Temperate Eastern Australia Research Articles

Metabarcoding airborne pollen from subtropical and temperate eastern Australia over multiple years reveals pollen aerobiome diversity and complexity

eDNA metabarcoding is an emergent tool to inform aerobiome complexity, but few studies have applied this technology with real-world environmental pollen monitoring samples. Here we apply eDNA metabarcoding to assess seasonal and regional differences in the composition of airborne pollen from routine samples collected across successive years. Airborne pollen concentrations over two sampling periods were determined using a continuous flow volumetric impaction air sampler in sub-tropical (Mutdapilly and Rocklea) and temperate (Macquarie Park and Richmond), sites of Australia. eDNA metabarcoding was applied to daily pollen samples collected once per week using the rbcL amplicon. Composition and redundancy analysis of the sequence read counts were examined. The dominant pollen families were mostly consistent between consecutive years but there was some heterogeneity between sites and years for month of peak pollen release. Many more families were detected by eDNA than counted by light microscopy with 211 to 399 operational taxonomic units assigned to family per site from October to May. There were 216 unique and 119 taxa shared between subtropics (27°S) and temperate (33°S) latitudes, with, for example, Poaceae, Myrtaceae and Causurinaceae being shared, and Manihot, Vigna and Aristida being in subtropical, and Ceratodon and Cerastium being in temperate sites. Certain genera were observed within the same location and season over the two years; Chloris at Rocklea in autumn of 2017–18 (0.625, p ≤ 0.004) and 2018–19 (0.55, p ≤ 0.001), and Pinus and Plantago at Macquarie Park in summer of 2017–18 (0.58, p ≤ 0.001 and 0.53, p ≤ 0.003, respectively), and 2018–19 (0.8, p ≤ 0.003 and 0.8, p ≤ 0.003, respectively). eDNA metabarcoding is a powerful tool to survey the complexity of pollen aerobiology and distinguish spatial and temporal profiles of local pollen to a far deeper level than traditional counting methods. However, further research is required to optimise the metabarcode target to enable reliable detection of pollen to genus and species level.

Evolutionary Relationships and Range Evolution of Greenhood Orchids (Subtribe Pterostylidinae): Insights From Plastid Phylogenomics.

Australia harbours a rich and highly endemic orchid flora with over 90% of native species found nowhere else. However, little is known about the assembly and evolution of Australia’s orchid flora. Here, we used a phylogenomic approach to infer evolutionary relationships, divergence times and range evolution in Pterostylidinae (Orchidoideae), the second largest subtribe in the Australian orchid flora, comprising the genera Pterostylis and Achlydosa. Phylogenetic analysis of 75 plastid genes provided well-resolved and supported phylogenies. Intrageneric relationships in Pterostylis were clarified and monophyly of eight of 10 sections supported. Achlydosa was found to not form part of Pterostylidinae and instead merits recognition at subtribal level, as Achlydosinae. Pterostylidinae were inferred to have originated in eastern Australia in the early Oligocene, coinciding with the complete separation of Australia from Antarctica and the onset of the Antarctic Circumpolar Current, which led to profound changes in the world’s climate. Divergence of all major lineages occurred during the Miocene, accompanied by increased aridification and seasonality of the Australian continent, resulting in strong vegetational changes from rainforest to more open sclerophyllous vegetation. The majority of extant species were inferred to have originated in the Quaternary, from the Pleistocene onwards. The rapid climatic oscillations during the Pleistocene may have acted as important driver of speciation in Pterostylidinae. The subtribe underwent lineage diversification mainly within its ancestral range, in eastern Australia. Long-distance dispersals to southwest Australia commenced from the late Miocene onwards, after the establishment of the Nullarbor Plain, which constitutes a strong edaphic barrier to mesic plants. Range expansions from the mesic into the arid zone of eastern Australia (Eremaean region) commenced from the early Pleistocene onwards. Extant distributions of Pterostylidinae in other Australasian regions, such as New Zealand and New Caledonia, are of more recent origin, resulting from long-distance dispersals from the Pliocene onwards. Temperate eastern Australia was identified as key source area for dispersals to other Australasian regions.

