Table 1: Stock status determination for Western Rocklobster
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)
Western Rocklobster is a single biological stock with a distribution along the mid-to-lower west coast of Western Australia1–2.
West Coast Rock Lobster Managed Fishery (Western Australia) biological stock
The biological stock status for Western Rocklobster 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 assessment3 estimates that egg production levels in each management region in 2010–11 were well above their respective threshold levels. This evidence indicates that the biomass of this biological stock is unlikely to be recruitment overfished.
The proportion of the legal biological stock harvested each fishing season is projected to remain below 55 per cent over the next four fishing seasons. This will ensure that egg production levels in each management region will remain above the respective thresholds with at least 75 per cent confidence3. This indicates that the current level of fishing mortality is unlikely to cause the biological stock to become recruitment overfished.
The stock assessments conducted for this fishery have been critically examined and reviewed each year since 1999 by external reviewers, as part of this fishery’s continued certification by the Marine Stewardship Council (MSC). The fishery has recently entered its third five-year MSC certification period (March 2012).
On the basis of the evidence provided above, the biological stock is classified as a sustainable stock.
Table 2: Western Rocklobster biology3
Longevity and maximum size |
20+ years; >15 cm CL |
Maturity (50%) |
5–7 years; 6.5–8.0 cm CL, depending on location |
CL = carapace length
Figure 1: Distribution of reported commercial catch of Western Rocklobster in Australian waters, 2010
- Catch of Western Rocklobster is taken by commercial fishers (using batten and beehive pots) and recreational fishers (using batten and beehive pots, and diving) throughout its geographic range.
- A sophisticated set of input and output controls has been applied to manage the Western Rocklobster biological stock in Australia:
- Up to the 2007–08 season, input controls were primarily used to manage the commercial fishery; they included total allowable effort, limited entry, limited pot usage rate, size limits, temporal closures and gear restriction.
- Since the 2008–09 season, the commercial fishery has been primarily managed using output controls, with a total allowable catch being applied. This approach was further developed in the 2010–11 season, when individual transferable quotas were introduced. In addition, most of the associated input controls (listed above) are still in place.
- In 2010–11, 279 commercial vessels reported catching Western Rocklobster, and an estimated 25 990 recreational fishers fished for rocklobster. There was no specifically recorded Indigenous catch for the season, and no catch was recorded for this sector in the National Recreational and Indigenous Fishing Survey4.
- In the 2010–11 season, the commercial and recreational sectors landed catches of 5501 tonnes (t) and 150 t, respectively.
Figure 2: Commercial catch of Western Rocklobster in Australian waters, 1964–65 to 2010–11 (fishing season)
The commercial catch of 5501 t for 2010–11 was slightly lower than the previous season’s commercial catch of 5899 t and well below the 10-year average of 9293 t. These reductions were due solely to reductions in the total allowable commercial catch, which were made in response to the recent series of low larval recruitments. Historically, the commercial catches of Western Rocklobster have fluctuated with changes in the levels of larval recruitment; these changes often correlate with oceanographic conditions (e.g. El Niño – Southern Oscillation events)5. However, since 2008–09, reductions in commercial catches have reflected the strict catch limits that have been imposed to maintain an adequate level of legal and mature lobsters during the seasons when the series of poor recruitments were predicted to enter the fishery3.
- The legislated design of rocklobster 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, rocklobster fishing occurs on sand areas around robust limestone reef habitats, covered with coralline 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 highly resistant to damage from rocklobster potting. The significant recent reductions in fishing effort will have reduced these risks even further6.
- The incidental capture of juvenile Australian Sea Lions, recognised as a management issue by the Department of Fisheries Western Australia, resulted in the introduction of sea lion excluder devices. These have reduced captures of Australian Sea Lions, and no captures were recorded in 2010–116.
- Australian Sea Lions, seals and sharks are particularly susceptible to injury or death through entanglement in uncut plastic bait bands. These bands also contribute to plastic debris washed up on shorelines. In 2012, a state-wide ban on the carriage of bait bands out to sea was implemented.
- Research monitoring of commercial bycatch occurs across the fishery. No issues of concern have been identified6.
- Annual variation in the abundance of puerulus (larval lobsters) has historically been associated with fluctuations in offshore water temperatures, the strength of the Leeuwin Current and the incidence of storm fronts crossing the west coast during spring5. More recently, other factors, such as offshore winds during settlement, have been identified as possible contributors to these variations.
- Many aspects of the Western Rocklobster’s life history, such as growth, migration, size at maturity and catchability, appear to be sensitive to changes in water temperature. Recent increasing long-term trends in water temperature have occurred at the same time as declines in size at maturity6 and size at migration7, and an increase in the proportion of female lobsters moulting out of setose in autumn8.
a Department of Fisheries, Western Australia