010–11 and the harvest strategy was revised in 20126, 20147 and 20158.
Elements of the current Commonwealth harvest strategy include: a tiered management approach (whereby a 150 tonnes (t) TAC is set as a ‘default opening’ TAC with operators managing voluntary industry closures to ensure no more than 50 t comes from any one bed and also to protect beds that do not meet the discard rate of less than 20 per cent of scallops smaller than 85 mm shell length [SL]); surveys to estimate biomass and determine areas of high density (with the option for two other tiers for setting a TAC including formal closures of some surveyed beds, depending on survey results); and a set of decision rules used to open an area to fishing (including a minimum size limit of 85 mm SL and a maximum discard rate of 20 per cent)
Scallop beds near King Island were fished in 2014 and the scallops were reportedly in good condition9. The beds were not surveyed before, or during, the 2014 season. Three beds in the area were surveyed before the 2015 season, with the harvestable biomass estimated at 9300 t10. Further pre-season surveys near King Island in June 2016 estimated the harvestable biomass at 16 500 t, spread across seven areas11.
In response to these results, the level of fishing effort and catch increased from very low levels in 2013 (182 t of a 1500 t TAC), to 2014 (1418 t of a 1500 t TAC) and increased again in 2015 to 2260 t (of a 2500 t TAC), which is the highest catch and effort since the fishery reopened in 2009. Given the uncertainty in biomass and the potential that biomass remains substantially reduced across the fishery, the impact of this catch on total biomass is unclear.
Evidence of low recruitment, effort contraction and reduced catch in the eastern part of the fishery indicate that the biomass in this area has declined compared to historical levels.
Three scallop beds were found in the western part of the fishery in 2014, in areas unfished for more than a decade. All three beds were reportedly in good condition and again yielded good catches in 2015.
Because surveys and fishing activity in recent years have focused on and around known beds, there is a lack of contemporary information from large parts of the historically fished area. The fact that Commercial Scallops experience sporadic die-back events means that confidence in biomass estimates decrease over time.
However, survey results from 2015 and 2016 estimate a larger biomass than has been seen in recent years, with recruitment having occurred around King Island sometime after a 2009 survey which failed to detect commercial quantities of scallops in the area. If this trend of increasing biomass and recruitment continues, it may provide confidence that, even while biomass across the fishery remains unknown, fishing mortality is at a level that is not preventing rebuilding.
A number of conflicting indicators, combined with a lack of information on scallop biomass across the majority of the fishery (including previously fished areas) means that there is insufficient evidence to confidently classify the status of this stock.
On the basis of the evidence provided above, the Bass Strait Central Zone Scallop Fishery (Commonwealth) management unit is classified as an undefined stock.
Commercial Scallop biology1–3,18
|Species||Longevity / Maximum Size||Maturity (50 per cent)|
|Commercial Scallop||7+ years; > 120 mm SH SHell length||2 years; 70–80 mm SL, depending on region|
Distribution of reported commercial catch of Commercial Scallop
|Total allowable catch|
|11 in BSCZSF|
- Bass Strait Central Zone Scallop Fishery (CTH)
|Commercial||2.26Kt in BSCZSF|
- Bass Strait Central Zone Scallop Fishery (CTH)
a Victoria – Commercial In Victoria, the reporting period is fishing season, which runs from 1 April–30 March.
b Victoria – Indigenous (management methods) 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 2015, there were no applications for customary fishing permits to access Commercial Scallop.
c Victoria – Indigenous (management methods) Subject to the defence that applies under Section 211 of the Native Title Act 1993 (Cth), and the exemption from a requirement to hold a Victorian recreational fishing licence, the non-commercial take by indigenous fishers is covered by the same arrangements as that for recreational fishing.
d Victoria – Commercial (catch) To protect commercial confidentiality of data, the catch in the Ocean Scallop Fishery (Victoria) and Port Phillip Bay Dive Scallop Fishery (Victoria) cannot be reported because there are fewer than five licence holders.
Commercial catch of Commercial Scallop - note confidential catch not shown.
Effects of fishing on the marine environment
- Commercial Scallops have been fished within the same regions repeatedly since the 1960s19, and the current impacts of dredging activities are considered less significant than those when the fishery began. This is because the long-term dredge fishery may have already resulted in benthic communities shifting in favour of those species that are less susceptible to dredging, or those most able to quickly recover20-22. Scallops are targeted where they are abundant and the effect on other species within the broader ecosystem tends to be minimal2, 23. An ecological risk assessment of the Bass Strait Central Zone Scallop Fishery found that none of the habitats assessed were at high risk24. Commercial Scallops, and associated benthic communities, are impacted by dredging over relatively brief periods of time and generally recover quickly25,26.
- Selective harvesting by the Port Phillip Scallop Dive Fishery has minimal impact on the surrounding environment and other fisheries15. It is difficult to identify any scenario where this dive fishery would have a detrimental impact on the local snapper fishery27.
Environmental effects on Commercial Scallop
- Changes in Commercial Scallop community structure can be driven more by environmental effects than fishing25. Recruitment of Commercial Scallops is sporadic, intermittent and poorly understood4. Natural mortality of scallops is highly variable and depends on factors including (but not limited to) density-dependent food shortages, seabed bottom type, disease, environmental conditions and predation28. Stock relationships are heavily influenced by ocean currents2. Climate change-induced changes in ocean currents and/or upwelling events are expected to affect recruitment. Recent research has shown that seismic surveying may impact the health and increase the mortality rate of scallops29.
- 1 Woodburn, L 1990, Genetic variation in southern Australian Pecten, in Proceedings of the Australasian Scallop Workshop. Tasmanian Government: Hobart.
