Eastern Australian Waters Research Articles

Molecular delimitation of cryptic Australian squid species of the genus Uroteuthis Rehder, 1945 (Cephalopoda: Loliginidae), provides a baseline of diversity to resolve classification challenges throughout the Indo-Pacific

ABSTRACT This study provides a comprehensive molecular phylogenetic analysis of Uroteuthis squid from the Indo-Pacific region. The main aim was to increase sample coverage from northern and eastern Australian waters to resolve the identity and distribution of Uroteuthis species taken by local fisheries. Two mitochondrial regions, cytochrome c oxidase subunit I (COI) and 16S ribosomal RNA (16S rRNA), were sequenced from 220 new specimens and analysed with a further 51 sequences from GenBank to create a combined phylogeny for the genus. Three nuclear regions, 18S ribosomal DNA (18S rDNA), 28S ribosomal DNA (28S rDNA) and rhodopsin, were also sequenced from representatives of each species. Based on the mitochondrial phylogeny plus distance and tree-based delimitation models, a COI species barcode gap of 4–5% is proposed for discriminating Uroteuthis species. Applying this gap partitioned many described species into species complexes; for example, U. duvaucelii, U. noctiluca and U. edulis resolved into 10 species. Although more conserved, mitochondrial 16S rRNA sequences differentiated all new species clades, whereas none of the nuclear markers resolved the closest species. Results confirm that neither U. chinensis nor U. edulis occurs in Australian waters. Five undescribed species are identified from northern and eastern Australia, of which four are consistent with earlier allozyme studies (and two align with existing DNA sequences). One is a new southeastern, deeper shelf species differentiated in this study, along with a sixth undescribed species from Indonesian waters. Results of the molecular analysis are now being used to inform complementary morphometric analyses for new species descriptions, and genetic stock structure assessments of these important fisheries resources.

Seasonal stratification and complex local dynamics control the sub-surface structure of marine heatwaves in Eastern Australian coastal waters

Marine heatwaves are extreme seawater temperature events that can have severe impacts on marine life. The extent of the ecological damage depends not only on the easily observed surface signature but on the marine heatwave structure at depth. However, due to a paucity of in situ sub-surface observations the vertical structure of marine heatwaves is poorly understood. Here we analyse the sub-surface coherence and controls of marine heatwaves using one of the world’s longest (28 years) records of daily sub-surface ocean temperature off Sydney, Australia. We show that seasonal stratification, large-scale circulation and local downwelling processes control the vertical coherence of coastal marine heatwaves. We define three classes of marine heatwaves which can extend through the water column, form in the shallow surface layer, or sub-surface independently, and are therefore not always evident in surface data. We conclude that sub-surface data need to be considered in monitoring marine heatwaves in coastal areas where maximum biological damage is reported.

Contrasting phytoplankton composition and primary productivity in multiple mesoscale eddies along the East Australian coast

Mesoscale eddies drive variability in phytoplankton functional trait composition and primary productivity (PP) relative to adjacent waters. Offshore waters in southeast Australia are subject to substantial mesoscale eddies that form when the East Australian Current (EAC) travels poleward along the coast, forming distinctive habitats in the upper ocean. Eddies provide an important enrichment mechanism in the nitrogen-limited waters of the Tasman Sea, yet there is limited knowledge of PP within cold- and warm-core eddies in the region and how physico-chemical and biological factors affect phytoplankton communities in this variable environment. We addressed the scarcity of observations by quantifying net PP using 13C isotopic enrichment incubations of surface waters over 10 degrees of latitude, comparing phytoplankton species composition in five different environments: a coastal shelf station, an oceanic cold and warm-core eddy, and a coastal dipole. Cold-core (cyclonic) eddies were significantly more productive than their warm-core (anticyclonic) counterparts (∼35 versus 0 mg C m−3 d−1), with centric diatoms the most prominent phytoplankton group, with a relatively high centric:pennate ratio. The diffuse attenuation coefficient, Kd (PAR), and silicate were the best overall predictors of phytoplankton composition, explaining 88% of variation based on pigment analysis and size fractionation. Variance in net PP did not correlate significantly with physico-chemical parameters frequently used in PP models (temperature, Kd [PAR], Chl a), yet inclusion of size-fractionated Chl a generated substantial improvement in our statistical model (from 36 to 77%). We show that cold-core eddies play a key role in regulating PP in eastern Australian waters and highlight a need for eddy-resolving models to incorporate descriptors of phytoplankton size structure to improve the accuracy of PP forecasts in eddy intensive regions.

