SURVEYS OF TROCHUS, HOLOTHURIA, GIANT CLAMS AND THE

Transcription

1 SURVEYS OF TROCHUS, HOLOTHURIA, GIANT CLAMS AND THE CORAL COMMUNITIES AT ASHMORE REEF, CARTIER REEF AND MERMAID REEF, NORTHWESTERN AUSTRALIA: 2003 MAX REES, JAMIE COLQUHOUN, LUKE SMITH AND ANDREW HEYWARD THE AUSTRALIAN INSTITUTE OF MARINE SCIENCE 2003 Produced for Department of Environment and Heritage

2 DISCLAIMER This report has been produced for the sole use of the party who requested it. The application or use of this report and of any data or information (including results of experiments, conclusions, and recommendations) contained within it shall be at the sole risk and responsibility of that party. AIMS do not provide any warranty or assurance as to the accuracy or suitability of the whole or any part of the report, for any particular purpose or application. Subject only to any contrary non-excludable statutory obligations neither AIMS nor its personnel will be responsible to the party requesting the report, or any other person claiming through that party, for any consequences of its use or application (whether in whole or part). 2

3 CONTENTS EXECUTIVE SUMMARY...5 CURRENT FINDINGS...6 HOLOTHURIA...6 TROCHUS...7 TRIDACNIDAE CLAMS...7 CORAL...8 MANAGEMENT RECOMMENDATIONS...8 BACKGROUND...12 ASHMORE REEF...14 CARTIER REEF...15 MERMAID REEF...16 METHODS...17 HABITATS...18 HOLOTHURIA...18 TROCHUS...19 TRIDACNIDAE CLAMS...20 CORALS...20 SURVEY DESIGN...20 RESULTS...21 HOLOTHURIA...22 TROCHUS...29 TRIDACNIDAE CLAMS...36 CORAL...41 SIGNIFICANT FINDINGS AND DISCUSSION...45 HOLOTHURIA...45 TROCHUS...45 TRIDACNIDAE CLAMS...47 CORAL...48 CONCLUSIONS...48 REFERENCES...51 ACKNOWLEDGEMENTS...55 APPENDICES

4 LIST OF FIGURES AND TABLES Figure 1: The far northwest continental shelf showing all Reefs Surveyed in 2003 (figure from AGSO, now GeoScience Australia). The majority of submerged reefs in this region are along the edge of the shelf, and may support additional populations of trochus and holothuria Figure 2: Map of Ashmore Reef showing the location of the different surveys undertaken in October 2000 and May The map shows the starting point for each census (for full GPS locations, see Appendix 3) Figure 3: Map of Cartier Reef showing the location of the different surveys undertaken in November 2001 and May (GPS locations see Appendix 3) Figure 5: Map of Ashmore Reef showing the location of the different habitat types (modified after Skewes et al., 1999) Figure 6: Very dense patches of the holothurian H. leucospilota. The survey identified two high-density areas for this species at Ashmore Reef. One location was previously identified in the 2000 survey Figure 7: Proportion of Holothuria for each species encountered on each of the three reefs. 24 Figure 8: Map of Ashmore Reef showing the relative abundance of T. nilotocus recorded at various sample sites in 2000 and Figure 9: Map of Ashmore Reef showing high-density trochus habitat (in red) calculated at 439 hectares Figure 10: Mean shell basal width of trochus for each reef surveyed in Figure 11: Size frequency distribution of trochus at the three reefs surveyed Figure 12: Average shell basal width of trochus at Ashmore and Cartier Reef in shallow and deep-water habitats Figure 13: Average shell basal width of trochus for different habitats at Ashmore Reef Figure 14: Channels caused by persistent wave and swell action on the southern reef crest at Ashmore Reef where high densities of T. niloticus can be found Figure 15: (A) T.maxima shown in situ on the reef crest/front. (B) Shown in relation to H.hippopus, the largest giant clam species T.gigas in their preferred habitat Figure 16: Dead T.maxima shown in situ on the reef crest/front Figure 17: Proportion of dead and living Tridacnidae clams of each species at Ashmore, Cartier and Mermaid Reefs Figure 18: Mean density of T. maxima clams inhabiting different reef habitats on all reefs. Data from Rose Atoll, Samoan Archipelago (Green and Craig, 1999) is included in Fig. 18(A) as it is considered a refuge for giant clams that have been heavily exploited in surrounding areas of that region Figure 19: (A) Bleached and dying hard coral Goniastrea australensis at Cartier Reef Figure 20: NOAA sea surface temperature anomaly chart indicating a potential bleaching hotspot in the region of Ashmore and Cartier Reefs for March Figure 21: Monthly sea surface temperature charted against coral bleaching threshold SST for Scott Reef Figure 22: Hard and soft coral cover at the AIMS long term monitoring sites at Mermaid and Clerke Reefs from 1994 to Table 1: Dates, number of days and transects completed by the AIMS survey team at each of the reefs in Table 2: Comparison of average densities for six species of holothurians between Ashore, Cartier, Mermaid, the GBR and the Coring-Herald Nature Reserve (and. ha -1,SE in brackets). Species contrasted are those surveyed and present in both regions. N/D indicates no data Table 3: Abundance, density, size and habitat of trochus at Ashmore in 2000 and Cartier in Table 4: Abundance, density, size and habitat of trochus at the three reefs surveyed in Table 5: Mean density of giant clams inhabiting various reef habitats (ind. ha -1,SE in brackets). Data from Rose Atoll, Samoan Archipelago (Green and Craig, 1999) is included, as it has been considered a refuge for giant clams that have been heavily exploited in surrounding areas of that region

5 EXECUTIVE SUMMARY Biologist from the Australian Institute of Marine Science returned to survey Ashmore and Cartier Reefs in May 2003, and Mermaid Reef and the Rowley Shoals were surveyed for the first time in June The objectives were to determine the distribution and abundance of Trochus niloticus and holothuria populations. In addition, the status of giant clam stocks and the coral communities at each of the reefs were investigated. The work was undertaken using the support from the ACV Dame Roma Mitchell, ACV Storm Bay and RV Cape Ferguson. Significant results were the high numbers of Trochus niloticus recorded at Ashmore Reef, widespread coral bleaching in the Ashmore and Cartier regions, and high densities of Holothuria nobilis at Mermaid Reef. The density and diversity of Trochus and holothuria at Cartier Reef were lower than at Ashmore and Mermaid Reefs. 5

6 CURRENT FINDINGS Holothuria Holothuria diversity and abundance varied between the three Australian government marine reserves of Ashmore, Cartier and Mermaid. Cartier has less than half the species of holothuria recorded at Ashmore and Mermaid Reefs. The densities of holothuria recorded at Cartier were very low compared to Ashmore and Mermaid. These differences in diversity and density may be related to Cartier Reef s small size, a history of unregulated access to traditional Indonesian fishers that can fish all habitats over a single tidal cycle, and a limited amount of suitable habitat to support a diverse and abundant community. There is no evidence of holothuria population increases at Cartier in the 18 months since the previous survey. In contrast, Ashmore Reef has the most diverse holothuria community of the three reserves and densities of most species are higher than at Cartier. Marsh et al. (1993) found Ashmore to have a particularly diverse and abundant holothuria community, recording 45 species, although many of these species are not regarded as commercially viable. The two most valued species today, Stichopus chloronotus and Thelenota ananas, have relatively high densities across all habitats at Ashmore (AFMA, 2003). Both of these species were previously regarded as low and medium value, respectively (South Pacific Commission, 1994). The highest value species, T. ananas (Prickly Red), is more abundant at Mermaid, than at Ashmore and Cartier Reef, but all three reefs have reasonably good stocks of this species. Species like Holothuria nobilis and Holothuria timana, which were previously regarded as high value, were rare or absent during the survey. However, both H. nobilis and H. timana were caught in significant numbers by Indonesian fishers in the 1980 s at Ashmore Reef (Russell and Vail 1988). The only reef with significant numbers of H. nobilis was Mermaid Reef. The high value Holothuria fuscogilva (White Teatfish) was found in low densities at Ashmore and Mermaid, but was not recorded at Cartier. 6

7 Interestingly, some high value commercial species were recorded immediately adjacent to the favoured anchorage site for passing Indonesian fishers, inside the deep lagoon near West Island at Ashmore. Fishers may be unable to freedive to the depths in which these individuals were found, and such habitats may provide a refuge for certain species. Trochus Calm conditions permitted a comprehensive census of the southern edge of Ashmore Reef in 2003, a habitat that had not been surveyed in previous years due to unfavourable weather. The highest densities of trochus recorded for the region were found within the narrow reef crest of Ashmore s southern edge (Fig. 9). This population is very important in a regional context, as it is the only large population found within the MOU Box. The population may provide brood stock for future recruitment to surrounding shoals and reefs in the region. Population estimates for trochus at Ashmore were much higher in 2003 than in 2000, because it included this large population that was previously inaccessible. In 2000, trochus densities were 6.4 ind. h -1, compared with 16.8 ind. h -1 for the same habitat in This difference does not indicate recovery of trochus in the low-density habitats, rather, the inclusion of the high-density habitat. Tridacnidae Clams The 2003 survey assessed densities of live and dead giant clams, at Ashmore, Cartier, and Mermaid Reefs. Population densities of live giant clams at Ashmore, Cartier, and Mermaid were similar to other reefs in the region where there has been little exploitation. A greater proportion of dead clams were found at Ashmore and Cartier Reefs than at Mermaid Reef. While this could be a result of Indonesia fishers, it may also be due to adverse environmental conditions (eg. warm water in 1998 and 2003 resulting in mass-bleaching and mortality). However, population numbers are relatively healthy on all reefs surveyed, compared with other reefs previously surveyed in the region. 7

