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Infectious diseases are recognized as one of the greatest global threats to biodiversity and ecosystem functioning. Consequently, there is a growing urgency to understand the speed at which adaptive phenotypes can evolve and spread in natural populations to inform future management. Here we provide evidence of rapid genomic changes in wild Australian blacklip abalone (Haliotis rubra) following a major population crash associated with an infectious disease. Genome scans on H. rubra were performed using pooled whole genome resequencing data from commercial fishing stocks varying in historical exposure to haliotid herpesvirus‐1 (HaHV‐1). Approximately 25,000 single nucleotide polymorphism loci associated with virus exposure were identified, many of which mapped to genes known to contribute to HaHV‐1 immunity in the New Zealand pāua (Haliotis iris) and herpesvirus response pathways in haliotids and other animal systems. These findings indicate genetic changes across a single generation in H. rubra fishing stocks decimated by HaHV‐1, with stock recovery potentially determined by rapid evolutionary changes leading to virus resistance. This is a novel example of apparently rapid adaptation in natural populations of a nonmodel marine organism, highlighting the pace at which selection can potentially act to counter disease in wildlife communities. [ABSTRACT FROM AUTHOR]

A key requirement for managing commercial fisheries is understanding the geographic footprint of the resource, the level of exploitation and the potential impacts of changing climate or habitat conditions. The development of spatially explicit predictive models of species distributions combined with predictions of changing oceanographic conditions provides the opportunity to obtain new insights of species‐habitat associations. Here, generalized linear models (GLMs) were used to model the abundance of two commercially important marine macro‐invertebrates, blacklip abalone Haliotis rubra and long‐spined sea urchin Centrostephanus rodgersii, along the coast of Victoria, Australia. We combined abundance data from fisheries independent diver surveys with environmental variables derived from bathymetric light detection and ranging (LiDAR) and oceanographic parameters derived from satellite imagery. The GLM was used to predict species responses to environmental gradients where reef complexity, sea surface temperature (SST) and depth were strongly associated with species distributions. The abundance of H. rubra declined with increasing summer SST. In comparison, the abundance of C. rodgersii increased with increasing winter SST. The GLM showed that the projected increase in ocean temperatures will likely lead to a decline in abundance across the H. rubra fishery. Conversely, a range expansion of C. rodgersii is likely due to the strengthening of the East Australian Current. For species that exhibit a high affinity to specific seascape features, this research demonstrated how recent advances in seabed mapping can allow the identification of areas with high conservation or fisheries value at a fine‐scale relevant to resource exploitation across large geographic regions. [ABSTRACT FROM AUTHOR]

Genes encoded in nuclear ribosomal DNA (nrDNA), which comprise a multi-family of genes with tandem repeat units, play an important role in nucleolus formation. In the present study, we sequenced and analysed the complete rDNA sequence of an economically important shellfish in Australia, Haliotis rubra. The single rDNA unit measured 9881 base pairs (bp) in length and included the following elements in order: 18S rRNA (1858 bp), internal transcribed spacers (ITS, 756 bp), 28S rRNA (3413 bp) and an intergenic spacer (IGS, 3854 bp). The phylogenetic tree was constructed using abalone ITS sequences; here, the relationship revealed that abalone species within the same region and with same chromosome number tended to cluster within a clade. The positions of putative transcription termination and RNA transcription initiation sites were predicted in the IGS region. A comparative sequence complexity analysis and dot plots revealed a high level of variability in the IGS. [ABSTRACT FROM AUTHOR]

Abstract: Fisheries management strategies usually do not consider secondary consequences of environmental shocks. A recent viral disease outbreak that decimated blacklip abalone populations in southern Australia had a much smaller impact on the region's less‐abundant greenlip abalone populations. Decreases in total allowable commercial catch (TACC) for blacklip abalone were partially offset by a transient increase in greenlip abalone TACC that peaked in 2010 and reduced to zero in 2013. A hypothesis that the greenlip abalone stock had declined was supported by a Bayesian analysis of catch rates (catch per unit effort, CPUE, as a proxy for biomass). The estimated decline is consistent with depletion of the relatively small and fragmented greenlip stock as an indirect consequence of the disease impact. Our analysis demonstrates a need to jointly monitor and manage substitute fisheries when one of the fisheries experiences depletion as a result of a natural disturbance event. Considerations for Management: Hierarchical Bayesian models can determine whether a shock to a natural resource indirectly affects related resources via a transfer of exploitation effort; Greenlip abalone stocks in western Victoria were generally poor in quality and infrequently exploited prior to the disease outbreak. Their low productivity rendered them vulnerable to the sudden increase in exploitation pressure, which could not be sustained once CPUE declined to 40–50 kg h−1, after which fishing activity ceased; A CPUE of 40 kg h−1 could be a precautionary limit reference point for triggering future greenlip abalone fishery closures; An increase in greenlip abalone legal minimum length (LML) to at least 140 mm would improve quality and profit; It is important to protect substitute resources from secondary exploitation when imposing restrictions on exploitation of resources that are adversely impacted by natural disturbance events. [ABSTRACT FROM AUTHOR]

Sulphated polysaccharides with anti-thrombotic and anti-coagulant activities have been found in various marine biota. In this study, a previously characterised anti-thrombotic and anti-coagulant extract from blacklip abalone was fractionated by anion exchange chromatography (AEC), pooled (on a sulphated polysaccharide basis) and administered to Wistar rats via oral gavage (N = 8) for assessment as an oral therapeutic. To ensure that the preparation had anti-coagulant activity prior to oral administration, it was assessed in rat blood by thromboelastography (TEG) significantly increasing reaction (R) time (or time until clot formation). Following in vitro confirmation of anti-coagulant activity, 40 mg of the preparation was orally administered to rats with blood samples collected at 2, 4, and 6 h post-gavage. Assessment of all blood samples by TEG showed some prolongation of R time from 355 to 380 s after 4 h. Dosing of the post-gavage blood samples with the abalone preparation to confirm anti-thrombotic activity in vitro revealed residual anti-coagulant activity, further suggesting that oral administration did increase anti-coagulant potential in the collected blood but that bioavailability was low. Assessment of tissues and haematological parameters showed no obvious harmful effects of the abalone preparation in animals. In summary, even though oral administration of fractionated and pooled blacklip abalone extract to rats delayed clotting after 4 h, bioavailability of the preparation appeared to be low and may be more appropriate for intravenous administration as an anti-thrombotic or anti-coagulant therapeutic. [ABSTRACT FROM AUTHOR]

