South-eastern Australian Waters Research Articles

Range extension of the Regulus seastar Pentaceraster regulus (Müller & Troschel, 1842) (Echinodermata: Asteroidea: Oreasteridae): evidence of tropicalization of the east Australian coast

The seastar Pentaceraster regulus (Müller & Troschel, 1842) is documented from the coastal estuary of Wallis Lake, New South Wales, Australia, c. 600 km from the nearest previous records at Lord Howe Island, an offshore area known to receive a tropical influence from the southern flowing East Australian Current, and between 640 to 800 km south of earlier published records from mainland areas to the north in Queensland. Historical data combined with contemporary observations provide evidence that this is a recent range extension and may be a further example of tropicalization of the south eastern Australian coastal waters. Records from Wallis Lake span a twelve year period and the most recent observations in 2020 indicate it is abundant, and there is considerable difference between the smallest and largest specimens present, suggesting a population that completes most or all of the life cycle is established in the estuary. Given the impacts range shifted species and other echinoderms are known to have in influencing ecosystem dynamics, it is suggested that further study of this seastar is prudent to determine what impacts it may have in the newly colonized area.

Biodiversity of intertidal marine flatworms (Polycladida, Platyhelminthes) in southeastern Australia.

Flatworms of the Order Polycladida are a group of free-living invertebrates found in a diversity of marine habitats, with over 800 species described worldwide. Marine flatworms are a conspicuous component of Australias marine fauna yet have received little attention. Less than 30 scientific articles have been published on Australian marine flatworms since 1855, of which only nine include species from southeastern Australia. Here, the biodiversity and distribution of species belonging to the Order Polycladida inhabiting intertidal rocky beaches in southeastern Australian waters were identified and analysed. Sampling was conducted at low tide along the coasts of New South Wales and Victoria. Collected samples were serially sectioned for comparative anatomical studies, and tissue was removed from each individual for molecular sequencing and analyses. Both nuclear and mitochondrial DNA sequences were obtained and used as an additional source of evidence for the description of new species as well as providing further insight into the phylogenetic relationships between them. A total of 20 species, six of which are new (e.g., Eulatocestus australis sp. nov.), and a new genus (Parabolia gen. nov.) have been described, as well as two new records for Australia (e.g., Stylochoplana clara Kato, 1937) have been identified increasing our knowledge of this important component of the Australian marine biota.

Spatiotemporal distributions of two sympatric sawsharks (Pristiophorus cirratus and P. nudipinnis) in south-eastern Australian waters

Sawsharks are one of the least well-known groups of sharks globally, yet they are caught in large numbers in south-eastern Australia. In this study we assessed spatiotemporal patterns of distribution of two co-occurring species of sawsharks, namely the common sawshark (Pristiophorus cirratus) and the southern sawshark (Pristiophorus nudipinnis), to guide future research in this area. To identify where the animals may occur in greater numbers, this study used the major commercial fishery datasets in the region, containing nearly 180000 catch records from 1990 to 2017. Several general patterns were evident. Sawsharks occurred at shallower and deeper depths than previously thought, and their geographical range was larger than documented in previous studies. Depth distributions of both species overlapped, but P. cirratus appeared more common in deeper water (at depths up to 500m), with peak common sawshark catch rates at ~400m. Seasonal standardised catch patterns across fishing methods suggested that migrations from deeper to shallower waters may occur in the Australasian autumn and winter. The greatest concentration of sawsharks, inferred by standardised catch rates, occurred to the east and west of Bass Strait between Tasmania and mainland Australia. Although standardised catch rates of sawsharks declined in gill-net fisheries by ~30%, primarily in the Bass Strait and Tasmania, sawsharks appear to be caught at consistent rates since the 1990s, inferring a possible resilience of these sharks to current levels of fishing pressure.

Whistle characteristics of newly defined species, the Burrunan dolphin (Tursiops australis), in coastal Victorian waters in Australia

A newly defined species, the Burrunan dolphin (Tursiops australis), was described in 2011 by Charlton-Robb et al., and is endemic to southern and south-eastern Australian coastal waters. This species' distribution is characterized by small, isolated, and genetically distinct populations. With only two known populations in Victoria, the species is now listed as “Threatened” under the Victorian Flora and Fauna Guarantee Act. Describing and quantifying the vocal repertoire of a species is critical for subsequent analysis of signal functionality, geographic variation, social relevance, and identifying threats associated with anthropogenic noise. Here, we present the first quantitative analysis of whistle characteristics for the species, undertaken on these endemic Victorian populations. Vocalizations of T. australis were recorded during population based surveys in 2007 and 2014 across the Gippsland Lakes and Port Phillip Bay, Victoria. Acoustic parameters of whistles were measured including minimum frequency ...

