Academic literature on the topic 'Blacklip abalone'

Abstract Saunders, T., Mayfield, S., and Hogg, A. 2009. Using a simple morphometric marker to identify spatial units for abalone fishery management. – ICES Journal of Marine Science, 66: 305–314. Managing stocks of sedentary marine invertebrates is complicated by the highly structured populations they form. Blacklip abalone (Haliotis rubra) form isolated populations with variable life-history characteristics. Many of the populations are “stunted”, attaining a lower maximum size than those in adjacent areas. To reduce the risks of overfishing and localized depletion, management units (MUs) that encompass individual populations need to be determined, then managed according to their life-history characteristics. Here, potential MUs in a South Australian abalone fishery were identified from the broad-scale, spatial distribution of stunted and “non-stunted” populations of blacklip abalone, by applying a morphometric marker to commercial shell samples. Key life-history parameters of the populations within the potential MUs were estimated using relationships between the morphometric marker and blacklip abalone biology. Data from fine-scale systematic sampling by commercial fishers were used to validate spatial patterns observed from the more broadly distributed commercial catch samples. The location, distribution, and size of potential MUs were largely inconsistent with those of current management. The locations of two MUs (in Gerloffs Bay) were consistent across the broad- and fine-scale datasets, with the fine-scale samples more informative for identifying a potential boundary between them. The disparity between these data and current management arrangements are highlighted, and approaches for modifying them are discussed. This approach is among the first to provide a practical means of more closely aligning the scales of assessment and management with biological reality for sedentary marine invertebrates.

The scale over which populations exchange individuals (migration) is central to ecology, and important for understanding recruitment and connectivity in commercial species. Field studies indicate that blacklip abalone (Haliotis rubra) have localised larval dispersal. However, genetic studies show differentiation only at large scales, suggesting dispersal over more than 100 km. Most genetic studies, however, have failed to test for subdivision at scales equivalent to field experiments. We used microsatellite DNA to investigate genetic structure at small scales (100 m to 10 km) in blacklip abalone in south-east Tasmania. We found significant subdivision (FST = 0.021; P < 0.05) among sites, and hierarchical FST analysis indicated 64% of genetic variation was at the smallest scale, supporting field studies that concluded larval dispersal is less than 100m. We also tested if genetic differentiation varied predictably with wave exposure, but found no evidence that differences between adjacent sites in exposed locations varied from differences between adjacent sites in sheltered populations (mean FST = 0.016 and 0.017 respectively). Our results show the usefulness of microsatellites for abalone, but also identify sampling scales as critical in understanding gene flow and dispersal of abalone larvae in an ecologically relevant framework. Importantly, our results indicate that H. rubra populations are self-recruiting, which will be important for the management of this commercial species.

Habitat characteristics can influence marine herbivore densities at a range of spatial scales. We examined the relationship between benthic habitat characteristics and adult blacklip abalone (Haliotis rubra) densities across local scales (0.0625–16 m2), at 2 depths, 4 sites and 2 locations, in Tasmania, Australia. Biotic characteristics that were highly correlated with abalone densities included cover of non-calcareous encrusting red algae (NERA), non-geniculate coralline algae (NCA), a matrix of filamentous algae and sediment, sessile invertebrates, and foliose red algae. The precision of relationships varied with spatial scale. At smaller scales (0.0625–0.25 m2), there was a positive relationship between NERA and ERA, and negative relationships between sediment matrix, sessile invertebrates and abalone densities. At the largest scale (16 m2), there was a positive relationship between NERA and abalone densities. Thus, for some biotic characteristics, the relationship between NERA and abalone densities may be scalable. There was very little variability between depths and sites; however, the optimal spatial scale differed between locations. Our results suggest a dynamic interplay between the behavioural responses of H. rubra to microhabitat and/or to abalone maintaining NERA free of algae, sediment, and sessile invertebrates. This approach could be used to describe the relationship between habitat characteristics and species densities at the optimal spatial scales.