Trophic niche of Australian cownose rays (Rhinoptera neglecta) and whitespotted eagle rays (Aetobatus ocellatus) along the east coast of Australia.

Australian cownose rays (Rhinoptera neglecta) and whitespotted eagle rays (Aetobatus ocellatus) are large myliobatiform rays that co‐occur off temperate eastern Australia. Here, we performed stable‐isotope analyses (δ13C, δ15N and δ34S) on fin clips of both species to gain insights into their trophic interactions and isotopic niches, and assess the effect of preservation (ethanol‐stored versus frozen) on isotopic values of fin‐clip tissue of R. neglecta. Linear mixed models identified species as the main factor contributing to variation among δ15N and δ34S values, and disc width for δ13C. Bayesian ecological niche modelling indicated a 57.4% to 74.5% overlap of trophic niches, with the niche of R. neglecta being smaller and more constrained. Because values of δ13C were similar between species, variation in isotopic niches were due to differences in δ15N and δ34S values. Linear mixed models failed to detect differences in isotopic values of ethanol‐stored and frozen fin tissue of R. neglecta. This study provides the first examination of the trophic ecology of R. neglecta and the comparison of isotopic niche with A. ocellatus, which will facilitate future research into the trophic interactions of these species and aid better resource management.

Genetic differentiation in the threatened soft coral Dendronephthya australis in temperate eastern Australia

AbstractThe endangered soft coral Dendronephthya australis faces substantial population decreases in central eastern Australian waters. Despite uncertainty about the cause of these declines, the population genetics of the species has not been investigated. Genetic analysis suggests that D. australis is a single species within the family Nephtheidae, confirming identifications based on morphological characteristics only. Soft coral colonies were distributed from Seahorse Gardens in Port Stephens to Jervis Bay in temperate Australian waters, a distance of some 400 km. Genetic differentiation was observed along this distribution using SNP genotyping. Relatively high levels of genetic differentiation were observed between Jervis Bay and the other sites, indicating limited gene flow between this location and others. Moreover, the genetic distinctiveness, low diversity and heterozygote excess at this southern location suggested that it was subjected to a recent population decline and genetic bottleneck. Colonies at Seahorse Gardens and Ettalong, approximately 150 km south of Seahorse Gardens, displayed greater genetic diversity, making these sites more likely to host ancestral populations and to have acted as refugia. Recent substantial decreases in population sizes at these locations are particularly concerning, and these locations require immediate conservation attention.

Epidemiology of exertional heat illness in Thoroughbred racehorses in temperate eastern Australia: The role of extrinsic (environmental) factors in disease causation

Summary A simple epidemiological model of disease causation is proposed for exertional heat illness (EHI) in Thoroughbred racehorses. The agent of disease causation that must be present for the condition to occur is strenuous exercise, producing substantial quantities of metabolic heat. This is stored during racing but must be dissipated rapidly in the post‐race period to prevent core body temperature rising to a critical level and causing the clinical manifestations of EHI. Environmental factors are next in the epidemiological triad, and it is a common misconception that these are the direct cause of EHI. In fact, environmental conditions enable EHI by either diminishing the evaporative capacity of the environment or promoting internal heat gain. This article deals with the specific effects of the four thermal elements, separately and in combination, on individual thermo‐effector mechanisms. The final component in the epidemiological triad is individual host factors. A critical premise of epidemiology is that conditions such as EHI may not occur randomly in a population but may be more likely to occur in some individuals due to the presence of certain factors that predispose them to the condition. For the purpose of assessing risk, it is not feasible to examine the balance between metabolic heat production and the intrinsic and extrinsic factors, which collectively determine each individual's heat stress response. Therefore, the measurement of environmental factors remains the only practical way of obtaining a credible risk assessment for EHI, so that effective countermeasures can be instigated and the welfare of our racehorses ensured.

An investigation into environmental variables influencing post-race exertional heat illness in thoroughbred racehorses in temperate eastern Australia.

