Recherche Archipelago Research Articles

First live records of the ruby seadragon (Phyllopteryx dewysea, Syngnathidae)

Until recently, only two species of seadragon were known, Phycodurus eques (the leafy seadragon) and Phyllopteryx taeniolatus (the common seadragon), both from Australia. In 2015, we described a new species of seadragon, Phyllopteryx dewysea (the ruby seadragon). Although the leafy and common seadragons are well known and commonly seen in aquarium exhibits world-wide, the ruby seadragon was known only from four preserved specimens, leaving many aspects of its biology unknown. Based on specimen records, it was speculated that the ruby seadragon normally lives at depths beyond recreational SCUBA diving limits, which may also explain why it went undiscovered for so long. The ruby seadragon also bears a superficial resemblance to the common seadragon, with a number of specimens misidentified in museum collections. The only recent live-collected specimen was trawled from the Recherche Archipelago, a cluster of over 100 islands in Western Australia. We took a small remotely operated vehicle (miniROV) to this locality to obtain the first images of live ruby seadragons. We made observations on the seadragon habitat and behavior, including feeding. We also provide new key observations on their morphology, notably that they lack dermal appendages and have a prehensile tail. We recommend that the ruby seadragon be protected as soon as practicable.

Taxonomic revision of Halimeda (Bryopsidales, Chlorophyta) in south-western Australia

Halimeda J.V.Lamour. is a green algal genus that is an important component of tropical reefs and lagoons. Although it does not generally occur outside the tropics, the range of one putatively widespread species, Halimeda cuneata Hering, in Western Australia extends southward past Cape Leeuwin to its southern extreme at Cape Howe and around to its most easterly record at Middle Island of the Recherche Archipelago. Previous molecular studies have shown that H. cuneata as recorded worldwide encompasses cryptic species diversity, with most of the cryptic entities being geographically isolated from the others. Halimeda cuneata has been the name consistently applied to specimens from the south-western coast of Australia, where it has been regarded as the only representative of its genus in the region. Using a combination of morphological features and assessment of species boundaries based on a plastid gene (tufA) and a nuclear protein-coding gene (HSP90), we have reassessed the supposed presence of H. cuneata in south-western Australia. Our results showed the existence of two species in the region, namely, H. versatilis J.Agardh, to which the name H. cuneata has been misapplied, and H. gigas W.R.Taylor, a central-Pacific species previously recorded only from tropical Australia.

A spectacular new species of seadragon (Syngnathidae).

The exploration of Earth's biodiversity is an exciting and ongoing endeavour. Here, we report a new species of seadragon from Western Australia with substantial morphological and genetic differences to the only two other known species. We describe it as Phyllopteryx dewysea n. sp. Although the leafy seadragon (Phycodurus eques) and the common seadragon (Phyllopteryx taeniolatus) occur along Australia's southern coast, generally among relatively shallow macroalgal reefs, the new species was found more offshore in slightly deeper waters. The holotype was trawled east of the remote Recherche Archipelago in 51 m; additional specimens extend the distribution west to Perth in 72 m. Molecular sequence data show clear divergence from the other seadragons (7.4–13.1% uncorrected divergence in mitochondrial DNA) and support a placement as the sister-species to the common seadragon. Radiographs and micro-computed tomography were used on the holotype of the new species and revealed unique features, in addition to its unusual red coloration. The discovery provides a spectacular example of the surprises still hidden in our oceans, even in relatively shallow waters.

Coastal Fish Assemblages Reflect Geological and Oceanographic Gradients Within An Australian Zootone

Distributions of mobile animals have been shown to be heavily influenced by habitat and climate. We address the historical and contemporary context of fish habitats within a major zootone: the Recherche Archipelago, southern western Australia. Baited remote underwater video systems were set in nine habitat types within three regions to determine the species diversity and relative abundance of bony fishes, sharks and rays. Constrained ordinations and multivariate prediction and regression trees were used to examine the effects of gradients in longitude, depth, distance from islands and coast, and epibenthic habitat on fish assemblage composition. A total of 90 species from 43 families were recorded from a wide range of functional groups. Ordination accounted for 19% of the variation in the assemblage composition when constrained by spatial and epibenthic covariates, and identified redundancy in the use of distance from the nearest emergent island as a predictor. A spatial hierarchy of fourteen fish assemblages was identified using multivariate prediction and regression trees, with the primary split between assemblages on macroalgal reefs, and those on bare or sandy habitats supporting seagrass beds. The characterisation of indicator species for assemblages within the hierarchy revealed important faunal break in fish assemblages at 122.30 East at Cape Le Grand and subtle niche partitioning amongst species within the labrids and monacanthids. For example, some species of monacanthids were habitat specialists and predominantly found on seagrass (Acanthaluteres vittiger, Scobinichthys granulatus), reef (Meuschenia galii, Meuschenia hippocrepis) or sand habitats (Nelusetta ayraudi). Predatory fish that consume molluscs, crustaceans and cephalopods were dominant with evidence of habitat generalisation in reef species to cope with local disturbances by wave action. Niche separation within major genera, and a sub-regional faunal break, indicate future zootone mapping should recognise both cross-shelf and longshore environmental gradients.