8 Coral The coral communities at Ashmore and Cartier Reef show clear signs of suffering from a coral-bleaching event in Affected corals were at various stages of deterioration. Many corals were bleached white, having expelled their symbiotic zooxanthellae, while others had died and were covered by filamentous algae. Sea surface temperatures, derived from satellite information, show that corals at Ashmore Reef were exposed to abnormally high water temperatures during the first quarter of It is likely that warm water was directly responsible for the mass-mortality at Ashmore in March Similar phenomena were observed on coral reefs around the world in 1998, including Scott Reef, 250 km southwest of Ashmore Reef. The distribution of coral at Ashmore reef is patchy, with large expanses of sand and loose rubble dominating the substrate. Some localised areas of high coral cover (approximately 50-60%) were evident prior to 2000, but were rare in Live unbleached coral rarely exceeded 30% cover. The average coral cover at Cartier Reef was approximately 10%, although there were some areas where coral cover was as high as 40-50%. Corals at Mermaid Reef had escaped any widespread mortality (bleaching), apart from the patchy destruction from anchoring vessels inside the lagoon and the affects of a cyclone in Overall, the coral community is in excellent health, although some disturbance attributed to anchor damage in the deep lagoon was observed. The damage from vessel anchoring was not extensive but is an obvious point of concern that could be alleviated through appropriately located moorings. MANAGEMENT RECOMMENDATIONS The current policy of a total ban on fishing at Ashmore (subsistence fishing is permitted within the West Island lagoon at Ashmore), Cartier, and Mermaid should be maintained and enforced more rigorously. Populations of trochus at Ashmore are healthier than previously thought and could provide an important 8

9 source of brood stock for stock enhancement in the broader region; particularly the extremely depleted stocks at Cartier, Scott, Seringapatam and the previously overfished trochus habitats of Ashmore Reef. A pattern of rapid declines shortly after the commencement of commercial fisheries suggests that T. niloticus is highly susceptible to overfishing (Castell, 1997). This vulnerability to overfishing may be due to a combination of factors: trochus inhabit a clearly-defined and easily accessible zone on coral reefs; the shell is easily found despite its inconspicuous colouration; and larval dispersal is most likely limited (Nash, 1993). Heavily depleted populations (i.e. Cartier Reef) will regenerate slowly, if at all, if recruitment is primarily localised. Recruitment from other reefs is likely to be only slight, or non existent (Nash, 1993), especially for isolated reefs like those in the MOU Box. The fact that the southern edge of Ashmore faces the prevailing weather and swell has protected high-density patches of trochus in this habitat, due to restricted access and logistical difficulties facing fishers using traditional methods and vessels. Effective monitoring, protection and recovery of stocks are reliant on a permanent Australian government presence at Ashmore Reef and other neighbouring reefs and shoals. This presence at Ashmore Reef is acting as a major deterrent to illegal fishers and must be retained. The level of presence should be year round, and larger than at present, because illegal fishing could significantly delay recovery of depleted stocks and further damage existing stocks. Since the recent protection of Cartier and Ashmore, fishing pressure is being directed to unprotected reefs (i.e. Scott, Seringapatam, Browse and other surrounding reefs and shoals). The recovery of trochus and holothuria populations at Ashmore and Cartier depends on the exclusion of illegal fishers. The recovery of stocks at other reefs that are not protected, such as Scott, Seringapatam and Browse, is very unlikely unless they are closed. Historically, both trochus and holothuria fisheries are highly susceptible to overfishing (Nash, 1993). 9

10 Monitoring trochus, holothuria, giant clam, and coral populations should be carried out every two to three years at the study reefs. Regular monitoring will detect any positive or negative changes in the distribution and abundance of stocks resulting from their protection, or from illegal fishing, which may still be occurring at low levels on these reefs. Thought should be given to extending the surveys to include the heavily fished reefs of Scott, Seringapatam, Browse and other such shoals in the MOU Box. Providing protection to some of the reefs in the MOU Box, however, may not reduce the number of traditional Indonesian fishers (effort) each year. Effort may change from closed reefs to open reefs, and from previously targeted species to other species, depending on their abundances, values, and market forces. A more thorough understanding of trochus and holothuria reproductive biology is required for the MOU Box populations. Data on size and age at maturity, dispersal distances, reproductive potential, and growth rates, are required to estimate a sustainable fishing effort (if any) and to provide the basis for estimating the recovery rates of these exploited species. High-value, shallow-water species of holothuria and trochus are depleted at Ashmore and Cartier Reefs. Without intervention, valued trochus and holothuria species depleted or absent from Cartier may not recover. The holothuria and trochus stocks at Scott and Seringapatam Reefs are seriously threatened with local extinction if unrestricted access to fishers continues. Even the low-value species like Holothuria leucospilota, which is relatively abundant at Ashmore Reef, is being grossly over-exploited on other emergent reefs of the MOU Box (AFMA, 2003). To ensure long-term sustainability of the traditional fishery, a broader marine resource management plan needs to be formulated that incorporates all the coral reefs and shoals of the MOU Box and the immediate region. Given the degree of depletion of targeted species on reefs and shoals of the MOU Box, the implementation of such a plan should be considered as a matter of urgency. The plan should allow for the recovery of the targeted stocks and 10

11 implementation of a sustainable harvesting system for traditional Indonesian fishers. A recovered and sustainable fishery is likely to provide much higher returns to traditional fishers than the current heavily depleted fishery. Protected biological refuges such as Ashmore and Cartier would be a critical part of the marine resource management system playing a role in maintaining biodiversity as well as sustaining the fishery in regional terms. 11

12 BACKGROUND Prior to the survey program for this report, surveys were conducted at Ashmore Reef in October 2000 and Cartier Reef in November 2001 by ecologists from the Australian Institute of Marine Science (AIMS). The preliminary objectives in 2000 and 2001 were to determine the distribution and abundance of holothuria and the commercial top shell, T. niloticus, evaluate different census techniques, develop and design a monitoring program of exploited species, and make recommendations for their management. The 2003 survey was expanded to include Mermaid Reef (Fig. 1) at the Rowley Shoals. Mermaid Reef is not part of the MOU Box and has been protected from traditional Indonesian fishing for more than a decade. Mermaid has higher latitude in relation to Ashmore/Cartier and is a greater distance from Indonesia (Fig. 1). Figure 1: The far northwest continental shelf showing all Reefs Surveyed in 2003 (figure from AGSO, now GeoScience Australia). The majority of submerged reefs in this region are along the edge of the shelf, and may support additional populations of trochus and holothuria. 12

13 Including Mermaid Reef in the 2003 survey was primarily to compare the population structure of holothuria, trochus, giant clam and coral communities between reefs with different fishing regimes and different levels of legislative protection. Indonesian fishers have utilised products derived from wild giant clams for many years. Indonesian law passed in 1987 protects all giant clams, though policing the law in Indonesia is difficult (Tomascik et al., 1997). Giant clams are also protected by international law under the CITES Convention. Dead and living clams were included in the survey even though the proportion may not be an accurate indicator of previous fishing pressure. It is known that the shell also has a commercial value despite some references reporting that only the flesh of the clam was targeted by certain fisherman (Tomascik et al., 1997; Campbell and Wilson, 1993). The primary objectives of the 2003 study were to: Provide new data on the current status of holothuria, trochus, giant clam and coral distribution and abundance at Ashmore, Cartier and Mermaid Reefs. Review previous information and provide further information that enables effective monitoring and management of Ashmore, Cartier and Mermaid Reefs. Provide recommendations on how to undertake future monitoring efforts, and management implications from the present study. Ashmore and Cartier Reefs are part of the MOU74 Box, an area managed by the Australian Government under the terms of an agreement between the Australian and Indonesian Governments. In 1983, Ashmore Reef was declared a national nature reserve while Cartier Reef was proclaimed a reserve in June While many reefs and shoals of the MOU74 Box allow for traditional Indonesian fishing, Ashmore Reef and now Cartier Reef do not. However, Indonesian fishers in traditional vessels (praus) can stop-over at Ashmore, replenish water supplies from a well on West Island, and undertake subsistence fishing only within West Island lagoon using a single line 13

14 (Environment Australia, 2002). Currently, Australian Customs Vessels (ACV) provide on site management throughout the year at Ashmore and Cartier Reefs, ensuring compliance to the Ashmore Reef National Nature Reserve and Cartier Island Marine Reserve Management Plan. Ashmore Reef Ashmore Reef (12 17 S, E) (Fig. 2) is a large emergent reef system, approximately 227km 2 in area, located on the northwestern extremity of the Sahul Shelf off the northwest coast of Australia. Figure 2: Map of Ashmore Reef showing the location of the different surveys undertaken in October 2000 and May The map shows the starting point for each census (for full GPS locations, see Appendix 3). Ashmore Reef is a shelf-edge atoll with an east-west orientation, situated to the north of the main belt of tropical cyclones that form in the Timor Sea (Berry, 1993). Reef morphology suggests that the prevailing swell is from the south, rather than from the west or southwest, as at Mermaid or Scott Reef further south. Due to the large breaks in the reef at Ashmore, there is less impounding of water within the lagoons as occurs at the Rowley Shoals (Berry and Marsh, 1986). A conspicuous feature of the reef is an extensive reef flat system, consisting of large areas of seagrass interspersed with corals and bare sandy flats. Ashmore 14

15 Reef is a very sandy reef with 70% sand cover (Skewes et. al., 1999). There is high cover of hard substrate such as pavement (18-33% cover) or consolidated rubble (27-32% cover) (Skewes et. al., 1999). The extensive sea-grass communities support a resident dugong population. Three sand cays have formed on the reef flat zone, West, Middle and East Islands. All three are vegetated, while only two have extensive bird populations. South of Middle Island are huge expanses of sand flat devoid of algal turf or seagrass, whereas the sand flats to the north of the island support prolific algal turf, some seagrass and a richer benthic fauna (Berry, 1993). The lagoon has two deep basins with maximum depths of approximately 30 metres. Numerous patch reefs of varying sizes rise from the sandy bottom, some reaching the surface at low spring tides. The western lagoon is deep ( 15m) with relatively clear water, while the eastern lagoon is shallow ( 10m deep) with highly turbid waters. Coral communities dominate the reef crest and slope, with more than 256 scleractinian coral species found at Ashmore Reef (Veron 1993). Cartier Reef Figure 3: Map of Cartier Reef showing the location of the different surveys undertaken in November 2001 and May (GPS locations see Appendix 3). 15

