Environment Institute Leaders publications

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Open Access
Declining water quality as a driver of changes to subtidal communities.
(2009) Gorman, Daniel; Connell, Sean Duncan; Gillanders, Bronwyn; School of Earth and Environmental Sciences : Ecology and Evolutionary Biology
This body of work examines the influence of land use on nearshore water quality, and how this can drive changes to algal and invertebrate communities along Australia's southern coastline. The overall aim of the thesis was to investigate links between increasing coastal water-column nitrogen concentrations (derived from terrestrial inputs) and the expansion of turf-forming habitats that can alter the structure and function of subtidal ecosystems. I initially tested whether human activities in coastal catchments can increase subsidies of nitrogen to open rocky coasts. I identified landscape-scale variation in the supply of Dissolved Inorganic Nitrogen (DIN) to coastal waters adjacent to natural, agricultural and urban catchments. Compared to natural catchments, subsidies of DIN were 8 - 407 times greater in urban catchments, and 1 - 63 times greater in agricultural catchments. Subsidies of nitrogen from urban catchments were attributed to the release of sewage effluent, as delineated by δ¹ ⁵N isotopic values of transplanted algae. Having made this link, I then assessed whether catchment-scale variation in nitrogen subsidies may predict patterns of subtidal habitat structure, particularly as related to theories of regime shifts from forested landscapes to structurally depauperate turf-forming habitats. I validated this hypothesis, demonstrating that both relative covers and patch-sizes of turfed habitat were greater where the ratio of terrestrial nitrogen inputs to ambient coastal resources was large. An important realisation was that loss of forests may be more strongly related to the size of subsidy (i.e. the relative increases in water column nitrogen concentrations along urban coasts) rather than the size of coastal populations. Together, these data link coastal development with modified land-to-sea subsidies, and indirectly support the model that ecological effects may be proportional to the disparity between donor and recipient resources. Having demonstrated a link between nitrogen subsidies and subtidal habitat change, I then investigated factors likely to initiate and maintain such shifts. My results demonstrate that nutrient elevation can alter the natural phenology of turfs, sustaining dense covers throughout periods of natural senescence (winter). Perennial turf covers are able to accumulate large volumes of sediment; a synergy can impede the winter recruitment of canopy-forming species (kelps and fucoid algae). My observations of reduced forest recovery along urban coasts serve to highlight the complex interaction between elevated nutrients, persistent turf covers and increased sediment accumulation, which can reduce the resilience of coastal ecosystems to disturbance. In recognition that regime shifts are likely to have consequences for higher trophic levels, I compared the diet of invertebrate herbivores from healthy and degraded coastlines using stable isotope analysis (δ¹³C and δ¹⁵N). Dietary modelling showed that turfs contributed more to the diet of consumers along degraded coastlines where turfed landscapes have replaced extensive covers of macroalgal forest. Additionally, there were strong correlations between covers of turfed habitat, herbivore diet and relative densities. Changes to ambient food quality associated with regime shift may be an important aspect of nutrient-driven change along human-dominated coastlines. The final component of my thesis redressed some of the uncertainty about restoration initiatives for urban coasts by demonstrating that regime shifts are not necessarily permanent. I showed that turf removal can facilitate the recovery of degraded forests. Future restoration, therefore, is a possible outcome of polices that aim to decouple the link between nutrient inputs and recalcitrant turfed habitats that prevent forest recovery. Initiatives that reduce nutrient discharge to coastal waters (e.g., wastewater recycling) are likely to restore the resilience of nearshore marine ecosystems and promote their rehabilitation.
Open Access
Disturbances that influence patterns of benthic assemblages.