Abalone viscera contain sulphated polysaccharides with anti-thrombotic and anti-coagulant activities. In this study, a hydrolysate was prepared from blacklip abalone ( Haliotis rubra) viscera using papain and bromelain and fractionated using ion exchange and size exclusion chromatography. Hydrolysates and fractions were investigated for in vitro thrombin inhibition mediated through heparin cofactor II (HCII) as well as anti-coagulant activity in plasma and whole blood. On the basis of sulphated polysaccharide concentration, the hydrolysate inhibited thrombin through HCII with an inhibitor concentration at 50% (IC50) of 16.5 μg/mL compared with 2.1 μg/mL for standard heparin. Fractionation concentrated HCII-mediated thrombin inhibition down to an IC50 of 1.8 μg/mL and improved anti-coagulant activities by significantly delaying clotting time. This study confirmed the presence of anti-thrombotic and anti-coagulant molecules in blacklip abalone viscera and demonstrated that these activities can be enriched with a simple chromatography regime. Blacklip abalone viscera warrant further investigation as a source of nutraceutical or functional food ingredients. [ABSTRACT FROM AUTHOR]

Abalone (Haliotis sp) has been used as a traditional functional food for many years by different cultures believing that consumption provides health benefits. We investigated the anti-inflammatory activity from blacklip abalone visceral waste. An extract was prepared from the viscera using digestion with the food grade proteases papain and bromelain followed by anion exchange chromatography (AEC). The anti-inflammatory potential of the extract and AEC fractions were investigated in comparison to a plant-derived positive control (quercetin) through the inhibition of lipopolysaccharide-stimulated nitric oxide production in RAW 264.7 monocytes. Significant anti-inflammatory activity was observed in response to the abalone extract and the unbound AEC material over a concentration (based on collagen) range of 12–96 µg/mL. Overall, results indicated that blacklip abalone extract has anti-inflammatory activityin vitro, warranting further investigation into the bioactive constituents that may be potential anti-inflammatory therapeutics. [ABSTRACT FROM AUTHOR]

Xanthorhodopsin (xR) is a member of the retinal protein family and acts as a proton pump in the cell membranes of the extremely halophilic eubacterium Salinibacter ruber. In addition to the retinal chromophore, xR contains a carotenoid, which acts as a light-harvesting antenna as it transfers 40% of the quanta it absorbs to the retinal. Our previous studies have shown that the CD and absorption spectra of xR are dramatically affected due to the protonation of two different residues. It is still unclear whether xR can bind cations. Electron paramagnetic resonance (EPR) spectroscopy used in the present study revealed that xR can bind divalent cations, such as Mn2+ and Ca2+, to deionized xR (DI-xR). We also demonstrate that xR can bind 1 equiv of Mn2+ to a high-affinity binding site followed by binding of ~40 equiv in cooperative manner and ~100 equiv of Mn2+ that are weakly bound. SQUID magnetic studies suggest that the high cooperative binding of Mn2+ cations to xR is due to the formation of Mn2+ clusters. Our data demonstrate that Ca2+ cations bind to DI-xR with a lower affinity than Mn2+, supporting the assumption that binding of Mn2+ occurs through cluster formation, because Ca2+ cations cannot form clusters in contrast to Mn2+. [ABSTRACT FROM AUTHOR]

Paralytic shellfish toxins (PST) were detected in abalone ( Haliotis rubra ) in April 2011 in south-east Tasmania, Australia, during a dinoflagellate bloom of Gymnodinium catenatum . This led to restrictions on abalone harvesting and triggered continued PST monitoring by Ultra Performance Liquid Chromatography (UPLC-FLD) of abalone and mussels ( Mytilus galloprovincialis ), and concurrent phytoplankton monitoring, between 2011 and 2013. PST up to 2437 μg STX eq kg −1 (three times the bivalve regulatory limit) were confirmed in abalone viscera, with toxicity up to 586 μg STX eq kg −1 in the muscular foot (mainly doSTX and minor proportions of STX and dcSTX). Mussels accumulated PST at a faster rate than abalone which suggests they can serve as sentinels of PST accumulation to inform abalone risk management protocols. Three lines of evidence for G . catenatum as the source of PST in abalone were established: (1) PST in abalone tissues increased and declined in association with dinoflagellate blooms; (2) G . catenatum DNA was detected by real-time PCR in abalone digestive tracts; and (3) the PST analogues (toxin profile) observed in both abalone viscera and mussels were similar suggesting a common PST source. This is the first time a conclusive linkage between the occurrence of PST in abalone and a dinoflagellate source has been demonstrated. [ABSTRACT FROM AUTHOR]

Waste generated from the processing of marine organisms for food represents an underutilized resource that has the potential to provide bioactive molecules with pharmaceutical applications. Some of these molecules have known anti-thrombotic and anti-coagulant activities and are being investigated as alternatives to common anti-thrombotic drugs, like heparin and warfarin that have serious side effects. In the current study, extracts prepared from blacklip abalone (Haliotis rubra) processing waste, using food grade enzymes papain and bromelain, were found to contain sulphated polysaccharide with anti-thrombotic activity. Extracts were found to be enriched with sulphated polysaccharides and assessed for anti-thrombotic activity in vitro through heparin cofactor-II (HCII)-mediated inhibition of thrombin. More than 60% thrombin inhibition was observed in response to 100 μg/mL sulphated polysaccharides. Anti-thrombotic potential was further assessed as anti-coagulant activity in plasma and blood, using prothrombin time (PT), activated partial thromboplastin time (aPTT), and thromboelastography (TEG). All abalone extracts had significant activity compared with saline control. Anion exchange chromatography was used to separate extracts into fractions with enhanced anti-thrombotic activity, improving HCII-mediated thrombin inhibition, PT and aPTT almost 2-fold. Overall this study identifies an alternative source of anti-thrombotic molecules that can be easily processed offering alternatives to current anti-thrombotic agents like heparin. [ABSTRACT FROM AUTHOR]