16 Cartier Reef (12 32 S, E) is a small oval shaped platform reef, approximately 12 km 2 in area, on the edge of the continental shelf off the northwest Kimberley coastline of Western Australia (Fig.1). Cartier has a small single, supratidal, unvegetated sand cay (Fig.3). Similar to Ashmore Reef, it is orientated with the long axis east west. The southern outer reef slope, exposed to the prevailing weather conditions, is wide, gently sloping, with very little hard coral growth, whereas the northern side drops off steeply to 20 m and soft coral growth is prolific. At the bottom of the drop-off is a sandy ledge approximately 45 m wide, preferred by many holothuria. The northern section of the reef has a crest of consolidated pavement, developing into a reef flat approximately 500 m wide, made of unconsolidated coral rubble and dead coral slabs, with a low cover of living coral growth and sparse Thalassia sp. (this report, Berry, 1993). Mermaid Reef Mermaid (17 7 S, E) is the northern most reef of the Rowley Shoals, approximately 89.1 km 2, located off the northwest coast of Australia. Mermaid is an emergent annular shelf reef with a north south orientation (Fig.4). Mermaid Reef is completely submerged at high tide so falls under Australian Government jurisdiction and was declared a Marine National Nature Reserve on 21 March The western side of the reef is comprised of approximately 500 m of outer reef flat, Figure 4: Map of Mermaid Reef 500 m of back reef flat and 1000 m of sand, whereas the eastern side has a showing the location of the surveys undertaken in June (For full GPS locations, see Appendix 3). total width of 600 m (Berry and Marsh, 1986). The outer reef slope of the western side is relatively barren and wave- 16

17 swept with spur and groove channels sloping to a coral covered ledge at 12 m and then dropping off to 30 m (This report; Berry and Marsh, 1986). The outer reef flat has low-growing corals and encrusting coralline algae, while the reef flat has a cover of living and dead coral with some algal turf. The back reef, which drops in elevation, has a diverse coral fauna including staghorn Acropora in some areas and patches of the seagrass, Thalassia hemprichii, which then gives way to a broad sand sheet with scattered patches of corals (Berry and Marsh, 1986). Mermaid Reef has a large single lagoon basin with average depths of 20 m enclosed by an outer reef rim with a small channel passage on the eastern side allowing anchorage within the lagoon. The lagoon floor is uneven, with numerous coral bommies and extensive live coral growth, consolidated and unconsolidated rubble and very little sand. The emergent rim of the reef impounds water at high tide. At low water, a large sand cay at the northern edge of the lagoon and several smaller cays to the west are exposed. The prevailing weather and swells come from the southwest and are responsible for forming the wider reef flats on the western margin of the reef. METHODS Fieldwork was carried out in two blocks: May 5-21 at Ashmore and Cartier and June 6-10 at Mermaid Reef. Field surveys for this report were more extensive than previous surveys with an additional reef included. Fieldwork relied on an AIMS survey team and the vessels and infrastructure of the Australian Customs Service (ACV Dame Roma Mitchell, ACV Storm Bay) at Ashmore and Cartier Reefs and the AIMS research vessel (RV Cape Ferguson) at Mermaid Reef. Due to the experience of the AIMS survey team at Ashmore in 2000 and Cartier in 2001 it was decided to use two broad census techniques: snorkel and dive (SCUBA) distance swim transects to census trochus, holothuria and clam populations. Due to the large size of the survey area and the time constraints on the survey team, these two methods enabled censuses of large areas of each reef at different depths and habitats. 17

18 HABITATS Trochus, species of holothuria, and giant clams, inhabit various parts of the reef with some over lap of preferred habitat (Fig. 5). Figure 5: Map of Ashmore Reef showing the location of the different habitat types (modified after Skewes et al., 1999). Holothuria Holothuria typically inhabit areas of the reef with a mixture of sand, rubble, hard substratum and small coral outcrops, located on the reef flat, bottom of the reef slope, reef front, and lagoon, although some species seem to have specific habitat requirements. For example Actinopyga mauritiana (Surf Redfish) inhabits hard reef substratum on the outside of the reef where there is breaking waves and strong currents (Uthicke, 1996), usually up to 10 m depth, the same habitat as T. niloticus. A. mauritiana attaches its tube feet firmly to the hard reef substratum to prevent being moved by the waves and currents (South Pacific Commission, 1979). Bohadschia graffei and Actinopyga lecanora prefer habitats with hard substrata but do not require habitats with breaking waves and strong currents (Uthicke, 1996) and are usually found at greater depths than A. mauritiana. Holothuria atra and 18

19 Stichopus chloronotus occur in two different habitats at different sizes. The smaller sized morphs occur in shallow habitats and the larger morphs in deeper habitats (Uthicke, 1996). T. ananas seems to be able to tolerate a wide variety of habitats, from shallow water sandy habitats to deep-water rubble and sand habitats. Many species are selective for particular grain sizes of sediments (fine or coarse) and are therefore restricted to habitats that have patches of a specific grain sized sediments i.e. Bohadschia argus, Holothuria edulis and S. chloronotus (Uthicke, 1996). The main habitat characteristics that determine distribution and abundance of the diverse community of holothuria at the survey reefs seems to be substrate type, sediment size, water depth and movement. Trochus Previous studies have shown that juvenile trochus are abundant chiefly on the reef flat habitat while adults are more common on the reef crest and slope (Colquhoun, 2001). The preferred habitat of trochus at Ashmore Reef is off the southern (windward) margin, which is gently inclined (approx. 5 ) forming a shelf of consolidated pavement approximately 150 m wide (Berry, 1993). Trochus inhabit very similar habitats at Cartier and Mermaid Reefs. Soft corals are dominant with hard corals sparsely scattered or in small isolated patches (Berry, 1993). The prevailing weather and strong tidal surge has formed surge channels in a spur and groove formation. These channels have smooth surfaces covered in turf algae, ideally suited to grazing trochus. Trochus typically inhabit hard reef or consolidated substratum on the crest, upper part of the reef slope and outer parts of the reef flat (This report). However they can also be found at depths of up to 30 m at the bottom of the reef slope, generally on dead coral slabs where there is an abundance of turf algae. Trochus are also occasionally found in smaller numbers on hard substratum in the back reef areas. The preferred habitat of trochus relates to both reef type and water movement, however regional differences in the ecology of trochus are inherent (Amos, 1991; Nash, 1993). 19

20 Tridacnidae Clams Typically, the giant clams of Ashmore, Cartier and Mermaid Reefs inhabit the shallow waters of the reef flat; lagoon and reef slope because light intensity and spectral quality affect their distribution (Yasin and Tan Shau-Hwai, 2000). At Mermaid, Ashmore and Cartier due to the high clarity of the water they are found deeper. There are eight known species of living giant clam, (Calumpong, 1992), six species occurring within the study area. Corals The coral communities of Ashmore, Cartier and Mermaid Reefs are reasonably distinctive, particularly by way of their relative size and geological structure. In terms of likeness the reefs are all geographically remote and characterised by clear deep warm oceanic waters, strong wave action on exposed outer slopes and a wide tidal range (Veron, 1986). The main habitats associated with live coral cover at the target reefs are: fore-reef slope, reef slope, reef crest, reef flat and back reef (Tomascik, 1997). The clear waters like that of Mermaid Reef allow coral communities to exist over a great depth range, powerful wave action on the outer slopes and the wide tidal range causes strong zonation among the benthic community, (Veron, 1986). Survey Design In order to optimise sampling time and efficiency the sampling design was stratified. Stratified sampling ensures the survey team covers the preferred habitats of the target species (trochus, holothuria and giant clams). With the help of satellite imagery, navigation charts and broad visual census potential habitat was identified for census and targeted. Unfortunately the sampling design is dependent on logistical constraints (time and money). Due to extremely dense patches of the Holothuria leucospilota in two particular regions they were not counted in those areas but were counted on all other transects (Fig. 6). Figure 6: Very dense patches of the holothurian H. leucospilota. The survey identified two high-density areas for this species at Ashmore Reef. One location was previously identified in the 2000 survey. 20

21 Distance Swim (snorkel) and Dive (SCUBA) Technique Three swimmers were dropped close to a chosen habitat. Each swimmer would spread out approximately 10 m apart and census a 500 m x 5 m area parallel to each other. Each of three swimmers would census 2500 m 2. Each distance swim with three swimmers would census a total area of 7500 m 2. Latitude and longitude of the start and finish points for all distance swims were recorded using a Geographical Positioning System (GPS). To census trochus the swimmer on the outside counted and measured the shell basal width of all trochus on the edge of the reef crest and the upper part of the reef slope. The middle and inner swimmers counted and measured the shell basal width of all trochus on the outer reef flat. For each distance swim all trochus were counted and shell basal width measured in an area of 7500 m 2 (2500 m 2 /swimmer) of reef substratum. The same technique was use to census holothuria and giant clams, however holothuria and giant clams were identified to species and counted but no measurements were recorded. Tridacnidae clam species census had to consider both living and dead specimens. The only dead clams included in the census were those with two halves of the shell still joined and intact but without the living tissue. In order to census the target species at greater depths (30 m) the same method was used except SCUBA replaced snorkel. RESULTS Conducive weather conditions during the survey allowed the team to census all target species at all reefs. Time constraints limited deep dives at Ashmore and Mermaid Reefs to only one at each reef in preferred trochus habitat, however the survey covered a considerable area and came up with some interesting findings (Table 1). 21