(2008) Roberts, Bethany K.; Connell, Sean Duncan; School of Earth and Environmental Sciences : Ecology and Evolutionary Biology
Understanding the influence of disturbance, both natural and human-induced, is a persistent challenge in ecology. Recently, attempts to predict future environments have focused on the consequences of broad scale disturbances. In this thesis I focus on environmental and trophic disturbances as shapers of benthic assemblages. There is growing recognition of the need for greater scientific investment in understanding environmental disturbances to balance the continuing focus of research assessing trophic theories (e.g. herbivory). Historically, it is these theories that have provided a cornerstone to describe and manage subtidal rocky coasts worldwide. In this thesis, therefore, I first assess how our ecological perception of such disturbances (i.e. water pollution and harvesting grazers) may vary as a consequence of the choice of taxonomic classifications used to observe benthic patterns (Chapter 2). I then assess how mechanical disturbance (i.e. wave exposure) may affect the morphology of benthic habitat (Chapter 3) and how temperature disturbances (i.e. oceanographic, cold water pulsing) may affect the consumers of these habitats (Chapter 4). The critical first finding centred on the effectiveness of alternate scales and metrics of taxonomic classification to detect the effects of water pollution (i.e. nutrient enhancement) as the largest disturbing agent on the benthos, and that this effect may be exacerbated by loss of grazers. While observations of the benthos as morphological groups detected the effects of enhanced nutrients, species diversity (as a measure of phylogenetic relatedness) was the only one of the chosen measures sensitive enough to detect the interaction of both top-down and bottom-up stressors. This chapter highlights the importance of choice of classification (e.g. morphology v. species) and indices (e.g. Shannon index v. ABC curves and phylogenetic diversity) in their potential to predetermine our perception of ecological change and thereby predict future environments. Mechanical disturbance (i.e. wave exposure) has been widely studied as a mechanism that creates new space for colonisation by alternate species, but is less well studied as a force that can change the shape of communities by mediating their morphology. Macroalgal morphology varies in response to wave exposure such that individuals at high exposures are often smaller than individuals in more sheltered environments. Observations not only confirmed these patterns for a general assemblage on a wave exposed southern coast, but reciprocal transplants of assemblages between exposures also revealed that morphological differences were likely to be a product of flexibility in morphological response of algae to local environments (Chapter 3). In contrast to the often multi-directional responses of a complex suite of morphological characters (e.g. smoothness, stipe length, frond width), overall size has the potential to be used as a broad and predictive tool to identify hydrodynamic stressors across an entire exposure gradient or geographic range. Strong trophic interactions are often considered characteristic of aquatic systems and due to their perceived ubiquity on temperate rocky coasts, there has been an emphasis in the literature on the influence of herbivores in determining assemblages. Given the importance of the link between herbivores and assemblage structure, in my final chapter I investigated the potential for disturbance to act indirectly on benthos by affecting the survivorship of an herbivorous urchin (Chapter 4). I used observations of variable temperature regimes in a region of upwelling to design an experiment that tested whether this temperature variation could negatively affect the survivorship of settling sea urchins (Heliocidairs erythrogramma). When exposed to cold water, mortality increased by up to 70 %, within 12 h of settlement, representing a massive loss of benthic consumers within a very short time scale. This result was used to assess the potential of temperature to indirectly influence benthic habitats across several spatial scales, a process that may have been profoundly underestimated. In summary, this thesis provides insight into environmental and trophic disturbances as shapers of benthic assemblage patterns, both as natural and human-induced phenomena. I show that our perception of ecological response to the combination of such disturbances can be contingent on the organisational scales and metrics used. Subtle differences in initial choice of such observational units may not only have large affects on the kinds of benthic patterns and disturbances ecologists detect, but also those that they pursue. I recognise that while some physical disturbances can appear subtle (e.g. morphological variation) or strong (e.g. high mortality rate of herbivores), their relative impacts on the broader assemblage (e.g. understorey flora and fauna) will often be dependent on biogeography. Integrating local-scale biological interactions with regional-scale physical processes, therefore, appears to be a potentially progressive line of future enquiry. Indeed, consideration of responses from the physiological through to physical and biogeographical scales will not only strengthen our understanding of the effects of alternate disturbance regimes, but also our predictive power to anticipate future change.
Open Access
The ecology of subtidal turfs in southern Australia.