Combining environmental gradients to explain and predict the structure of demersal fish distributions

AbstractAim Species distribution modelling was used to investigate relationships between benthic environmental variables and patterns of demersal fish species distributions using fish occurrence data collected from spatially sparse point sampling. Our goals were to determine: (1) the relative importance of different environmental variables, (2) whether accurate predictions can be developed from these models, and (3) how a comparison of the models against known species ecology can be used to assess model relevance and to provide further insights that could drive future studies of these species.Location The Recherche Archipelago, southern Western Australia.Methods Fish distribution data were collected using baited remote underwater video systems (BRUVS): environmental characteristics (substrate type, macroalgal type and presence of sessile biota) were derived from the video footage; and water depth was measured with a depth sounder. Two species distribution modelling techniques were used to explore and quantify the contribution of environmental characteristics to distribution models of 10 temperate marine fish species.Results Substrate type (reef, sand, cobble) was the most influential variable, and water depth and macroalgal type influenced the probable occurrence of species even over the same substrate type. The probable occurrences of all but one fish species were predicted very successfully, with observed presences being predicted correctly with accuracies > 76%. These predictions were possible due to strong associations between these species and benthic features recorded in this study (substrate type, depth and macroalgal type).Main conclusions The results demonstrate that the combined influence of multiple environmental gradients must be considered to further develop our understanding of how the environment structures demersal fish distributions. The species distribution models not only agreed with the known ecology of the species examined in detail, but also provided more information on the strength of each environmental attribute and interactions between attributes. These interactions may have previously been misinterpreted as, for example, a depth‐driven response. Additional drivers of distribution that were previously not considered, such as the presence of macroalgae, were also found to have influence. This information thus provides a better description of a species’ niche, which is of value to both species management and conservation.

Formation, morphology and preservation of high-energy carbonate lithofacies: Evolution of the cool-water Recherche Archipelago inner shelf, south-western Australia

Cool-water carbonate environments are responsible for up to one third of the carbonate sediment produced on continental shelves, and are useful modern analogues for many geologically ancient carbonate deposits. On modern and ancient high wave-energy carbonate ramps, it has been suggested that wave abrasion generally limits sediment accumulation to the outer shelf. Sediment are produced on the modern inner shelf, although few studies have investigated processes of sedimentation in these energetic environments. The Recherche Archipelago, in the west of the Great Australian Bight (GAB), was examined to better identify processes of carbonate sedimentation and preservation on extremely high energy shelves. Surficial sediments, video traverses, multibeam sonar data, cores and shallow seismics were analysed. These data reveal that the topographically varied environment of the Recherche Archipelago experienced gradual, episodic accumulation of a prograding sediment wedge, with substantially thicker deposits located on the lee side of topographic highs. Modern sediment accumulation is largely restricted to the shoreface and inner shelf, where the highly discontinuous, storm influenced blanket of Holocene sediment comprises a shore-attached quartzose sediment prism, leeward accretionary wedges and rhodolith beds above a laterally-continuous Pecten-dominated basal transgressive lag. Storm events play an important role in these environments, resulting in a mostly bare ‘shaved’ middle and outer shelf, onshore sediment transport, reworking of particles and periodic removal of sediment. The modern Recherche Archipelago is a high energy end-member of cool-water carbonate environments, in which calcareous algae dominate sediment production. Modern Esperance Bay provides a useful analogue for the interpretation of high-energy palaeoenvironments, and demonstrates that in addition to sea level change, wave energy and local geomorphology are important considerations for carbonate facies reconstructions. This study has presented new information for carbonate inner shelves that differs from classic carbonate ramp models, showing that ancient rhodolith-bearing carbonate deposits have the potential to form and be preserved in very high energy settings.

