Western Coast Of Australia Research Articles

Crossing latitudes--long-distance tracking of an apex predator.

Tiger sharks (Galeocerdo cuvier) are apex predators occurring in most tropical and warm temperate marine ecosystems, but we know relatively little of their patterns of residency and movement over large spatial and temporal scales. We deployed satellite tags on eleven tiger sharks off the north-western coast of Western Australia and used the Brownian Bridge kernel method to calculate home ranges and analyse movement behaviour. One individual recorded one of the largest geographical ranges of movement ever reported for the species, travelling over 4000 km during 517 days of monitoring. Tags on the remainder of the sharks reported for shorter periods (7-191 days). Most of these sharks had restricted movements and long-term (30-188 days) residency in coastal waters in the vicinity of the area where they were tagged. Core home range areas of sharks varied greatly from 1166.9 to 634,944 km2. Tiger sharks spent most of their time in water temperatures between 23°-26°C but experienced temperatures ranging from 6°C to 33°C. One shark displayed seasonal movements among three distinct home range cores spread along most of the coast of Western Australia and generalized linear models showed that this individual had different patterns of temperature and depth occupancy in each region of the coast, with the highest probability of residency occurring in the shallowest areas of the coast with water temperatures above 23°C. These results suggest that tiger sharks can migrate over very large distances and across latitudes ranging from tropical to the cool temperate waters. Such extensive long-term movements may be a key element influencing the connectivity of populations within and among ocean basins.

Decadal increase in NingalooNiñosince the late 1990s

Ningaloo Nino refers to the episodic occurrence of anomalously warm ocean conditions along the subtropical coast of Western Australia (WA). Ningaloo Nino typically develops in austral spring, peaks in summer, and decays in autumn, and it often occurs in conjunction with La Nina conditions in the Pacific which promote poleward transport of warm tropical waters by the Leeuwin Current. Since the late 1990s, there has been a marked increase in the occurrence of Ningaloo Nino, which is likely related to the recent swing to the negative phase of the Interdecadal Pacific Oscillation (IPO) and enhanced El Nino–Southern Oscillation variance since 1970s. The swing to the negative IPO sustains positive heat content anomalies and initiates more frequent cyclonic wind anomalies off the WA coast so favoring enhanced poleward heat transport by the Leeuwin Current. The anthropogenically forced global warming has made it easier for natural variability to drive extreme ocean temperatures in the region.

For a long time nothing happened: Settler colonialism, deferred action and the scene of colonization in Kim Scott’s That Deadman Dance

That Deadman Dance (2010) is Kim Scott’s third novel and his second to win the premier literary prize in Australia, the Miles Franklin Award. Scott’s novel is set in the period of contact between European settlers and the Indigenous Noongar people on the south coast of Western Australia at the beginning of the nineteenth century. Scott’s father was Noongar and his writing is positioned in the interplay between cultures and histories. In this article, I argue that contact fiction is conditioned by the psychoanalytic principle of deferred action and use Scott’s novel to exemplify this argument.

Malimup: A Tasmanian Aboriginal Hoabinhian site in the southwest of Western Australia?

The Hoabinhian technocomplex of Southeast Asia is characterised by distinctive pebble edge tools which are also found in Australia, but only in the southeast, including Tasmania. Charlie Dortch in the early 1970s reported a unique site with Hoabinhian tools in southwest Australia at Malimup, Western Australia (WA), dated to the recent past. An analysis of the pebble edge tools from Malimup showed they were similar to those from eastern Australia, which in turn were similar to the Southeast Asian ones. While it is possible that local Aboriginal people may have made these tools, it seems unlikely, given that no other such site has been found anywhere in WA. In considering the possibility that the site represents the presence of Aboriginal people from elsewhere in Australia during the early historical period, the most likely candidates are suggested to be Aboriginal women from Tasmania. Such women are documented as having lived with European sealers along the south coast of WA, and the site at Malimup is in a location suitable for a sealing camp, and near where sealers are reputed to have been active. It is further speculated that these tools may have been used for processing ochre, an activity of traditional significance to Tasmanian Aboriginal women, perhaps helping them come to terms with an unfamiliar environment. Such a suggestion may help shed light on the role of pebble tools elsewhere in Australia and indeed Southeast Asia.