- 2 Semmens, JM, et al 2015, Establishing fine-scale industry based spatial management and harvest strategies for the Commercial Scallop fishery in South East Australia, final report to the Fisheries Research and Development Corporation, project 2008/022. FRDC: Canberra.
- 3 Ovenden, JR, et al. 2016, Stirred but not shaken: population and recruitment genetics of the scallop (Pecten fumatus) in Bass Strait, Australia. ICES Journal of Marine Science: Journal du Conseil.
- 4 Peterson, CH, Summerson, HC and Fegley, SR 1988, Ecological consequences of mechanical harvesting of clams. Fishery Bulletin, 85(2): p. 281-298.
- 5 Australian Fisheries Management Authority 2007, Harvest strategy for the Bass Strait Central Zone Scallop Fishery. Australian Fisheries Management Authority: Canberra.
- 6 Australian Fisheries Management Authority 2012, Harvest strategy for the Bass Strait Central Zone Scallop Fishery. Australian Fisheries Management Authority: Canberra.
- 7 Australian Fisheries Management Authority 2014, Harvest Strategy for the Bass Strait Central Zone Scallop Fishery. Australian Fisheries Management Authority: Canberra.
- 8 Australian Fisheries Management Authority 2015, Harvest Strategy for the Bass Strait Central Zone Scallop Fishery. Australian Fisheries Management Authority: Canberra.
- 9 Australian Fisheries Management Authority 2015, Bass Strait Central Zone Scallop Fishery Resource Assessment Group (ScallopRAG) Meeting 23, Meeting Minutes; Date: 2 March 2015. AFMA: Canberra.
- 10 Knuckey, I, Koopman, M and Davis, M 2015, Bass Strait and Central Zone Scallop Fishery — 2015 Survey, project 2015/001291. Australian Fisheries Management Authority: Canberra.
- 11 Knuckey, I, Koopman, M and Davis, M 2016, Bass Strait and Central Zone Scallop Fishery – 2016 Survey, project 2016/0804. Australian Fisheries Management Authority: Canberra.
- 12 Harrington, J, Leporati, S and Semmens, JM 2010, 2009 Victorian Scallop Fishery Survey, final report to Fisheries Victoria. Tasmanian Aquaculture and Fisheries Institute, University of Tasmania: Hobart.
- 13 Semmens, JM and Jones, N 2012, Victorian scallop fishery survey final report. Institute for Marine and Antarctic Studies, University of Tasmania: Hobart.
- 14 DEPI 2014, Commercial Scallop Dive Fishery (Port Phillip) – Survey Results for 2014. Fisheries Victoria: Melbourne
- 15 DEDJTR 2016, Draft Port Phillip Scallop Dive Fishery Management Plan. Fisheries Victoria: Melbourne.
- 16 DEPI 2013, Commercial Scallop Dive Fishery (Port Phillip Bay) Baseline Management Arrangements. Fisheries Victoria: Melbourne.
- 17 Henry, GW and Lyle, JM 2003, The National Recreational and Indigenous Fishing Survey - project 99/158 FRDC: Canberra.
- 18 Young, P and Martin, R 1989, The scallop fisheries of Australia and their management. Reviews in Aquatic Sciences, 1(4): p. 615-638.
- 19 Gwyther, D, et al. 1991, Fisheries and Aquaculture: Australia, in Scallops: Biology, Ecology and Aquaculture, Editors: Shumway, SL and Parsons, GJ. Elsevier: New York.
- 20 Jennings, S and Kaiser, MJ 1998, The Effects of Fishing on Marine Ecosystems, in Advances in Marine Biology, Editors: Blaxter, JHS, Southward, AJS and Tyler PA. Academic Press. p. 201-352.
- 21 Kaiser, MJ, et al. 2002, Modification of marine habitats by trawling activities: prognosis and solutions. Fish and Fisheries, 3(2): p. 114-136.
- 22 Young, P, et al. 1988, Variability in spatfall and recruitment of commercial scallops (Pecten fumatus) in Bass Strait, in Proceedings of the Australian Scallop Workshop. Tasmanian Government: Hobart.
- 23 Haddon, M, Harrington, J and Semmens, JM 2006, Juvenile scallop discard rates and bed dynamics: testing the management rules for scallops in Bass Strait, final report to the Fisheries Research and Development Corporation, project 2003/017. FRDC: Canberra.
- 24 Hobday, A, et al. 2007, Ecological risk assessment for the effects of fishing: Bass Strait Central Zone Scallop Sub-Fishery, report to the Australian Fisheries Management Authority. Australian Fisheries Management Authority: Canberra.
- 25 Currie, DR and Parry, GD 1999, Impacts and efficiency of scallop dredging on different soft substrates. Canadian Journal of Fisheries and Aquatic Sciences, 56(4): p. 539-550.
- 26 Harrington, J, Haddon, M and Semmens, JM 2008, Facilitating industry self-management for spatially managed stocks: A scallop case study, final report to the Fisheries Research and Development Corporation, project 2005/027. FRDC: Canberra.
- 27 Kennelly, S 2013, Review of potential interactions between snapper and the proposed commercial scallop dive fishery in Port Phillip Bay. Fisheries Victoria: Melbourne.
- 28 Gwyther, D and McShane, PE 1988, Growth rate and natural mortality of the scallop Pecten alba tate in Port Phillip Bay, Australia, and evidence for changes in growth rate after a 20-year period. Fisheries Research, 6(4): p. 347-361.
- 29 Ryan D. Day, RD, McCauley, RD, Fitzgibbon, QP, Hartmann, K and Semmens, JM 2016, Assessing the impact of marine seismic surveys on southeast australian scallop and lobster fisheries, final report to the Fisheries Research and Development Corporation, project 2012/008. FRDC: Canberra