Studies of the diet of abalone and other herbivorous gastropods, based on gut contents, may be biased against some species of algae, especially those that are most preferred. The blacklip abalone Haliotis rubra was fed for short periods on monospecific diets of eight algae, including red, brown and green species that span the range of preference. In addition, two preferred species were fed to abalone after one month's, one week's, or no starvation. The number of recognizable fragments of each alga per unit volume of crop contents was examined. Although key characters of some species remained recognizable even at an advanced stage of digestion, other algae were intrinsically less recognizable. Preferred red algae disappeared rapidly after one week's or no starvation but more slowly after one month's starvation. Less preferred algae were not eaten without a long starvation period and became unrecognizable relatively slowly, especially the least preferred brown algae Ecklonia radiata and Phyllospora comosa, which have high polyphenol contents. Thus, the gut contents of starved abalone in the field contain recognizable fragments of less preferred species for long periods, whereas well-fed abalone retain recognizable fragments of preferred species only for short periods.

Recruitment rates of blacklip abalone (Haliotis rubra) post-larvae were measured at fortnightly intervals for a year in southern Tasmania on larval collectors made of transparent, corrugated plastic. The settlement plates were conditioned prior to use in a flow-through sea-water system in a two-stage process. A film of diatoms (mainly Nitzschia and Navicula species) was first established on the plates, which were then grazed by juvenile H. rubra. This allowed second-phase algae (principally Myrionema species) to become established. The plates were then periodically deployed at a depth of ~7 m. Larval settlement occurred mainly during the austral winter and early spring. A peak settlement rate of 1408 post-larvae per collector (2347 post-larvae m-2) occurred in mid August. Methods of measuring larval or immediate post-larval abundance are reviewed with regard to their use in the assessment and management of abalone fisheries.

Populations of blacklip abalone (Haliotis rubra) from southern Australia have been investigated genetically using protein gel electrophoresis. Allele frequency and genotype distributions were analysed to provide information on population structure, gene flow patterns and genetic differentiation among local populations. Breeding populations appear to be large. Measures of genetic distance reveal an 'isolation by distance' broad-scale population structure, although significant genetic heterogeneity can occur between sites < 3 km apart. Reasons for this apparent contradiction are discussed. It is concluded that zones of about 500 km of coastline, corresponding to 'neighbourhood size', could be recognized for the conservation of regional gene pools, but that stock-recruitment relationships need to be established on a localized basis.

This thesis focussed on the effects of a range of trace metals on various stages of Haliotis rubra development. The trace metals assessed in this thesis were the essential metals Cu, Zn and Fe; and, the non-essential metals Hg, Cd and Pb. Copper and Hg proved to be the two most toxic metals to the life stages of H. rubra studied. The concentrations affecting normal development of the fertilised egg exposed for 48h showed a decreasing order of toxicity with 48hEC50 recorded at 7µg Cu/L, 20µg Hg/L, 42µg Zn/L, 4,102µg Fe/L, 4,515µg Cd/L, and 5,111µg Pb/L. Settlement and metamorphosis occur in normal larvae when aged 5 days, and exposure of the 5 day old larvae to the metals for 48h resulted in impaired crawling success at 128µg/L Cu and Hg, and 1250µg Cd/L. Settlement was inhibited after exposure to 128µg Cu/L, 32µg Hg/L, and 1250 Cd/L. Metamorphosis of larvae 96h after exposure was inhibited by 32µg Cu/L, 512µg Zn/L, 32µg Hg/L and 625µg Cd/L. The rate of meta morphosis was enhanced after exposure to Cu and Hg at 0.5µg/L and 64 - 256µg Zn/L. Exposure to Zn at concentrations 64, 128 and 256 µg Zn/L caused an increased rate of settlement and metamorphosis. Juvenile H. rubra exposed to the six metals for 96h were most sensitive to Cu, which produced a 96hLC50 of 87µg Cu/L compared to Hg with a 96hLC50 of 173µg Hg/L. Juvenile H. rubra were relatively insensitive to Zn and Cd with the 96h LC50 of 1730µg Zn/L and 3700µg Cd/L, respectively. Exposure to individual solutions of Cu, Zn, and Cd for 28 days resulted in juvenile H. rubra bioaccumulating significant concentrations of metals in the visceramantleedible foot muscle. Accumulation of Hg was greater in the mantle-viscera-edible foot muscle. Following exposure, depuration in clean seawater for 28 days produced varying decreases in metal concentrations for each tissue compartment. Sodium-potassium activated ATPase (Na+,K+-ATPase) activity in the gills of juvenile H. rubra was significantly affected following expos ure to the trace metals for 28 days, with a decreasing order of effect on enzyme activity of Hg-Cu-Cd-Zn. Depuration of H. rubra in clean seawater for 28 days resulted in the recovery of Na+,K+-ATPase activity to varying degrees. The recovery of ATPase activity was more efficient following exposure to Cd-Zn-Cu-Hg. The overall results of this thesis provide initial baseline information to evaluate the sensitivity of H. rubra to trace metal toxicants, and these results may be utilised by regulators for establishing marine water quality guidelines to protect H. rubra and other abalone species in their natural habitats.