(2005) Russell, Bayden D.; Gillanders, Bronwyn; Connell, Sean Duncan; School of Earth and Environmental Sciences
Assemblages of algae are altered by both bottom - up ( e.g. nutrient availability ) and top - down ( e.g. herbivory ) processes. As a result of the increasing human population in coastal areas, massive changes are forecast to benthic habitats in response to increasing coastal nutrient concentrations and a reduction in consumers. To identify the scales over which nutrients may have an effect, abundance of turf - forming algae growing as epiphytes on kelp ( Ecklonia radiata ) were related to water nutrient concentration across temperate Australia. In general, the percentage cover of epiphytes was greatest at sites with the greatest nutrient concentrations. By experimentally elevating mean nitrate concentration from the low 0.064 ± 0.01 µmol L [superscript - 1 ] to 0.121 ± 0.04 µmol L [superscript - 1 ], which was still only ~ 5 % of that measured on a more eutrophic coast, I was able to increase the percentage cover of epiphytes to match those seen on nutrient rich coasts, despite not matching the nutrient concentrations on those coasts. Hence, it appears that the effects of elevated nutrients will be disproportionately large on relatively oligotrophic coasts. Nutrient concentrations were also experimentally elevated to test whether the presence of an algal canopy or molluscan grazers were able to counter the effects of nutrient enrichment on algal assemblages. The loss of canopy - forming algae is likely to be a key precursor to nutrient driven changes of benthic habitats, because nutrients had no direct effect on algal assemblages in the presence of canopy - forming algae. In the absence of canopy - forming algae, space was quickly monopolised by turf - forming algae, but in the presence of elevated nutrients grazers were able to reduce the monopoly of turf - forming algae in favour of foliose algae. This switch in relative abundance of habitat may reflect greater consumption of nutrient rich turf - forming algae by grazers, possibly creating more space for other algae to colonise. Importantly, greater consumption of turf - forming algae in the presence of elevated nutrients may act as a mechanism to absorb the disproportionate effect of nutrients on oligotrophic coasts. In southern Australia, canopy - forming algae have a negative impact on the abundance of turf - forming algae. To assess the mechanisms by which an algal canopy may suppress turf - forming algae, abrasion by the canopy and water flow were experimentally reduced. Abrasion by the canopy reduced the percentage cover and biomass of turf - forming algae. In contrast to predictions, biomass and percentage cover of turf - forming algae were also reduced when water flow was reduced. Light intensity was substantially reduced when there was less water flow ( because of reduced movement in algal canopy ). However, the reduction in available light ( shading ) did not account for all of the observed reduction in biomass and percentage cover of turf - forming algae, suggesting that other factors are modified by water flow and may contribute to the loss of turf - forming algae. Habitat loss and fragmentation are well known to affect the diversity and abundance of fauna in habitat patches. I used experimental habitats to assess how fragmentation of turf habitats affects the diversity and abundance of two taxa of macroinvertebrates with different dispersal abilities. I established that increased isolation of habitats reduced the species richness and abundance of invertebrates with slow rates of dispersal, while the species richness and abundance of invertebrates with fast rates of dispersal were greatest in habitats that were far apart. In summary, this thesis provides an insight into some of the impacts associated with human populations in coastal areas, namely increased nutrient inputs, loss of grazers ( e.g. harvesting ), and loss of canopy algae and fragmentation of habitats. I show that increased nutrient concentrations in coastal waters can alter the relative abundance of algal species, and that some effects of elevated nutrients can be absorbed by the presence of grazers. I also show that elevated nutrients have no effect on algal assemblage in the presence of canopy - forming algae, and that canopies can suppress the colonisation of turf - forming algae. Finally, I show that the fragmentation of turf habitats affects taxa of invertebrates with different dispersal abilities in different ways. Whilst the contemporary ecology of much of the temperate Australian subtidal coast is considered to be relatively unaffected by human activity, this thesis shows that changes to top - down and bottom - up processes could have large consequences for habitats and their inhabitants.
