Commercial Scallop ​​Pecten fumatus

Management of scallop fisheries is complex, with all three jurisdictions using slightly different management strategies. Scallop stocks have shown repeated ‘boom and bust’ phases in the past, with the busts often resulting in extended fishery closures. Sustainability objectives are strongly reliant on the minimum size limit in each jurisdiction—an area is only open to fishing if less than 20 per cent of the scallops are under the minimum size. Estimating the biomass of Commercial Scallops is difficult because of highly variable recruitment3. In Victoria, the fishery may also be closed if average meat weight falls below 10 grams.

Commonwealth

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 was reopened in 2009 under a new harvest strategy4. Commercial Scallops experienced a reported die-off in 2010. In 2012, the harvest strategy was revised to provide more flexibility⁵.

Elements of the Commonwealth harvest strategy include:

• surveys to estimate biomass and determine areas of high density
• a set of decision rules that are used to open an area to fishing, including a minimum size limit of 90 mm shell length and a maximum discard rate (20 per cent) of animals below this size
• identification of at least two viable fishing areas, with a minimum of 40 per cent of the combined pool of viable areas closed to fishing
• a requirement that closed viable fishing areas contain a minimum of 500 tonnes (t) of estimated biomass in total.

Abundance surveys in 2013 estimated around 4000 t of Commercial Scallop across two beds, but only around 650 t were densely aggregated. These beds also contained a high proportion (31–71 per cent) of undersized scallops. The fishery was opened with an exemption from the 90 mm minimum size limit, and a temporary 85 mm limit applied instead. The latter size limit is still within the size range for scallops that are 3 years or older6. Only 189 t of the 1500 t total allowable catch (13 per cent) was harvested by the 13 active vessels in 2013.

Although management measures for the Bass Strait Central Zone Scallop Fishery are designed to prevent the stock from becoming recruitment overfished, it is not clear whether the stock biomass has recovered from its previous recruitment overfished state. Also unknown is the impact of the reported die-off in 2010 on total biomass and recruitment. As such, insufficient information is available to confidently classify the status of this stock⁷.

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

Tasmania

The harvest of Commercial Scallops in Tasmanian waters is regulated through a minimum size limit of 90 mm shell length, which is a proxy for animals aged 3 years or older that have spawned at least twice⁶. The minimum size limit can be changed for specific areas of the fishery, if appropriate.

The Tasmanian fishery is managed similarly to the Bass Strait Central Zone Scallop Fishery. The main difference is that there is no requirement to close a proportion of the beds found during abundance surveys. This is because refuge for scallops is provided by the prohibition of fishing in waters less than 20 m deep, and the large number of dredge-prohibited areas around the state that protect scallop habitat.

The Tasmanian fishery was closed to fishing in 2009 and 2010 because of low scallop abundance and a high proportion of undersized animals. In 2013, industry statewide surveys generally found low levels of scallop abundance but did identify two beds containing commercial quantities that met the harvest strategy guidelines: one on the state’s north-west coast and the other on the east coast. These areas were subsequently opened for fishing, with a lower size limit of 85 mm applied to the north-west bed. This was considered appropriate given historically slow growth rates in this region and the fact that the revised size limit is still within the size range of scallops aged 3 years or more⁶.

Part of the east coast bed was voluntarily closed by industry in July 2013 when a large proportion of juveniles were discovered in the northern section. By the end of 2013, 1260 t of the 1489 t total allowable catch across both beds (85 per cent) had been taken by 13 vessels (half the number of vessels operating a decade earlier). Although harvesting is managed to prevent the stock becoming recruitment overfished, the historical status of the Tasmanian stock is unclear. In particular, it is not known whether the stock is recruitment overfished, and there is insufficient information available to confidently classify the status of this stock.

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

Victoria

Surveys undertaken in 2009⁸ and 2012⁹ of the historically fished scallop beds found low scallop densities and negligible recruitment. Consequently, the total allowable catches for the 2010–11, 2011–12 and 2012–13 fishing seasons were set at zero. Landings and participation were also very low for the 2013–14 season, when 1.5 t per licence was allocated to facilitate exploratory fishing to collect information, in lieu of a more expensive biomass survey. Insufficient information is available to confidently classify the status of this stock.

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