Estimating contemporary genetic structure and population connectivity in marine species is challenging, often compromised by genetic markers that lack adequate sensitivity, and unstructured sampling regimes. We show how these limitations can be overcome via the integration of modern genotyping methods and sampling designs guided by LiDAR and SONAR data sets. Here we explore patterns of gene flow and local genetic structure in a commercially harvested abalone species ( Haliotis rubra) from southeastern Australia, where the viability of fishing stocks is believed to be dictated by recruitment from local sources. Using a panel of microsatellite and genomewide SNP markers, we compare allele frequencies across a replicated hierarchical sampling area guided by bathymetric LiDAR imagery. Results indicate high levels of gene flow and no significant genetic structure within or between benthic reef habitats across 1400 km of coastline. These findings differ to those reported for other regions of the fishery indicating that larval supply is likely to be spatially variable, with implications for management and long-term recovery from stock depletion. The study highlights the utility of suitably designed genetic markers and spatially informed sampling strategies for gaining insights into recruitment patterns in benthic marine species, assisting in conservation planning and sustainable management of fisheries. [ABSTRACT FROM AUTHOR]

The thermal denaturation and stability of hemocyanin purified from the marine mollusc Haliotis rubra were investigated. The protein has been previously shown to have strong antiviral properties; however, its therapeutic efficacy has been limited by the stability of its formulation. Denaturation of the hemocyanin was found to be irreversible by the absence of an endotherm on rescanning calorimetric traces. Two denaturation transitions were observed at 78.9 and at 85.1 °C in a 100 mM Tris/HCl buffer at pH 7.6 at a scan rate of 1 K min. These denaturation peaks were found to be scan rate dependent, suggesting a kinetically rather than thermodynamically controlled denaturation process. The clear prominence of two distinct transitions has not been previously reported for any hemocyanin protein so far. The accurate deconvolution of these two peaks was due to the high resolution of the TA nano-DSC calorimeter used for this work. The activation energy for the first transition was determined to be 535 ± 65 kJ mol, which compares well with values reported previously for hemocyanins in related species. Scans performed at various protein concentrations showed no change in unfolding kinetics, suggesting that a change in oligomeric state does not occur at the onset of denaturation. While the irreversible unfolding of hemocyanins from other species has been reported previously, the denaturation temperature and kinetics vary dramatically from species to species, and the observed H. rubra hemocyanin denaturation has not been noted before. [ABSTRACT FROM AUTHOR]

Sulphated polysaccharides with anti-thrombotic and anti-coagulant activities have been found in various marine biota. In this study, a previously characterised anti-thrombotic and anti-coagulant extract from blacklip abalone was fractionated by anion exchange chromatography (AEC), pooled (on a sulphated polysaccharide basis) and administered to Wistar rats via oral gavage (N = 8) for assessment as an oral therapeutic. To ensure that the preparation had anti-coagulant activity prior to oral administration, it was assessed in rat blood by thromboelastography (TEG) significantly increasing reaction (R) time (or time until clot formation). Following in vitro confirmation of anti-coagulant activity, 40 mg of the preparation was orally administered to rats with blood samples collected at 2, 4, and 6 h post-gavage. Assessment of all blood samples by TEG showed some prolongation of R time from 355 to 380 s after 4 h. Dosing of the post-gavage blood samples with the abalone preparation to confirm anti-thrombotic activity in vitro revealed residual anti-coagulant activity, further suggesting that oral administration did increase anti-coagulant potential in the collected blood but that bioavailability was low. Assessment of tissues and haematological parameters showed no obvious harmful effects of the abalone preparation in animals. In summary, even though oral administration of fractionated and pooled blacklip abalone extract to rats delayed clotting after 4 h, bioavailability of the preparation appeared to be low and may be more appropriate for intravenous administration as an anti-thrombotic or anti-coagulant therapeutic.

Infectious pathogens figure prominently among those factors threatening marine wildlife. Mass mortality events caused by pathogens can fundamentally alter the structure of wild fish stocks and depress recruitment rates and yield. In the most severe instances, this can precipitate stock collapses resulting in dramatic economic losses to once valuable commercial fisheries. An outbreak of a herpes-like virus among commercially fished abalone populations in the south-west fishery of Victoria, Australia, during 2006-2007, has been associated with high mortality rates among all cohorts. Long-term records from fishery-independent surveys of blacklip abalone Haliotis rubra (Leach) enabled abundance from pre- and post-viral periods to be analysed to estimate stock density and biomass. The spatial distribution of abundance in relation to physical habitat variables derived from high-resolution bathymetric LiDAR data was investigated. Significant differences were observed in both measures between pre- and post-viral periods. Although there was some limited evidence of gradual stock improvement in recent years, disease-affected reefs have remained below productivity rates prior to the disease outbreak suggesting a reduction in larval availability or settlement success. This was corroborated by trends in sublegal sized blacklip abalone abundance that has yet to show substantial recovery post-disease. Abundance data were modelled as a function of habitat variables using a generalised additive model (GAM) and indicated that high abundance was associated with complex reef structures of coastal waters (<15 m). This study highlights the importance of long-term surveys to understand abalone recovery following mass mortality and the links between stock abundance and seafloor variability. [ABSTRACT FROM AUTHOR]

This study developed a technique of sperm cryopreservation using liquid nitrogen ( LN) vapour in farmed blacklip abalone Haliotis rubra through evaluating the following five key factors: (1) cryoprotectant agent ( CPA) toxicity; (2) cooling temperature; (3) thawing temperature; (4) sperm to egg ratio and (5) sugar addition, using sperm motility or fertilization rate as quality assessment indicators. The results demonstrated that 6% dimethyl sulfoxide ( DMSO) was the best single CPA for sperm cryopreservation in this species. The highest post-thaw sperm motility was achieved when sperm were exposed to LN vapour for 10 min at 5.2 cm above the LN surface and thawed at 60°C and recovered at 16°C in seawater baths. Post-thaw sperm motility was found to be significantly higher when 6% DMSO was used in combination with 1% or 2% glucose than 6% DMSO alone. Further evaluation of fertilization rate between these CPAs showed that 6% DMSO+2% glucose achieved the highest fertilization rate of 70% at a sperm to egg ratio of 10 000:1. [ABSTRACT FROM AUTHOR]

The article focuses on the comparison between karyological studies of mollusks Haliotis rubra, Haliotis laevigata and the interspecific hybrid. It calculated lengths and centromeric index and analyzed homologous chromosomes. It elucidates the high chromosome morphology compatibility between H. rubra and H. laevigata allowing a normal meiotic process and inheritance of a complete genetic background in the chromosome set of first generation interspecific hybrid.