Exertional heat illness (EHI) is a syndrome that occurs when metabolic heat production from muscular contraction exceeds the rate at which it can be dissipated. Core body temperature rises to critical levels, causing hyperthermia and central nervous system dysfunction. Best practice for the prevention of EHI centres around early detection, rapid response and aggressive cooling. Advance planning enables risk mitigation measures. The more that is known about EHI in horses, the better prepared those in the positions of responsibility can be to anticipate events in which the risk of EHI may be elevated. This prospective, observational study investigated environmental risk factors associated with the occurrence of EHI. From 2014 to 2018, the number of horses exhibiting the symptoms of post-race EHI was recorded at 73 convenience sampled race meetings. Of the 4809 starters, the signs of EHI were recorded for 457. Thermal environmental data were measured and included ambient temperature, radiant heat, vapor pressure (humidity) and wind speed (WS). Mixed linear regression models were computed to assess the associations between the occurrence and incidence of post-race EHI and the four thermal environmental variables. The analysis showed that vapor pressure and WS had the largest effects on the occurrence of post-race EHI. The major limitations were that the race meetings selected were convenience sampled according to attendance by the first author and individual horse data were not available. EHI is influenced by a complex interaction of independently acting environmental variables, but warm, windless, humid days are most likely to result in the cases of EHI.

Bad neighbours: amphibian chytrid fungus Batrachochytrium dendrobatidis infection dynamics in three co-occurring frog species of southern Sydney, Australia.

Wildlife disease is a major cause of global biodiversity loss. Amongst the most devastating is the disease chytridiomycosis, caused by the amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd). This disease has contributed to declines and extinctions in hundreds of amphibian species, but not all species are affected equally. Some amphibian hosts are capable of carrying high levels of Bd infection without population declines, acting as reservoir species for the pathogen and driving population declines in sympatric species. In Australia, several species have been proposed as reservoir species; however, our understanding of Bd is derived from studies that are highly geographically and taxonomically biased, and our ability to extrapolate from these systems is unknown. We examined the prevalence and intensity of Bd infection in 3 frog species in a previously unstudied host-pathogen system in temperate eastern Australia: the Blue Mountains tree frog Litoria citropa, a poorly-known species predicted to be susceptible to Bd infection; and the common eastern froglet Crinia signifera and the stony creek frog L. lesueuri, which have both been identified as reservoir species in other regions. We found that L. citropa and L. lesueuri were infected with Bd at a high prevalence and often high intensity, while the reverse was true for C. signifera. All species were detected at moderate abundance and there was no evidence of morbidity and mortality. Our findings do not support C. signifera and L. lesueuri being reservoir species in this system, highlighting the importance of region-specific studies to inform conservation management.

The effects of water temperature on the juvenile performance of two tropical damselfishes expatriating to temperate reefs

Ocean warming associated with global climate change is already inducing geographic range shifts of marine species. Juvenile coral reef fishes transported into temperate latitudes (termed ‘vagrant’ fishes) can experience winter water temperatures below their normal thermal minimum. Such environmental extremes may increase energetic costs for such fishes, resulting in reduced performance, which may be the governing factor that limits the potential for poleward range expansion of such fishes. This study compared the juvenile physiological performance and behaviour of two congeneric tropical damselfishes which settle during austral summer months within temperate eastern Australia: Abudefduf vaigiensis have an extended southern range, and lower threshold survival temperature than the congeneric A. whitleyi. Physiological and behavioural performance parameters that may be affected by cooler temperature regimes at higher latitudes were measured in aquaria. Lower water temperature resulted in reduced growth rates, feeding rates, burst escape speed and metabolic rates of both species, with significantly reduced performance (up to six-fold reductions) for fishes reared at 18 °C relative to 22 °C and 26 °C. However, A. whitleyi exhibited lower growth rates than A. vaigiensis across all temperatures, and lower aerobic capacity at the lowest temperature (18 °C). This difference between species in growth and metabolic capacity suggests that the extended southern distribution and greater overwintering success of A. vaigiensis, in comparison to A. whitleyi is related to thermal performance parameters which are critical in maintaining individual health and survival. Our results support previous findings in the region that water temperature below 22 °C represents a critical physiological threshold for tropical Abudefduf species expatriating into temperate south-eastern Australia.