22 Table 1: Dates, number of days and transects completed by the AIMS survey team at each of the reefs in Reef Ashmore Cartier Mermaid Survey dates May 5-10, May June 6-10 No. of survey days Number of trochus swims (7500 m 2 ) Number of Holothuria swims (7500 m 2 ) 30 4(2)* 21 Number of Deep dives (7500 m 2 ) Total census area (hectares) *Four swims were 7500 m 2 each; two swims were m 2 each. Holothuria The density/hectare, proportion and diversity of holothuria recorded at each reef were quite variable (Fig. 7; Appendix 1). Ashmore Reef had the most diverse community of holothuria with seventeen species recorded during the survey. Fifteen species were recorded at Mermaid Reef and Cartier Reef had the lowest diversity with eight species recorded (Appendix 1). Notable at Cartier Reef was the absence of many high value commercial species (Appendix 1). The most valued commercial holothurian currently is T. ananas, however prices are dynamic and would depend on availability and other market forces (Appendix 2). T. ananas was present on all reefs with densities highest at Mermaid (8.82 ind. ha -1 ; 1.83 SE), then Ashmore (3.82 ind. ha -1 ; 0.87 SE) and the lowest at Cartier (0.57 ind. ha -1 ; 0.29 SE) (Table 5; Appendix 1). T. ananas was recorded in shallow and deep-water habitats at Ashmore and Mermaid Reefs but only in deep-water habitats at Cartier Reef (Table 5; Appendix 1). The next high value species is currently S. chloronotus (Appendix 2), which was absent from Mermaid and Cartier Reefs but had high densities (6.75 ind. ha -1 ; 1.59 SE) at Ashmore Reef and consistent numbers across all habitats within the reef (Table 5; Appendix 1). Mermaid Reef also had high densities of H. nobilis (9.24 ind. ha -1 ; 2.13 SE) relative to Ashmore Reef (0.40 ind. ha -1 ; 0.13 SE) and Cartier Reef with zero recorded (Table 5, Appendix 1). Very high densities of H. leucospilota in excess of ind. ha -1 were estimated at two distinct areas within the reef at Ashmore (Fig. 6). GPS 22

23 positions were recorded for both areas in order to monitor the variability over time. Elsewhere on the reef at Ashmore H. leucospilota had very low densities (0.73 ind. ha -1 ; 0.26 SE), (0.04 ind. ha -1 ; 0.04 SE) for Mermaid Reef and zero for Cartier Reef (Appendix 1). H.atra occurred in very high densities within all habitats on all reefs except for the reef crest habitat at Cartier Reef (Appendix 1). Proportionally H. atra was the most abundant species at all reefs (Fig. 7). However it was difficult to distinguish whether H. atra or H. leucospilota was the most abundant species at Ashmore Reef. Holothuria were not recorded on the reef crest at Cartier Reef and only H. atra and H. argus were recorded within the reef flat habitat (Appendix 1). At Cartier, the only substantial numbers of holothuria were recorded on the deep distance dives, however these numbers were considerably lower in comparison to the other two reefs (Appendix 1). 23

24 0.5 Ashmore Reef 0.4 proportion H. atra S. chloronotus 0.5 T. ananas A. mauritiana H. edulis S. variegatus H. fuscopunc. T. anax B. graeffei H. leucospilota species H. coluber B. argus H. nobilis A. sp. H. fuscogilva A. lecanora B. marmorata Cartier Reef 0.4 proportion H. atra S. chloronotus T. ananas A. mauritiana H. edulis S. variegatus H. fuscopunc. T. anax B. graeffei H. leucospilota species H. coluber B. argus H. nobilis A. sp. H. fuscogilva A. lecanora B. marmorata Mermaid Reef proportion H. atra S. chloronotus T. ananas A. mauritiana H. edulis S. variegatus H. fuscopunc. T. anax B. graeffei H. leucospilota H. coluber species B. argus H. nobilis A. sp. H. fuscogilva A. lecanora B. marmorata Figure 7: Proportion of Holothuria for each species encountered on each of the three reefs. 24

25 Table 2: Comparison of average densities for six species of holothurians between Ashore, Cartier, Mermaid, the GBR and the Coring-Herald Nature Reserve (ind. ha -1,SE in brackets). Species contrasted are those surveyed and present in both regions. N/D indicates no data. Reef/Study Ashmore Reef, Timor sea This Report Cartier Reef, Timor Sea This Report Mermaid Reef, North west Shelf This Report 5 reefs Coringa- Herald NNR Oxley et al., (2003) 5 reefs Coringa- Herald NNR Oxley et al., (2003) 26 Outer shelf reefs GBR Benzie and Uthicke, (2003) 33 Mid shelf reefs GBR Benzie and Uthicke, (2003) Ashmore Reef, Timor Sea Smith et al., (2001) Cartier Reef, Timor Sea Smith et al., (2002) Habitat Zone 0.40 Total (0.13) Sandy Lagoon Deep water (0.28) 1.04 Reef flat (0.45) 0.15 Reef crest (0.13) Total 0 Deep water 0 Reef flat 0 H.nobilis H.atra S.chloronotus B.argus A.mauritiana T.ananas (4.26) 6.75 (1.59) 0.46 (0.19) 2.72 (0.98) (2.04) (6.55) (0.39) (5.68) (1.49) (0.48) (2.91) (15.72) (4.98) (6.77) (3.14) (0.29) (0.64) (0.59) 0 (0.35) (0.08) (0.31) 0 (1.07) (0.31) 2.31 (1.13) (0.87) 0.29 (0.29) 8.29 (2.26) 0.35 (0.24) 2.69 (1.17) 0.57 (0.29) 2.15 (0.97) 0.69 (0.37) 0 0 Reef crest Total 9.24 (2.13) (2.48) (1.43) 0.66 (0.26) 8.82 (1.83) Deep water 0.53 (0.36) (6.94) (4.79) (6.20) Reef flat (2.85) (3.16) (1.71) 0.88 (0.38) 9.94 (2.34) Reef crest (6.00) (3.23) 0 (0.53) (0.36) (0.86) Reef flat 1.60 (3.58) Back reef 6.04 (9.68) Reef flat (9.13) Reef flat 6.07 (8.60) 21.8 (21.8) (141.40) (166.57) (275.65) 0.60 (1.34) (24.40) (55.33) (163.78) 0.20 (0.45) 4.44 (2.68) 4.11 (4.88) 5.75 (9.07) (2.35) 5.9 (8.23) Not counted 1.22 (5.30) Not counted 0.74 (2.51)) Reef flat Reef flat

26 H. nobilis (Black Teatfish) Black often covered in fine sand, occurs in average densities of approx 10 animals per hectare and prefers shallow reef bottoms. It has high to moderate commercial value, has a thick body wall and has very low 25 abundance at Ashmore and Cartier Reefs in comparison to abundances at Mermaid Reef, and mid-outer regions of the GBR. Mean No Per Hectare / H. atra (Lollyfish) 0 Ashmore Cartier Mermaid Coringa Herald GBR Out Shelf GBR Mid Shelf Black often covered in fine sand, occurs in average densities of several hundred animals per hectare and occurs across all reef habitats. It has low commercial value and has a thin body wall. The numbers on the reef flat at Ashmore are consistent with those seen on other reefs in the GBR. At Cartier reef the overall density was lower than other reefs surveyed (Table 5). Mean No Per Hectare Location / Ashmore Cartier Mermaid Coringa Herald GBR Out Shelf GBR Mid Shelf Location 26

27 S. chloronotus (Greenfish). Dark green with orange tipped papillae, occurs in average densities of several hundred animals per hectare across all reef habitats. It has a relatively thin body wall and has previously been reported to have low commercial value (Conand, 1994), however AFMA reported the species to be of high value following interviews with fishers at Scott Reef in 2003 (Appendix 2). Interestingly there were no 300 S.chloronotus recorded at Mermaid 250 Reef in any of the habitats (Table / ). Mean No Per Hecatre B. argus (Leopard Fish) Mottled brown-orange with a cream appearance, occurs in average densities of animals per hectare across all reef habitats though generally in low abundance on the reef crest. It has relatively low commercial value, has a moderately thick body wall and often extrudes cuverian tubules when disturbed. At Ashmore reef there were no B.argus on the reef flat although they were found in the other habitats (Table 5). The overall density of the population was greater at Mermaid Reef than elsewhere. Mean No Per Hectare Ashmore Ashmore Cartier Cartier /2002 Mermaid Mermaid Coringa Herald Location Coringa Herald Location GBR Out Shelf GBR Out Shelf GBR Mid Shelf GBR Mid Shelf 27

28 T. ananas ( Prickly Redfish) Reddish/brown with a distinctive appearance due to pointed teats all over the body surface occurs in average densities of 20 animals per hectare and can be found across all reef habitats. It has a very thick body wall and high commercial value (the highest according to AFMA, 2003) (Appendix 2). Though densities are low on the reef flat at all reefs in comparison to Mermaid, other habitats are able to support higher numbers and 14 appear to be preferred, particularly 12 deeper water (Table 5). The overall 10 density of the population was 8 greater at Mermaid Reef than 6 elsewhere. 4 Mean No Per Hectare / Ashmore Cartier Mermaid Coringa Herald GBR Out Shelf GBR Mid Shelf Location 28

29 Trochus Some of the significant findings of the 2003 survey are the high variability in trochus population density, mean shell basal width (MSW) and abundance between reefs. The distribution of trochus on the survey reefs was also interesting with clear patterns emerging (Fig. 8). The highest densities of animals were recorded on the southern side of Ashmore Reef, facing the prevailing weather conditions (Fig. 8), with densities decreasing down the eastern and northern sides. Figure 8: Map of Ashmore Reef showing the relative abundance of T. nilotocus recorded at various sample sites in 2000 and There was also a large difference in density and abundance between the 2000 and 2003 survey at Ashmore. The average density/ hectare of trochus on the reef crest/slope during the 2000 survey at Ashmore was 6.4 (Table 3) compared to for the 2003 survey (Table 4). This difference is attributed primarily to not being able to sample the southern side of Ashmore Reef due to unfavourable weather conditions during the 2000 survey. Only 34 trochus with a MSW of 88mm were found at Ashmore in 2000 whereas 1462 with a MSW of 81 mm were recorded in 2003 (Table 4). The difference in MSW between surveys may be attributed to the large difference in the number of 29