A study was initiated to determine the effect of selected factors on the reproductive development and early life history of blacklip (Haliotis rubra) and greenlip (H. laevigata) abalone relevant to their wild fisheries or aquaculture. In both species, the rate of gonadal and larval development was proportional to water temperature, but the relationship was not simply multiplicative, rather there was a critical minimum water temperature below which development was arrested, known as the Biological Zero Point (BZP). The BZP for gonadal development was 7.8 degrees C for H. rubra and 6.9 degrees C for H. laevigata. Corresponding BZP values for larval development were 7.8 degrees C and 7.2 degrees C, respectively. Observations of larval development relative to temperature enabled a description of the Effective Accumulative Temperature (EAT; the cumulative difference between the culture temperature and the BZP, calculated hourly) for prominent developmental stages. The difference between the EAT for metamorphic competence and that for hatchout (i.e. the interval during which the larvae remain in the water column) was 1120 and 1160 EAT degrees C-h for blacklip and greenlip abalone, respectively. These values, in combination with water temperature data, enable the prediction of the dispersal window for each species in situ. Spawning performance of blacklip and greenlip abalone was also affected by temperature, with both sexes of each species producing significantly more gametes when conditioned at 16 degrees C than 18 degrees C. Sperm production of H. rubra was an order of magnitude greater than that of equivalent sized H. laevigata. There was no apparent difference in the lipid or fatty acid composition of the ovary or testis between pre- and post-spawning animals of either species, presumably because of partial spawning and/or incomplete resorption of the gonad. Likewise, a 4 degrees C difference in conditioning temperature (i.e. 14 degrees C vs 18 degrees C) was insufficient to elicit changes in tissue biochemistry. There was a significant interaction between sperm density and contact time on the fertilisation success of eggs from both blacklip and greenlip abalone. Prolonged exposure (> 1200 s for H. rubra and > 480 s for H. laevigata) to concentrated sperm (i.e. 107 ml-1) resulted in egg destruction. Analysis of CoVariance of F50 values (i.e. the sperm concentration required for 50% fertilisation, derived from the linear regression of logit (proportion of eggs fertilised) versus sperm density) between species across a range of contact times demonstrated that contact time had a significant effect (p < 0.001) whereas species did not (p = 0.22). The lack of a species effect suggests that the fertilisation potential of blacklip and greenlip abalone eggs are similar, at least across the range of sperm densities and contact times used.

