Search

Abstract In South Africa, kelp forests and associated temperate reefs dominate the nearshore subtidal zone in the southern Benguela, with kelp forests covering approximately 1000 km of the coastline. These ecosystems provide a range of goods and services that are of immense ecological, social and economic importance. A number of valuable species on these subtidal reefs are overexploited and have reached a state of crisis since the 1990s. Many linefish stocks are considered collapsed or overexploited, West Coast rock lobster populations are estimated to be at < 3% of pre-exploitable biomass and abalone are similarly overexploited, with two of the four major historical fishing grounds now closed to fishing. The current value of this ecosystem is estimated at US$ 434 million year− 1 (ZAR 5.8 billion year− 1), of which c. US$ 290 million year− 1 (ZAR 3.9 billion year− 1) contributes to the South African gross domestic product (GDP), with ecotourism contributing almost 40% of this, followed by recreational fishing (28%), and commercial and illegal fishing (c. 15–16% each). Income currently generated by fisheries is greatly reduced, with some sectors worth less than half of their value in the 1990s. Indirect ecosystem services are valued at US$ 144 million year− 1 (ZAR 1.9 billion year− 1) but aren't realised in the country's GDP as they do not provide direct economic value. Given the importance of the Benguela nearshore region to low-income coastal communities, particularly in the face of increased climate variability, striking a balance between rebuilding depleted stocks and meeting the socio-economic needs of those reliant on them will require a renewed focus on coastal research, with an emphasis on co-ordinated interdisciplinary projects. Highlights • A number of valuable species in southern Benguela subtidal reefs are overexploited. • Current value of this ecosystem is estimated at US$ 434 million year− 1. • Ecotourism and fishing have the greatest value of the direct ecosystems services. • Fisheries income currently generated is greatly reduced compared to the 1990s. • Indirect ecosystem services are important. [ABSTRACT FROM AUTHOR]

South African rhinoceros (e.g. Diceros bicornis) and abalone (Haliotis midae) have in common that they both are harvested under open-access conditions, are high-value commodities and are traded illegally. The difference is that a legal market for abalone already exists. An open-access deterrence model was developed for South African abalone, using Table Mountain National Park as a case study. It was found that illegal poaching spiked following the closure of the recreational fishery. The resource custodian's objective is to maximise returns from confiscations. This study showed that a legal trade results in a 'trading on extinction' resource trap, with a race for profits, an increase in the probability of detection after a poaching event and the depletion of populations. In contrast with HS Gordon's seminal article (J Polit Econ 1954;62:124-142), profit maximisation does not automatically improve the sustainability of the resource. Under certain conditions (e.g. a legal trade with costly enforcement), profit maximisation may actually deplete abalone populations. The article also has implications for rhino populations, as a legal trade is currently proposed. [ABSTRACT FROM AUTHOR]

The shell of the European abalone Haliotis tuberculata is a model for studying mechanisms of mollusc shell formation, but the early steps of shell formation and calcification remain poorly documented. The microstructure and the mineralogical and geochemical composition of larval and juvenile shells were investigated by scanning electron microscopy, infrared spectroscopy and ion microprobe analyses (NanoSIMS). Analyses were performed on shells obtained from controlled fertilisations at the hatchery France-Haliotis (Plouguerneau, France) in July 2009 and 2010 using abalone from Roscoff. Shell cross sections revealed the microstructural arrangement of the developing shell, showing progressive biomineral organisation into two differentiated layers, i.e. the outer granular and the internal nacreous layer. Infrared analysis confirmed that the European abalone shell, at every stage of development, was mostly composed of CaCO in the form of aragonite. Variations in trace element composition, i.e. Sr/Ca, were measured in the different stages and correlated with micro-structural changes in the shells. Experimental manganese labelling of live abalones produced cathodoluminescence marks in the growing shell sections. The increase in shell thickness can be used to determine the growth rate of an early adult abalone shell. [ABSTRACT FROM AUTHOR]