Temperate predators and seasonal water temperatures impact feeding of a range expanding tropical fish

Range expansions of species due to climate change threaten the function and composition of marine ecosystems globally, yet factors constraining or facilitating this redistribution are poorly understood. Native predators may constrain prey shifting poleward through consumption, or by restricting their feeding activity. However, the extent that native predators impact range-expanders will likely be structured by physiological mismatches between these groups, associated with water temperatures. We examined how temperate predators and seasonal water temperature affected foraging of the planktivorous tropical reef fish, Abudefduf vaigiensis, within temperate southeastern Australian waters, an emerging new range. Foraging excursions of A. vaigiensis were compared between predator-rich marine reserves and predator-depauperate fished reefs during summer and winter (~18 and 22 °C water, respectively). A. vaigiensis foraged with shorter excursions in marine reserves than fished reefs and higher excursions during summer than winter. Effects of predation risk and water temperature on A. vaigiensis foraging were isolated in an aquarium experiment. Groups were held at 18 or 22 °C and visually exposed to a temperate predator, a predator control (temperate herbivore) and an empty tank. Foraging excursions and feeding rates were reduced when exposed to predators at 22 °C, but did not differ between predator and the predator control or empty tank at 18 °C. Results suggest temperate predators may restrict range expansions of A. vaigiensis by reducing its’ food intake during summer months. But winter water temperatures may limit feeding, independent of predation risk. Protection of predators from fishing should improve resistance of some marine ecosystems to impacts of range expanding prey.

Bioaccumulation of PCBs in liver tissue of dusky Carcharhinus obscurus, sandbar C. plumbeus and white Carcharodon carcharias sharks from south-eastern Australian waters

Polychlorinated biphenyls (PCBs) are ubiquitous pollutants in the marine environment that are known to accumulate in apex predators such as sharks. Liver samples from dusky Carcharhinus obscurus, sandbar Carcharhinus plumbeus, and white Carcharodon carcharias sharks from south-eastern Australian waters were analysed for the seven indicator PCBs 28, 52, 101, 118, 138, 153 and 180. Median ∑PCBs were significantly higher in white than sandbar sharks (3.35 and 0.36μgg−1 lipid, respectively, p=0.05) but there were no significant differences between dusky sharks (1.31μgg−1 lipid) and the other two species. Congener concentrations were also significantly higher in white sharks. Significant differences in PCB concentrations between mature and immature dusky (3.78 and 0.76μgg−1 lipid, respectively) and sandbar (1.94 and 0.18μgg−1 lipid, respectively) sharks indicated that PCB concentrations in these species increased with age/growth. Higher-chlorinated congeners (hexa and heptachlorobiphenyls) dominated results, accounting for ~90% of ∑PCBs.

Phenotypic plasticity and biogeographic variation in physiology of habitat-forming seaweed: response to temperature and nitrate.

Southeastern Australian waters are warming at nearly four times the global average rate (~0.7°C·century(-1) ) driven by strengthening incursions of the warm oligotrophic East Australian Current. The growth rate hypothesis (GRH) predicts that nutrient depletion will impact more severely on seaweeds at high latitudes with compressed growth seasons. This study investigates the effects of temperature and nutrients on the ecophysiology of the habitat-forming seaweed Phyllospora comosa in a laboratory experiment using temperature (12°C, 17°C, 22°C) and nutrient (0.5, 1.0, 3.0μM NO3 (-) ) scenarios representative of observed variation among geographic regions. Changes in growth, photosynthetic characteristics (via chlorophyll fluorescence), pigment content, tissue chemistry (δ(13) C, % C, % N, C:N) and nucleic acid characteristics (absolute RNA and DNA, RNA:DNA ratios) were determined in seaweeds derived from cool, high-latitude and warm, low-latitude portions of the species' range. Performance of P.comosa was unaffected by nitrate availability but was strongly temperature-dependent, with photosynthetic efficiency, growth, and survival significantly impaired at 22°C. While some physiological processes (photosynthesis, nucleic acid, and accessory pigment synthesis) responded rapidly to temperature, others (C/N dynamics, carbon concentrating processes) were largely invariant and biogeographic variation in these characteristics may only occur through genetic adaptation. No link was detected between nutrient availability, RNA synthesis and growth, and the GRH was not supported in this species. While P.comosa at high latitudes may be less susceptible to oligotrophy than predicted by the GRH, warming water temperatures will have deleterious effects on this species across its range unless rapid adaptation is possible.