Spatial Dynamics and Fine-Scale Vertical Behaviour of Immature Eastern Australasian White Sharks (Carcharodon carcharias).

Knowledge of the 3-dimensional space use of large marine predators is central to our understanding of ecosystem dynamics and for the development of management recommendations. Horizontal movements of white sharks, Carcharodon carcharias, in eastern Australian and New Zealand waters have been relatively well studied, yet vertical habitat use is less well understood. We dual-tagged 27 immature white sharks with Pop-Up Satellite Archival Transmitting (PSAT) and acoustic tags in New South Wales coastal shelf waters. In addition, 19 of these individuals were also fitted with Smart Position or Temperature Transmitting (SPOT) tags. PSATs of 12 sharks provided useable data; four tags were recovered, providing highly detailed archival data recorded at 3-s intervals. Horizontal movements ranged from southern Queensland to southern Tasmania and New Zealand. Sharks made extensive use of the water column (0-632 m) and experienced a broad range of temperatures (7.8-28.9 °C). Archival records revealed pronounced diel-patterns in distinct fine-scale oscillatory behaviour, with sharks occupying relatively constant depths during the day and exhibiting pronounced yo-yo diving behaviour (vertical zig-zag swimming through the water column) during the night. Our findings provide valuable new insights into the 3-dimensional space use of Eastern Australasian (EA) white sharks and contribute to the growing body on the general ecology of immature white sharks.

Preliminary Data about Habitat Use of Subadult and Adult White Sharks (Carcharodon carcharias) in Eastern Australian Waters.

Simple SummaryIn eastern Australia, the movement of subadult and adult white sharks is poorly understood as very few animals are encountered. To investigate how deep they dive, where they travel and water temperatures they live in, we tagged three white sharks (340–388 cm total length) between May 2021 and January 2022. All sharks moved away from the coast after release and preferred offshore habitats. The three sharks mainly stayed within 50 m of the surface, in water temperatures between 14–19 °C and dived deeper during the day. They all moved north–south along the coastline and spent little time in the same location but there was evidence that they stayed in some locations longer than others. Very little information is available for adult white sharks in eastern Australia and studies like this provide key information about their preferences. As they travel long distances it is important for multijurisdictional management to effectively mitigate human-shark interactions whilst supporting conservation efforts.In eastern Australia, white sharks (Carcharodon carcharias) are targeted in shark control programs, yet the movement of subadults and adults of the eastern Australasian population is poorly understood. To investigate horizontal and vertical movement and habitat use in this region, MiniPAT pop-up satellite archival tags were deployed on three larger white sharks (340–388 cm total length) between May 2021 and January 2022. All sharks moved away from the coast after release and displayed a preference for offshore habitats. The upper < 50 m of the water column and temperatures between 14–19 °C were favoured, with a diel pattern of vertical habitat use evident as deeper depths were occupied during the day and shallower depths at night. Horizontal movement consisted of north–south seasonality interspersed with periods of residency. Very little information is available for adult white sharks in eastern Australia and studies like this provide key baseline information for their life history. Importantly, the latitudinal range achieved by white sharks illuminate the necessity for multijurisdictional management to effectively mitigate human-shark interactions whilst supporting conservation efforts of the species.