Waste generated from the processing of marine organisms for food represents an underutilized resource that has the potential to provide bioactive molecules with pharmaceutical applications. Some of these molecules have known anti-thrombotic and anti-coagulant activities and are being investigated as alternatives to common anti-thrombotic drugs, like heparin and warfarin that have serious side effects. In the current study, extracts prepared from blacklip abalone (Haliotis rubra) processing waste, using food grade enzymes papain and bromelain, were found to contain sulphated polysaccharide with anti-thrombotic activity. Extracts were found to be enriched with sulphated polysaccharides and assessed for anti-thrombotic activity in vitro through heparin cofactor-II (HCII)-mediated inhibition of thrombin. More than 60% thrombin inhibition was observed in response to 100 μg/mL sulphated polysaccharides. Anti-thrombotic potential was further assessed as anti-coagulant activity in plasma and blood, using prothrombin time (PT), activated partial thromboplastin time (aPTT), and thromboelastography (TEG). All abalone extracts had significant activity compared with saline control. Anion exchange chromatography was used to separate extracts into fractions with enhanced anti-thrombotic activity, improving HCII-mediated thrombin inhibition, PT and aPTT almost 2-fold. Overall this study identifies an alternative source of anti-thrombotic molecules that can be easily processed offering alternatives to current anti-thrombotic agents like heparin.

For the first time wild-caught Tasmanian abalone, Haliotis rubra , have been reported to contain paralytic shellfish toxins (PSTs). This observation followed blooms of the toxic dinoflagellate Gymnodinium catenatum . No illnesses were reported, but harvesting restrictions were enforced in commercial areas. Abalone were assayed using HPLC-FLD methodology based on AOAC official method 2005.06. An uncommon congener, deoxydecarbamoyl-STX (doSTX), was observed in addition to regulated PSTs as unassigned chromatographic peaks. A quantitative reference material was prepared from contaminated Tasmanian abalone viscera and ampouled at 54.2 μmol/L. The LD 50 of doSTX via intraperitoneal injection was 1069 nmol/kg (95% confidence limits 983–1100 nmol/kg), indicating it is nearly 40 times less toxic than STX. A toxicity equivalence factor of 0.042 was generated using the mouse bioassay. Levels of PSTs varied among individuals from the same site, although the toxin profile remained relatively consistent. In the foot tissue, STX, decarbamoyl-STX and doSTX were identified. On a molar basis doSTX was the dominant congener in both foot and viscera samples. The viscera toxin profile was more complex, with other less toxic PST congeners observed and was similar to mussels from the same site. This finding implicates localised dinoflagellate blooms as the PST source in Tasmanian abalone. [ABSTRACT FROM AUTHOR]

Hierarchical sampling and subsequent microsatellite genotyping of >2300 Haliotis laevigata (greenlip abalone) from 19 locations distributed across five biogeographic regions have substantially advanced our knowledge of population structure and connectivity in this commercially important species. The study has found key differences in stock structure of H. laevigata compared with the sympatric and congeneric Haliotis rubra (blacklip abalone) and yielded valuable insights into the management of fisheries targeting species characterized by spatial structure at small scales (i.e. S-fisheries). As with H. rubra, H. laevigata comprise a series of metapopulations with strong self-recruitment. However, the spatial extent of H. laevigata metapopulations (reefal areas around 30 km2; distances of up to 135 km are effective barriers to larval dispersal) was substantially greater than that identified for H. rubra (Miller et al. 2009). Differences in the dynamics and scale of population processes, even between congeneric haliotids as made evident in this study, imply that for S-fisheries, it is difficult to generalize about the potential consequences of life history commonalities. Consequently, species-specific management reflective of the population structure of the target species remains particularly important. This will likely require integration of information about stock structure and connectivity with data on life history and population dynamics to determine the necessary input (e.g. number of fishers, fishing effort) and output (e.g. minimum legal size, total allowable catch) controls to underpin their sustainable management. [ABSTRACT FROM AUTHOR]

Few studies examine the long-term effects of changing predator size and abundance on the habitat associations of resident organisms despite that this knowledge is critical to understand the ecosystem effects of fishing. Marine reserves offer the opportunity to determine ecosystem-level effects of manipulated predator densities, while parallel monitoring of adjacent fished areas allows separating these effects from regional-scale change. Relationships between two measures of benthic habitat structure (reef architecture and topographic complexity) and key invertebrate species were followed over 17 years at fished and protected subtidal rocky reefs associated with two southern Australian marine reserves. Two commercially harvested species, the southern rock lobster ( Jasus edwardsii) and blacklip abalone ( Haliotis rubra) were initially weakly associated with habitat structure across all fished and protected sites. The strength of association with habitat for both species increased markedly at protected sites 2 years after marine reserve declaration, and then gradually weakened over subsequent years. The increasing size of rock lobster within reserves apparently reduced their dependency on reef shelters as refuges from predation. Rising predation by fish and rock lobster in the reserves corresponded with weakening invertebrate-habitat relationships for H. rubra and sea urchins ( Heliocidaris erythrogramma). These results emphasise that animal-habitat relationships are not necessarily stable through time and highlight the value of marine reserves as reference sites. Our work shows that fishery closures to enhance populations of commercially important and keystone species should be in areas with a range of habitat features to accommodate shifting ecological requirements with ontogenesis. [ABSTRACT FROM AUTHOR]

A legal minimum length (LML) aims to protect spawning biomass but the implementation uncertainty associated with broad-scale LMLs is rarely assessed. LML estimates can require both growth and maturity data; however, growth data is often lacking and this can limit the estimation of an appropriate LML. To overcome the shortfall in growth data, a method is introduced for inferring growth parameters from size at maturity data. In this way, fine-scale theoretical LML estimates were obtained in the absence of empirical growth data. A total of 252 populations of blacklip abalone (Haliotis rubra) were examined and, of those, 46 were identified as having a relatively lower level of protection because they matured at larger sizes. These 46 populations are potentially at greater risk of over-fishing as a consequence of implementation uncertainty. Furthermore, the majority of the 46 populations were in an economically valuable region of the fishery. With extensive data on size at maturity, the relative risk to recruitment potential can be assessed and equalised across a fishery. [ABSTRACT FROM AUTHOR]