This thesis examines the release and long-term (>2 years) survival and growth of hatchery-reared larval and juvenile blacklip abalone (Haliotis rubra Leach), on natural coastal reefs in New South Wales (NSW), Australia. Abalone are demersal, relatively sedentary, marine molluscs, that support important commercial, recreational and indigenous fisheries in numerous locations around the world. This thesis was developed in response to substantial depletions of local populations of H. rubra along >250 km of the NSW coast and the ineffectiveness of traditional fisheries management strategies to arrest these declines. These failures stem from demographic processes, common to haliotids, that limit their ability to re-establish populations that have been subject to substantial decline. A series of laboratory and field experiments were designed and conducted to examine a range of factors, and their interactions, that can have substantial affects on the success of releasing hatchery-reared H. rubra to natural reefs. The principal finding was that successful stock enhancement of local populations can be achieved, and the greatest value of a stock enhancement strategy is likely to be gained where the primary management objective is rebuilding depleted natural populations. Methodology, baseline targets and other recommendations are provided that would aid implementation of a stock enhancement management strategy to complement current traditional fisheries management approaches. The objectives of the research in this thesis were to: 1) investigate factors affecting the settlement, metamorphosis and early growth of H. rubra larvae; 2) batch-tag larvae and juveniles to enable their identification when recaptured; 3) develop and test methods for the successful release of larvae and juveniles; 4) develop a monitoring strategy to estimate the abundance of released abalone through time; 5) quantify long-term survival and growth to provide minimum targets for stock enhancement; 6) determine the impact of releasing juveniles on wild populations; 7) provide a bio-economic analysis and; 8) provide recommendations for the implementation of a stock enhancement management strategy for H. rubra in NSW. The release of larvae to natural reefs requires them to be exposed to a number of handling and transport processes. In laboratory experiments conducted in this thesis, greater proportions (commonly >75%) of larvae settled, metamorphosed and grew to larger sizes when exposed to settlement substrata for longer periods of time (>24 hours). There was a lower settlement response in the presence of water flow, although the addition of gamma-aminobutyric acid (GABA) increased the proportion of larvae that settled within short periods of time, i.e. 25 - 100% more in ≤60 sec.. Larvae were resistant to simulated handling and transport processes, indicating their utility for stock enhancement. The tagging of larvae and juveniles is fundamental to assessing the success of an enhancement program. Hatchery-reared H. rubra larvae and juveniles were successfully batch-tagged. The tagging procedures provided an indelible mark, enabling the identification of individuals once recaptured, and unambiguous differentiation from wild conspecifics. Successful batch-tagging was also critical for the assessment of subsequent field experiments undertaken in this thesis. Larvae were batch-tagged with the epi-fluorescent dye, calcein. Laboratory experiments demonstrated that the tagged larval shell was clearly visible in the spire of juvenile shells after >250 days. The recapture of tagged and released larvae from natural reefs, >500 days after release, confirmed the persistence of this tag. A reliable and cost-effective method for batch-tagging juveniles was through the use of a commercial diet that resulted in the distinctive blue-green colouration of the shell. The presence of this blue-green colouration differentiated released juveniles from those in naturally occurring populations, could be observed with the naked eye, without the need for a UV light source, and persisted on the spire of individuals for >900 days. Methods of releasing H. rubra larvae and juveniles were developed and tested in a series of laboratory and field experiments. A deployment pump that included a pressurised container and hose, was used to successfully release larvae to natural reefs. The addition of GABA and refrigeration during simulated transport, and the stage of release from the deployment pump, significantly affected the number of larvae delivered through the pump. The release of larvae to physical shelters on the reef significantly increased the numbers that settled, and their survivorship. There was added complexity in the process of releasing juveniles than with that for larvae. The use of a deployment device (PVC tube, ~300 x 125 x 65 mm), that was securely placed onto the substratum, was integral to the successful release of juveniles. Use of these devices in a standard release protocol ensured the limited physical handling of juveniles and provided a simple, cost effective and efficient method for the release of large numbers to areas of natural reef. A monitoring strategy was developed and tested to enable accurate estimates of the abundance and therefore survival of released H. rubra ,of a variety of life history stages, to be measured. The abundance of H. rubra juveniles is difficult to accurately assess on natural reef because of their cryptic distribution among complex topography in rocky habitat. As a consequence, the precision and relative accuracy of methods to sample released abalone was examined in a series of field experiments, and included the dispersal of juveniles from deployment devices. The most accurate and precise estimates of the number of H. rubra surviving were detected using methods that disturbed the habitat, i.e. turning over boulders, within a release location, and multiple sampling approaches were required to measure the abundance of abalone of different sizes. For larvae, the collection of boulders provided more accurate estimates of abundance than samples taken using a venturi-lift. For juveniles, thorough searching of boulder substratum and more replicates provided more accurate estimates of abundance. Further, stratified sampling among habitats after natural disturbance revealed greater densities of H. rubra in 'solid habitat', and spatially stratified sampling indicated juveniles can disperse up to 10 m from their release point in <8 days. The success of a stock enhancement strategy is determined by the net value it adds to a population. This necessitates estimates of the long-term survival and growth of released individuals, the impact released individuals have on the extant population, and the bio-economic feasibility of an enhancement strategy. Rates of survival and growth varied substantially among releases and locations. However, the long-term survival of batch-tagged and released larvae and juveniles demonstrated that local populations of abalone could be enhanced with significantly greater numbers of juveniles surviving at multiple release locations than at control locations after >2 years. The release of juveniles had no detectable affect on the mean total number of wild conspecifics or wild recruits over these time scales. Long-term survival of released larvae and juveniles was generally low (<0.03%, range: 0 - 0.03% and; <4%, range: 0 - 10%, respectively). However, at three of the twelve juvenile release locations it exceeded that expected for wild abalone (range: 4 - 10%). Growth rates of released juveniles (range: 18 - 47 mm.yr-1) indicated that they would generally reach sexual maturity within 2 - 3 years and exceed the minimum legal length within 4.5 years. A deterministic, bio-economic model was used to analyse the net present value (NPV) of a stock enhancement strategy for H. rubra in NSW, against an alternate investment return of 10% p.a.. Positive NPV occurred where long-term survival was >4% and where growth rates were higher than average rates reported in this research, or beach price exceeded $AUD 34.kg-1. Low rates of long-term survival of larvae suggests their large-scale release is unlikely to provide a viable stand alone option to successfully enhance local populations of H. rubra. The survival and growth of released juveniles, to replicate locations, demonstrated that depleted local populations of H. rubra in NSW can be enhanced, and that a stock enhancement program can complement the NSW Abalone Fishery management strategy. The success of any large-scale stock enhancement program will be determined by the definition of its objectives. Outcomes from this thesis suggest that the greatest value of a stock enhancement strategy will be gained where its primary objective is to rebuild depleted populations, rather than optimise commercial yield through the release of individuals to overcome recruitment limitation or to harvest released individuals at a larger size. The decision to implement such a program, including explicit description of its primary objective, is required to be made among well-informed representatives of all stakeholders. Further, this decision needs to be made with a thorough understanding of the current biological structure of the populations, including the nature of population depletions, the economic status of the fishery and in light of current, complementary and alternative management arrangements that may provide comparative increases in net value.