The diverse Grania fauna (Clitellata: Enchytraeidae) of the Esperance area, Western Australia, with descriptions of two new species

Seven species of the marine enchytraeid genus Grania Southern, 1913 are described from sediments sampled during the 2003 International Workshop on the Marine Flora and Fauna of Esperance Bay and the Recherche Archipelago, on the southern coast of Western Australia. Two species are new to science, the euryhaline Tasmanian G. dolichura Rota and Erséus, 2000 represents a new record for the state, and the remaining four species were known from other parts of Western Australia. Grania quaerens sp. n. is recognized by having a high chaetal index ( = short chaetal foot), small coelomocytes, penial apparati with long whip‐like terminal stylets, conspicuous spermathecae with ectally bulbous ducts, and ectally granulated ampullae housing sperm rings in their ental region. Grania sperantia sp. n. is readily distinguishable by the complete lack of lateral chaetae, a multiple‐banded pattern of the clitellum, extremely long sperm funnels, and the intrasegmental location of the spermathecal pores. The latter new species and four others in the collection (G. bykane Coates, 1990, G. crassiducta Coates, 1990, G. dolichura, and G. ersei Coates, 1990) are remarkable in possessing the head organ, a sensory structure unique to Grania that was not noted previously in Western Australian species. When considering the whole genus, the geographic pattern of the head organ appears southern‐centred: of the 17 species of Grania reported to possess it, as many as 13 inhabit the southern latitudes. The seventh species of the Esperance collection, G. vacivasa Coates and Stacey, 1993, is notable for the kind of items found in its gut and the unusual appearance of its pygidium.

The influence of geomorphology and sedimentary processes on shallow-water benthic habitat distribution: Esperance Bay, Western Australia

The mapping of seabed environments is fundamental to successful fisheries management and environmental monitoring, however, there is an emerging need to better characterise habitats based upon appropriate physical parameters. In this study, relationships between seabed geomorphology and the distribution of benthic habitats were examined using multibeam sonar, underwater video, predicted wave energy, and sediment data for Esperance Bay, part of the Recherche Archipelago. This shallow (<50 m), high energy, biogenic sediment dominated environment is located in temperate southwestern Australia. Exposure to wave energy appears to determine the distribution of unconsolidated substrate, and is the most useful regional scale predictor of rhodolith and seagrass habitats. Although they are intermittently smothered by mobile sediments, limestone reefs provide habitat for a wide range of sessile organisms, even in very high wave exposure environments. The distribution of rhodolith beds is related to poorly sorted sediments that contain high gravel, mud, and CaCO 3 percentages. Our results reveal that in the Recherche Archipelago, wave abrasion coupled with localised sediment transport and accumulation play a major role in increasing the diversity of inner shelf benthic habitats. This highlights the value of assessing geomorphic processes in order to better understand the distribution and structure of benthic habitats.

Do surrogates describe patterns in marine macroalgal diversity in the Recherche Archipelago, temperate Australia?

Abstract Surrogates aim to predict species diversity and to minimize sampling effort. Here the value of surrogates for marine macroalgae is tested. Higher taxonomic levels and dominant taxa were evaluated as surrogates for detecting patterns in macroalgal species diversity (derived from species‐level biomass data) in the Recherche Archipelago, Western Australia. Data were stratified by two island groups (inshore and offshore), three depth intervals (&lt;10 m, 10–20 m, &gt;20 m), and two exposures to wave energy. Correlations between similarity matrices from surrogate and species diversity data matrices were analysed using a modified Spearman rank correlation (rs). The ability of surrogates to detect differences between exposures to wave energy was also investigated using analysis of similarity. Species diversity data were aggregated to higher taxonomic levels and were either fourth‐root or presence/absence (richness) transformed. Species richness was the most consistent surrogate (rs‐values&gt;0.69, P=0.001). Genus‐level richness was also strongly correlated to species diversity in the Recherche Archipelago, except in depths &lt;10 m where patterns in diversity were characterized by species turnover. At offshore islands in depths 10–20 m and &gt;20 m, family‐ and order‐level biomass data were suitable surrogates owing to the abundance of Alariaceae (Order Laminariales) represented by a single genus and species. Surrogates using biomass data from the orders Laminariales, Ceramiales, Dictyotales and Fucales were also successful at offshore islands in middle to deeper depths. At inshore islands in depths 10–20 m and &gt;20 m, genera from the orders Gigartinales, Fucales and Ceramiales were strongly correlated to species biomass data. Surrogates, like species richness, that were strongly correlated to species biomass data were also able to distinguish between exposures to wave energy, based on analysis of similarity tests. Sampling effort would be reduced if collecting richness data in species‐rich macroalgal assemblages such as those found in temperate Australia. Copyright © 2006 John Wiley &amp; Sons, Ltd.

