This section provides a brief summary of salient information related to the assessment of the ecological components of the West Coast Managed Lobster Fishery (WCRLF). The western rock lobster Panulirus cygnus (George 1962) is found in temperate waters off the west coast of Western Australia, where juveniles inhabit shallow reefs (< 40 m depth) and adults (> 80 mm carapace length) inhabit habitats of deep offshore (> 40 m depth) including coral reefs in the Houtman Abrolhos Islands (Abrolhos Islands).
Management 1.2
In the cold-water southern areas of their range, WRLs mature at about 6-7 years or about 90 mm carapace length. In the warmer northern waters near Kalbarri and the Abrolhos Islands, they mature at smaller sizes, typically around 70 mm carapace length (Melville-Smith and de Lestang 2006).
Marine Stewardship Council Certification 1.3
Ecological Risk Assessment (ERA) 1.4
Environmental Management Strategy 1.5
Retained and Bycatch species 2
The most important conserved species are listed below according to the resource group they come from. All conserved species comprise less than 5% of the landings of this fishery, with the dominant conserved species (octopus) accounting for only 0.2% of the western rock lobster landings in 2015.
Results 2.2
Commercial monitoring records show a number of fish species, sharks and some smaller crustaceans have been returned, with the vast majority returned alive. Given the likely overestimates of numbers from commercial monitoring compared to those from CDRs (Table 2.2), the estimates of species returned to the sea are considered to be an upper limit.
Retained Species 2.3
As WRL is fished along the mid and lower west coast of Western Australia (Figure 1.1), there is significant overlap with species caught as part of the West Coast Demersal Scalefish Resource. Us/Publications/Pages/Integrated-Fisheries-Management.aspx and a report on the status of demersal fish stocks off the west coast of Australia at: http://www.fish.wa.gov.au/Documents/research_reports/frr253 .pdf .
Bycatch 2.4
Bait 3
Ministerial and Departmental announcements regarding the management changes to the herring fishery can be found at: . http://www.fish.wa.gov.au/About-Us/Media-releases/Pages/_archive/Getting-the-balance-right-for-Herring-recovery.aspx, http://www.fish. wa.gov.au/Species/Australian- Herring/herring-management/Pages/Herring-Management.aspx & .. http://www.fish.wa.gov.au/Documents/recreational_fishing/additional_fishing_information/re building_the_herring_stock.pdf . Links to herring status reports and external reviews of status reports, together with a biological summary of Australian herring and a Department of Recreation pamphlet are provided in the footnote below.10 Now only small quantities of herring are caught in WA for human consumption.
Endangered, threatened and protected species 4
Sea lions and SLEDS 4.1
Both internal and external structures ensure that the diagonal distance from the SLED to the neck of the jar does not exceed 132mm. Mandatory introduction of SLEDs in areas with "potential interaction with sea lions" occurred in November 2006 on the central coast of the state (Figure 4.2). The discovery of the dead sea lion pup in the Abrolhos Islands and the fragility of these populations led to the same SLED design used on the mainland being implemented in SLED areas in the Abrolhos Islands.
Risk areas for interactions in the Abrolhos Islands were identified as being in waters with a depth of 0-20 m around the Easter and Pelsaert groups (South), which are areas of distribution of sea lion cubs and frequent foraging by sea lions. juveniles and females of the sea (Figure 4.2). Following the introduction of SLED in the central west coast area during the 2006/07 seasons, the risk of pot sea lion interactions was reduced from moderate to low in ERA 2007 (Stoklosa 2007).
Cetaceans 4.2
Performance measure target area (green) Gear modifications were introduced in June 2014, in the middle of the migration season. To reduce the number of entanglements with migrating whales, legal gear modifications were implemented on 1 July 2014. They were based around a reduction in the use of rope, the elimination of slack lines on the surface and a reduction in the number of buoys used (Table 4.1; How et al. 2015).
As gear modifications were introduced during the 2014 migration season, the 2015 compliance statistics represent the first full year of compliance data regarding whale entanglement modifications. This assessment included expected changes in whale population size, reporting rate, commercial fishing effort and implementation of gear modifications (started in July 2014).
Dusky Whalers (Carcharhinus obscurus) 4.3
Thus, nine warnings were given to commercial fishermen and three violations were issued to commercial fishermen. The model also highlighted the northern part of the migration and water depths m (20–29 fathoms) as the times and areas most associated with entanglement (for full details of the assessment, see How et al.
Turtles 4.4
Understanding Habitat Structure 5
Habitats used by the western rock lobster 5.1
Migratory immature 'whites' are regularly caught on sandy or muddy bottoms in deeper water, but are unlikely to seek refuge in these habitats due to lack of shelter and food.
Broad scale benthic habitat mapping the extent of western 5.2 rock lobster fishery
Hills were shaded on the bathymetry grid to enhance the geomorphological features of the seafloor (b and c). The overall accuracy of the map was calculated by dividing the overall accuracy by the total number of points in the error matrix. LiDAR provides high-resolution bathymetric data, with much of the West Coast bioregion (Hillarys to Horrocks) first surveyed in 2016.
Year Study Source/ Publications Region Scale Methodology Classification System 2008 Marine Futures (Radford et al. 2008) Abrolhos Islands. 2008 Marine Futures (Radford et al. 2008) Jurien Bay (10–80 m) Fine Multibeam Hydroacoustics Towed Video Transect CART, BRUVs.