Diel and seasonal variation in heterobranch sea slug assemblages within an embayment in temperate eastern Australia

Biodiversity surveys of marine species are largely conducted during the day, and often over relatively short timeframes, due to practical, operational, and budgetary constraints. As a consequence, surveys can underestimate biodiversity for some groups, such as heterobranch (formerly opisthobranch) molluscs, where abundances vary seasonally by orders of magnitude and different species are active at different times of the day. Here, we quantitatively assess day/night (diel) and seasonal variation in heterobranch sea slug assemblages using monthly, diel scuba surveys for 13 months at three sites in Port Stephens, New South Wales (NSW). All heterobranch sea slugs encountered in 50 × 5-m belt transects were recorded using identical survey methods both during the day and at night. Significant differences were detected between day and night assemblages, with species richness and abundance being consistently higher at night. Significant cyclical patterns were also detected in sea slug assemblages over the duration of the study, for both day and night assemblages, with species assemblages changing throughout the study period. The results demonstrate that marine diversity studies conducted only during the day, and those which do not account for all seasons, are likely to underestimate diversity and abundance of molluscs, particularly heterobranch sea slugs. It is, therefore, important that studies which aim to provide a comprehensive catalogue of molluscan biodiversity include not only day-time surveys, but also those conducted at night. They should also include temporal replication in order to capture ephemeral species.

Changes in deep reef benthic community composition across a latitudinal and environmental gradient in temperate Eastern Australia

Deep reef assemblages in south-eastern Australia are poorly described, and have been surveyed by only a few studies conducted over small spatial scales. Here, we characterise the composition of deep (~30-90 m depth) sessile invertebrate communities from sub-tropical (27°S) to temperate eastern Australia (43°S). We estimated the cover of 51 preselected invertebrate types from over 1700 seafloor images collected by an autonomous underwater vehicle from >105 km of transects across the study region. Seafloor images were assessed using 3 alternative schemes reflecting different resolution of benthic invertebrate groupings, including the broad- level Collaborative and Automated Tools for Analysis of Marine Imagery project (‘CATAMI’) classification recently developed as a generic scoring approach for seafloor imagery. Ordination using canonical analysis of principal coordinates indicated a clear latitudinal gradient in benthic community composition and, particularly when based on individual morphotypes, 3 distinct community types (sub-tropical, warm temperate and cool temperate). Changes in community structure mostly correlated with primary productivity and the temperature climatology, while local-scale variability in community composition was most related to depth. Along with the gradual shift in deep reef community composition across latitudes, region-specific sessile invertebrates might serve as useful indicators of change in these deep benthic communities under future changes in ocean climate in the region, which has been identified as a global hotspot for ocean warming. Our methodological approach has general applicability for large-scale surveying and monitoring of benthic communities using underwater imagery.

Age and growth parameters for three heavily exploited shark species off temperate eastern Australia

AbstractThe removal of large predatory sharks from the world's oceans poses profound threats to marine community structure and species conservation. Effective management of exploited shark stocks requires a sound understanding of the life histories of target species. Here we provide the first assessment of age and growth for Carcharhinus brevipinna in Australian waters, and for C. obscurus and C. plumbeus in eastern Australian waters, based on interpretations of vertebral growth bands. In doing so, we provide arguably among the most robust growth parameters to date for the abovementioned taxa on the bases of genetic validation and sample size and distribution, but acknowledge equally a range of limitations—most notably those associated with vertebral ageing and our lack of age validation. Comparatively, the three species displayed both contrasts and consistencies in their growth characteristics off Australia's southeast coast. For all three sharks, rates of growth were greatest in the years immediately after birth, males grew more rapidly than females in the juvenile phase, and females were observed to grow larger, live longer and were generally larger at any given age. Longevity and all modelled growth parameters (L∞, k and L0), however, differed among the three species, and appeared to challenge the findings for conspecific populations in other parts of the world. The validity of these latter comparisons is, however, compromised by a range of confounding factors. Nevertheless, we provide the least conservative k estimates for C. obscurus and C. plumbeus of those previously reported, and extend maximum age estimates for C. brevipinna. In this way, our results have important implications for the assessment of natural mortality, productivity, and hence resilience to stock depletion, in these species in southeastern Australian waters.