Open Access
Regional and local patterns in kelp morphology and benthic assemblages
(2005) Fowler-Walker, Meegan J.; Connell, Sean Duncan; Gillanders, Bronwyn; School of Earth and Environmental Sciences
Most ecologists work at scales where complexity is greatest ( i.e. local ), and it is not surprising, therefore, that we tend to be captivated by the description and explanation of local variation whilst being pessimistic about the existence of broader patterns. Using a character ( kelp morphology ) known for its local and unaccounted variation, the morphology of the canopy - forming algae Ecklonia radiata ( Phaeophyta ) was quantified across > 5000 km of temperate Australian coastline, ( i ) between different configurations of algal stand ( i.e. monospecific vs mixed - species stands ) and ( ii ) across multiple spatial scales. A key result was that despite variation at local scales ( km ), differences between stands became increasingly clear at broad scales ( 1000 ' s km ), which supports the idea that large - scale patterns can emerge from apparent stochasticity at small scales. Within each stand, regional scale differences in morphological characters were evident ( i.e. Western Australia = South Australia ≠ Eastern Australia ). These characters correlated with geographic and environmental variables to indicate that the majority of morphological variation across temperate Australia was accounted for by longitude, wave exposure, water temperature and plant density. Morphological differences associated with environmental factors may reflect a plastic response to the local environment, or alternatively may reflect genetically fixed traits ( i.e. ecotypes ). An independent test of morphological variation associated with wave exposure environments, using a reciprocal transplant experiment, revealed that morphological plasticity was the mechanism enabling E. radiata to adopt different morphologies between exposure environments. The presence of kelp canopies has strong spatial relationships with organisms growing underneath them, and variation in the morphology of these canopies may facilitate distinct assemblages within the understorey habitat. Variation in the morphology of E. radiata was found to be associated with the structure of understorey assemblages, over broad spatial scales. This canopy - understorey association revealed two ' types ' of kelp forest ; one characteristic of Western and Southern Australia and the other of Eastern Australia. Patterns of canopy - benthos association have mostly been done on horizontal surfaces and experimental tests showed that such patterns on horizontal surfaces were not representative of vertical surfaces, which enables us to recognize the conditions for which we can reliably anticipate the structure of benthic organisms, thereby improving the predictive power of models that account for widespread patterns in subtidal heterogeneity. In conclusion, this thesis suggests that there are fundamental differences between the ecology of kelp forests at local scales ( i.e. between types of stand ) and at regional scales ( i.e. between the south and east coast of temperate Australia ), reflecting differences in kelp morphology that may be caused by environmental conditions ( e.g. exposure ) and may influence associated taxa ( e.g. understorey ). Consideration of such local - scale variation ( specificity ) when testing for the existence of broad - scale phenomena ( generality ) not only strengthens our understanding of the ecology of subtidal forests, but will also improve the predictive power of further research in this system.
Open Access
Stable isotopes of estuarine fish: experimental validations and ecological investigations.
(2012) Bloomfield, Alexandra Louise; Gillanders, Bronwyn; Connell, Sean Duncan; School of Earth and Environmental Sciences
Stable isotopes of carbon and nitrogen are commonly used in ecological research to determine food webs and trace anthropogenic inputs. These applications rely on understanding isotope signature differences between an animal and its food. When an animal consumes a food item, or changes diet, it does not instantaneously reflect the isotope ratios of that food item. The isotopic signature of animal tissue gradually approaches equilibrium with the isotopic signature of its food, as molecules are turned over and new food items are assimilated into tissues. Stable isotope ratios also change between food consumed and animal tissues that are commonly sampled. The difference in stable isotope ratios between an animal's tissue and the food it consumes is called discrimination. The rate of change, or tissue turnover, and discrimination of stable isotopes varies among and within animals, and with environmental factors. I investigated the effects of temperature and diet on these isotope parameters for two fish species and applied results to improve determination of autotrophic sources within estuaries. I studied two common, omnivorous, estuarine fishes found in South Australia: black bream (Acanthopagrus butcheri) and yellow-eye mullet (Aldrichetta forsteri). Temperature and diet affected both tissue turnover rates and discrimination of carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope ratios in fish muscle. Fish reared at warmer temperatures generally had faster tissue turnover rates and smaller discrimination factors than fish reared at cooler temperatures. However, temperature interacted with diet quality to affect δ¹³C discrimination. Fish fed diets with low C:N ratios had larger δ¹³C discrimination at warmer temperatures than at cooler temperatures. This may be caused by fish catabolising more protein for energy and therefore being able to store more lipids at cooler temperatures than warmer temperatures. Fish fed diets with high C:N ratios were the opposite, with larger δ¹³C discrimination at cooler temperatures than at warmer temperatures. Compound-specific δ¹⁵N analyses were performed on amino acids from