Metal and metalloid concentrations in the tissues of dusky Carcharhinus obscurus, sandbar C. plumbeus and white Carcharodon carcharias sharks from south-eastern Australian waters, and the implications for human consumption

Shark fisheries have expanded due to increased demand for shark products. As long-lived apex predators, sharks are susceptible to bioaccumulation of metals and metalloids, and biomagnification of some such as Hg, primarily through diet. This may have negative health implications for human consumers. Concentrations of Hg, As, Cd, Cu, Fe, Se and Zn were analysed in muscle, liver and fin fibres (ceratotrichia) from dusky Carcharhinus obscurus, sandbar Carcharhinus plumbeus, and white Carcharodon carcharias sharks from south-eastern Australian waters. Concentrations of analytes were generally higher in liver than in muscle and lowest in fin fibres. Muscle tissue concentrations of Hg were significantly correlated with total length, and >50% of sampled individuals had concentrations above Food Standards Australia New Zealand’s maximum limit (1mgkg−1ww). Arsenic concentrations were also of concern, particularly in fins. Results warrant further investigation to accurately assess health risks for regular consumption of shark products.

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

Abstract The 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.

Latitudinal, ontogenetic, and historical shifts in the diet of a carnivorous teleost, Arripis trutta, in a coastal pelagic ecosystem altered by climate change

Changes to the global climate are driving alterations to boundary current-influenced marine ecosystems. The diet of a pelagic teleost, Arripis trutta, was examined in the East Australian Current (EAC)-dominated coastal waters of southeastern (SE) Australia. The diet of A. trutta was dominated by pelagic baitfish, primarily Australian sardine (Sardinops sagax) and scads (Trachurus spp.). Diet varied substantially with both latitude and season linked to variability in the distribution and abundance of key prey species. An ontogenetic diet shift occurred, with crustaceans and polychaetes making up a large proportion of the diet of small fish compared with the dominance of baitfish at larger sizes. The diet of A. trutta has undergone a dramatic shift from one dominated by krill (Nyctiphanes australis) historically to baitfish today. This change is consistent with a well-documented regime shift caused by the increasing intensity of the EAC on coastal SE Australian waters. Understanding the temporal dynamics of this ecosystem is crucial for management of coastal fisheries and also for understanding the impacts of climate change on boundary current-dominated marine ecosystems worldwide.

C-AMP Dependent Protein Kinase a Inhibitory Activity of Six Algal Extracts from South Eastern Australia and Their Fatty Acid Composition

c-AMP dependent protein kinase (protein kinase A, PKA) is an important enzyme involved in the regulation of an increasing number of physiological processes including immune function, cardiovascular disease, memory disorders and cancer. The objective of this study was to evaluate the PKA inhibitory activity of a range of algal extracts, along with their fatty acid composition. Six algal species were investigated including two Chlorophyta (Codium dimorphum and Ulva lactuca), two Phaeophyta (Phyllospora comosa and Sargassum sp.) and two Rhodophyta (Prionitis linearis and Corallina vancouveriensis), with the order of PKA inhibitory activity of their extracts identified as follows: brown seaweeds > red seaweeds > green seaweeds with the brown alga Sargassum sp. exhibiting the highest PKA inhibitory activity (84% at 100 microg/mL). GC/MS analysis identified a total of 18 fatty acids in the six algal extracts accounting for 72-87% of each extract, with hexadecanoic acid and 9,12-octadecadienoic acid as the dominant components. The most active extract (Sargassum sp.) also contained the highest percentage of the saturated C14:0 fatty acid (12.8% of the total extract), which is a known to inhibit PKA. These results provide the first description of the PKA inhibitory activity of marine algae along with the first description of the fatty acid composition of these six algal species from South Eastern Australian waters. Importantly, this study reveals that abundant and readily available marine algae are a new and relatively unexplored source of PKA inhibitory compounds.