The influence of bait position on the catch of target and non-target sharks in a SMART drumline bather protection program

There is increasing support for shark bite mitigation measures, such as SMART (Shark-Management-Alert-in-Real-Time) drumlines that minimise impacts on target sharks and other marine animals. On the east coast of Australia, SMART drumlines are used in a shark management program to catch and relocate white (Carcharodon carcharias), tiger (Galeocerdo cuvier), and bull sharks (Carcharhinus leucas; herein referred to as target sharks). This study examines the effect of bait position relative to the seabed on SMART drumline catches in eastern Australian waters, aiming to optimise catches of target sharks while reducing bycatch. Over 17 months, SMART drumlines were deployed at Ballina and Evans Head, New South Wales. Trace extensions were attached to 3.2 m standard traces to test the effect of bait height above the seabed on shark catch in an experimental design that alternated bait position every fortnight. White and tiger shark catches accounted for 67% of the total catch, whereas bull sharks were infrequently caught (3%). Bait position above the seabed did not significantly influence catch probability of white and tiger sharks. However, catches of Critically Endangered grey nurse sharks (Carcharias taurus) and false alarm events significantly increased when baits were closer to the seabed. Catches of white and tiger sharks varied throughout the year and were linked to seasonal water temperature changes. The standard traces effectively caught target shark species whilst reducing catches of grey nurse sharks and false alarm events, highlighting that the trace length currently used for NSW SMART drumline deployments is optimal.

Deciphering the Trophic Ecology of Three Marlin Species Using Stable Isotope Analysis in Temperate Waters Off Southeastern Australia

Understanding the unique feeding behaviours of oceanic fish, such as marlin, is key to their effective management. Marlin are notoriously difficult to study, however, and the limited research on marlin feeding shows that diet can vary greatly between species and geographic regions. One region where marlin feeding behaviours are particularly poorly understood are temperate eastern Australian waters. This study collected marlin tissue from game fishing tournaments between latitudes 32°43′06.5″S/152°08′50.1″E to 34°40′12.9″S/150°51′34.3″E between 2010 and 2021, and used stable isotope analysis (SIA) to assess the trophic ecology of the three species of marlin occurring in the region: black (Istiompax indica), blue (Makaira nigricans), and striped (Kajikia audax) marlin. All species had similar δ13C values, but δ15N differed between species, with higher variability observed in blue marlin than in the other two species. Sulphur isotopes were key in identifying the relative contribution of coastal or benthic influences on marlin diet, with δ34S suggesting that blue marlin had less coastal/benthic dietary influence than black or striped marlin. Incorporation of δ34S into SIA for marlin is thus recommended for future studies. Some differences in isotope values across locations and dates were found, however, the uneven sample sizes due to the opportunistic sampling limited the ability to understand spatial or seasonal differences. These findings show that marlin followed similar dietary trends to conspecifics in other regions despite temperate eastern Australian waters being one of the few with three marlin species commonly co-occuring. This suggests that interspecies resource competition is not a major force driving the demography of these species in eastern Australian waters. This research highlights a need for specific management strategies at a species level, particularly for blue marlin. Future research incorporating prey isoscapes and baselines assessed over a wider range of marlin sizes is suggested to further improve our knowledge and capacity to manage the marlin of eastern Australian waters.

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.

Range extension of the Regulus seastar Pentaceraster regulus (Müller &amp; 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.

Assessing the Use of Molecular Barcoding and qPCR for Investigating the Ecology of Prorocentrum minimum (Dinophyceae), a Harmful Algal Species.