Remotely Monitoring Change in Vegetation Cover on the Montebello Islands, Western Australia, in Response to Introduced Rodent Eradication

The Montebello archipelago consists of 218 islands; 80 km from the north-west coast of Western Australia. Before 1912 the islands had a diverse terrestrial fauna. By 1952 several species were locally extinct. Between 1996 and 2011 rodents and cats were eradicated, and 5 mammal and 2 bird species were translocated to the islands. Monitoring of the broader terrestrial ecosystem over time has been limited. We used 20 dry-season Landsat images from 1988 to 2013 and estimation of green fraction cover in nadir photographs taken at 27 sites within the Montebello islands and six sites on Thevenard Island to assess change in vegetation density over time. Analysis of data averaged across the 26-year period suggests that 719 ha out of 2169 ha have increased in vegetation cover by up to 32%, 955 ha have remained stable and 0.6 ha have declined in vegetation cover. Over 492 ha (22%) had no vegetation cover at any time during the period analysed. Chronological clustering analysis identified two breakpoints in the average vegetation cover data occurring in 1997 and 2003, near the beginning and end of the rodent eradication activities. On many islands vegetation cover was declining prior to 1996 but increased after rodents were eradicated from the islands. Data for North West and Trimouille islands were analysed independently because of the potential confounding effect of native fauna being introduced to these islands. Mala (Lagorchestes hirsutus) and Shark Bay mice (Pseudomys fieldi) both appear to suppress native plant recruitment but not to the same degree as introduced rodents. Future research should assess whether the increase in vegetation cover on the Montebello islands is due to an increase in native or introduced plants.

Prograded foredunes of Western Australia's macro‐tidal coast – implications for Holocene sea‐level change and high‐energy wave impacts

AbstractThe Holocene evolution of the Canning Coast of Western Australia has largely been overlooked so far mainly due to its remoteness and low population density. We report on new data from a sequence of foredunes inside the macro‐tidal Admiral Bay, 110 km southwest of Broome. Based on sediment cores, differential global positioning system (dGPS)‐based elevation transects, and stratigraphical analyses on outcrops of the relict foredunes, we aim at reconstructing Holocene coastal changes and relative sea levels (RSLs), as well as identifying and dating imprints of extreme‐wave events. Sedimentary analyses comprise the documentation of bedding structures, foraminiferal content and macrofaunal remains, grain size distribution, and organic matter. The chronological framework is based on 26 carbon‐14 accelerator mass spectrometry (14C‐AMS) datings.Marine flooding of the pre‐Holocene surface landward of the 2.5 km‐wide foredune barriers occurred 7400–7200 cal bp, when mangroves colonized the area. After only 200–400 years, a high‐energy inter‐tidal environment established and prevailed until c. 4000 cal bp, before turning into the present supralittoral mudflat. During that time, coastal regression led to beach progradation and the formation of aligned foredunes. Drivers of progradation were a stable RSL or gradual RSL fall after the mid‐Holocene and a positive sand budget. The foredunes overlie upper beach deposits located up to >2 m above the present upper beach level and provide evidence for a higher mid‐Holocene RSL. Discontinuous layers of coarse shells and sand are intercalated in the foredunes, indicating massive coastal flooding events. One such layer was traced over three dune ridges and dated to c. 1700–1550 cal bp. However, it seems that most tropical cyclones induce net erosion rather than deposition at aligned foredunes and thus, they are only suitable for reconstructing temporal variability if erosional features or sedimentation reliably tied to these events can be identified and dated accurately. Copyright © 2014 John Wiley & Sons, Ltd.