A review of giant roughies of the genus Hoplostethus (Beryciformes, Trachichthyidae), with descriptions of two new Australasian species

Ro berts, C.D. & Gomon, M.F. 2012. A review of giant roughies of the genus Hoplostethus (Beryciformes, Trachichthyidae), with descriptions of two new Australasian species. Memoirs of Museum Victoria 69: 341–354. Hoplostethus gigas McCulloch, 1914 and two previously unnamed species of the genus that reach a similarly ‘giant’ size are described. The redescription of H. gigas, which is confined in distribution to the southern coast of Australia, is based on specimens identified as comprising at least part of McCulloch’s type series (one herein designated lectotype), together with subsequently collected material. The very similar H. melanopeza sp. nov., occurring in northern New Zealand and southeastern Australian waters, as well as seamounts in the intervening Tasman Sea, is distinguished by the distinctly black outer margins of fins in large adults and count of predorsal scales. The New Caledonian H. grandperrini sp. nov., known only from the two types, differs from previously described species in having the combination of 17 or 18 pectoral–fin rays, 13 or 14 abdominal scutes, 19 or 20 total gill rakers and a buccal cavity that is mostly pale, the only black pigmentation occurring posterior to the gill arches.

Pop-up archival satellite tagging of Carcharias taurus: movements and depth/temperature-related use of south-eastern Australian waters

Knowledge of migratory movements and depth/temperature-related use of coastal waters by sharks can lead to more sustainable fisheries and assist in managing the long-term conservation of those species now considered threatened. Pop-up archival satellite tags (PATs) provide an alternative to conventional tagging for documenting migratory movements. This study focussed on the migratory movements of Carcharias taurus, a critically endangered shark found along the east coast of Australia. From October 2003 to July 2008, 15 C. taurus individuals were tagged with PATs with varying deployments (60–150 days) and acoustic tags linked to an acoustic monitoring system providing accurate geo-location. Distances moved by C. taurus individuals ranged from 5 to 1550 km and varied according to sex and season. Migrations north and south were punctuated en route by occupation of sites for varying periods of time. The deepest depth recorded was 232 m off South West Rocks on the New South Wales mid-north coast. On average, C. taurus males and females spent at least 71% of their time in waters <40 m and 95% of their time in waters 17–24°C. By mainly occupying inshore waters, C. taurus is exposed to potentially adverse fishing-related interactions that may be difficult to mitigate.

Genetic stock structure of blue-eye trevalla (Hyperoglyphe antarctica) and warehous (Seriolella brama and Seriolella punctata) in south-eastern Australian waters

Blue-eye trevalla (Hyperoglyphe antarctica), blue warehou (Seriolella brama) and silver warehou (Seriolella punctata) from the family Centrolophidae are three commercially important species in the Australian fishery. These species are currently managed as single stocks. We tested the hypothesis that patterns of phenotypic structuring in these species reflect underlying genetic stock structure using an analysis of mitochondrial DNA control region sequences. The analysis revealed high levels of haplotype diversity within populations. The most common haplotypes for the species occurred in all geographical locations sampled. For S. brama, although structuring was not significant after Bonferroni correction, differences between two sites were sufficient to warrant caution in the management of fishery zones for this species. There were also some indications of structuring when sites were grouped into common regions. Demographic analysis suggested that S. brama might have had a history of population bottlenecks followed by sudden population expansion, potentially contributing to genetic structuring in the fishery. No structuring was detected for H. antarctica and S. punctata. The present study highlights the need for, and the utility of, multiple sources of information, that is, genetic, phenotypic, behavioural and ecological, when managing marine fisheries and the need to take a cautionary approach to the interpretation of genetic data for fisheries management.

Dietary comparisons of six skate species (Rajidae) in south-eastern Australian waters

The diet of six skate species caught as bycatch in south-eastern Australian waters was examined over a 2-year period. The skates were segregated into two regions (continental shelf and continental slope) based on prey species and depth of capture. The shelf group consisted of four species, Dipturus sp. A, D. cerva, D. lemprieri and D. whitleyi, while the slope group comprised two species, Dipturus sp. B and D. gudgeri. The two groups varied in feeding strategies with the shelf species generally occupying a broader feeding niche and preying on a larger diversity of prey including a variety of crustaceans (brachyurans, anomurans, achelates, carideans and dendobranchiates), cephalopods, elasmobranchs and teleosts. Within the slope group, Dipturus sp. B and D. gudgeri were more specialised. Dipturus sp. B preyed primarily on anomurans (galatheids) and bachyurans (homolids), whereas D. gudgeri preyed primarily on teleosts. A size related change in diet was evident for all species with the exception of D. gudgeri in which all sizes preyed predominantly on teleosts. Smaller representatives of the four shelf species all preyed on numerous amounts of caridean shrimps, in particular Leptochela sydniensis. In contrast, the continental slope species, Dipturus sp. B consumed anomurans when small, shifting to brachyurans with increasing size. Of the six skate species examined in this study, three were secondary consumers (trophic level 4). Although ANOSIM found significant differences in dietary composition between species within groups, there was some overlap in prey species amongst co-existing skates, which suggests that there is some degree of resource partitioning amongst them.