30 animals measured at each survey. At Ashmore Reef, the southern crest and slope area, where most trochus occurred, is categorised as the high-density trochus habitat in this report. The area calculated for the high-density trochus habitat can be seen in Figure 9. Sixty trochus were found at Cartier in 2003 with a MSW of 92.4 compared to 58 with a MSW of 97.8 mm in At Mermaid Reef a total of 146 trochus with a MSW of were found (Table 4, Fig. 10). Density/hectare between reefs and between surveys is considerably different (Table 3, Table 4). A difference in density between surveys is largely due to differences in survey method i.e. number of samples, technique and area sampled. From the surveys we were able to estimate the area of preferred trochus habitat for each reef (Table 4). 30

31 Table 3: Abundance, density, size and habitat of trochus at Ashmore in 2000 and Cartier in Reef Ashmore (October Cartier (November 2001) 2000) Total no. of trochus Average shell basal width (mm) Average density/hectare Total no. of hectares Table 4: Abundance, density, size and habitat of trochus at the three reefs surveyed in Reef Ashmore highdensity Ashmore low-density (remainder) Cartier Mermaid Total no. of trochus Average shell basal width (mm) Maximum density/hectare in trochus habitat Total reef area (hectares) 22,700 22, ,000 Trochus habitat (hectares) Average density/hectare in preferred trochus habitat Trochus population estimate 67, 559 7,763 1,422 28,769 Figure 9: Map of Ashmore Reef showing high-density trochus habitat (in red) calculated at 439 hectares. 31

32 Mermaid Reef is considerably smaller in total area than Ashmore, however the area of preferred trochus habitat is similar at both reefs if all habitat where trochus are found on both reefs is considered (Table 4). Even though the area of preferred trochus habitat at Ashmore and Mermaid is similar the density/hectare and size structure is very different (Table 4). The population size structure of trochus at each reef surveyed is quite different (Fig. 10), however the sample size at Cartier and Mermaid was much smaller than at Ashmore (Table 4) mean basal width (mm) Ashmore Cartier Mermaid Reef Figure 10: Mean shell basal width of trochus for each reef surveyed in The population size structure at Ashmore ranged from mm MSW with the majority of animals in the mm size class (Fig. 11). The population at Cartier had the same size range as Ashmore, however the majority of animals were in the mm size class (Fig. 11). The population size structure at Mermaid ranged from mm with the majority of animals in the mm range (Fig. 11). 32

33 600 Ashmore Reef Cartier Reef 16 number of animals Mermaid Reef size class (mm) Figure 11: Size frequency distribution of trochus at the three reefs surveyed. 33

34 Other interesting findings regarding the population dynamics of trochus at Ashmore and Cartier were differences in the size structure in different water depths (Fig. 12) and horizontally across preferred trochus habitat from the reef crest to the top of the reef slope (Fig. 13) The MSW for trochus in shallow water (0-15 m) was considerably lower than in deep water at Ashmore and Cartier, however only 7 and 38 animals were collected in deep water and 1455 and 22 in shallow water respectively (Fig. 12). The MSW for Ashmore and Cartier was 81 mm and 78 mm in shallow water and 103 mm and 101 mm in deep water respectively (Fig. 12). 110 Deep (15-30 m) Shallow (0-15 m) mean basal width (mm) N=7 N=38 80 N=1455 N=22 Ashmore Reef Cartier Figure 12: Average shell basal width of trochus at Ashmore and Cartier Reef in shallow and deep-water habitats. There is an obvious size gradient of trochus from the reef crest to the top of the reef slope (Fig. 13) and continuing into deeper water (Fig. 13). Animals on the reef crest have a smaller MSW (77 mm) than animals on the reef flat (81.5 mm) and on the reef slope (83.5 mm) (Fig. 13). 34

35 mean basal width (mm) Reef Crest Reef Flat Reef Slope reef zone Figure 13: Average shell basal width of trochus for different habitats at Ashmore Reef. Although it was not quantified, observers noted that the density of trochus was variable within the reef habitats they occupied. Approximately 80% of all the trochus found in the high-density habitat on the southern fringe of Ashmore occurred in a distinct microhabitat; spur and groove surge channels formed by the prevailing swells (Fig. 14). Figure 14: Channels caused by persistent wave and swell action on the southern reef crest at Ashmore Reef where high densities of T. niloticus can be found. 35

36 Tridacnidae Clams Three species of giant clam from the family Tridacnidae were included in the survey at the target reefs; Tridacna maxima, Tridacna gigas and Hippopus hippopus (Fig. 15) Six of the eight known giant clam species were identified during the surveys: T. maxima, T. gigas, H. hippopus, T. squamosa, T. derasa and T. crocea; However due to the possibility of taxonomic imprecision and in the interest of census efficiency only three species were recorded in the census that could be considered a vulnerable target to traditional Indonesian fishers (ie. Non-boring clams). Certain species of giant clams inhabit the same areas of reef and it was problematic to quickly and accurately distinguish among all species during census swims. (A) Figure 15: (A) T.maxima shown in situ on the reef crest/front. (B) Shown in relation to H.hippopus, the largest giant clam species T.gigas in their preferred habitat. (B) Dead clams were also counted for the three target species but only when both halves of the shell were present and intact (Fig. 16). Figure 16: Dead T.maxima shown in situ on the reef crest/front. The proportion of dead and living individuals of the three species of giant clam was estimated from the 2003 survey at all reefs (Fig. 17). Of significance is the high proportion of dead H. hippopus compared to living at Ashmore and Cartier Reefs (Fig. 17). At Ashmore there were higher numbers of dead H. 36

37 hippopus (798) than living (740) (Fig. 17). Cartier had 715 living H. hippopus and 544 dead. Mermaid had very low numbers of H. hippopus with 46 living and 9 dead recorded. No living T. gigas were found at Cartier, however 1 dead specimen was recorded (Fig. 17). This is in contrast to Ashmore with 49 living and 13 dead and Mermaid with 79 living and 5 dead. Mermaid Reef recorded the highest number of living T. maxima (793) and T. gigas (79) of the three reefs and the lowest number of living H. hippopus (46 animals) (Fig. 17). Living T. maxima had the most widespread distribution occurring in all threereef habitats on all reefs (Fig. 18). Living T. gigas occurs in all reef habitats at Ashmore, was absent from Cartier and was only recorded on the reef flat habitat at Mermaid. Living H. hippopus occur in all reef habitats at Ashmore, on the reef crest and reef flat at Cartier but not in deep water and only on the reef flat at Mermaid. T. maxima populations were healthy on the reef crest of all three reefs except for a small number of dead animals on the reef crest at Ashmore (Fig. 18). 37

38 N=456 Ashmore Reef Live clam Dead clam N= N=740 N= N= N=25 T. maxima T. gigas T. hippopus 1.0 Cartier Reef Live clam Dead clam 0.8 N=1 proportion 0.6 N= N=715 N= N= T. maxima T. gigas T. hippopus 1.0 Mermaid Reef Live clam Dead clam 0.8 N=793 N=79 N= N=9 N=17 N=5 T. maxima T. gigas T. hippopus species Figure 17: Proportion of dead and living Tridacnidae clams of each species at Ashmore, Cartier and Mermaid Reefs. The observed density of T. maxima populations on the reef crest at Ashmore and Cartier Reefs was similar to a study of giant clam density at Rose Atoll in the Samoan Archipelago (Green and Craig, 1999), however the density of T.maxima on the reef crest at Mermaid Reef was greater (Fig. 18A). 38

39 180 Numbers per Hectare Reef crest Reef flat Deep water 20 (A) T. maxima 0 Mermaid Cartier Ashmore Rose Atoll Reef Reef crest Reef Flat Deep Water 140 Numbers per Hectare (B) H.hippopus 0 Mermaid Cartier Ashmore Location 7 6 Reef Crest Reef Flat Deep Water Numbers per Hectare (C) T.gigas 0 Mermaid Cartier Ashmore Location Figure 18: Mean density of T. maxima clams inhabiting different reef habitats on all reefs. Data from Rose Atoll, Samoan Archipelago (Green and Craig, 1999) is included in Fig. 18(A) as it is considered a refuge for giant clams that have been heavily exploited in surrounding areas of that region. 39

40 An interesting observation when compared to Rose Atoll is the number of giant clams recorded on the reef flat at the target reefs. At Rose Atoll the reef flat supported the greatest number of giant clams (T. maxima) for that reef. At Ashmore and Cartier reefs it is H.hippopus that is the dominant species in that zone (Table 5.). The density of live H.hippopus on the reef flat at Cartier Reef was more than three times that recorded in the survey of T.maxima for the same habitat at Rose Atoll (Table 5.). The densities of H.hippopus at Ashmore Reef on the reef flat were also very high. An exception to this pattern was apparent at Mermaid Reef where H.hippopus occurred in very low densities. The density of T.gigas at Mermaid Reef was similar to that of Ashmore. Both reefs supported the highest density of T.gigas individuals for that species in deep water and on the reef flat. Table 5: Mean density of giant clams inhabiting various reef habitats (ind. ha -1,SE in brackets). Data from Rose Atoll, Samoan Archipelago (Green and Craig, 1999) is included, as it has been considered a refuge for giant clams that have been heavily exploited in surrounding areas of that region. Tridacna maxima Mermaid Reef zone Reef Reef crest (45.86) Reef flat (1.69) Deep water (8.80) Cartier Reef (3.87) 1.72 (0.75) 4.31 (1.24) Reef crest 0 0 Tridacna 4.77 gigas Reef flat (1.21) Deep water (0.54) Reef crest (1.41) (20.95) Hippopus hippopus Reef flat (0.64) (34.57) 0.22 Deep water (0.22) 0 Ashmore Reef Rose Atoll (5.06) (12.00) (1.73) (19.00) 5.43 (1.29) (0.28) (2.43) (0.43) (3.01) (16.42) (0.50) - 40