Prorocentrum minimum is a species of marine dinoflagellate that occurs worldwide and can be responsible for harmful algal blooms (HABs). Some studies have reported it to produce tetrodotoxin; however, results have been inconsistent. qPCR and molecular barcoding (amplicon sequencing) using high-throughput sequencing have been increasingly applied to quantify HAB species for ecological analyses and monitoring. Here, we isolated a strain of P. minimum from eastern Australian waters, where it commonly occurs, and developed and validated a qPCR assay for this species based on a region of ITS rRNA in relation to abundance estimates from the cultured strain as determined using light microscopy. We used this tool to quantify and examine ecological drivers of P. minimum in Botany Bay, an estuary in southeast Australia, for over ~14 months in 2016–2017. We compared abundance estimates using qPCR with those obtained using molecular barcoding based on an 18S rRNA amplicon. There was a significant correlation between the abundance estimates from amplicon sequencing and qPCR, but the estimates from light microscopy were not significantly correlated, likely due to the counting method applied. Using amplicon sequencing, ~600 unique actual sequence variants (ASVs) were found, much larger than the known phytoplankton diversity from this region. P. minimum abundance in Botany Bay was found to be significantly associated with lower salinities and higher dissolved CO2 levels.

Stock structure and effective population size of the commercially exploited gummy shark Mustelus antarcticus

The Australian gummy shark Mustelus antarcticus is distributed across southern and eastern Australian waters and is the main target of a large shark fishery. Commercial harvest of the species is considered sustainable based on biomass estimates that show recovery from past overexploitation. However, the effective population size and genetic-based assessments of stock structure remain unresolved. We evaluated the genetic structure and effective population size (Ne) of the gummy shark using genome-wide single nucleotide polymorphisms. We found genetic divergence between individuals from the east coast and those along the south coast, resulting in 2 discrete populations with signatures of adaptive divergence. Spatial analyses revealed widespread gene flow within each of these populations, with some evidence for mild isolation-by-distance observed using individual-based tests. Demographic modelling of each population showed a comparatively rapid decline of Ne in the most recent past compared to more historical projections, with evidence that such declines have occurred to the point where genetic variation could be at risk. The identification of 2 divergent populations of gummy shark suggests that management should consider each individually to ensure the long-term sustainability of the species.

Habitat use and movement patterns of tiger sharks (Galeocerdo cuvier) in eastern Australian waters

Abstract Understanding the movement of marine predators is vital for effective conservation and management. Despite being targeted by shark control programs, the tiger shark, Galeocerdo cuvier, is poorly studied off eastern Australia. To investigate the horizontal movement and habitat use in this region, 16 sharks (157–384 cm total length) were tagged with MiniPAT pop-up satellite archival tags in 2018 and 2019. Eleven of these individuals were also fitted with satellite-linked radio transmitting tags. After release, most sharks moved off the continental shelf and headed north, associating with seamounts as they moved towards Queensland. During their time at liberty they transited through temperate, sub-tropical and tropical waters and spent the majority of time in the upper 50 m of the water column and at temperatures between 22 and 25˚C. Horizontal movement was focused in waters off the continental shelf. Increased movement over shelf waters occurred during the austral spring and summer when the East Australian Current is at its strongest and warm waters encroach the continental shelf. Broad latitudinal movement along the east coast of Australia was evident and highlights the connectivity between tropical and warm-temperate regions.

Dynamic variability of the phytoplankton electron requirement for carbon fixation in eastern Australian waters

Fast Repetition Rate fluorometry (FRRf) generates high-resolution measures of phytoplankton primary productivity as electron transport rates (ETRs). How ETRs scale to corresponding inorganic carbon (C) uptake rates (the so-called electron requirement for carbon fixation, e,C), inherently describes the extent and effectiveness with which absorbed light energy drives C-fixation. However, it remains unclear whether and how e,C follows predictable patterns for oceanographic datasets spanning physically dynamic, and complex, environmental gradients. We utilise a unique high-throughput approach, coupling ETRs and 14C-incubations to produce a semi-continuous dataset of e,C (n = 80), predominantly from surface waters, along the Australian coast (Brisbane to the Tasman Sea), including the East Australian Current (EAC). Environmental conditions along this transect could be generally grouped into cooler, more nutrient-rich waters dominated by larger size-fractionated Chl-a (>10 um) versus warmer nutrient-poorer waters dominated by smaller size-fractionated Chl-a (< 2 um). Whilst e,C was higher for warmer water samples, environmental conditions alone explained less than 20% variance of e,C, and changes in predominant size-fraction(s) distributions of Chl-a (biomass) failed to explain variance of e,C. Instead, NPQNSV was a better predictor of e,C, explaining 55% of observed variability. NPQNSV is a physiological descriptor that accounts for changes in both long-term driven acclimation in non-radiative decay, and quasi-instantaneous PSII downregulation, and thus may prove a useful predictor of e,C across physically-dynamic regimes, provided the slope describing their relationship is predictable.

