Commercial Scallop ​​Pecten fumatus

Jayson Semmensa, David Jarvisb, Matthew Piasentec, Melissa Schubertd, Sevaly Sene, Andy Mooref, Ilona Stobutzkif and Nic Martonf

Commercial Scallop

Table 1: Stock status determination for Commercial Scallop









Stock status








Proportion of spawning stock protected by spatial closure, minimum size limits

Proportion of spawning
stock protected by minimum size limits

Proportion of spawning stock protected by spatial closure, minimum size limits

BSCZSF = Bass Strait Central Zone Scallop Fishery (Commonwealth); SF [TAS] = Scallop Fishery (Tasmania); SF [VIC] = Scallop Fishery (Victoria)

Stock Structure

Multiple scallop beds are fished commercially in Commonwealth waters, Victoria and Tasmania. These beds tend to have different age classes of Commercial Scallop and may or may not have been fished in the past. Commercial Scallops within the embayments of Port Phillip Bay in Victoria and D'Entrecasteaux Channel in Tasmania are genetically distinct biological stocks1. In the open water the biological stock structure is uncertain, with research currently underway. The species appears to show spatially complex genetic structuring, most likely as a result of non-random dispersal and subsequent settlement of larvae2. Given this uncertainty, Commercial Scallop is assessed at the jurisdictional level.

Stock Status

Management of Commercial Scallop fisheries is complex, with each of the three jurisdictions using different management strategies. Options for rationalisation of the management strategies are currently being jointly assessed by the three jurisdictions.

Commercial Scallop stocks have experienced repeated 'boom and bust' phases, with the busts often resulting in extended closure of the fisheries. Sustainability objectives rely strongly on the minimum size limit in all three jurisdictions, with areas only opened to fishing if 20 per cent of the scallops are under the minimum size (that is, most of the scallops in the bed are mature and have had an opportunity to spawn). This rule is known as the '20 per cent discard rule'. In Victoria, the fishery may also be closed if average meat weight falls below 10 grams. Estimating the biomass of Commercial Scallop is difficult because of survey costs, and sporadic and intermittent recruitment3.


Following three years of closure under a ministerial direction, the Bass Strait Central Zone Scallop Fishery was reopened in 2009 under the current harvest strategy framework. The harvest strategy in use in 2010 uses a spatial management approach, in which most of the fishery remains closed while specific areas are opened to fishing.

Elements of the strategy include:

  • surveys to estimate biomass and determine areas of high density
  • decision rules that are used to open an area to fishing—these include a maximum discard rate and minimum size limits (20 per cent of catch below the minimum size of 9 cm shell length)
  • a requirement for at least two viable areas to be identified; at least 40 per cent of the viable areas and a total biomass of at least 500 tonnes (t) will remain closed to fishing.

Five viable beds were identified in 2010 and, under the spatial management approach, four were closed to fishing. The minimum size limit and closed area requirements protect a proportion of the stock from fishing pressure. The objective is to prevent overfishing of recruits. A total allowable catch (TAC) of 2500 t was set, of which 2184 t was caught.

The biomass of the stock was classified as recruitment overfished prior to the closure. In 2010 the fishery experienced a widespread die-off and the cause is unknown. The extent of recovery of the stock from its previously overfished state, and the impact of the reported die-offs on total biomass levels are not known. Consequently, it is not clear whether the stock is currently recruitment overfished4.

On the basis of the evidence provided above, Commercial Scallop in the Commonwealth-managed area is classified as an undefined stock.


For Victorian managed stocks, there is a minimum size limit of 8 cm shell length. The Victorian scallop fishery extends 20 nautical miles from the Victorian coastline, with most fishing occurring in eastern Victoria. Commercial Scallop fishing is not permitted in Victorian bays or inlets.

A 2009 fishery survey5 found low densities of Commercial Scallop and negligible recruitment. As a result, the total allowable commercial catch (TACC) for the 2010–11 and 2011–12 fishing seasons was set at zero. Although strategies are in place to prevent overfishing, the historical status of the Victorian stocks is unclear; in particular, it is unclear whether the stocks were recruitment overfished historically.

On the basis of the evidence provided above, Commercial Scallop in Victoria is classified as an undefined stock.