experimental black bream muscle tissues to see if the change in δ¹⁵N of amino acids could explain the bulk change in δ¹⁵N of whole muscle tissue. Some amino acid δ¹⁵N results mirrored those of bulk δ¹⁵N analyses suggesting that they may be non-essential amino acids, although there was large variation among individual fish. Wild fish commonly consume more than one dietary item, necessitating the use of mixing models to determine source contributions to diets. Omnivores consume animal and plant matter that can differ greatly in their elemental composition and this can affect the uptake of isotopic signatures from different food sources. I tested the importance of using elemental concentration in mixing models by combining two diets with different carbon and nitrogen concentrations and feeding them to yellow-eye mullet. I compared measured δ¹³C and δ¹⁵N of fish muscle with predicted values calculated with and without using elemental concentration. Using elemental concentration in mixing models improved estimates of predicted isotopic signatures. The experimentally derived discrimination factors for black bream and yellow-eye mullet were used to investigate the relative importance of autotrophic sources to their diets in four estuaries in South Australia. Isotope signatures of carbon and nitrogen can also be used to investigate ecological niches of animals, as isotope signatures reflect what an animal has eaten from different habitats and environments. I expected the isotopic niches of black bream and yellow-eye mullet to overlap, due to their shared environmental tolerances and feeding habits, as they are commonly found in the same estuaries. However, I found no overlap in isotopic niches between black bream and yellow-eye mullet. In some estuaries the autotrophic sources that black bream and yellow-eye mullet relied on were similar, however, in these estuaries fish appeared to be either feeding at different trophic levels or were likely not in competition with one another as they were caught in different areas within estuaries. The separate isotopic niches of black bream and yellow-eye mullet may be caused by habitat partitioning or interspecific competition within the estuaries studied. I used δ¹⁵N of black bream muscle to trace anthropogenic inputs of nutrients across a range of estuaries and related nutrient concentrations of estuarine waters to black bream abundance and recruitment. Black bream abundance and recruitment showed subsidy-stress responses to nutrient concentrations of ammonia, oxidised nitrogen and orthophosphorus, with peaks in abundance and recruitment occurring at low concentrations. A positive linear relationship was found between ammonia concentration of estuarine waters and δ¹⁵N of black bream. This suggests that anthropogenic ammonia was being taken up into the food web, or directly by black bream, and affecting black bream abundance and recruitment. In summary, I found environmental factors affected stable isotope signatures of fish muscle tissue. These results further show how important it is to quantify isotope parameters for individual species. Future research should focus on how to quantify influences on isotope signatures that cannot be determined in the field, such as ration intake, and how to account for these factors in field studies.
Open Access
Strength of sea urchin herbivory and condition from biogeographic to organismal scales.
(2012) Livore, Juan Pablo; Connell, Sean Duncan; School of Earth and Environmental Sciences
Amongst the many ecological processes that can have an influence on community structure within marine ecosystems, herbivory is recognised as having an important role. Algae are not only living components of the community, they often provide a physical structure, food and protection indispensable for many other species. Therefore, understanding herbivore behaviour and their effects on the surrounding habitat is vital to further comprehend benthic marine ecosystem dynamics. Strength of herbivory is often determined by simple numbers of individual herbivores. There are however, other factors that may influence herbivore feeding behaviour such as food quantity and quality. Changes in food availability can have a strong influence on the dynamics of consumers that rely on allochthonous sources as their main supply of energy. I tested the hypothesis that a decrease in per capita food supply to a sedentary herbivore has a negative effect on herbivore condition and also affects the surrounding habitat through changes herbivore feeding behaviour. The reduction in food supply had a negative influence on herbivore gonad condition, whilst concomitant increases in consumer density caused greater foraging of the surrounding habitat. Poor consumer condition can be the result of food limitation and in some cases can lead to stronger herbivory. This process could help explain barrens creation across many subtidal rocky coasts. Ecological traits may have a stronger influence on population and community dynamics than currently acknowledged; particularly sedentary herbivores that may be incapable of migrating to alternate environments. I assessed the effects of origin of food and its frequency of delivery on sea urchin behaviour and condition. Higher consumption rates and poorer condition were associated with food originating from sheltered coasts; coinciding with observations of urchin over-grazing in this type of Environment. Whilst algae derived from exposed coasts caused lower consumption rates and better condition; coinciding with no urchin over-grazing on exposed reefs. Understanding such trait-mediated responses to allochthonous food may assist the development of more comprehensive models that account for variation in strength of herbivory. Many studies have focussed on foraging of canopy-forming algae by sea urchins associated with barrens, however, foraging effects of urchins not associated with barrens is less clear. I tested the hypothesis