Catch me if you can! The story of a colonial ascidian’s takeover bid in Western Australia

In 2010, Didemnum perlucidum F. Monniot, 1983, a potentially invasive colonial ascidian, was found for the first time in Western Australia (WA). During routine introduced marine pest monitoring along the WA coast in 2011–2012, the Department of Fisheries confirmed additional disjunct populations in a span of ~ 2,800 km along the coast. Colonies of the ascidian were apparently flourishing in water temperatures from tropical through to temperate. Colour was not a reliable detection method for this colonial ascidian. Colonies in winter showed the expected senescence, becoming smaller, friable and often partially detached from the substrate. While winter monitoring would reduce likelihood of detection, it may present the best opportunity for eradication. Due to the widespread distribution, eradication of D. perlucidum is now unlikely. However, implementing local control measures to protect high value areas, such as marine parks or protected areas, from incursions remains feasible. A robust monitoring program is vital to detecting D. perlucidum early in its invasion history, and that would provide the best opportunity for local eradication effort.

Phyllosomata associated with large gelatinous zooplankton: hitching rides and stealing bites

Abstract During a zooplankton survey 350 km off the coast of Western Australia, we captured a large and robust zooid of a salp (Thetys vagina), to which six late stage larvae (phyllosomata) of the western rock lobster (Panulirus cygnus) were attached. High-throughput sequencing analyses of DNA extracts from midgut glands of the larvae confirmed that each phyllosoma had consumed mainly salp tissue (x¯ = 64.5% ± 15.9 of DNA reads). These results resolve long-standing conjecture whether spiny lobster phyllosomata attach to large gelatinous hosts to feed on them.

Calibration of pelagic stereo‐BRUVs and scientific longline surveys for sampling sharks

SummaryOur understanding of the ecology of sharks and other highly mobile marine species often relies on fishery‐dependent data or extractive fishery‐independent techniques that can result in catchability and size‐selectivity biases. Pelagic Baited Remote Underwater stereo‐Video Systems (pelagic stereo‐BRUVs) provide a standardized, non‐destructive and fishery‐independent approach to estimate biodiversity measures of fish assemblages in the water column. However, the performance of this novel method has not yet been assessed relative to other standard sampling techniques.We compared the catch composition, relative abundance and length distribution of fish assemblages sampled using pelagic stereo‐BRUVs and conventional scientific longline surveys. In particular, we focused on sharks of the family Carcharhinidae (requiem sharks) to assess the sampling effectiveness of this novel technique along a latitudinal gradient off the coast of Western Australia. We calibrated the sampling effort required for each technique to obtain equivalent samples of the target species and discuss the advantages, limitations and potential use of these methods to study highly mobile species.The proportion of sharks sampled by pelagic stereo‐BRUVs and scientific longline surveys was comparable across the latitudinal gradient.Carcharhinus plumbeuswas the most abundant species sampled by both the techniques. Longline surveys selected larger individuals of the family Carcharhinidae in comparison with the length distribution data obtained from pelagic stereo‐BRUVs. However, the relative abundance estimates (catch per unit of effort) from the pelagic stereo‐BRUVs were comparable to those from 5 to 30 longline hooks.Pelagic stereo‐BRUVs can be calibrated to standard techniques in order to study the species composition, behaviour, relative abundance and size distribution of highly mobile fish assemblages at broad spatial and temporal scales. This technique offers a non‐destructive fishery‐independent approach that can be implemented in areas that may be closed to fishing and is suitable for studies on rare or threatened species.

A Dynamical Model for the Leeuwin Undercurrent

Abstract Recently, Furue et al. explored analytic solutions to a dynamical model for the Leeuwin Current system (LCS) off the coast of Western Australia. Their linear, variable density, two-layer model reduces to a one-layer system near the coast. The circulation is determined by matching solutions in the coastal and offshore regions across the “grounding line” and displays many features observed in the LCS. However, it does not include a Leeuwin Undercurrent (LUC). Here, that model is extended considering an across-shore density gradient (front) caused by relatively light, tropical water being carried poleward by the Leeuwin Current (LC). As a result of including the front, the LCS circulation changes considerably; the LC deepens and strengthens significantly toward the pole, and the LCS now includes an equatorward LUC on the offshore edge of the LC. Differences in density and sea surface height across the front both contribute to the pressure gradient driving the LUC.

Allopatric speciation within a cryptic species complex of Australasian octopuses.

