Western Rock Lobster Panulirus cygnus

Simon de Lestanga
Western Rock Lobster

Table 1: Stock status determination for Western Rock Lobster

Jurisdiction

Western Australia

Stock

WCRLF

Stock status

Sustainable

Indicators

Egg production relative to mid-1980s levels, harvest rate


WCRLF = West Coast Rock Lobster Managed Fishery (Western Australia)


Stock Structure

Western Rocklobster is a single biological stock with a distribution along the mid-to-lower west coast of Western Australia1–2.


Stock Status

West Coast Rock Lobster Managed Fishery (Western Australia) biological stock The stock status for Western Rock Lobster (Panulirus cygnus) is determined using the egg production and harvest rate outputs from a stock assessment model that is based on a broad range of fishery data and fishery-independent monitoring3. The most recent assessment estimates that egg production in each management region in 2013 was well above the respective threshold levels. This evidence indicates that the biomass of this stock is unlikely to be recruitment overfished.

The proportion of the legal stock harvested each fishing season is currently based on maximum economic yield principles4 and is projected to remain below 45 per cent over the next four fishing seasons. This provides at least 75 per cent confidence that egg production levels in each management region will remain above the respective thresholds3. This indicates that the current level of fishing mortality is unlikely to cause the stock to become recruitment overfished.

The stock assessments conducted on the fishery have been critically examined and reviewed on an annual basis since 1999 by external reviewers, as part of the fishery’s continued certification by the Marine Stewardship Council (MSC). In March 2012, the fishery entered its third 5-year MSC certification period.

On the basis of the evidence provided above, the biological stock is classified as a sustainable stock.

Table 2: Western Rocklobster biology1

Longevity and maximum size

20+ years; >150 mm CL

Maturity (50%)

5–7 years; 65–80 mcm CL, depending on location

CL = carapace length


Figure 1: Distribution of reported commercial catch of Western Rock Lobster in Australian waters, 2013

Figure 1: Distribution of reported commercial catch of Western Rock Lobster in Australian waters, 2013 (fishing season: 15 January 2013 – 14 January 2014)




Table 3: Main features and statistics for Western Rock Lobster fisheries in Australia, 2013 (fishing season: 15 January 2013 – 14 January 2014)

Jurisdiction

Western Australia

Fishing methods

Commercial

Batten and beehive pots

✓

Recreational

Batten and beehive pots

✓

Diving

✓

Indigenousa

Batten and beehive pots

✓

Diving

✓

Management methods

Commercial

Limited entry

✓

Size limits

✓

Total allowable catch

✓

Gear restrictions

✓

Spatial closures

✓

Recreational

Bag limits

✓

Size limits

✓

Gear restrictions

✓

Spatial closures

✓

Temporal closures

✓

Indigenousa

Bag limits

✓

Size limits

✓

Gear restrictions

✓

Active vessels

Commercial

251 in WCRLF

Catch

Commercial

5641 t in WCRLF

Recreational

128 t

Indigenous

Unknown

Markets

Domestic

✓

Export

✓


WCRLF = West Coast Rock Lobster Managed Fishery (Western Australia)

a 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 recreational fishing licence, the non-commercial take by indigenous fishers is covered by the same arrangements as that for recreational fishing.


Figure 2: Commercial catch of Western Rock Lobster in Australian waters, 1964 to 2013 (fishing seasons)

Figure 2: Commercial catch of Western Rock Lobster in Australian waters, 1964 to 2013 (fishing seasons)

Note: ‘Fishing season’ represents a different timeframe across the data series. From 1964 to 2011, a season ran from 15 November to June or August the following year (for example, 1964 = November 1964 to August 1965). In 2011, the season was extended by changing the season start and finish dates. The 2011 season was extended to 14 months (15 November 2011 – 14 January 2013) to reschedule the start time, and the total allowable catch increased to 6900 tonnes, corresponding to the longer season. The 2013 season was the first under the new timeframe (15 January 2013 – 14 January 2014).




Effects of fishing on the marine environment
  • The legislated design of rock lobster pots (batten and beehive), including the materials they are made from, prevents ‘ghost fishing’ problems. A study of human impacts on the marine environments of the Abrolhos Islands estimated that potting impacts less than 0.3 per cent of the surface area of fragile habitat (corals). For the coastal fishery, rock lobster fishing occurs on sand areas around robust limestone reef habitats, covered with coralline algae and macro-algae such as kelp (Ecklonia spp.). This type of high-energy coastal habitat is regularly subjected to swell and winter storms, and so is considered highly resistant to damage from rock lobster potting. The significant recent reductions in fishing effort will have reduced these risks even further5.
  • The incidental capture of juvenile sea lions, recognised as a management issue by the Western Australian Department of Fisheries, has resulted in the introduction of sea lion excluder devices in high-risk areas. This has reduced captures of sea lions, and no captures were recorded in 2010–115.
  • Sea lions, seals and sharks have been found to be particularly susceptible to injury or death through entanglement in uncut plastic bait bands. Historically, these bands also contribute to plastic debris washed up on shorelines. In 2012, a statewide ban on the carriage of bait bands out to sea was implemented.
  • Research monitoring of commercial bycatch occurs continuously across the fishery; no issues of concern have been identified5.
  • Interactions between pot ropes/floats and migrating whales have historically remained between zero and four whales per migration season (May–November). However, a marked increase in interactions has occurred since 2011, as a result of a combination of an increase in the whale population and an expansion of the fishing season. This increase has been recognised as a management issue, and the Western Australian Department of Fisheries has implemented management changes to reduce interactions during the 2014 migration season. These include reducing pot usage (maximum of 60 pots per vessel), using negatively buoyant float lines and trialling acoustic pingers. Two Fisheries Research and Development Corporation projects have been initiated to investigate this issue.

Environmental effects on Western Rock Lobster
  • Annual variation in the abundance of puerulus (post-larval lobsters) has historically been associated with fluctuations in offshore water temperatures during the early larval phase; water temperatures are influenced by the strength of the Leeuwin Current and the incidence of storm fronts crossing the west coast during spring6. More recently, other factors, such as timing of the onset of spawning (which is affected by water temperature), have been identified as possible contributors to these variations—in particular, the 7 years of below-average settlement (2006–07 to 2012–13). including the record low settlement of 2008–095.
  • Many aspects of the Western Rock Lobster life history, such as growth, migration, size at maturity and catchability, appear to be sensitive to changes in water temperature7–9. Increasing trends in long-term water temperature have co-occurred with declines in the size at maturity9 and size at migration10, and an increase in the proportion of female lobsters moulting out of setose in autumn8.

a Department of Fisheries, Western Australia