Epidemiological theory suggests that pathogens will not cause host extinctions because agents of disease should fade out when the host population is driven below a threshold density. Nevertheless, infectious diseases have threatened species with extinction on local scales by maintaining high incidence and the ability to spread efficiently even as host populations decline. Intertidal black abalone (Haliotis cracherodii), but not other abalone species, went extinct locally throughout much of southern California following the emergence of a Rickettsiales-like pathogen in the mid-1980s. The rickettsial disease, a condition known as withering syndrome (WS), and associated mortality occur at elevated water temperatures. We measured abalone body temperatures in the field and experimentally manipulated intertidal environmental conditions in the laboratory, testing the influence of mean temperature and daily temperature variability on key epizootiological processes of WS. Daily temperature variability increased the susceptibility of black abalone to infection, but disease expression occurred only at warm water temperatures and was independent of temperature variability. These results imply that high thermal variation of the marine intertidal zone allows the pathogen to readily infect black abalone, but infected individuals remain asymptomatic until water temperatures periodically exceed thresholds modulating WS. Mass mortalities can therefore occur before pathogen transmission is limited by density-dependent factors. [ABSTRACT FROM AUTHOR]

The existence of an allometric relationship between mortality rates and body mass has been theorized and extensively documented across taxa. Within species, however, the allometry between mortality rates and body mass has received substantially less attention and the consistency of such scaling patterns at the intra-specific level is controversial. We reviewed 73 experimental studies to examine the relationship between mortality rates and body size among seven species of abalone ( Haliotis spp.), a marine herbivorous mollusk. Both in the field and in the laboratory, log-transformed mortality rates were negatively correlated with log-transformed individual body mass for all species considered, with allometric exponents remarkably similar among species. This regular pattern confirms previous findings that juvenile abalones suffer higher mortality rates than adult individuals. Field mortality rates were higher overall than those measured in the laboratory, and the relationship between mortality and body mass tended to be steeper in field than in laboratory conditions for all species considered. These results suggest that in the natural environment, additional mortality factors, especially linked to predation, could significantly contribute to mortality, particularly at small body sizes. On the other hand, the consistent allometry of mortality rates versus body mass in laboratory conditions suggests that other sources of mortality, beside predation, are size-dependent in abalone. [ABSTRACT FROM AUTHOR]

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]

The article presents a study on the relationship of population connectivity of Ezo abalone Haliotis discus hannai in the northern Miyagi coast of Japan with the formation of harvest refugia. It states the use of hydrodynamic and particle-tracking models which objectives include clarification of process of larval dispersal, quantification of distance of dispersal, and estimation of connectivity. It says that the study calls for investigation of larval dispersal in marine reserve management.

The purpose of this study was to link toxicokinetics/toxicodynamics and subcellular partitioning for assessing the susceptibility and the growth inhibition risks of abalone Haliotis diversicolor supertexta exposed to waterborne and foodborne cadmium (Cd) and silver (Ag). We reanalyzed published data on growth inhibition and subcellular partitioning associated with the present mechanistic model to explore the correlations among elimination ( k), detoxification ( k), and recovery ( k) rate constants and to assess the growth inhibition risk. We found a positive correlation among k, k, and k in abalone exposed to Ag. We also employed a life-stage based probabilistic assessment model to estimate the growth inhibition risk of abalone to environmentally relevant Cd (5-995 μg l) and Ag (0.05-9.95 μg l) concentrations in Taiwan. The results showed that abalone had a minimum 20% probability of the growth inhibition risk exposed to Cd, whereas Ag exposure was not likely to pose the risk. The maximum biomasses were estimated to be 0.0039 and 0.0038, 61.61 and 43.87, and 98.88 and 62.97 g for larvae, juveniles, and adults of abalone exposed to the same levels of Cd and Ag, respectively. Our study provides a useful tool to detect potential growth biomass of abalone populations subjected to Cd and Ag stresses and mechanistic implications for a long-term ecotoxicological risk assessment in realistic situations. [ABSTRACT FROM AUTHOR]