Despite extensive revisions over recent decades, the taxonomy of benthic octopuses (Family Octopodidae) remains in a considerable flux. Among groups of unresolved status is a species complex of morphologically similar shallow-water octopods from subtropical Australasia, including: Allopatric populations of Octopus tetricus on the eastern and western coasts of Australia, of which the Western Australian form is speculated to be a distinct or sub-species; and Octopus gibbsi from New Zealand, a proposed synonym of Australian forms. This study employed a combination of molecular and morphological techniques to resolve the taxonomic status of the ‘tetricus complex’. Phylogenetic analyses (based on five mitochondrial genes: 12S rRNA, 16S rRNA, COI, COIII and Cytb) and Generalised Mixed Yule Coalescent (GMYC) analysis (based on COI, COIII and Cytb) distinguished eastern and Western Australian O. tetricus as distinct species, while O. gibbsi was found to be synonymous with the east Australian form (BS = >97, PP = 1; GMYC p = 0.01). Discrete morphological differences in mature male octopuses (based on sixteen morphological traits) provided further evidence of cryptic speciation between east (including New Zealand) and west coast populations; although females proved less useful in morphological distinction among members of the tetricus complex. In addition, phylogenetic analyses suggested populations of octopuses currently treated under the name Octopus vulgaris are paraphyletic; providing evidence of cryptic speciation among global populations of O. vulgaris, the most commercially valuable octopus species worldwide.

Water temperature and fish growth: otoliths predict growth patterns of a marine fish in a changing climate.

Ecological modeling shows that even small, gradual changes in body size in a fish population can have large effects on natural mortality, biomass, and catch. However, efforts to model the impact of climate change on fish growth have been hampered by a lack of long-term (multidecadal) data needed to understand the effects of temperature on growth rates in natural environments. We used a combination of dendrochronology techniques and additive mixed-effects modeling to examine the sensitivity of growth in a long-lived (up to 70 years), endemic marine fish, the western blue groper (Achoerodus gouldii), to changes in water temperature. A multi-decadal biochronology (1952-2003) of growth was constructed from the otoliths of 56 fish collected off the southwestern coast of Western Australia, and we tested for correlations between the mean index chronology and a range of potential environmental drivers. The chronology was significantly correlated with sea surface temperature in the region, but common variance among individuals was low. This suggests that this species has been relatively insensitive to past variations in climate. Growth increment and age data were also used in an additive mixed model to predict otolith growth and body size later this century. Although growth was relatively insensitive to changes in temperature, the model results suggested that a fish aged 20 in 2099 would have an otolith about 10% larger and a body size about 5% larger than a fish aged 20 in 1977. Our study shows that species or populations regarded as relatively insensitive to climate change could still undergo significant changes in growth rate and body size that are likely to have important effects on the productivity and yield of fisheries.

Scaevola xanthina (Goodeniaceae), a new yellow-flowered species from the south coast of Western Australia

<i>Scaevola xanthina</i> (Goodeniaceae), a new yellow-flowered species from the south coast of Western Australia

William Dampier: Navigator Extraordinary

This paper looks at the navigational challenges faced by William Dampier when, as Captain of the Royal Navy ship Roebuck, in 1699, he approached, and then found his way along the coast of Western Australia (at that time known as New Holland). A discussion of the methods and instruments available to Dampier is followed by consideration of how, and with what success, he went about his task. Dampier's own account of the voyage was included in his book A Voyage to New Holland (Dampier, 1703) although this is likely to have been heavily edited, and perhaps even rewritten by a “man of letters” to make it more attractive to the general public. For this reason and, bearing in mind that autobiographical work may contain omissions or otherwise be slanted to show the writer in his best light, the navigational information in his book has been cross-checked with the Roebuck's original Master's Log, held by the UK National Archives at Kew (Documents ADM 52/94). Jacob Hughes was the ship's Master, but the Log entries were written in at least two hands.