Aspects of the reproductive biology of dusky, spinner and sandbar sharks (Family Carcharhinidae) from the Tasman Sea

Increased harvest pressure exerted on sharks worldwide has created a necessity for more information concerning the basic biology of targeted species. This study marks the first dedicated assessment of the reproductive biology of Carcharhinus obscurus, C. brevipinna and C. plumbeus in eastern Australian waters, where these species support a demersal longline fishery. We found all three to be late maturing species of low reproductive output, suggestive of an overarching susceptibility to stock depletion in the region. Length- (L50, cm LT) and age-at-maturity (A50, years), for females and males were respectively 281.1 and 15.5, and 271.9 and 14.6 for C. obscurus; 224.9 and 10.1, and 208.9 and 8.5 for C. brevipinna; and, 174.8 and 9.5, and 164.5 and 7.0 for C. plumbeus. Uterine fecundity (i.e. litter size) was observed at 5–12 (=9.6), 5–14 (=10.6) and 3–12 (=7.8) for the same three species respectively, and increased significantly with maternal length in C. brevipinna. Length-at-birth (L0, cm LT) ranged from 92 to 96 for C. obscurus, 79–82 for C. brevipinna and 66–76 for C. plumbeus, and all three species exhibited lengthy gestation periods, overall embryonic sex ratios of 1:1 and synchronous parturition in autumn. However, given limitations with respect to sample size and temporal distribution inherent in this study, the reproductive parameters defined herein are necessarily preliminary. Nevertheless, this research challenges a range of findings emanating from other parts of the world and, in doing so, raises pertinent questions relating to the resilience to targeted fishing activities of these species in New South Wales waters compared to other oceanic regions. Moreover, it reinforces the importance of locally derived demographic parameters for population modelling and stock assessment.

Characterisation of Ascaridoid larvae from marine fish off New Caledonia, with description of new Hysterothylacium larval types XIII and XIV

Here we report occurrence of six different morphotypes of ascaridoid type larvae from 28 species of fish collected from New Caledonian waters. The larvae were morphologically identified as Anisakis type I, Hysterothylacium type VI and new larval types XIII and XIV, Raphidascaris larval type and Terranova larval type II. Representatives of each morphotype were subjected to the amplification of the second internal transcribed spacers (ITS-2) of ribosomal DNA (rDNA) and those sequences were compared with ITS-2 sequences of other ascaridoid nematodes previously deposited in GenBank. ITS-2 sequences of Anisakis larval type I were identical to those of A. typica. ITS-2 sequences of Hysterothylacium larval type VI in the present study were identical to those previously found in Eastern Australian waters. No match was found for ITS-2 sequences of Hysterothylacium larval types XIII and XIV; therefore, the specific identities of these larval types remain unclear. ITS-2 sequences of Raphidascaris larval type were identical to those of R. trichiuri, which have previously been reported in Taiwanese waters. Terranova larval type II in the present study had identical ITS-2 sequences with Terranova larval types reported from Australian waters, however, the specific identity is unknown. This taxonomic work is essential if further research on these zoonotic parasites is to be effective. This includes investigations into such aspects as life cycle studies, impacts on human health and risk assessment for their transmission to humans.