Abstract: Haemolymph and tissue samples of Haliotis rubra × laevigata hybrid abalone were taken during a routine stock movement procedure on an Australian abalone farm to look for biochemical and histological changes associated with anaesthesia and/or manual movement of the abalone, both of which are used in commercial stock movement operations. Sections of the left kidney, the gill and the surface of the foot were examined under light microscopy and a scoring system was used to measure observed changes and compare treatment groups to controls. The left kidney of anaesthetised abalone contained less protein and haemocytes than control or manually moved abalone on the day of anaesthesia (p<0.05), but returned to baseline levels within 1day. The foot muscle of anaesthetised and moved abalone had areas of denuded epithelium 5days after anaesthesia (p<0.05). Protein, phosphate, magnesium, sodium, chloride, calcium and potassium levels were measured in the cell-free haemolymph. The protein levels were significantly elevated compared to controls on the day after anaesthesia and manual movement (p<0.05), but declined to baseline levels within 3days. There were no significant differences in the other measured ions. Benzocaine anaesthesia, with or without subsequent movement, led to greater histological changes in tissues of abalone, than manual movement without anaesthetic. Comparison of physiological and histopathological changes with haemolymph immune assays may show whether the non-destructive haemolymph sampling can provide early warning of stressors that cause tissue damage. The methods used can be applied to scientifically assess any husbandry procedures with a view to improve stock management and productivity. [Copyright &y& Elsevier]

Industry participation in co-management has become a cornerstone of assessing the blacklip abalone, Halitois rubra, fisheries of South-Eastern Australia. Engaging industry in developing and implementing management strategies is aimed at stemming recent trends of stock depletion and reduced harvest. An alternative to the current strategy for determining harvests is under consideration. A central question is: which management strategy is most likely to maintain sufficient biomass to produce consistent harvest rates into the future? This question is addressed using a Systems Dynamics modeling approach. We evaluated the two strategies of harvest management planning under (i) unchanging environmental conditions and (ii) following a high-mortality event. To assess the performance of each strategy, an existing abalone model was used to estimate yield and mature biomass over three decades (>5 generations). A strategy using mean length of commercial catch as a novel performance measure generally provided a better path to recovery from the high-mortality event than the current harvest threshold strategy. [ABSTRACT FROM AUTHOR]

The potential for restocking with hatchery organisms as a tool to rebuild depleted populations of blacklip abalone(Haliotis rubra)was investigated through replicated, control-impact studies in New South Wales, Australia. Long-term survival (>2 years) of hatchery-reared and released abalone, their impact on wild abalone abundance, and the effect of diffuse versus concentrated release was investigated on natural reefs. Long-term survival of released hatchery abalone varied between releases but averaged about that expected for wild abalone. There was no significant effect of released juveniles on the persistence or recruitment of wild abalone. Significantly greater numbers of all (released and wild) abalone persisted at release locations through time, while the total number of wild abalone increased significantly through time at release and control locations. There was no significant difference in long-term survival of abalone released in clusters of high density (2–4%) or in a diffuse or concentrated array (0–9%). These results show that restocking can supplement natural rebuilding processes of depleted wild abalone populations in New South Wales, Australia. [ABSTRACT FROM PUBLISHER]

Background: Global climate change has resulted in a southerly range expansion of the habitat modifying sea urchin Centrostephanus rodgersii to the east coast of Tasmania, Australia. Various studies have suggested that this urchin outcompetes black-lipped abalone (Haliotis rubra) for resources, but experiments elucidating the mechanisms are lacking. Methodology/Principal Findings: We outline a new framework involving experimental manipulations and Markov chain and Pareto modelling to examine the effects of interspecific competition between urchins and abalone and the effect of intraspecific competition in abalone, assessed as effects on behaviour. Manipulations of abalone densities had no detectable effect on urchin behavioural transitions, movement patterns or resightability through time. In contrast, additions of urchins resulted in abalone shifting microhabitats from exposed to sheltered positions, an increase in the proportion of mobile abalone, and declines in abalone resightability through time relative to controls without the urchins. Our results support the hypothesis of asymmetrical competitive interactions between urchins and abalone. Conclusions/Significance: The introduction of urchins to intact algal beds causes abalone to flee and seek shelter in cryptic microhabitat which will negatively impact both their accessibility to such microhabitats, and productivity of the abalone fishery, and will potentially affect their growth and survival, while the presence of the abalone has no detectable effect on the urchin. Our approach involving field-based experiments and modelling could be used to test the effects of other invasive species on native species behaviour. [ABSTRACT FROM AUTHOR]

Commercial abalone divers make decisions about the location of their harvesting activities at a relatively fine scale. Management of these abalone fisheries, however, is normally conducted at a larger scale. To gauge the implications of this dichotomy, the following question was asked: Would it be worthwhile managing the fishery at a finer scale that corresponds with the harvesters' spatial preferences? To answer this, an existing abalone model was applied to a population of blacklip abalone, Haliotis rubra Leach. The model simulates both the existing practice of large scale spatial management combined with smaller scale spatial harvest and an alternative practice, whereby management and harvest are synchronised at a similarly small scale. It was concluded that the costs and effort associated with managing at a finer scale would unlikely yield benefits substantial enough to justify its implementation. [ABSTRACT FROM AUTHOR]

Abstract: Australian abalone production has been affected by outbreaks of abalone viral ganglioneuritis (AVG) caused by a herpesvirus (AbHV). In this study, we undertook experimental transmission trials by immersion to study the abalone immune response to infection with AbHV. Representative cellular and humoural immune parameters of abalone, including total haemocyte count (THC), superoxide anion (SO) and antiviral activity against herpes simplex virus type 1 (HSV-1), were examined in apparently healthy (sub-clinical) and moribund abalone after challenge. In the early infection, sub-clinical stage (days 1–3), THC was found to increase significantly in infected abalone. TaqMan qPCR confirmed 20.5% higher viral load in moribund abalone compared to apparently healthy abalone, indicating that the abundance of AbHV within abalone is linked to their clinical signs. At the clinical stage of infection, THC was significantly lower in moribund abalone, but increased in AbHV-exposed but apparently healthy abalone, in comparison to non-infected controls. SO was reduced in all abalone that were PCR-positive for AbHV. THC and SO level were found to be negatively correlated with the presence of AbHV in abalone, but no effect of AbVH exposure was observed on the haemolymph antiviral activity. These results suggest that abalone mount an initial cellular immune response to AbHV infection, but this response cannot be sustained under high viral loads, leading to mortality. [Copyright &y& Elsevier]