The role of visual and chemical cues in host detection by the symbiotic shrimp Gnathophylloides mineri

The use of visual and chemical cues in host detection is regarded as important but relatively unknown for many symbionts. The small circumtropical caridean shrimp Gnathophylloides mineri forms a close symbiotic association with sea urchins, particularly Tripneustes gratilla, in many parts of the world. G. mineri is known to occur in temperate eastern Australia but the breadth of host use and selection of hosts amongst different species of sea urchins is relatively unknown. The abundance of G. mineri on three co-occurring species of sea urchins, T. gratilla, Heliocidaris tuberculata and Pseudoboletia indiana were measured in eastern Australia. These species of sea urchins were chosen because of either a known prior association with this shrimp elsewhere in the world, or due to their abundance in the area in temperate Australia where the shrimp occurs. Field collections showed that the association between shrimp and sea urchin appears extremely host-specific, with G. mineri only observed on T. gratilla, at an average density of two shrimp per sea urchin. Moreover, the majority of symbionts occurred on the underside (oral region) of T. gratilla. A visual laboratory experiment showed that G. mineri would actively move towards T. gratilla in preference to the other potential host species in the absence of chemical signals. Using a Y-maze, we tested the reaction of G. mineri to the absence of visual signals but the presence of chemical signals originating from their host, and from other species of potential host sea urchins. Seawater alone was used as a negative control. We demonstrated that G. mineri could detect T. gratilla from a distance, the same host that the shrimp are associated with in the field, using visual and chemical cues. Moreover, G. mineri react quickly to visual and chemical host signals by moving towards T. gratilla in preference to other species of sea urchins or in the absence of a signal. The relative importance of visual versus chemical cues is, however, unknown.

Distinct Bradyrhizbium communities nodulate legumes native to temperate and tropical monsoon Australia

Geographic isolation and growing climate aridity played major roles in the evolution of Australian legumes. It is likely that these two factors also impacted on the evolution of their root-nodule bacteria. To investigate this issue, we applied a multilocus sequence analysis (MLSA) approach to examine Bradyrhizobium isolates originating from temperate areas of Western Australia (WA) and the tropical-monsoon area of the Northern Territory (NT). The isolates were mostly collected from the nodules of legumes belonging to tribes, genera and species endemic or native to Australia. Phylogenetic analyses of sequences for the housekeeping atpD, dnaK, glnII, gyrB, recA and 16S rRNA genes and nodulation nodA gene revealed that most isolates belonged to groups that are distinct from non-Australian Bradyrhizobium isolates, which is in line with earlier studies based on 16S rRNA gene sequence analyses. Phylogenetic analysis of the nodA data allowed identification of five major Clades among the WA and NT isolates. All WA isolates grouped in a subgroup I.1 of Clade I with strains originating from temperate eastern Australia. In contrast, the NT isolates formed part of Clades I (subgroup I.2), III (subgroup III.3), IV, V and X. Of these nodA clades, Clade I, Clade IV, Clade X presumably have an Australian origin. Overall, these data demonstrate that the impact of geographic isolation of the Australian landmass is manifested by the presence of numerous unique clusters in housekeeping and nodulation gene trees. In addition, the intrinsic climate characteristics of temperate WA and tropical-monsoon NT were responsible for the formation of distinct legume communities selecting for unrelated Bradyrhizobium groups.

Coastal wetlands of temperate eastern Australia: will Cinderella ever go to the ball?

The many sheltered embayments, riverine estuaries and drowned river valleys of temperate eastern Australia support a large area and a wide diversity of coastal wetlands. This region also supports over one-half of the country’s population and includes its major tourist and industrial centres. The story of Cinderella provides an excellent simile for the status of coastal wetlands in this region of Australia: coastal wetlands provide extremely valuable ecosystem services (indeed, of considerably greater value than those provided by an equivalent area of inland wetland), yet they are undervalued by the general community, by natural-resource managers and by funding agencies. The selective investment of ecological research (including rehabilitation studies) into inland wetlands – and in particular into floodplain wetlands of the Murray–Darling Basin – has left us inadequately equipped to understand how temperate coastal wetlands function, how they will respond to climate change, and how degraded sites can be rehabilitated. Not only is an increase in research funding required, but funding has to be coordinated and focussed. The problem, however, is not only a lack of research funding; at a more fundamental level, the widespread ignorance of the value of temperate coastal wetlands needs also to be addressed.