Highway or country road: algal recruitment with distance from an island reef

Subtidal macroalgal assemblages differed among islands within the Recherche Archipelago, Western Australia, with respect to species biomass. To investigate whether macroalgal populations were maintained locally, settlement plates were moored in 10 to 15 m depths at a reef sampled for macroalgal diversity, and 20, 50, 100, and 500 m away from the reef. Plates were retrieved after eight months and assemblage differences were compared with distance from the sampled reef. Macroalgal richness decreased with distance from an island assemblage and molluscan richness increased. At 500 m away, the number of algal recruits was negligible and the number of bivalves was relatively high.

EFFECTS OF ISLAND GROUPS, DEPTH, AND EXPOSURE TO OCEAN WAVES ON SUBTIDAL MACROALGAL ASSEMBLAGES IN THE RECHERCHE ARCHIPELAGO, WESTERN AUSTRALIA1

Temperate Australia has a speciose highly endemic algal flora. This study explored the influence of geographical isolation between islands, depth and exposure to ocean swells on the diversity of macroalgae in the Recherche Archipelago (Western Australia). Macroalgae were harvested (0.25‐m2 quadrats) from sites at two exposures (sheltered and exposed to wave energy), three depths (&lt;10, 10–20, and 21–28 m), and two island groups (three islands within Esperance Bay and three islands outside the bay). A total of 220 species were collected. Species richness and biomass were significantly different at the smallest spatial scale (0.25 m2), and density of overstory species decreased with depth. Results from analysis of similarity tests suggested that macroalgal assemblages differed with depth, exposure and to a lesser extent with island group. Assemblage differences were often associated with particular overstory or understory taxa and not the entire assemblage composition. Average species richness·0.25 m−2 ranged from 13 to 29 species, typically with a few species contributing more than 50% of average biomass. Species richness was maintained by species turnover at the 0.25‐m2 spatial scale. Our results suggest that richness in temperate Australia is maintained by turnover of broadly distributed species. More dominant species in assemblages were associated with differences in depth and exposure to ocean swells. Our findings support the hypothesis of a geographical transition of dominant species from kelp‐dominated in the west to a fucalean‐dominated assemblage in the Recherche Archipelago and east of the Great Australian Bight.

The Leeuwin Current, eddies and sub-Antarctic waters off south-western Australia

Data from a research vessel cruise in late 1994 and several years of satellite observations revealed complex interactions of ocean features off south-western Australia. The ship measurements showed that the Leeuwin Current (LC) commonly ran at 0.5 m s–1 above the upper continental slope and extended down to approximately 250 m. South of the continent, a 200-km diameter anticyclonic eddy depressed the ocean structure in the upper 1000 m. The eddy showed influences of the LC, deep mixing in winter and summer heating. The sub-Antarctic water around the eddy was cooler, fresher and richer in nutrients and oxygen than both the eddy and the LC. Satellite thermal and topographic measurements showed that cyclonic eddies accelerated the LC along the southern upper continental slope, whereas anticyclonic eddies diverted it out to sea and then back again. The images suggested that weak eddies originating east of the Great Australian Bight migrate westward, first encountering the continental slope off the Recherche Archipelago. There, the anticyclonic eddies take on warm water from the LC and strengthen. Several anticyclonic eddies were followed westward beyond the archipelago for 18 months as they drifted at up to 5 km day–1 and interacted with the LC and with one another.

Distribution and abundance of New Zealand fur seals, Arctocephalus forsteri, in South Australia and Western Australia

A survey to determine the distribution and abundance of New Zealand fur seals, Arctocephalus forsteri, in South Australia and Western Australia was conducted in January-March 1990. Minor surveys were conducted in the summers of 1987-88, 1988-89 and 1990-91. Although the surveys were primarily of black pups in breeding colonies, opportunity was taken to count fur seals of all age-classes, including those in non-breeding colonies. Pups were counted and, in more accessible and larger colonies, numbers of pups were estimated by a mark-recapture technique. The latter technique gave higher estimates than counting, and was considered more accurate. In South Australia, the seals extend from The Pages in Backstairs Passage to Nuyts Reef in the Great Australian Bight. In Western Australia, the range comprised islands on the south coast from the Recherche Archipelago to islands near Cape Leeuwin. There are 29 breeding localities; 13 are in South Australia and 16 in Western Australia. Eighteen of these have not been reported previously. The term ''breeding locality'' is used for aggregations of breeding colonies as well as for isolated breeding colonies. Estimates of the number of pups for the 1989-90 breeding season were 5636 in South Australia and 1429 in Western Australia. This leads to a population estimate of approximately 34600 seals in these two states (using a multiplier of 4.9). But such estimates of overall abundance must be treated cautiously as the multiplier incorporates estimates of population parameters not available for A. forsteri. Most of the population (77%) is in central South Australian waters (from Kangaroo Island to the southern end of Eyre Peninsula). With the estimate of 100 for a breeding colony in southern Tasmania, the population of New Zealand fur seals in Australia can be estimated at 34700. Historical aspects of some colonies are outlined and evidence for increases described. The largest breeding localities are at South Neptune Islands (1964 pups) and North Neptune Islands (1472). The combined Neptunes group accounts for 49% of the pup estimate for Australia. One-fifth of the pups are from colonies on Kangaroo Island and the nearby Casuarinas.