For Tasmanian-managed stocks, there is a minimum size limit of 9 cm shell length, which is a proxy for the Commercial Scallop being 3+ years of age and having had at least two major spawnings6. The minimum size limit ensures that a proportion of the mature stocks receive negligible fishing mortality, which prevents recruitment overfishing. The Tasmanian fishery was closed to fishing in 2009 and 2010 because the majority of scallops were below the minimum size. Although harvesting is managed with the aim of preventing the stocks becoming recruitment overfished, the historical status of the Tasmanian stocks is unclear; in particular, it is unclear whether the stocks are recruitment overfished.

On the basis of the evidence provided above, Commercial Scallop in Tasmania is classified as an undefined stock.

Table 2: Commercial Scallop biology1–2,6

Longevity and maximum size

7+ years; >12 cm shell length


Second year (~7–8 cm shell length, depending on region)

Figure 1: Distribution of reported catch of Commercial Scallop in Australian waters, 2010

Figure 1: Distribution of reported catch of Commercial Scallop in Australian waters, 2010

Main features and statistics for Commercial Scallop stocks/fisheries in Australia in 2010
  • Commercial Scallops are caught commercially using steel scallop dredges.
  • The stock is managed by the Commonwealth, Tasmania and Victoria using a range of input and output controls:
    • Input controls include spatial and temporal closures, limited entry, and gear and vessel restrictions.
    • Output controls include size limits and commercial TACs.
  • In 2010, Commercial Scallop catch was reported by 18 commercial vessels in the Commonwealth. There were no vessels fishing in Tasmania (fishery closed) or Victoria (zero TACC).
  • Total commercial catch of Commercial Scallop in 2010 was 2184 t, taken from the Commonwealth. There is an annual recreational dive fishery in Tasmania; however, the main recreational fishing area was closed in 2010, so total recreational catch was negligible. There is negligible Indigenous catch.

Figure 2: Commercial Scallop catch in Australian waters, 2000–10 (calendar year)

Figure 2: Commercial Scallop catch in Australian waters, 2000–10 (calendar year)

Catch Explanation

Commercial Scallop catches increased rapidly to unsustainable levels in the 1980s and again in the 1990s. It is difficult to separate the fishery and environmental effects that cause the 'boom and bust' nature of the fisheries3.

Management controls have subsequently reduced the catch to much lower levels, but there have still been periods of closure. Spatial management (small area open, large area closed) was introduced into the Tasmanian fishery in 2003, following earlier closures between 2000 and 2002. The Commonwealth fishery was closed due to low stock levels in 1999 and again between 2006 and 2008, by ministerial direction. The Commonwealth fishery reopened in 2009 under a spatial management arrangement (small area open, large area closed) similar to Tasmania.

From 2001–02 to 2008–09, the Victorian fishery was open with relatively low TACCs, in the range of 207 t (2004–05) to 916 t (2007–08). Although the fishery was technically open in 2009–10, no TACC was allocated, and thus no catch was taken.

Effects of fishing on the marine environment
  • Because Commercial Scallops are targeted in tightly defined regions where they are abundant, the effect on other species within the broader ecosystem tends to be minimal7.
  • Commercial Scallops and their associated benthic community are most affected by dredging in the short term, but can recover very quickly8–9.
  • Since Commercial Scallops have been fished within the same regions repeatedly since the 1960s10, the effect of dredging on the current community structure is expected to be less significant now because the long-term dredge fishery may have shifted the benthic community in favour of species that are less susceptible to dredging, or more able to quickly recover11–13.

Environmental effects on Commercial Scallop
  • Recruitment of Commercial Scallop is sporadic and intermittent. More significantly, the stock– recruitment relationship of scallops is poorly understood3. Scallops are also known to have highly variable levels of natural mortality, which are attributable to density-dependent food shortages, seabed bottom type, disease, environmental conditions and predation, as well as other, inexplicable causes14.
  • Stock relationships are influenced by ocean currents2. Changes in ocean currents through climate change or upwelling events would be expected to affect recruitment.
  • Changes in Commercial Scallop community structure can be driven more by environmental effects than dredging impact8.

a Institute for Marine and Antarctic Studies, Tasmania
b Department of Primary Industries, Parks, Water and Environment, Tasmania
c Australian Fisheries Management Authority
d Department of Primary Industries, Victoria
e FERM Pty Ltd
f Australian Bureau of Agricultural and Resource Economics and Sciences