Thermotolerance and the effects of hypercapnia on the metabolic rate of the ophiuroid Ophionereis schayeri: Inferences for survivorship in a changing ocean

Global warming is causing the oceans to simultaneously warm, decrease in pH and increase in pCO 2, stressors that will have deleterious impacts on physiological function in marine biota. To address questions on future vulnerabilities in a conspicuous component of the shallow water biota of temperate eastern Australia, the impact of projected (2100 and beyond) temperature and pH/ pCO 2 change on respiration in the brittle star Ophionereis schayeri was investigated. Survivorship at elevated temperature was also investigated. Temperature and pH conditions experienced by this species in the field were determined to place experiments in the context of present and near future scenarios and to assess current tolerance levels with regard to tidal variation in temperature and pH. The acute metabolic response (M O2) of O. schayeri to pH/ pCO 2 was measured with animals acclimated to 19 °C, low summer sea surface temperature (SST) and 25 °C (+ 1 °C max summer SST). Temperature had the predicted effect on oxygen uptake, with the Q 10 being 2.6 at normal pH 8.2. It was predicted that hypercapnia/low pH (7.4–7.8) would be stressful to O. schayeri and that this would be reflected by a decrease in respiration rate. Hypercapnia ( pCO 2 ≥ 1000 μatm) had a narcotic effect causing lethargy in O. schayeri. In the pH 7.8 treatments narcotic effects may have contributed to the decrease in oxygen uptake observed. This pH level is near the lower range of pH experienced by this species in the field and it is likely that short term metabolic depression may be a routine response strategy for O. schayeri. However, at pH 7.6 and 7.4 O. schayeri exhibited a significant increase in oxygen uptake associated with copious secretion of mucus, a stress response. During five week acclimation experiments at control (22 °C) and elevated (25 °C) temperatures, mortalities were 1.3% and 15%, respectively. The brittle stars did not cope with higher temperatures (≥ 26 °C). It appears that 25 °C approximates the thermotolerance threshold for O. schayeri indicating that this species is living near its upper limit. Local populations of this brittle star may not cope with a more permanent increase in environmental pCO 2 and temperature due to climate change.

Biological control of Salvinia molesta by Cyrtobagous salviniae in temperate Australia

A three year study of the interaction of salvinia weevil, Cyrtobagous salviniae, with Salvinia molesta was undertaken in temperate Eastern Australia. Releases of C. salviniae were made on rivers, creeks and dams from spring to mid summer of the first year and 12 sites were monitored. Eight sites were controlled by C. salviniae within 12 months, however the weevil failed to persist long term at some sites in still water habitats of creeks and dams. Better control was achieved at sites with higher temperatures and higher salvinia nitrogen levels. Biological control is an important salvinia management option in temperate regions and is now being used by weed management organisations.

The seasonal phenology of Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) in Queensland

Abstract Bactrocera tryoni is a polyphagous fruit fly, originally endemic to tropical and subtropical coastal eastern Australia, but now also widely distributed in temperate eastern Australia. In temperate parts of its range, B. tryoni populations show distinct seasonal peaks driven by changing seasonal climates, especially changing temperature. In contrast to temperate areas, the seasonal phenology of B. tryoni in subtropical and tropical parts of its range is poorly documented and the role of climate unknown. Using a large, historical (1940s and 1950s) fruit fly trapping dataset, we present the seasonal phenology of B. tryoni at nine sites across Queensland for multiple (two to seven) years per site. We correlate monthly trap data for each site with monthly weather averages (temperature, rainfall and relative humidity) to investigate climatic influences. We also correlate observed population data with predicted population data generated by an existing B. tryoni population model. Supporting predictions from climate driven models, B. tryoni did show year‐round breeding at most Queensland sites. However, contrary to predictions, there was a common pattern of a significant population decline in autumn and winter, followed by a rapid population increase in August and then one or more distinct peaks of abundance in spring and summer. Mean monthly fly abundance was significantly different across sites, but was not correlated with altitudinal, latitudinal or longitudinal gradients. There were very few significant correlations between monthly fly population size and weather variables (either for the corresponding month or for up to 3 months previously) for eight of the nine sites. For the southern site of Gatton fly population abundance was correlated with temperature. Results suggest that although climate factors may be influencing patterns of B. tryoni population abundance in southern subtropical Queensland, they are not explaining patterns of abundance in northern subtropical and tropical Queensland. In the discussion we focus on the role of other factors, particularly larval host plant availability, as likely drivers of B. tryoni abundance in tropical and subtropical parts of its range.