Abstract: Established fishery-independent survey designs to measure change in the absolute density and biomass of greenlip abalone (leaded-line; LL) have proved impractical for the assessment of blacklip abalone. Due to the contagious distribution of this species among relatively complex and inaccessible habitat, a stratified survey design and modified radial transect (cross drop; CD) survey method was developed. Surveys were undertaken before and after known levels of commercial fishing to compare the accuracy, precision and efficiency of the LL and CD methods at detecting changes in the legal and sub-legal density and legal biomass of blacklip populations. Differences in length structures indicated substantial declines in the legal-size proportion of the population and emergence of sub-legal-sized blacklip, after commercial fishing. Strong correlations of repeated counts of legal, sub-legal and total abalone along survey transects provided strong evidence of the reliability of survey data among divers. CD and LL surveys typically recorded similar changes in density and biomass of legal and sub-legal sized blacklip abalone following commercial fishing. Although estimates from LLs were more precise, those from CDs provided more consistent measures of declines in legal density and biomass within fished areas and took less time to complete. Thus, CD surveys allow a greater number of primary sampling units to be conducted within a given time, thereby improving the precision of estimates. Power analysis identified that the power of the CD surveys to detect a decline in the legal biomass was >85%. These findings validate the CD survey method as a tool for monitoring blacklip abalone populations through time as a component of a stock assessment program and have subsequently been used to further improve the current survey design in South Australia. They also demonstrate that reliable measures of change in population size and structure can be obtained for species similarly distributed in complex reef systems. [Copyright &y& Elsevier]

Abstract: Elevated water temperature can act as a stressor impacting the immune responses of molluscs, potentially increasing their susceptibility to microbial infections. Abalone are commercially important marine molluscs that have recently experienced disease outbreaks caused by a herpesvirus and Vibrio bacteria. Sampling of wild-caught Haliotis rubra showed a significant correlation between water temperature and both antiviral and antibacterial activity, with higher activity in summer than in winter months. However, antibacterial activity was compromised in favour of antiviral activity as the water temperatures peaked in summer. A controlled laboratory experiment was then used to investigate several immune responses of H. rubra, including total haemocyte count (THC), stimulated superoxide anion production (SO), antiviral activity against a model herpesvirus, herpes simplex virus type 1 and antibacterial activity against a representative pathogenic bacterium, Vibrio anguillarum, over one week after raising water temperature from 18 to 21 or 24 °C. THC and SO increased at day 1 and then dropped back to control levels by days 3 and 7. By comparison, the humoural immune parameters showed a delayed response with antibacterial and antiviral activity significantly increasing on days 3 and 7, respectively. Consistent with the field study, antibacterial activity became significantly depressed after prolonged exposure to elevated temperatures. A principal components analysis on the combined immune parameters showed a negative correlation between antiviral and antibacterial activity. SO was positively correlated to THC and neither of these cellular parameters were correlated to the humoural antimicrobial activity. Overall, this study indicates that abalone may have more resilience to viruses than bacterial pathogens under conditions of elevated temperature, such as those predicted under future climate change scenarios. [Copyright &y& Elsevier]

Intensive fishing can cause dramatic, long-lasting shifts in benthic habitat. This study used three approaches to test whether overharvesting of blacklip abalone ( Haliotis rubra) can cause a shift in benthic habitat to a configuration that is unsuitable for abalone, on the east coast of Tasmania, Australia. After 18 months of removing abalone from rocks, encrusting red algae (ERA) became overgrown by filamentous and foliose algae, sessile invertebrates and accumulated sediment. The differences in the community composition between locations, sites nested within locations and rocks were minor. Throughout the study, abalone were largely associated with areas of rock covered in ERA but avoided other habitats. A transplant experiment demonstrated that abalone preferred areas of rock covered in ERA but move away from overgrown rocks. These results suggest overharvesting of abalone results in a shift to benthic habitat poorly preferred by abalone. This could form a positive feedback loop that limits recovery of abalone populations and ERA. [ABSTRACT FROM AUTHOR]

Aim We modelled the spatial abundance patterns of two abalone species ( Haliotis rubra Donovan 1808 and H. laevigata Leach 1814) inhabiting inshore rocky reefs to better understand the importance of current sea surface temperature (SST) (among other predictors) and, ultimately, the effect of future climate change, on marine molluscs. Location Southern Australia. Methods We used an ensemble species distribution modelling approach that combined likelihood-based generalized linear models and boosted regression trees. For each modelling technique, a two-step procedure was used to predict: (1) the current probability of presence, followed by (2) current abundance conditional on presence. The resulting models were validated using an independent, spatially explicit dataset of abalone abundance patterns in Victoria. Results For both species, the presence of reef was the main driver of abalone occurrence, while SST was the main driver of spatial abundance patterns. Predictive maps at c. 1-km resolution showed maximal abundance on shallow coastal reefs characterized by mild winter SSTs for both species. Main conclusions Sea surface temperature was a major driver of abundance patterns for both abalone species, and the resulting ensemble models were used to build fine-resolution predictive range maps ( c. 1 km) that incorporate measures of habitat suitability and quality in support of resource management. By integrating this output with structured spatial population models, a more robust understanding of the potential impacts of threatening human processes such as climate change can be established. [ABSTRACT FROM AUTHOR]

Abstract: Three candidate, non-nested, growth models (von Bertalanffy, Gompertz and inverse logistic) were fitted to multiple samples of tag-recapture data (n =27 samples) to determine the best statistical model for blacklip abalone (Haliotis rubra) populations in Tasmania, Australia. Wild populations of blacklip abalone were sampled for growth data using tag-recapture methods. The best statistical model was identified for each sample using Akaike''s Information Criteria and Akaike weights to measure the relative statistical fit. Using these criteria, the best fitting model was the inverse logistic for 21 of the 27 samples, both the von Bertalanffy and the Gompertz models were the best fitting model in three samples each. When the inverse logistic was the best fitting model it was the best unambiguously, as indicated by the high Akaike weight values (generally ; 0.65–1.0). In contrast, when either the von Bertalanffy or the Gompertz growth models were statistically optimal, the highest Akaike weights ranged between 0.15 and 0.44 across both models. We conclude that the use of either the von Bertalanffy or Gompertz growth models in the assessment of Tasmanian blacklip abalone would be statistically sub-optimal and may mislead assessments of Tasmanian abalone stocks. The inverse logistic model can be considered as a good candidate growth model for other fished invertebrate stocks. [Copyright &y& Elsevier]

A 6-week growth rate trial of 6.7 mm ± 1.35 SD long blacklip abalone ( Haliotis rubra) fed one of four graded protein feeds (26%, 32%, 37%, 45% crude protein, CP) resulted in a maximum average growth rate of 81 μm day−1 (percentage daily weight gain of 5.2% day−1) with the 45% CP diet. Based on the results, a new, simple, non-destructive method to calculate the relative utilization efficiencies (RUE) of nutrients is presented to estimate the relative contributions of a nutrient to growth, body maintenance and the excess used for energy. Calculations of RUE of protein estimated that at the maximum growth rate, 59% of the CP was responsible for growth, while 31% was used for body maintenance and an excess of 10% was lost and presumably catabolized for energy and carbohydrate anabolism. At the %CP where the highest proportion of CP was used for growth, i.e. the maximum RUE of protein for growth (slightly higher at 62%), 35% was used for body maintenance and only 3% of the excess was lost to energy. [ABSTRACT FROM AUTHOR]