41 Coral Ashmore Reef The percent coral cover at Ashmore Reef was patchy and highly variable depending on habitat. Areas that once supported high live coral cover have been reduced since the initial 2000 survey. Some mortality appeared to be very recent and can be clearly attributed to coral bleaching as many corals were bleached and dying while the survey was in progress (Fig. 19). (A) (B) Figure 19: (A) Bleached and dying hard coral Goniastrea australensis at Cartier Reef. (B) Bleached and dying soft coral Sinularia sp., at Ashmore reef, (both images taken in May 2003). Bleaching of corals is caused by induced stress in coral colonies that may be the result of changes in local environmental conditions such as elevated seawater temperatures, changes in salinity or turbidity. Sea surface temperatures in the region during March 2003 were elevated and the NOAA bleaching hotspot indicators showed potential for widespread coral bleaching during that period (Fig. 20). 41

42 Figure 20: NOAA sea surface temperature anomaly chart indicating a potential bleaching hotspot in the region of Ashmore and Cartier Reefs for March Temperature data from Scott Reef also indicates that temperatures exceeding the bleaching threshold for coral were reached in the months of December, January and February 2003 (Fig. 21). Coral Bleaching Threshold SST = Maximum Monthly Mean SST + 1 degree C Figure 21: Monthly sea surface temperature charted against coral bleaching threshold SST for Scott Reef. 42

43 The areas of highest coral cover at Ashmore Reef were located in various parts of the deep lagoon. Outcrops of high coral cover were mixed with discrete patches of low live coral cover surrounded by expanses of sand and sandy rubble. Some reef slope communities supported high coral cover with 30-40% cover being the highest estimate. Ashmore Reef s underwater landscape is vast and has extensive sand dominated lagoons that support very little coral overall. The overall live coral cover at Ashmore Reef may be less than 5%, however Ashmore has the most diverse community of scleractinian corals of all the reefs in the northwest of Western Australia (Veron, 1993). Bleaching events may reduce this diversity possibly creating localised extinctions of some species of coral. Cartier Reef At Cartier reef the areas of high coral cover were associated with the deepwater communities surrounding the reef and the reef slope. Bleaching has also depleted the coral community at Cartier with an estimated 30% of the live corals affected. The reef flat at Cartier has very low coral cover however the substrate consisted of a high proportion of dead coral. The water level in the lagoon has caused many colonies of Porites sp. and Heliopora coerulea to have a common growth form; a flattened dead upper surface often exposed between tides with laterally spreading live coral growing in the vertical plane around the circumference of the colony. Live coral cover overall at Cartier Reef was estimated at 10%. There were patches of higher (40-50%) live coral cover occurring on the outer slopes, a mixture of hard and soft corals dominating the northern side while hard corals were more dominant in the shallow slope of the southern side. Mermaid Reef Mermaid Reef did not experience the same widespread bleaching during 2003 that affected both Ashmore and Cartier. As a result the coral community appeared to be in good health despite some signs of degradation in the deep lagoon where obvious anchor damage could be sighted. Some patches of coral at Mermaid were estimated at 50% on the outer slopes, which is 43

44 consistent with historical long-term monitoring data collected from that reef (Fig. 22). The percent cover estimates presented in Fig. 22 are based on the AIMS LTM sites located on the outer slope to the south of the lagoon channel entrance. The last time videographic monitoring data was collected was 2001 and it is hoped that new data will be collected in In 1996 all of the Rowley Shoals were affected by a cyclone, Imperieuse Reef was most severely affected and Mermaid the least. The time series (Fig. 22) clearly shows the decline of corals from the 1996 cyclone event. There does appear to have been a steady decline in coral cover at Mermaid, which can be explained through some mortality due to bleaching in 1997 and Visual estimates during the 2003 surveys were qualitative and cannot be presented in the same form as the LTM data below. It would be expected that new data to be collected in 2004 will display and upward growth trend in the overall live cover as the community appears to have stabilised following these natural disturbances. The overall live coral cover for Mermaid Reef is estimated at 25% due mainly to the high coral cover of its vast deep lagoon. The corals of the lagoon have long been under threat from vessel anchoring activity. Areas of fragile branching Acropora sp. have been reduced to patches of rubble and whilst the damage from anchoring may be present throughout the lagoon much of it was noticed in the favoured sites for anchoring near the entrance. 60 (A) Hard Corals 50 Mermaid Reef Clerke Reef percentage (%) Year of Census 10 8 (B) Soft Corals Mermaid Reef Clerke Reef percentage (%) Year of Census Figure 22: Hard and soft coral cover at the AIMS long term monitoring sites at Mermaid and Clerke Reefs from 1994 to

45 SIGNIFICANT FINDINGS AND DISCUSSION Holothuria Holothuria population numbers are highly variable between the three Australian Government marine reserves of Ashmore, Cartier and Mermaid Reefs. Cartier has very low stocks of all species, which is probably related to Cartier Reef s small size, the limited amount of suitable habitat and the ability of traditional Indonesian fishers to access all habitats during a single tidal cycle. There is no evidence of increased populations of holothuria in the 18 months since the previous survey at Cartier or Ashmore Reef. In contrast, Ashmore Reef has a more diverse holothuria community. While some moderately valued species are relatively abundant, the high value species (H. nobilis and H. timana) are rare or were not found. Both H. nobilis and H. timana were caught in significant numbers by Indonesian fishers in the 1980 s at Ashmore Reef (Russell and Vail 1988). In this survey, the only reef we found significant numbers of H. nobilis was Mermaid Reef. H. fuscogilva (White Teatfish) was found in low densities at Ashmore and Mermaid but was absent at Cartier. Interestingly, some high value species were recorded immediately adjacent to the favoured anchorage site for passing Indonesian fisherman inside the deep lagoon near West Island. The high value species T. ananas is relatively abundant at Mermaid compared with Ashmore followed by Cartier Reef. All three reefs have reasonably good stocks of the species. It is likely that the difficulty in free diving to the depths in which these species are found has limited fishing effort and thus provided a refuge from Indonesian fishers. Trochus Overall This survey has found significant populations of T. niloticus at both Ashmore and Mermaid Reefs. Surveys in 1998 and 2000 revealed only small stocks of trochus (29.8 and 6.4 per hectare, respectively) at Ashmore Reef. However, neither survey was able to census the exposed southern edge of the reef 45

46 because of adverse weather conditions. The calm weather conditions during May 2003 allowed extensive surveys of this southern edge. Average densities of trochus in this habitat were found to be 153 individuals per hectare. It is likely that a combination of the year round on site management and compliance and the adverse weather conditions associated with this habitat (eg. wave action, tide, wind and currents) exclude traditional Indonesian fishers from accessing and targeting this habitat for trochus and other valued species, thereby providing a refuge for this species. Similar to Ashmore, the deep water habitats of Cartier Reef are likely to provide a refuge for trochus from the traditional fishing methods of reef walking and free-diving. The 2003 Cartier surveys found that two-thirds of the trochus were found in depths greater than 15 metres. Interestingly, higher densities of trochus were found in 2003 compared to 2001 at Cartier Reef (Smith et al., 2001). Ashmore Reef The major difference between the surveys at Ashmore Reef in 2000 (Smith et al., 2002) and 2003 (this report) is that a thorough census of the exposed southern section of the reef could be completed. Major populations of T. niloticus were found along this reef edge with densities of 153 per hectare, on average. Due to a significant history of fishing exploitation at Ashmore by traditional Indonesian fishers, it was assumed, prior to the 2003 survey, that the trochus population was severely depleted to the point of requiring the benefits of some type of stock enhancement (e.g. reseeding or translocation). This population is very important in a regional context, as it is the only reasonable population, (in terms of numbers) found within the MOU Box since surveys were first conducted in the mid 1980 s. Stocks of T. niloticus at Ashmore could provide brood stock for successful regeneration of other less populated areas of the reef and surrounding reefs such as Cartier and Scott Reef. Obviously, our population estimates for trochus at Ashmore Reef are far higher for 2003 than 2000 because we surveyed trochus rich habitats not previously surveyed. In 2000 trochus densities were 6.4 ind. h -1, whereas in 2003 within the same habitats densities were 16.8 ind. h -1. This increase 46

47 cannot be attributed to recovery due to different back reef sites being sampled in 2003 and A census of one site during the 2003 survey at Ashmore recorded 35 trochus, accounting for over half the trochus recorded in the lowdensity trochus habitat for the whole survey. This site was the closest site to the high-density trochus habitat and may receive considerable recruitment from the high-density area. If this site were excluded from the density analysis, densities for the low-density trochus habitat in 2003 would be similar to those in 2000 (9.3 ind. h -1 ; 3.85 SE). Cartier Reef The reef edge on the southern side of Ashmore Reef is exposed to the prevailing weather and consequently the trochus population has been protected from fishers because of their inability to access this reef front in traditional sailing vessels. This is not the case for Cartier Reef where trochus numbers are very low (13.2 ind. hectare -1 ), with most found in deep water m (38) rather than shallow water 0-15 m (22). Cartier Reef is much smaller and more accessible to fishers than Ashmore. Reef walking and skin diving at low tide allows trochus from all habitats at Cartier Reef down to the depth limits of the individual diver to be exploited. The trochus population at Cartier Reef seems heavily overexploited and in need of some type of enhancement (e.g. translocation). This might be viable due to the large number of animals available at Ashmore, the close proximity of the two reefs and the available preferred trochus habitat to enhance. However unless levels of management and compliance are enforced, similar to Ashmore Reef, this exercise may prove to be unproductive due to continued illegal fishing at this reef. Tridacnidae Clams There has been some concern that Indonesian fishers have been targeting giant clams at Ashmore, Cartier and other reefs in the MOU Box. Consequently, this survey assessed densities of both live and dead clams, at Ashmore, Cartier and Mermaid Reefs. We found population densities of live giant clams at the target reefs are similar to other reefs where there has been little exploitation. However, quantifying exploitation rates is very difficult and 47