A study was initiated to determine the effect of selected factors on the reproductive development and early life history of blacklip (Haliotis rubra) and greenlip (H. laevigata) abalone relevant to their wild fisheries or aquaculture. In both species, the rate of gonadal and larval development was proportional to water temperature, but the relationship was not simply multiplicative, rather there was a critical minimum water temperature below which development was arrested, known as the Biological Zero Point (BZP). The BZP for gonadal development was 7.8 degrees C for H. rubra and 6.9 degrees C for H. laevigata. Corresponding BZP values for larval development were 7.8 degrees C and 7.2 degrees C, respectively. Observations of larval development relative to temperature enabled a description of the Effective Accumulative Temperature (EAT; the cumulative difference between the culture temperature and the BZP, calculated hourly) for prominent developmental stages. The difference between the EAT for metamorphic competence and that for hatchout (i.e. the interval during which the larvae remain in the water column) was 1120 and 1160 EAT degrees C-h for blacklip and greenlip abalone, respectively. These values, in combination with water temperature data, enable the prediction of the dispersal window for each species in situ. Spawning performance of blacklip and greenlip abalone was also affected by temperature, with both sexes of each species producing significantly more gametes when conditioned at 16 degrees C than 18 degrees C. Sperm production of H. rubra was an order of magnitude greater than that of equivalent sized H. laevigata. There was no apparent difference in the lipid or fatty acid composition of the ovary or testis between pre- and post-spawning animals of either species, presumably because of partial spawning and/or incomplete resorption of the gonad. Likewise, a 4 degrees C difference in conditioning temperature (i.e. 14 degrees C vs 18 degrees C) was insufficient to elicit changes in tissue biochemistry. There was a significant interaction between sperm density and contact time on the fertilisation success of eggs from both blacklip and greenlip abalone. Prolonged exposure (> 1200 s for H. rubra and > 480 s for H. laevigata) to concentrated sperm (i.e. 107 ml-1) resulted in egg destruction. Analysis of CoVariance of F50 values (i.e. the sperm concentration required for 50% fertilisation, derived from the linear regression of logit (proportion of eggs fertilised) versus sperm density) between species across a range of contact times demonstrated that contact time had a significant effect (p < 0.001) whereas species did not (p = 0.22). The lack of a species effect suggests that the fertilisation potential of blacklip and greenlip abalone eggs are similar, at least across the range of sperm densities and contact times used.