We determined how varying stocking density and food ration can influence the growth, mortality and biomass return of abalone raised in slab tanks. The abalone used were 2- year-old hybrids of Haliotis laevigata and Haliotis rubra. The experimental design involved replicate tanks and three levels of each factor (normal practice and ±20% density or food ration). Although increasing density from that typically used in farm practices reduced the growth rate by roughly 6%, biomass return increased by 15.5%, over the 9-month period. Increasing feed ration by 20% boosted biomass by significantly increasing abalone growth during the first 3 months by 4%, but was less effective as the animals grew. Growth, mortality and food conversion ratios were optimized in tanks with a low density and a low feed ration, but economic gains were dominated by the increased biomass return from tanks with a higher stocking density. It is thought that reduced dissolved oxygen and differing access to food contributed to the patterns observed. [ABSTRACT FROM AUTHOR]

In molluscs, the neurotransmitter serotonin (5-HT) has been linked to a variety of biological roles including gamete maturation and spawning. The possible involvement of 5-HT in abalone gamete release was demonstrated by a dose-dependent increase in Haliotis rubra gonad contractile bioactivity following 5-HT stimulation. Physiological functions associated with 5-HT, are mediated through binding to 5-HT receptors. A cDNA encoding a putative 5-HT receptor consisting of 359 amino acids was isolated from the tropical abalone H. asinina, termed 5-HT1 ha. The 5-HT1 ha shares G-protein-coupled receptor motifs with metazoan 5-HT receptors, including predicted transmembrane domains, active sites for protein kinase action, and N-linked glycosylation sites. However, the third intracellular loop of 5-HT1 ha is relatively short, and only six transmembrane domains are predicted, implying a truncated receptor. Phylogenetic analysis with known 5-HT receptor genes suggests that 5-HT1 ha belongs to the type 1 5-HT receptor family. Expression analysis by RT-PCR showed that 5-HT1 ha mRNA was present in all tissues examined, including the neural ganglia and gonad tissues. Immunocytochemistry revealed the presence of 5-HT1 ha specifically within the soma of neuronal cells located in the outer cortex of both cerebral and pleuropedal ganglia. In ovarian and testicular tissues, 5-HT1 ha immunoreactivity was observed in epithelial cells of the outer capsule and connective tissue of the trabeculae to which the gamete follicles adhere. Whether this receptor transcript is translated to a functional protein needs to be verified, but if so, it could play a role in reproduction. [ABSTRACT FROM AUTHOR]

Many species of sedentary marine invertebrates exhibit large spatial variation in their morphology, which allow them to occupy a broad geographic distribution and range of environmental conditions. However, the detection of differences in morphology amongst variable environments cannot determine whether these differences represent a plastic response to the local environment, or whether morphology is genetically fixed. We used a reciprocal transplant experiment to test whether ‘stunted’ blacklip abalone ( Haliotis rubra) are the result of a plastic response to the environment or fixed genetic trait. Furthermore, we related environmental factors, that affect food availability (density of abalone, water movement, algal cover and reef topography), to differences in growth and morphology. Morphological plasticity was confirmed as the mechanism causing morphological variation in H. rubra. Individuals transplanted to sites with ‘non-stunted’ H. rubra grew significantly faster when compared to stunted controls, whilst individuals transplanted to stunted sites grew significantly slower compared to non-stunted controls. The growth response was greater for individuals transplanted from ‘non-stunted’ to ‘stunted’ sites, suggesting that the environmental stressors in morphologically ‘stunted’ habitat are stronger compared to locations of faster growing morphology. We propose that these differences are related to resource availability whereby low algal cover and topographic simplicity results in stunted populations, whereas high algal abundance and topographic complexity results in non-stunted populations. [ABSTRACT FROM AUTHOR]

The article explores the competition between an invasive sea urchin and fished abalone and its effect on body condition, reproduction and survivorship of incursion of the urchin Centrostephanus rodgersii in Tasmania. It looks into the interactions with other large herbivore on subtidal rocky reefs with Haliotis rubra that shows a negative relationship between densities of several spatial scales and the effects of intra-interspecific competition. The study claims that the invader Centrostephanus rodgersii is the superior competitor in interactions with other abalone fishery.

Growth and reproduction of triploid and diploid blacklip abalone Haliotis rubra (Leach, 1814) were compared in a 30-month study. Triploidy was induced by inhibition of the second polar body formation using 6-dimethylaminopurine (6-DMAP) or cytochalasin B (CB). There were no significant differences in growth and survivorship between triploid and diploid abalone. However, triploid abalone had a more elongated shell and greater foot muscles than diploid abalone. A slightly curvilinear growth in shell length was conformed to all treatments. While diploid abalone had reached sexual maturity and spawned during the study, gonadal development and gamete maturation were abnormal in triploids. Female triploids lacked an apparent gonad at the macroscopic level but microscopic examination revealed that they had a thin layer of oogonia development. In contrast, male triploids were able to form similar-sized gonads to diploids during most of the reproductive period, but with brown-yellow discolouration and stalled gametogenesis at spermatocyte formation. Sex ratio of triploid abalone did not deviate from 1:1. With the onset of sexual maturation, growth and gonadal maturation occurred concurrently in diploid abalone, and there was no indication that growth of (diploid) abalone was reduced. [ABSTRACT FROM AUTHOR]

Overexploitation of marine species invariably results in population decline but can also have indirect effects on ecological processes such as larval dispersal and recruitment that ultimately affect genetic diversity and population resilience. We compared microsatellite DNA variation among depleted and healthy populations of the black-lip abalone Haliotis rubra from Tasmania, Australia, to determine if over-fishing had affected genetic diversity. We also used genetic data to assess whether variation in the scale and frequency of larval dispersal was linked to greater population decline in some regions than in others, and if larval dispersal was sufficient to facilitate natural recovery of depleted populations. Surprisingly, allelic diversity was higher in depleted populations than in healthy populations ( P < 0.05). Significant subdivision across hundreds of metres among our sampling sites ( FST = 0.026, P < 0.01), coupled with assignment tests, indicated that larval dispersal is restricted in all regions studied, and that abalone populations across Tasmania are largely self-recruiting. Low levels of larval exchange appear to occur at the meso-scale (7–20 km), but age estimates based on shell size indicated that successful migration of larvae between any two sites may happen only once every few years. We suggest that genetic diversity may be higher in depleted populations due to the higher relative ratio of migrant to self-recruiting larvae. In addition, we expect that recovery of depleted abalone populations will be reliant on sources of larvae at the meso-scale (tens of km), but that natural recovery is only likely to occur on a timescale unacceptable to fishers and resource managers. [ABSTRACT FROM AUTHOR]