48 may vary considerably from year to year.for example Rose Atoll, an unexploited reef in Samoa, has densities of 25 T. maxima per hectare (Green and Craig, 1999). In comparison, Cartier, Ashmore and Mermaid had 15, 28 and 123 individual per hectare, respectively. A larger proportion of dead clams were found at Ashmore and Cartier Reefs than at Mermaid Reef. While this could be a result of Indonesia fishers, it is more likely a result of adverse environmental conditions at Ashmore and Cartier Reefs. The hot water in 1998 and 2003 could have caused bleaching and extensive mortality within these clam populations. Importantly though, population numbers are very healthy on all reefs we surveyed. Coral Ashmore and Cartier Reefs have been severely affected by coral bleaching in Widespread coral death has occurred in these areas, which will alter the benthic community dynamics of these areas as various fouling organisms move in to colonise dead coral skeletons. Coral bleaching has not occurred at Mermaid Reef but it was affected by a cyclone in Hard coral cover steadily increased after the cyclone until 1997 and then slightly declined up to 2001, however the current health of the hard coral community is good. Soft coral cover also declined as a result of the 1996 cyclone but steadily increased from 1997 to 2001 and is currently in a state of good health. There is evidence of localised destruction in the coral dominated deep lagoon, which can most likely be attributed to vessel anchoring activity. CONCLUSIONS The two repeat surveys at Ashmore and Cartier Reefs in 2000, 2001 and 2003 and the initial survey at Mermaid Reef in 2003 have provided excellent baseline data from which spatial and temporal trends in trochus and holothuria populations can be monitored in the future. It has required repeat surveys to ensure a comprehensive census of all the different habitats and their associated fauna within Ashmore and Cartier, however logistical 48

49 restraints (time and money) have not allowed such a thorough census of Mermaid Reef. Census methods have been streamlined to ensure maximum coverage of habitats within each reef using the most accurate and efficient method possible. Representative sites associated with high and low density trochus habitat and different holothuria, giant clam and coral species at Ashmore and Cartier Reefs can now be chosen to monitor in the future. Future monitoring will be focused on detecting fluctuations in population size and structure of particular species of interest i.e. trochus and high value holothuria. Sites sampled in previous surveys have not been replicated sufficiently to enable trends in population size and structure to be detected currently, however due to considerable spatial sampling to date this can be achieved more efficiently in future surveys. The rationale for future monitoring needs to be developed. Target reefs, habitats, species and sites to be monitored need to be identified and the sampling design, stratification, effort and replication determined. Ashmore Reef is extremely important ecologically to the region for reasons already expressed in Environment Australia s management plan. When considering only holothuria communities and trochus populations Ashmore reef is vital to the region due to it s diverse community of holothuria, more diverse than both Cartier and Mermaid Reefs, and large trochus population, considerably larger than both Cartier Reef and Mermaid Reef. Due to the close proximity of Cartier Reef to Ashmore and the overexploited condition of holothuria and trochus populations at Cartier, trochus and holothuria populations from Ashmore Reef could be used to enhance stocks at Cartier, using various stock enhancement techniques, if natural recovery seems unlikely. Overexploited trochus stocks can be reduced to such a low abundance that successful spawning and hence recruitment may not occur at all. The sperm concentration in the water, upon release by the males, may not be sufficient to stimulate the females to release eggs. This may be the case at Cartier but will not be confirmed until future monitoring is concluded and trends analysed. It is 49

50 evident from similar fisheries that if egg-per-recruit analysis shows that less than 25% of the original egg production remains, then there are grounds for concern that the stock may collapse due to a decline in the recruitment rate (Nash, 1993). However, if more than 60% of the egg production remains, recruitment rates, and the fishery, are probably stable (Nash, 1993). Unfortunately the original egg production is not known from the overexploited stocks in the region. Regionally, the management of coral reefs and associated stocks in the northwest of Western Australia has focused on one main reef in the MOU Box, Ashmore Reef and Cartier Reef to a lesser extent. Currently Ashmore Reef has a permanent management and compliance presence of ACVs, however Cartier Reef, even though relatively close does not have such a rigorous management regime. For overexploited stocks to recover or be enhanced successfully, illegal fishing must be stopped at Cartier Reef. The permanent presence at Ashmore needs to be extended to include Cartier Reef or any other reef where it is deemed that fishing is illegal. Closing reefs to fishing will not necessarily stop the flow of traditional Indonesian fishing boats exploiting resources annually in this region. These fishers will only go to other reefs in the MOU Box where fishing is still legal (Scott, Seringapatam and Browse Reefs) or other surrounding reefs or shoals out the MOU Box where fishing is illegal. The traditional Indonesian fishers are very poor and have been fishing this region for generations, so a reduction in fishing effort across the region is unlikely. All the reefs and shoals in the northwest of Western Australia that are potentially vulnerable to legal and illegal fishing need to be managed on a regional basis. A more permanent presence or more regular patrols, along similar lines to the management at Ashmore Reef, would help stop declines in biodiversity across the region. 50

51 REFERENCES Amos, M. (1991) Experiences in trochus resource assessment and field survey: Workshop+ on trochus resource assessment, development and management (Port Vila, Vanuatu, 13 May-02 June 1991). ICFMAP Technical Document 13, SPC, Noumea. pp. 9. Benzie, J.A.H., Uthicke, S. (2003) Stock size of bêche-de-mer, recruitment patterns and gene flow in black teatfish, and recovery of over-fished black teatfish stocks, on the Great Barrier Reef. FRDC Project 97/344. Australian Institute of Marine Science, Townsville, 86p. Berry, P.F. (1993) Historical background, description of the physical environments of Ashmore Reef and Cartier Island and notes on exploited species. In: Marine Faunal Surveys of Ashmore Reef and Cartier Island North-western Australia (Berry, P.F. ed.). Records of the Western Australian Museum, Supplement No 44, pp Berry, P.F., Marsh, L.M. (1986) Part I. History of investigation and descriptions of the physical environment. In: Faunal surveys of the Rowley Shoals, Scott Reef and Seringapatam Reef (Berry, P.F. ed.). Records of the Western Australian Museum, Supplement No. 25, Calumpong, H.P. (1992) The Giant Clam: an ocean manual. Australian Centre for International Agricultural Research, Canberra. Cannon, L.R.G., Silver, H. (1987) Sea cucumbers of northern Australia. Queensland Museum, Brisbane. 60 p. Castell, L.L. (1997) Population studies of juvenile Trochus niloticus on a reef flat on the north-eastern Queensland coast, Australia. Marine and Freshwater Research 48:

52 Colquhoun, J.R. (2001) Habitat preferences of juvenile trochus in Western Australia: implications for stock enhancement and assessment. SPC Trochus Information Bulletin #7: Conand, C. (1994) Sea Cucumbers and Bêche-de-mer of the Tropical Pacific: A handbook for fishers. Rev. ed. SPC No. 18. South Pacific Commission, Noumea. Environment Australia (2000) Ashmore Reef National Nature Reserve and Cartier Island Marine Reserve Management Plans. Environment Australia, Canberra. Environment Australia (2002) Mermaid Reef Marine National Nature Reserve Plan of Management. Environment Australia, Canberra. Green, A., and Craig, P. (1999) Population size structure of giant clams at Rose Atoll, an important refuge in the Samoan Archipelago. Coral Reefs Vol. 18: Hammond, L.S., Birtles, R.A., Reichelt, R.E. (1985) Holothuroid assemblages on coral reefs across the central section of the Great Barrier Reef. Proceedings 5 th Coral Reef Congress, Tahiti 5: Heyward, A.J., Pinceratto, E., Smith, L., (1997) Big Bank Shoals of the Timor Sea: An environmental resource atlas. BHP Petroleum and Australian Institute of Marine Science. 115 p. 52

53 Long, B.G., Pioner, I.R., Harris, A.N.M. (1993) Method of estimating the standing stock of Trochus niloticus incorporating Landsat satellite data, with application to the trochus resources. Marine Biology 115(4): Nash, W.J. (1993) Chapter 14: Trochus, In: Nearshore Marine Resources of the South Pacific (Wright, A., Hill, L. eds.) pp Oxley, W.G., Ayling, A.M., Cheal, A.J. and Thompson, A.A. (2003) Marine Surveys undertaken in the Coringa-Herald National Nature Reserve, March- April 2003, Australian Institute of Marine Science, Report produced for CRC Reef for Environment Australia. Russell, B.C., Vail, L.L. (1988) Report on Traditional Indonesian Fishing Activities at Ashmore Reef Nature Reserve. NT Museum of Arts and Sciences Report, Darwin. 179pp. Skewes, T.D., Dennis, D.M., Jacobs, D.R., Gordon, S.R., Taranto, T.J., Haywood, M., Pitcher, C.R., Smith, G.P., Milton, D., Poiner, I.R. (1999) Survey and stock estimates of the shallow reef (0-15m) deep) and shoal area (15-50m deep) marine resources and habitat mapping within the Timor Sea Mou74 Box. Volume1: Stock estimates and stock status. CSIRO Report. 71 pp. Smith, L., Rees, M., Heyward, A., Colquhoun, J. (2001) Survey 2000: bêchede-mer and trochus populations at Ashmore Reef. Report produced for Environment Australia. Australian Institute of Marine Science, Townsville. Smith, L., Rees, M., Heyward, A., Colquhoun, J. (2002) Stocks of trochus and bêche-de-mer at Cartier Reef: 2001 surveys. Report produced for Environment Australia. Australian Institute of Marine Science, Townsville. 53