Mammalian herbivores in Australia transport nutrients from terrestrial to marine ecosystems via mangroves

Abstract:Nutrient subsidies from one ecosystem to another serve a critical link among ecosystems. The transfer of materials across the terrestrial-to-marine boundary is considered to be driven by hydrological connectivity, but animal movement can provide another pathway for nutrient transfers. In two separate studies we assessed the role mammals (bats and kangaroos) play in alleviating nutrient limitation in mangrove forests in Australia. At Lizard Island, we measured tree growth and foliar elemental and isotopic composition of trees growing within and outside a large flying fox roost. In Western Australia, we measured foliar elemental and isotopic composition of trees within two forests frequented by kangaroos that feed in spinifex grasslands and shelter in the shade of the mangroves. We compared those with mangroves from adjacent forests that are not frequented by kangaroos. We show that at both locations, the mangrove forest receives terrestrial nutrient subsidies through animal movement. At Lizard Island dominant mangrove species were significantly enriched in nitrogen within the bat roost, as evidenced by higher foliar N concentrations (by up to 150%), N:P and N:C ratios in trees within the roost compared with trees outside the roost. The isotopic signature of foliar N was significantly enriched in 15N by 1–3‰ within the roost, further suggesting that the source of the N enrichment was the bat roost. Growth rates of mangroves within the roost were nearly six times higher than trees outside the roost. In the arid coast of Western Australia, we show elevated foliar 15N abundance of up to 3‰ in mangroves where kangaroos shelter relative to trees where they do not. Thus, this study presents two examples for mammalian herbivore mediated localized transport of nutrients from terrestrial to marine ecosystems, consequently affecting mangrove tree growth, productivity and forest structure.

Evaluating success of translocations in maintaining genetic diversity in a threatened mammal

The effectiveness of fauna reintroduction programs has been limited by the availability of source animals and the lack of follow up monitoring to assess whether viable populations have been successfully established, particularly in terms of conserving genetic diversity. Here we present genetic assessment of the translocation of golden bandicoots (Isoodon auratus) from a large source population on Barrow Island off the north-west coast of Western Australia to two other island sites and a mainland fenced enclosure. We assessed the genetic diversity of animals translocated to each site and their wild-born progeny, and whether wild-born animals showed evidence of genetic bottlenecks or genetic drift from the source population. Encouragingly, we found no significant loss of genetic diversity in any of the wild-born populations compared to the source population and no significant increase in inbreeding or relatedness amongst wild-born individuals compared to founder populations two years post-translocation. However, we detected an approximately 10-fold reduction in effective population size between founding and wild-born populations. We found no apparent differentiation between wild-born populations and the original source population, or between wild-born animals and their respective founders. Population viability modeling predicts that each of the translocated populations is susceptible to loss of genetic diversity over time. Taken together these results suggest that the golden bandicoot reintroduction program has been initially successful as a result of large founding sizes and high reproductive rates; however, ongoing augmentation will be required to prevent genetic erosion and maintain evolutionary potential in the long-term.

Summer circulation dynamics within the Perth coastal waters of southwestern Australia

The dynamics of the summer circulation in the coastal waters off Perth in Western Australia were investigated during a two-month field experiment. The study included the deployment of an array of moorings spanning the outer shelf, the inner shelf, within the inshore Perth coastal lagoon, and in the large coastal embayment of Cockburn Sound. The results revealed highly transient coastal circulation patterns that responded to variability in both the locally- and remotely-generated forcing. Local wind forcing played a primary role in driving much of the alongshore current variability at the shallower (<20m depth) inshore sites, with a well-defined peak wind forcing time scale of ~1 week that fell within the synoptic weather band in the region. Due to the mean northward wind stress that persisted during this summer period, a mean northward current of 0.05–0.1ms−1 was observed at these inshore sites. Large-scale variations in alongshore water level (pressure) gradients also episodically generated strong along- and cross-shore current oscillations throughout the region. Major events were associated with the propagation of coastally-trapped waves generated by a tropical low pressure system far (~1000km) to the north of Perth, which propagated down the Western Australia coast. On the outer shelf, local wind forcing played a minor (but still not a negligible) role in driving alongshore current variability, with this momentum balance instead dominated by the alongshore pressure gradient variability. Due to the unusually large alongshore pressure gradient that persists year round along the Western Australia coast, currents on the shelf were on average southward. However, large-scale northward reversals of the shelf flow were also observed when northward wind stresses were sufficiently large and/or the local alongshore pressure gradient became episodically weak.