Plants of the Recherche Archipelago, W.A. (some adjustments to published records, and a list of the species collected there by Robert Brown)

Plants of the Recherche Archipelago, W.A. (some adjustments to published records, and a list of the species collected there by Robert Brown)

The Vertebrate Fauna of Houtman's Abrolhos (Abrolhos Islands), Western Australia.

SUMMARY. Mammals.—The two indigenous species of Mammals are only found in the Wallaby Group, the Wallaby on both the large islands, the Rat, as far as is known, only on East Wallaby Island. The latter is probably, and the former certainly, subspecificailly distinct from the mainland species. Snakes.—The three species of snakes do not appear to differ from the mainland forms. At present two have been found only on West Wallaby Island and the third on East Wallaby Island. Lizards.—-Four families are represented by some 19 species. The seven species of Geckonidae iire only known from the Wallaby Group, the two species of Pygopodidae only from West Wallaby Island, and the single species of Agamidae from the Wallaby Islands and North Island. The Scincidae are represented throughout the group, though we only met with the smaller species of Lygosoma outside the Wallaby Group; one of the larger forms, Egernia stokesi was, however, formerly plentiful on Rat Island. Froas.—Nothing is known no to the habitat of the two species recorded from the group. Birds.—of the 12 land-birds recorded from the Abrolhos, four Kestrel, Robin, Song-Lark, and Pipit) are certainly only casual visitors, five others (Rail, Crake, Kingfisher, Swallow, and White-eye) are probably visitors From the mainland, though all but the Crake and Kingfisher have been known to breed; the remaining three are almost certainly residents. Of these, the Pigeon and the Quail are found in the Wallaby Group and on North Island, the Scrub-Wren only on the Wallaby Islands. The two latter are subspecifically distinct from the mainland forms. Looking now of the different groups of islands we find that West Wallaby Islad has two snakes and two slow-worms confined to it, East Wallaby Island has one snake and one rat confined to it, whilst the two Wallaby Islands possess subspecies of a wallaby and a bird peculiar to them. The Wallaby Islands, with North Island, possess also one lizard and two birds not found in the other groups, one of the birds being a subspecies peculiar to the group. This distribution strengly suggests that the whole land-fauna of the group has been derived from the Wallaby Islands *. One of the chief features of the weather on the Abrolhos is the prevalence during the summer of “southerly busters,” estremely strong southerly winds. The presence of the two birds on North Island is thus easily accounted for, and it, is noteworthy that the one lizard which habitually climbs bushes is the one which has managed to reach that island. Doubtless at times the Lushes on the sand-hills which it frequents are blown into the sea, and occasionally reach North Island. The fact that the smaller skinks are found on many of the small sandy islets seems to show that the sea is no great burrier to their distribution. Probably their eggs are not damaged by floating in sea-water for some time. The larger Spiny-tailed Skink, Egernia stokesi, is a favourite food of the Sea-Eagles, and it is possible that individuals may be captured by them on the Wallaby Group and coppied to that Island, and if one occasionally escaped this would account for their presence on that group. A striking feature of the Abrolhos land-fauna is its southern character. Our knowledge of the distribution of animals in Western Australia is perhaps not sufficient to allow us to be dogmatic on the point, but there is every indication that when the islands were peopled from the mainland the fauna of the Geraldton district must have approximated much more than it does now to that of the extreme south-west. The range of Macropus eugenii does not now extend much north of Perth, whilst Epimys fuscipes is only known from the south coast and the islands of the Recherche Archipelago. Ortygodes varius and Cosmopelia elegans are not recorded from farther north than the Moore River, though it is not improbable that they may occur; Porzamoidea plumbea is not recorded from north of Perth. The most northerly record that I know for Denisonia coronata and for Egernia whitei, “Perth,” is less than 30 iniles north of Perth. Lygosoma richardsoni is known only from the Abrolhos. The remainder of the species are found farther north on the mainland, but there is not one of them which is not found in the south-west.