54 South Pacific Commission. (1979). Bêche-de-mer of the Tropical Pacific: A handbook for fishermen. Handbook No. 18, South Pacific Commission, Noumea, New Caledonia. Tomascik, T., Mah, A.J., Nontji, A., and Moosa, M. (1997) The Ecology of the Indonesian Seas Part II, Periplus Editions (HK) Ltd, Chapters 21, 23: , Uthicke, S. (1996) Bêche-de-mer: A Literature Review on Holothurian Fishery and Ecology. Australian Institue of Marine Science, Townsville, Queensland, Australia. Uthicke, S. Benzie, J.A.H. (2000) Effect of bêche-de-mer fishing on densities and size-structure of Holothuria nobilis (Echinodermata: Holothuriodea) populations on the Great Barrier Reef. Coral Reefs 19: Veron, J.E.N. (1986) Reef-building corals. In: Faunal surveys of the Rowley Shoals, Scott Reef and Seringapatam Reef, North-western Australia (Berry, P.F. ed.), Records of the Western Australian Museum, Supplement No. 25, pp Veron J.E.N. (1993) Hermatypic corals of Ashmore Reef and Cartier Island. In: Marine Faunal Surveys of Ashmore Reef and Cartier Island, North-western Australia (Berry, P.F. ed.), Records of the Western Australian Museum, Supplement No. 44, pp Yasin, Z., Shau-Hwai, A. T. (2000) Quantitative and qualitative effects of light on the distribution of giant clams at the Johore Islands in South China Sea. Phuket Marine Biological Center Special Publication 21(1):

55 ACKNOWLEDGEMENTS We would like to thank the crew (Australian Customs Service personnel) of the ACV Dame Roma Mitchell and ACV Storm Bay for their assistance, knowledge and good humour. Baru Sadarun of the Indonesian Ministry of Fisheries for his insight and assistance in the field. Daniel Dwyer of Darwin for his language interpreter skills and patience. Rachel Waugh for her constant support. Kim Brooks and Dr. Michael Mackie for their field assistance. Melissa Dray for assistance with data. APPENDICES Appendix 1. Comparison of average densities of all holothurian species between Ashmore, Cartier, Mermaid (ind. Ha -1,SE in brackets) Ashmore Reef Total SS/SW RF RC DW atra (4.26) 6.57 (2.04) (15.72) (6.77) (5.68) surf red 2.72 (0.98) (0.64) 5.71 (2.91) chloronotus 6.75 (1.59) 7.14 (6.55) 9.39 (4.98) 7.85 (3.14) 3.81 (1.49) ananas 3.82 (0.87) 0.29 (0.29) 0.35 (0.24) 2.69 (1.17) 8.29 (2.26) argus 0.46 (0.19) 0.57 (0.39) (0.29) 0.67 (0.48) edulis 2.56 (0.71) (1.23) 5.24 (1.72) anax 1.11 (0.42) (0.16) 3.22 (1.25) graeffei 0.76 (0.32) (0.77) 1.24 (0.59) fuscopunctata 1.37 (0.35) 0.57 (0.57) (0.84) 2.48 (0.62) fuscogilva 0.21 (0.08) 0.29 (0.29) (0.09) 0.48 (0.20) nobilis 0.40 (0.13) (0.45) 0.15 (0.13) 0.48 (0.28) variegatus 1.95 (0.52) 3.14 (1.93) 5.22 (2.20) 0.31 (0.23) 1.81 (0.75) marmorata 0.03 (0.03) (0.09) actinopyga 0.31 (0.15) (0.17) 0.08 (0.09) 0.76 (0.43) leucospilotta 0.73 (0.26) 2.29 (1.31) 1.57 (1.00) 0.46 (0.35) 0.10 (0.09) coluber 0.70 (0.44) 0.29 (0.29) 3.83 (2.44) 0 0 lecanora 0.06 (0.04) (0.09) 0.10 (0.09) 55

56 Cartier Reef Total DW RF RC atra surf red 1.31 (0.59) 0.08 (0.08) 0.31 (0.31) 2.31 (1.13) (0.31) 0 0 chlorinotus ananas 0.57 (0.29) 2.15 (0.97) 0 0 argus 0.82 (0.35) 1.54 (1.07) 0.69 (0.37) 0 edulis anax (0.11) (0.42) 0 0 graeffei fuscopunctata (0.32) (1.07) 0 0 fuscogilva nobilis variegatus marmorata actinopyga (0.20) (0.70) 0 0 leucospilotta coluber lecanora 0.08 (0.08) 0.31 (0.31) 0 0 Mermaid Reef Total DW RC RF atra surf red (2.48) (6.94) 0.66 (0.26) (3.23) 0.53 (0.36) (3.16) 0.88 (0.38) chlorinotus ananas 8.82 (1.83) (6.20) 2.40 (0.86) 9.94 (2.34) argus 8.75 (1.43) (4.79) 0.53 (0.53) 9.13 (1.71) edulis 5.28 (1.16) (5.38) 2.93 (1.85) 2.13 (0.64) anax 0.33 (0.19) 2.13 (1.16) graeffei 1.48 (0.42) 5.60 (1.98) 0.27 (0.27) 0.88 (0.35) fuscopunctata 0.16 (0.13) 1.07 (0.83) 0 0 fuscogilva 0.12 (0.07) 0.53 (0.36) (0.06) nobilis 9.24 (2.13) 0.53 (0.36) 9.07 (6.00) (2.85) variegatus 0.91 (0.44) 0.53 (0.53) 0.27 (0.27) 1.19 (0.65) marmorata 0.37 (0.24) (0.35) actinopyga 2.85 (0.65) 5.07 (2.39) 1.33 (0.93) 2.75 (0.78) leucospilotta 0.04 (0.04) (0.27) 0 coluber lecanora (0.08) (0.27) (0.27) (0.09) 56

57 Appendix 2. Current prices derived from traditional fisherman at Scott Reef 2003 (Current Indonesian exchange rate A$1.00=5,550 rupiah, 50,000 rupiah = A$9.00, source: AFMA) Species Price rupiah/kilogram (dry weight) Holothuria atra 35,000 Stichopus chloronotus 100,000 Thelenota ananas Up to 125,000 Actinopyga mauritiana 65,000 Holothuria edulis 35,000 Stichopus variegates 80,000 Holothuria leucospilota 10,000 Bohadschia argus 45,000 Holothuria nobilis 65,000 Actinopyga sp. Up to 50,000 Holothuria fuscogilva Up to 85,000 Actinopyga lecanora Up to 50,000 Bohadschia marmorata 45,000 Appendix 3: GPS positions for the sampling sites at Ashmore, Cartier and Mermaid Reefs in 2003 Ashmore Reef Transect Reference No. Start/Finish Positions Latitude Deg (S) Latitude Mins Longitude Deg (E) Longitude Mins Tro 1 S Tro 1 F Tro 2 S Tro 2 F Tro3 S Tro3 F Tro4 S Tro4 F DP1 S Tro5 S Tro5 F Tro6 S Tro6 F Tro7 S Tro7 F SP1 S DP2 S Sw1 S Sw1 F Sw2 S Sw2 F Sw3 S Sw3 F

58 Sw4 S Sw4 F Sw5 S Sw5 F Sw6 S Sw6 F Sw7 S Sw7 F Sw8 S Sw8 F Sw9 S Sw9 F Sw10 S Sw10 F Sw11 S Sw11 F DP3 S Sw12 F Sw13 S Sw13 F Sw14 S Sw14 F Sw15 S Sw15 F Tro8 S Tro8 F Tro9 S Tro9 F Tro10 S Tro10 F Tro11 S Tro11 F DP4 S Sw16 S Sw16 F Sw17 S Sw17 F Sw18 S Sw18 F Sw19 S Sw19 F DP5 S DP5 F Sw20 S Sw20 F DP6 S Tro12 S Tro12 F Sw21 S Sw21 F Sw22 S

59 Sw22 F Sw23 S Sw23 F Sw24 S Sw24 F Tro13 S Tro13 F Tro14 S Tro14 F Sw25 S Sw25 F Sw26 S Sw26 F Sw27 S Sw27 F Sw28 S Sw28 F Sw29 S Sw29 F Sw30 S Sw30 F DP7 S DP7 F DP8 S DP8 F Cartier Reef Transect Start/Finish Latitude Deg (S) Latitude Mins Longitude Deg (E) Longitude Mins CT1 S CT1 F CT2 S CT2 F CT3 S CT3 F CT4 S CT4 F CT5 S CT5 F CS1 S CS1 F CS2 S CS2 F CS3 S CS3 F CS4 S CS4 F CD1 S CD1 F CT6 S Reference No. 59

60 CT6 F CT7 S CT7 F CT8 S CT8 F CD2 S CD2 F CS5 S CS5 F CS6 S CS6 F CD3 S CD3 F CT9 S CT9 F CD4 F CD5 S CD5 F CD6 S CD7 S CD7 F Mermaid Reef Transect Start/Finish Latitude Deg (S) Latitude Mins Longitude Deg (E) Longitude Mins ML1 S ML1 F ML2 S ML2 F MS1 S MS1 F ML3 S ML3 F ML4 S ML4 F ML5 S ML5 F ML6 S ML6 F ML7 S ML7 F MS2 S MS2 F ML8 S ML8 F ML9 S ML9 F ML10 S ML10 F MD1 S MD1 F Reference No. 60

61 ML11 S ML11 F ML12 S ML12 F ML13 S ML13 F MS3 S MS3 F ML14 S ML14 F ML15 S ML15 F MD2 S MS4 S MS4 F ML16 S ML16 F MD3 S MD3 F MD4 S MD4 F ML17 S ML17 F MD5 S MD5 F ML18 S ML18 F ML19 S ML19 F MD6 S MD6 F ML20 S ML20 F ML21 S ML21 F MS5 S MS5 F

62 Appendix 4: Images of Holothuria from the surveys. (A) (B) (C) (D) (E) (F) (A) H. nobilis (black teatfish), (B) H. fuscogilva (white teatfish), (C) H. fuscogilva (white teatfish), (D) A.mauritania (surf redfish), (E) T. ananas (prickly redfish), (F) S. chlorinotus (greenfish). 62

63 (A) (B) (C) (D) (E) (F) (A) A. Lecanora (stonefish), (B) A.miliaris (blackfish), (C) T. anax (amberfish), (D) H. fuscopunctata (elephants trunkfish), (E) H. variegatus (curryfish), (E) H. variegatus (curryfish). 63

64 (A) (B) (B) (D) (E) (F) (A) B. argus (leopardfish), (B) H. graeffei, (C) H. atra (lollyfish), (D) H. edulis (pinkfish), (E) B. marmorata (brown sandfish), (E) H. leucospillotta (chocolatefish). 64