Indicators of recovery for orange roughy (Hoplostethus atlanticus) in eastern Australian waters fished from 1987

Abstract Compared to an 18 year New Zealand study ( Clark et al., 2000 ) we found multiple signs of recovery for orange roughy in Australian waters. Orange roughy were listed as conservation dependent in Australian waters in 2006, with most stocks reported to be well below 20% of estimated pre-fishing equilibrium biomass and closed to targeted fishing. The largest known spawning aggregations occur on the east coast of Tasmania. This area has been fished and monitored since 1987. A specific monitoring programme was established in 2006 to determine whether and at what rate the spawning sites would rebuild. Acoustic biomass estimates were on average 1.5 times higher than that expected from a recent stock assessment and between 2006 and 2013 have shown an increasing then decreasing trend. Positive signs of a population recovery include an increased biomass at the spawning sites since fishing ceased, large change in the age structure of the population and a 74% increase in the reproductive potential of females since 1987. Given the late maturation of orange roughy entering the spawning biomass (∼30 years) and the short duration of fishing (∼26 years), these changes represent pre-fishing recruitment still entering the fishery. Biomass, age and length frequency data were variable between and within spawning sites; this complicates the use of a single or multiple spawning sites to monitor the exploitation and recovery of the fishery.

Tiger shark (Galeocerdo cuvier) movement patterns and habitat use determined by satellite tagging in eastern Australian waters

Partial migration is considered ubiquitous among vertebrates, but little is known about the movements of ocean- odromous apex predators such as sharks, particularly at their range extents. PAT-Mk10 and SPOT5 electronic tags were used to investigate tiger shark (Galeocerdo cuvier) spatial dynamics, site fidelity and habitat use off eastern Australia between April 2007 and May 2013. Of the 18 tags deployed, 15 recorded information on depth and/or temperature, and horizontal movements. Tracking times ranged between four and 408 days, with two recovered pop-up archival tags allow- ing 63 days of high-resolution archived data to be analysed. Overall mean proportions of time-at-depth revealed that G. cuvier spent the majority of time-at-depths of 500 m) occurred mostly

Genetic structure and diversity of two highly vulnerable carcharhinids in Australian waters

Molecular techniques were employed to investigate genetic structure and diversity in dusky Carcharhinus obscurusand sandbar C. plumbeussharks in the Indo-Australian region. Tissue samples of 423 C. obscurusand 442 C. plumbeusdefined 18 and 11 mtDNA ND4 haplo- types, respectively. For C. obscurus, weak genetic differentiation was detected be tween eastern and western Australian waters (pairwise Φ ST = 0.04437, p 100 at any particular location. Off Australia's temperate east coast, C. obscurusand C. plumbeusexhibited strong sim- ilarities in genetic structure, suggestive of similar evolutionary histories in the region. In addition, genetic validation revealed observers to be highly accurate in the identification of both target spe- cies in an eastern Australian shark fishery. Our findings contribute valuable information for the management and conservation of both species.

Linking spatial stock dynamics and economics: evaluation of indicators and fishery management for the travelling eastern king prawn (Melicertus plebejus)

Abstract Reduced economic circumstances have moved management goals towards higher profit, rather than maximum sustainable yields in several Australian fisheries. The eastern king prawn is one such fishery, for which we have developed new methodology for stock dynamics, calculation of model-based and data-based reference points and management strategy evaluation. The fishery is notable for the northward movement of prawns in eastern Australian waters, from the State jurisdiction of New South Wales to that of Queensland, as they grow to spawning size, so that vessels fishing in the northern deeper waters harvest more large prawns. Bioeconomic fishing data were standardized for calibrating a length-structured spatial operating model. Model simulations identified that reduced boat numbers and fishing effort could improve profitability while retaining viable fishing in each jurisdiction. Simulations also identified catch rate levels that were effective for monitoring in simple within-year effort-control rules. However, favourable performance of catch rate indicators was achieved only when a meaningful upper limit was placed on total allowed fishing effort. The methods and findings will allow improved measures for monitoring fisheries and inform decision makers on the uncertainty and assumptions affecting economic indicators.

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.