During winter months, a novel overwintering mode of transferring juvenile abalones to open seawaters in southern China rather than keeping them in closed land-based nursery systems in northern China is a popular practice. The initial size, stocking density and sorting are among the first considerations when establishing an abalone culture system. This study aimed to investigate the effects of these factors on the growth of juvenile Pacific abalone, Haliotis discus hannai Ino, during overwintering. Juvenile abalones were reared in multi-tier basket form for overwintering in open seawaters in southern China for 106 days. The daily growth rates (DGRs) in the shell length of all experimental groups ranged from 67.08 to 135.75 μm day−1, while the specific growth rates (SGRs) were 0.2447–0.3259% day−1. Variance analysis indicated that both DGRs and SGRs in shell length were significantly affected by the initial body size and stocking density. Furthermore, the effects of stocking density on DGRs and SGRs varied with the initial size. However, sorting abalones according to their initial sizes may not be necessary in practice as sorting did not alter growth significantly at all densities in this study. Factors potentially affecting abalone growth such as genetic control and intraspecific competition were discussed. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the long-term spatial and temporal variation of red abalone fisheries in terms of productivity on the Northern Channel Islands. The study uses modern ecological data, historical accounts, commercial red abalone catch records, and zooarchaeological data for examining the continuity and resilience of red abalone fisheries. The study revealed a complex combination of top-down and bottom-up controls of the kelp forest and red abalone in California based on the archaeological, historical, and ecological data.

Survival of post-settlement abalone when 'weaning' them from diatoms onto macroalgae/artificial feed remains unpredictable for farmers. It is hypothesised that spirulina algae, which are high in protein, may be a suitable feed ingredient for weaning abalone. Over a period of 27 days, the growth and survival of juvenile (4-6 mm shell length) Haliotis midae were compared when weaned from diatoms onto agar-bound, 48% protein diets with either spirulina, fishmeal, or fishmeal and spirulina as the sources of nutrition. Agar-gel alone was used as a control (0% protein), and a commercial abalone diet, Abfeed®-S34 (34% protein), was included as a reference. Abalone that were fed fishmeal and spirulina combined performed best in both weight and shell-length gain (36.87 ± 2.19 mg and 2.29 ± 0.05 mm). The growth of agar-fed control animals was worst of all treatments (1.26 ± 2.03 mg and 0.19 ± 0.14 mm) and had a markedly reduced survival rate (18.6 ± 5.5%). Growth in abalone that were fed the spirulina only (9.41 ± 3.39 mg and 0.58 ± 0.27 mm) was better than the control-fed abalone and was substantially lower than other diet treatments, but not significantly different from them. Abalone that were fed Abfeed®-S34 only had a significantly higher condition factor (0.91 ± 0.02) compared with those fed the control (0.70 ± 0.09) and the combined diet (0.75 ± 0.01), and a significantly higher soft-body tissue to shell mass ratio (2.38 ± 0.14) than those fed spirulina only (1.67 ± 0.15) or the control (1.05 ± 0.09). Agar was a suitable medium for binding and presenting dietary ingredients to abalone at weaning, and fishmeal or a fishmeal-spirulina combination provided sufficient protein and energy for good growth and survival. Spirulina as a single-ingredient feed is not recommended. [ABSTRACT FROM AUTHOR]

Abstract: Since 1997 the Eastern Cape of South Africa has become a major source of supply for the illicit abalone trade as illegal fishers have located a substantial abalone (Haliotis midae) resource. We determined illegal fishing effort and yield in the Port Elizabeth-based abalone fishery, and used biological indices to determine the impact of fishing on the abalone stock. The failure of the state to issue fishing rights and conduct effective sea-based compliance, combined with the incentives to fish abalone (high price, low cost, ease of access) created the conditions for a full scale illegal fishery to emerge very rapidly. By 2005, the scale of the fishery was remarkable: a fleet of 30 purpose built vessels existed, harvesting 1000–2000tons of abalone with an export value of 35–70 million USD per year. The uncontrolled fishing effort had a dramatic effect on the stock: the average size of abalone decreased significantly, densities declined in the sampling areas, but recruitment of young abalone was still observed at the heavily fished Cape Recife site. It is concluded that the illegal fishing operations and the resultant ecological effects on the abalone resource, reflect deficiencies in South Africa''s current abalone fisheries management and compliance paradigm. [Copyright &y& Elsevier]