The objective of this study was to identify QTL for growth rate in the blacklip abalone Haliotis rubra using selective DNA pooling. Three full-sibling families of H. rubra derived from crosses of wild broodstock were used. DNA was extracted from the largest and smallest 10% of progeny and combined into two pools for each phenotypic tail. The DNA pools were typed with 139 microsatellites, and markers showing significant differences between the peak height ratios of alleles inherited from the parents were individually genotyped and analysed by interval mapping. A strong correlation ( r = 0.94, P < 0.001) was found between the t-values from the analysis of pools and the t-values from the analysis of individual genotypes. Based on the interval mapping analysis, QTL were detected on nine linkage groups at a chromosome-wide P < 0.01 and one linkage group at a chromosome-wide P < 0.05. The study demonstrated that selective DNA pooling is efficient and effective as a first-pass screen for the discovery of QTL in an aquaculture species. [ABSTRACT FROM AUTHOR]

Abstract  Beach-cast kelp (the most widely used feed for commercially grown South African abalone) is plentiful during winter months when periodic storms cause kelp to wash ashore. During summer, however, this resource is not always readily available and farmed abalone are often starved for short periods. The aim of this research was to assess how periodic kelp starvation influences growth of the commercially grown abalone, Haliotis midae Linnaeus. Growth of grow-out abalone was monitored on a commercial abalone farm over a period of six months and consisted of 3 treatments with 2 replicates (n = ±250 abalone per replicate). The treatments were: Control (abalone always given more kelp than what they typically needed); Treatment 1 (abalone fed their weekly ration only once a week); Treatment 2 (abalone fed half their weekly ration every 3 and then 4 days respectively). While the data at first suggest that the control animals outperform the treatment animals, after undergoing an initial adjustment period to the new feeding regime, the treatment animals perform better. Weight gain and feed conversion efficiencies show that the treatment animals perform better overall. The control animals generally required much more feed to produce comparable increases in both length and weight compared to the treatment animals. This study has shown that periodic bouts of starvation is beneficial to Haliotis midae, allowing variable growth spurts when returned to full feed rations. [ABSTRACT FROM AUTHOR]

Abalone are common herbivores throughout temperate and tropical waters, and yet the contribution of red and brown macroalgae to the diet of wild abalone remains unclear. In the northern hemisphere, adult abalone are considered to consume predominantly brown algae, but in the southern hemisphere abalone are thought to prefer red algae. Conventional methods such as gut content analysis and feeding trials provide some insight into diet choice, but the associated biases of these techniques create uncertainty surrounding the aforementioned variability in abalone diet. We use combined stable isotope and fatty acid analysis to determine the relative contribution of red algae, brown algae and detritus/microalgae to the diet of wild abalone in Tasmanian waters. Stable isotopes of carbon suggest that brown algae and/detritus are a more important source of carbon than red algae. Fatty acid analysis confirmed the larger contribution of brown algae to the diet of abalone, and also identified the bacterial and diatom component of detritus to be an important contributor to abalone diet. These results show combined use of chemical tracers to be a promising technique for resolving abalone diet, and challenge current perceptions regarding spatial variability in abalone diet choice. [ABSTRACT FROM AUTHOR]

A new description of growth in blacklip abalone (Haliotis rubra) with the use of an inverse-logistic model is introduced. The inverse-logistic model avoids the disadvantageous assumptions of either rapid or slow growth for small and juvenile individuals implied by the von Bertalanffy and Gompertz growth models, respectively, and allows for indeterminate growth where necessary. An inverse-logistic model was used to estimate the expected mean growth increment for different black-lip abalone populations around southern Tasmania, Australia. Estimates of the time needed for abalone to grow from settlement until recruitment (at 138 mm shell length) into the fishery varied from eight to nine years. The variability of the residuals about the predicted mean growth increments was described with either a second inverse-logistic relationship (standard deviation vs. initial length) or by a power relationship (standard deviation vs. predicted growth increment). The inverse-logistic model can describe linear growth of small and juvenile abalone (as observed in Tasmania), as well as a spectrum of growth possibilities, from determinate to indeterminate growth (a spectrum that would lead to a spread of maximum lengths). [ABSTRACT FROM AUTHOR]

The availability of literature regarding sublethal and chronic toxicity of heavy metals to early life stages of marine species is restricted to a few species of invertebrate mollusks. The early life stage of abalone, an important gastropod both environmentally and commercially, has been involved in limited research investigating the effects of heavy metal toxicity. Fertilized eggs of Haliotis rubra were exposed to a range of dissolved nominal concentrations of cadmium, copper, iron, lead, mercury, and zinc in individual solutions for 48 h. After 48 h of exposure, the test was completed by recording survival success and morphological abnormalities of veliger larvae in each heavy metal treatment. The mean 48-h median effective concentrations affecting normal morphological development of veliger larvae determined in this test shows a decreasing order of toxicity of copper (7 µg/L), mercury (21 µg/L), zinc (35 µg/L), iron (4,102 µg/L), cadmium (4,515 µg/L), and lead (5,111 µg/L). [ABSTRACT FROM AUTHOR]

A population of Haliotis rubra Leach at Blubber Head in south-eastern Tasmania, Australia (43°19′S; 147°04′E) was sampled between February 1984 and October 1985. Relatively large numbers of 30 to 45 d-old new recruits were observed entering the population between October and February of each year. The annual instantaneous rate of natural mortality, Z, was 0.70 during the second year of life. The rate of natural mortality declined with age. The onset of sexual maturity began at 4 to 5 yr of age or an approximate maximum length of 90 mm, and most abalone in the population were mature at 6 to 7 yr of age or at lengths>110 mm. The onset of sexual maturity coincided with a decline in growth rates and the emergence of abalone from the subboulder habitat. These observations are discussed in the light of previous observations of population structure in haliotid populations. [ABSTRACT FROM AUTHOR]