This study investigated how the combined stressors of ocean warming and acidification (reduced pH and elevated CO\(_2\)) impact seaweed species that the commercially exploited blacklip abalone (Haliotis rubra) relies on for all components of its life cycle. The impacts of warming and acidification on seaweeds that provide habitat, a food source or induce settlement of larvae, were assessed through a series of manipulative laboratory experiments. To provide context for experimental work, a field survey was undertaken that examined seaweed biomass, species composition and nutritional quality (fatty acid composition and nitrogen content) in three sites that spanned a latitudinal gradient in eastern Tasmania (Chapter 2). Results showed that the nutritional quality of the understory seaweeds consumed by H. rubra increased from the northern to southern site. This increase was consistent with higher productivity of H. rubra in the southern region and was driven by a higher biomass of red species at the southern sites, which were rich in polyunsaturated fatty acids (PUFA) and nitrogen. Most studies examining the response of seaweeds to ocean acidification in laboratory studies have used experimental treatments based on future projections for the open ocean. This is problematic as pH within seaweed beds is highly variable (compared to stable open ocean), and pH fluctuations can influence the response of seaweeds to acidification. Chapter 3 examined the effect of fluctuating pH on two sympatric red seaweeds (Callophyllis lambertii and Plocamium dilatatum) under both current and future ocean pH. Only C. lambertii was affected by fluctuating pH, with reduced growth and photosynthetic rates relative to the static conditions. The differential responses of two sympatric red seaweeds led to the incorporation of pH fluctuations in the treatments of all subsequent experiments, to provide environmental realism. Chapter 4 investigated the influence of marine heatwaves along with future warming and acidification on the brown seaweed Phyllospora comosa, which forms primary habitat for H. rubra and is an important food source. P. comosa was physiologically tolerant to marine heatwaves under both current and future ocean conditions. This tolerance was likely due to an adjustment in fatty acid composition with a reduction in the proportion of PUFA to saturated fatty acids (SFA) maintaining optimum membrane fluidity at elevated temperatures. Furthermore, energetic savings arising from increased CO\(_2\) supply (i.e. acidification) may have facilitated this adjustment when marine heatwaves were superimposed on future ocean warming and acidification. Chapter 5 examined the effects of warming and acidification on crustose coralline algae (CCA) that are known to induce settlement of H. rubra larvae. A scenario-based approach was used in which the responses of CCA (genus Sporolithon) cultured under current ocean temperature and pH were compared to responses under temperature and pH levels expected by 2030, 2050 and 2100 (RCP 8.5 emissions scenario). Results suggest that CCA are likely to be significantly negatively affected by combined warming and acidification as soon as 2030. The findings of this thesis suggest that the key habitat forming seaweed in abalone habitat, P. comosa, is likely to acclimate to future ocean conditions. However, this acclimation mechanism (reduction in PUFA), along with a reduction in nitrogen content observed under global ocean change in both P. comosa and C. lambertii, may lead to a significant reduction the nutritional quality of these seaweeds for H. rubra. Whether other seaweeds utilised as food sources such as the red seaweeds that were abundant in our southern field sites will respond in similar ways requires investigation. Recruitment of H. rubra larvae may be negatively impacted within the next two decades via adverse impacts of climate change on CCA assemblages. These findings highlight the need for managers of commercially exploited species to consider the effects of climate change on the seaweeds they rely on.