Ecosystem 6
Diet and trophic interactions 6.1
Howard 1988 Seven Mile 2-4 m Eelgrass Gut Contents Small Post-Sand Bass (Psammaperca Lobster Vulnerability. Edgar 1990a; Cliff Head < 5 m Amphibolis, Gut Contents Juveniles Cantharidus lepidus Lobsters can significantly b; c and Seven. -85 mm ) which in large amounts consumed when seasonally abundant at Cliff Head and polychaetes consumed in large numbers when seasonally abundant at Seven Mile Beach.
Jernakoff 1993 Seven < 5 m Natural habitats Gut content Post-dominant food products were Post-pueruli that did not forage.
Areas Closed to Fishing 6.2
- Target species (P. cygnus)
- Benthic Assemblages
- Fish Indicators
- Big Bank
A Scientific Advisory Group (SAG) was established in February 2009 to independently review the methods to be used in the associated project, including the size and location of the closure area. WRL in deep water increased at all locations regardless of protection status (Figure 6.2). WRL catch rates increased in the Leeman closed area (L2) and all fisheries (L1, JN and JS), but the increase was greater in the closed area.
The greater increase in undersized fish catch rates in Jurien than in Leeman is also reflected in the size structure (Figure 6.3). In conjunction with annual breeding stock surveys, independent surveys have been conducted in the Big Bank region since 2009.
Other Relevant Research 7
Houtman Abrolhos Islands 7.1
The interpolated benthos habitat map for the MWADZ sites gives a 60% probability of habitat occurrence (Figure 7.2). Benthic mapping of this process overlaps some areas of multi-beam hydroacoustic mapping from the Marine Futures Project (Radford et al. 2008). Collaboration is underway with the University of Western Australia to compare multi-beam and single beam hydroacoustic methods for detecting habitat changes.
PotBOT – Fishery Dependent Habitat Data Collection 7.2
Broad scale WRL habitat association
Catch Discharge Records (CDR) contain fishing data (e.g., fishing effort recorded as the number of potlifts) collected by commercial WRL fishers and aggregated at a resolution of 10 arcminute blocks covering the size of the fishery (Figure 7.4a). These CDR blocks are overlaid on the habitat distribution map to show the distribution of total effort (Figure 7.4b), total catch (Figure 7.4c) and catch rate (Figure 7.4d) data. Figure 7.4 Distribution of major habitats showing a) catch removal blocks (CDR), b) sum of fishing effort (including catches of both red and white lobster), c) sum of catches and d) the catch percentage as of 2015 on the size of the fishery. Reef and kelp dominate coastal habitats, particularly in the southernmost region of the fishery (Figure 7.5a), while invertebrate invertebrates tend to dominate in the northern regions (Figure 7.5b).
In general, fishing effort is concentrated in areas with the highest proportions of reef and reef with kelp, with inshore reefs targeted more than offshore systems (Figure 7.5c). Total catches show similar patterns (Figure 7.5d), but the catch rate (number of WRL per pot lift) increases markedly as you move offshore (Figure 7.5e) and may be the result of lower fishing pressure offshore.
Shallow-water research 7.3
However, if the high abundances of Boullanger's common use zone were excluded, the overall abundance between the fished and unfished areas is less pronounced (Figure 7.10). Similar to the trends observed in mean abundance, the general use areas observed the highest CPUE for all WRL observed (Figure 7.11). The general application areas also recorded higher CPUE when comparing male and female WRL overall, under size (<76 mm) and size (>=76 mm) (Figure 7.11).
This is also evident in this study, with significantly smaller 'size' WRL in the shallow water than submeasures (Figure 7.11). A similar but less clear pattern is shown from UVC data inside and outside the SZ at Rottnest Island, with generally more WRL examined inside the sanctuary zones than the adjacent fished sites (Figure 7.17).
Climate Change 7.4
Future SZ surveys, especially for crayfish species, should require the inclusion of several independent methods to robustly assess SZ performance but also population dynamics. Of a total of 157,740 individuals sampled, the Order Amphipoda comprised almost half of all individuals and was three times more abundant than the second most abundant taxon (Class Gastropoda), which were twice that of Isopoda, Tanaidacea and Ostracoda (class) . There was considerable spatial and seasonal variation in community composition, particularly between tropical/subtropical and temperate sites.
This difference was believed to be due to the greater abundance of taxa in the temperate locations compared to the tropics. Climate change parameters such as increased water temperature and salinity, as well as less frequent and severe storms, significantly affected the abundance of a number of taxa commonly found on the collectors.
The effect of climate change on the spiny lobster (Panulirus cygnus) fishery in Western Australia. Chubb CF, Barker EH and Dibden CJ. Big Bank region with limited entry for spiny lobster Panulirus cygnus. Orientation and migratory dynamics of the western rock lobster, Panulirus cygnus, in Western Australia.
Fisheries Fact Sheet: Western Rock Lobster. http://www.fish.wa.gov.au/Documents/Recreational%20fishing/Fact%20sheets/fact_shee t_western_ rock_lobster.pdf. Spatial and temporal variation in size at maturity of the western rock lobster Panulirus cygnus George.