that the sedentary (largely site attached) sea urchin Heliocidaris erythrogramma has detectable effects on the canopy-forming and understory algae. In a location where densities were at the upper limits of their range of a region that lacks sea urchin barrens, algal cover was estimated beneath and immediately around sea urchins. The area under the urchins was consistently bare rock. Sea urchin removal experiments showed that canopy-forming algae were able to develop in greater covers after 16 months and approached those in areas that naturally lacked urchins. In the area immediately surrounding the sea urchins, turf-forming algae dominated the first 5-6 cm, whilst at 8 cm canopy-forming algal cover matched areas without urchins. Cover of canopy-forming algal can be reduced in the presence of non-barren forming urchins, albeit only within a few centimetres of individual urchins. This suggests that such organismal-scale effects may have an influence on the ecology of rocky coasts with dense populations of these urchins (e.g. sheltered coasts). In conclusion, strength of herbivory can depend on many factors that vary across a broad range of scales. In this thesis, I provide knowledge on some of the factors associated with herbivory by the purple sea urchin, Heliocidaris erythrogramma. I show that herbivore abundance and condition which can directly affect strength of herbivory vary at regional (i.e. Eastern Australian Current v. Leeuwin Current) and local scales (ie. sheltered v. exposed coasts). I also demonstrate that drift-algal quantity and origin can have a strong influence on sea urchin condition and feeding behaviour. Finally, the organismal scale effect (i.e. centimetres) may not only be detectable but also influential at some places and scales. Together, these results suggest that populations of herbivores, their condition and impact, may have predictable effects from local through regional scales. The integration of such dependencies to general models may contribute to a more comprehensive understanding of rocky subtidal ecosystems.
Open Access
Using shell morphology to characterise abalone populations across multiple spatial scales.
(2009) Saunders, Thor M.; Mayfield, Stephen; Connell, Sean Duncan; School of Earth and Environmental Sciences : Ecology and Evolutionary Biology
Many sedentary marine invertebrates have a fine-scale (100s m) population structure that complicates their conservation and management. This is a consequence of the limited information on the boundaries between component populations and the biological variability among them. Blacklip abalone (Haliotis rubra) form discrete populations many of which are ‘stunted’ with individuals reaching a maximum length less than those in adjacent areas. A range of morphological measurements from samples of stunted and ‘non-stunted’ H. rubra collected from sites spread across broad (10s km) and fine (100s m) spatial scales in southern South Australia. In addition, information on the growth, size at maturity and fecundity of H. rubra was obtained from these same sites. The ratio between shell length and shell height showed clear and significant differences among samples from stunted and non-stunted sites. The fine-scale morphometric collections suggested that stunted populations existed at smaller spatial scales compared to those for non-stunted populations. Spatial variation in these key life history parameters could primarily be attributed to differences between stunted and non-stunted sites. Relationships between each of these parameters and the ratio between shell length and shell height were also examined. The spatial patterns in morphology and biology were highly correlated suggesting that shell length:shell height ratio can be used as a simple ‘morphometric marker’ to distinguish among populations of abalone and identify their biological characteristics. The detection of differences H. rubra morphology among variable environments cannot determine whether these differences represent a plastic response to the local environment, or whether morphology is genetically fixed. A reciprocal transplant experiment was used to test whether stunted H. rubra are the result of a plastic response to the environment or fixed genetic trait. Furthermore, environmental factors that affect food availability were related to differences in 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, while individuals transplanted to stunted sites grew significantly slower compared to non-stunted controls. It is suggested that these differences are related to resource availability with areas limited in food supply resulting in stunted populations and areas with abundant food resulting in non-stunted populations. To reduce the risks of over-fishing and localised depletion of H. rubra, management units (MUs) that encompass individual populations need to be determined and then managed according to their life-history characteristics. Potential MUs in the South Australian abalone fishery were identified from the broad-scale, spatial distribution of stunted and non-stunted populations of H. rubra, by applying the morphometric marker to commercial shell samples. Key life-history parameters of the H. rubra populations within the potential MUs were estimated using relationships between this marker and H. rubra 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 that of current management. The locations of two MUs were consistent across the broad- and fine-scale datasets with the fine-scale samples being more informative for identifying a potential boundary between these. These results suggest that this morphometric marker can used as a tool for the spatial management of abalone fisheries by simply and inexpensively inferring key biological parameters for individual populations and identify the boundaries among these based on these differences. 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.

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