Mesoscale distribution of larval Euphausia similis in various water masses of the East Australian Current

Larval Euphausia similis were collected off temperate eastern Australia in spring 2004 and 2006 to evaluate the relationships between larval populations, mesoscale oceanographic variability, and the wider planktonic community. Larval E. similis were present in greater numbers in the East Australian Current (EAC) relative to productive coastal waters. Larval E. similis density was homogenous across the EAC—Tasman Sea frontal region, but larvae were smaller in the Tasman Sea. Larval E. similis density was not enhanced within a cold core eddy relative to the surrounding EAC. We observed a negative correlation between larval E. similis density and larval fish density, and a weak positive correlation with fluorescence. Evaluation of a significant fish density×fluorescence interaction term showed that the effect of fish density was reduced at high fluorescence values. Analysis of normalized biomass size spectrum (NBSS) provided evidence for potential competitive exclusion of copepods by krill. Data presented in this study suggest a predatory influence on surface E. similis populations by mesopelagic larval fish. The degree of predation appears to be dependent on food availability, potentially mediated by changes in the physiological condition of krill.

The influence of sex and maturity on the diet, mouth morphology and dentition of the Port Jackson shark, Heterodontus portusjacksoni

Dietary studies are essential for an understanding of elasmobranch ecology and their role in marine ecosystems. The diet, head morphology and dentition of Heterodontus portusjacksoni, an abundant, epibenthic shark in the coastal waters of temperate eastern Australia, were examined in 2004–2005. The stomach contents of the juvenile, subadult and adult stages of 136 males and 100 females were examined. Diets were broad (32 prey taxa), but dominated by molluscs, teleosts and cephalopods. Analyses of stomach contents data demonstrated that diet differed significantly by ontogenetic stage, but not by sex. Juveniles and subadults consumed mainly benthic infauna and epifauna, with subadults ingesting greater amounts of diogenid crustaceans, and adult diets dominated by demersal/pelagic prey. Trophic level differed ontogenetically, from secondary consumers as juveniles and subadults to tertiary consumers as adults. The mainly tricuspidate juvenile dentition changed with maturity to a greater proportion of large molariform distal teeth, whereas the snout and jaw lengthened and broadened. Adult males retained a greater proportion of anterior S-family teeth than females, which was most likely related to copulation. The ontogenetic variation in dietary composition, facilitated by differences in dentition and mouth morphology, demonstrated that dietary resources were partitioned ontogenetically.

Redescription of two species of wobbegongs (Chondrichthyes: Orectolobidae) with elevation of Orectolobus halei Whitley 1940 to species level

Two closely related species of the genus Orectolobus (Orectolobidae), O. ornatus (De Vis) and O. halei Whitley, are redescribed based on fresh material from temperate eastern Australia. Although described as a subspecies by Whitley (1940), O. halei was formerly synonymized with O. ornatus because of the lack of research material to assess their conspecificity. Due to its smaller size, O. ornatus was previously thought to be the juvenile form of the larger O. halei. Orectolobus ornatus occurs from Port Douglas, (Queensland) to Sydney (New South Wales) whereas O. halei occurs from Southport (Queensland) around the southern coast to Norwegian Bay (Western Australia). Both species are commercially targeted within the hook and line fishery off New South Wales. Orectolobus ornatus differs from O. halei in color pattern, a smaller adult size, fewer dermal lobes at the posterior preorbital group, lower vertebral and spiral valve counts, and the absence of supraorbital knob. Morphometrically, O. ornatus has a longer pelvic fin to anal fin interspace, smaller pectoral fins, smaller head dimensions, and relatively smaller claspers in mature specimens.