Descriptions of rajid egg cases from southeastern Australian waters

Egg cases from nine skate species occurring in Tasmanian waters were examined and measured. A species-specific identification key is provided for eight of these species. The key was developed primarily from fresh egg cases dissected from the oviduct, although specimens collected from the ocean floor or found dried on the beach were also used to test the key. Egg cases for the ninth species could not be included because the only egg case pair recovered was partially formed. A diagnosis of the posterior end of this egg case is provided.

Chemical diversity in south-eastern Australian saline lakes II: biotic implications

This study explores how differences in ionic composition of south-eastern Australian saline lake waters, caused by path differentiation according to the Eugster–Jones–Hardie models of solute evolution and halite recycling, influence species composition of ostracod faunas. Ostracod occurrences are reported as physiologically important ionic ratios set in a marine–meteoric framework, with chemical boundaries determined by mixing and evaporation models. The occurrence of halophilous ostracods coincides with changes in the ionic structure of lake waters. Chemical diversity is found to be biologically important, with most ostracods preferring a specific pathway of the Eugster–Jones–Hardie models. Path preference predominantly reflects the different tolerance ranges of species to a combination of Na+/H+, Na+/Ca2+ and alkalinity/Cl– activity ratios, which probably govern acid–base balance and Na+ and Ca2+ regulation. An alkalinity/Cl– activity ratio of ~–2.3 corresponds to the main division in the ostracod data and reflects the abrupt change in alkalinity/Cl– ratios that occurs when a seawater-like solute matrix is diluted with a large amount of meteoric water (95%). Most halobiont ostracods occur in waters enriched with Na–Cl as a result of halite recycling. Evidence is presented that the same geochemical processes are relevant to other aquatic organisms (e.g. zooplankton, diatoms, insects) found in salt lakes.

Some morphometric and biochemical features of ready‐to‐migrate silver and pre‐migratory yellow stages of the shortfin eel of south‐eastern Australian waters

The mean total length (LT), mass and age of ready to migrate female silver shortfin eels Anguilla australis from the Hopkins River estuary and the mouth of the Merri River in south‐eastern Australia, were 83·2 ± 1·2 cm, 1051 ± 51 g, and 17·2 ± 1·79 years, respectively. The eye index (IE) of the silver shortfin eels was < 5·2 (mean 7·64 ± 0·29) and differed significantly from that of the yellow shortfin eels collected from two other sites. The IE increased with LT (mm) and was related by log IE= 2·656 log LT6·925. The per cent moisture, protein and ash content of the liver of silver shortfin eels was significantly lower than in yellow shortfin eels, but lipid content was significantly higher in the former (35·5 ± 2·0%). The mean mass μg mg lipid −) of saturates (230·4 ± 2·6 v. 181·7 ±2·6), monoenes (367·4 ± 6·3 v. 290·8 ± 8·9) and PUFA (177·3 ± 5·3 v. 159·7 ± 4·6) in muscle was significantly higher, and the great majority of individual fatty acids was found also in higher quantities in silver shortfin eels. In the liver, the PUFA found in the highest quantity was 22:6n‐3, except in shortfin eels from Hopkins River estuary, and the amount of 18:2n‐6 in the liver of silver shortfin eels was significantly higher than that in yellow shortfin eels but the reverse was true of 20:4n‐6. In both muscle and liver tissues the saturate 16:0 and the monoene 18:ln‐9 collectively accounted for >50% of all the fatty acids in the lipid.

Some morphometric and biochemical features of ready-to-migrate silver and pre-migratory yellow stages of the shortfin eel of south-eastern Australian waters

Some morphometric and biochemical features of ready-to-migrate silver and pre-migratory yellow stages of the shortfin eel of south-eastern Australian waters

The benthic dinoflagellate genus Amphidinium in south-eastern Australian waters, including three new species

Seventeen species of the mainly sand-dwelling genus Amphidinium are reported from south-eastern Australian waters. Three new species are described: A. boggayum, A. mootonorum and A. yuroogurrum. Additional features from previously described species are presented, including non-motile cell stages. Nine of these species are new records for Australia; however, these species are probably widespread and common. Two potentially ichthyotoxic species of Amphidinium were commonly found: A. carterae and A. cf. operculatum. A table of morphological characters is compiled as a step towards recognizing new characters with which to group species of this presently artificially defined unarmoured dinoflagellate genus.