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]

Mayfield, S., McGarvey, R., Carlson, I. J., and Dixon, C. 2008. Integrating commercial and research surveys to estimate the harvestable biomass, and establish a quota, for an “unexploited” abalone population. – ICES Journal of Marine Science, 65: 1122–1130. A key challenge facing many fisheries managers is the absence of information on the level of harvestable biomass. We describe an integrated, two-stage survey approach that was used to measure the spatial distribution and harvestable biomass of a largely unexploited metapopulation of greenlip abalone (Haliotis laevigata) over a large area of northwestern Spencer Gulf, South Australia. In stage 1, commercial fishers conducted systematic surveys to identify subareas with abalone at harvestable densities. Cpue measures from these surveys were used to map and stratify a bounded survey subregion, within which leaded-line, research-diver surveys measured absolute density and harvestable biomass (stage 2). Decision tables, showing minimum biomass at various probabilities vs. harvest fraction, were developed to provide a risk-assessment framework for quota setting. Within two years, our approach allowed, first, the mapping of the broad-scale, spatial distribution and abundance of greenlip abalone in an area of 1143 km2, second, the estimation of harvestable biomass in a smaller (16.9 km2) area, and finally, the allocation by State fishery managers of an additional quota inside a newly defined management subzone. The collaborative approach we describe for providing estimates of absolute biomass over large spatial scales affords multiple advantages for the assessment and management of invertebrate dive fisheries. [ABSTRACT FROM PUBLISHER]

The dramatic declines in abalone Haliotis spp. fishery production have been documented all over the world. Release of hatchery-reared juveniles into natural habitats has been considered as one measure to sustain and/or augment the current fishery production of abalone, as well as to restore collapsed abalone stocks. However, attempts at abalone release programmes have only been undertaken at experimental scales, except for Japan, where large-scale stock enhancement programmes for abalone have been undertaken since late 1960s. To evaluate the potential of stock enhancement for abalone, we analysed the release surveys of 13 case studies in Japan in terms of the overall recapture rate (number of recaptures through a lifetime/number of juveniles released), yield per release (YPR, yields from released individuals), the economic efficiency of releases (ratio of income from recaptured abalone to release cost) for each release year, and the contribution of hatchery releases to total catches for each fishing year. The average estimates for overall recapture rates (0.014–0.238) and YPR (3.1–60.3 g/individual) varied between locations and release years. The economic efficiency was estimated at 0.4–6.2. The released abalone contributed 6.9–83.5% to total catches. Hatchery releases could augment total production at some locations, but the success of release programmes would be limited by the carrying capacity at release areas, because density-dependent mortality occurred following releases in some cases. Throughout Japan, the annual catch of abalone has continuously declined from ∼6500 t in 1970 to ∼2000 t in the mid-1990s, despite the increase in the number of hatchery releases. Based on the estimates for YPR, the magnitude of the abalone releases on a national scale has not been sufficiently large to sustain the total production of Japanese abalone, which has primarily fluctuated according to the abundances of wild populations. Our results suggest that releases should be targeted at local populations in regions where stock enhancement is predicted to have the greatest chance of success, and the magnitude of releases should be considered carefully and determined for each region by taking the local carrying capacity into account. We also address the future prospects of abalone stock enhancement. [ABSTRACT FROM AUTHOR]

Illegal harvesting is a cause for concern in many of the world's fisheries. Over the last decade, the abalone resource in South Africa has come under severe fishing pressure, largely because of increased and unmitigated levels of poaching. The unquantified illegal exploitation of this resource is a major impediment to management, because understanding of abalone population dynamics is affected. Incorrect assessments of population abundance could lead to inadequate attempts by management to stem the decline. Here, population trends along the west coast of South Africa are investigated. A simple discrete-time logistic model was used to estimate parameters within a maximum likelihood statistical framework by fitting to available catch rate data. To address the problem of unknown levels of illegal catch, interview data were collected on non-commercial catch trends and the model was structured to allow this catch to be estimated during the fitting process. The results show that such a participatory approach to stock assessment can lead to an improved understanding of resource dynamics, illustrating the benefit this approach may have for management. [ABSTRACT FROM AUTHOR]