Biogeographic discordance of molecular phylogenetic and phenotypic variation in a continental archipelago radiation of land snails

BackgroundIn island archipelagos, where islands have experienced repeated periods of fragmentation and connection through cyclic changes in sea level, complex among-island distributions might reflect historical distributional changes or local evolution. We test the relative importance of these mechanisms in an endemic radiation of Rhagada land snails in the Dampier Archipelago, a continental archipelago off the coast of Western Australia, where ten morphospecies have complex, overlapping distributions.ResultsWe obtained partial mtDNA sequence (COI) for 1015 snails collected from 213 locations across 30 Islands, and used Bayesian phylogenetic analysis and Analysis of Molecular Variance (AMOVA) to determine whether geography or the morphological taxonomy best explains the pattern of molecular evolution. Rather than forming distinct monophyletic groups, as would be expected if they had single, independent origins, all of the widely distributed morphospecies were polyphyletic, distributed among several well-supported clades, each of which included several morphospecies. Each mitochondrial clade had a clear, cohesive geographic distribution, together forming a series of parapatric replacements separated by narrow contact zones. AMOVA revealed further incongruence between mtDNA diversity and morphological variation within clades, as the taxonomic hypothesis always explained a low or non-significant proportion of the molecular variation. In contrast, the pattern of mtDNA evolution closely reflected contemporary and historical marine barriers.ConclusionsDespite opportunities for distributional changes during periods when the islands were connected, there is no evidence that dispersal has contributed to the geographic variation of shell form at the broad scale. Based on an estimate of dispersal made previously for Rhagada, we conclude that the periods of connection have been too short in duration to allow for extensive overland dispersal or deep mitochondrial introgression. The result is a sharp and resilient phylogeographic pattern. The distribution of morphotypes among clades and distant islands is explained most simply by their parallel evolution.

Production and persistence of subtropical grasses in environments with Mediterranean climates

The agricultural region of south-west Western Australia (WA) has a Mediterranean climate, characterised by a winter-dominant rainfall pattern. Perennial subtropical grasses are increasingly being grown to increase productivity and reduce erosion on infertile sandy soils in the northern agricultural region (NAR) of WA, an area with mild winters and dry, hot summers. However, little information exists on the persistence of different species or their expected seasonal production and feed quality. On the south coast of WA, an area with dry, warm summers and a maritime influence, kikuyu (Pennisetum clandestinum) has been widely sown, but there is little information on the potential of other subtropical grasses. To address these issues, five trials were established across the agricultural area of south-west WA to measure the seasonal production, feed quality and persistence of the main, commercially available subtropical grasses over 3–4 years. This study demonstrates that subtropical grasses have a long-term role in the NAR in areas with mild winters and/or where the rainfall is &gt;400 mm. The best performing subtropical grasses across a range of sites were panic grass (Megathyrsus maximus) and Rhodes grass (Chloris gayana). These species can be expected to have a water-use efficiency of ~10 kg ha–1 mm–1 over a 12-month period, provided there is a good perennial grass density. On the south coast, panic grass, Rhodes grass and setaria (Setaria sphacelata) persisted well and produced significantly more biomass than kikuyu. These grasses could complement kikuyu by increasing out-of-season production. At Kojonup, a more inland site, most of the subtropical grasses died over winter from a combination of occasional frosts and cold, wet soils. However, kikuyu re-grew from rhizomes in spring and maintained &gt;90% ground cover 4 years after sowing. The results from these experiments are likely to be applicable to other regions across the globe with Mediterranean climates and similar soil types.

Two new species of box jellies (Cnidaria: Cubozoa: Carybdeida) from the central coast of Western Australia, both presumed to cause Irukandji syndrome

Two new species of box jellies (Cnidaria: Cubozoa: Carybdeida) from the central coast of Western Australia, both presumed to cause Irukandji syndrome