Abstract: We evaluated the persistence and possible recovery of two depleted marine mollusks, the red (Haliotis rufescens) and black abalone (H. cracherodii), in central California, USA. Monitoring over 32-years did not reveal increasing or decreasing trends in red abalone abundances and sizes over the past three decades, in the absence of harvesting. Comparisons between marine reserves protected for at least 25 years and sites with open public access showed significant difference in size structure for black abalone, with individuals greater than 8 cm in shell length comprising 14–37% of animals in reserves and 2–11% at open-access sites, and a trend for greater abundances of red abalone within reserves. Despite no increasing trends, protection in one of the no-take reserves, the Hopkins marine life refuge (HMLR), has led to persistence of red abalone populations over multiple generations, at average densities of 0.2individuals/m2. At other locations, both within the HMLR and elsewhere, red abalone densities are lower than at the location where long-term studies were conducted (av. 0.03animals/m2), and an order of magnitude lower than for black abalone (av. 0.4 animals/m2). These results suggest that continued fishery closure and protection in no-take reserves are effective tools for allowing persistence of abalone populations, though there are no signs of recovery to levels comparable to those preceding fisheries collapse. Such failure to recover is most likely associated with high natural mortality and possibly continued illegal take, but not with processes underlying low abalone population levels elsewhere, including food or habitat limitation, recruitment failure, or disease. Linking current structure and trends to specific processes is a crucial first step towards devising focused strategies for conserving and re-building depleted marine populations. [Copyright &y& Elsevier]

Fishery policy formation is a multilateral political process that typically involves conflicting attitudes towards management, and opposing interests among resource users. As fisheries resources continue to decline, conflict between and within fishing sectors will grow. The challenge for fisheries policy makers is to ensure fisheries resources are evenly allocated among the stakeholders whilst managing resources in a sustainable manner. Australian fisheries management has been revolutionized by the introduction of Integrated Fisheries Management (IFM), which is based on a systematic approach involving the inclusion of all sectors in the management process. This approach means determining the total amount of fish that can be harvested from a fishery and then adopting management strategies for allocating explicit catch shares between the competing sectors. The recent increased burden on fisheries stocks, caused by higher recreational user participation, has forced policy makers to make large changes relating to the allocation of resources. Policy makers in Western Australia, aware of conflict developing between users of the abalone resource, developed a unique management system based on resource sharing. By integrating the recreational sector in the overall management process, the primary objective of the new agenda is to decrease conflict between competing users and develop a management system without partisanship. [ABSTRACT FROM AUTHOR]

Intertidal size-frequency distributions and densities for Haliotis midae and Turbo sarmaticus were examined at 10 sites experiencing varying pressure of human exploitation along the southern section of the Eastern Cape coast, South Africa. Target species' densities and maximum sizes were related both to the numbers of collectors on the shore and to indirect indicators of exploitation such as number of households in the vicinity and distance to the nearest beach access point. For both species, there was variation in density (P < 0.05) and size (P < 0.05) among sites, with densities ranging between 0.03-2.23 m-2 and 0.07-4.93 m-2 for H. midae and T. sarmaticus, respectively. Maximum sizes ranged between 49.4-153.5 mm (H. midae) and 28.3-104.4 mm (T. sarmaticus) shell length. Population parameters such as mean maximum size and total density were significantly negatively related to exploitation indicators for both species. In addition, densities of sexually mature and legal-size individuals of T sarmaticus were significantly negatively related to the number of households. However, only for H. midae were densities of sub-adults significantly negatively related to the number of collectors, suggesting that reproduction of abalone may be suppressed at the most exploited sites. Exploitation of T sarmaticus tends to be localized near population centres, whereas H. midae is collected over a larger range of sites. Overall, T. sarmaticus is less affected by exploitation than H. midae. [ABSTRACT FROM AUTHOR]

Haliotis midae (perlemoen) is the only southern African species of abalone to be commercially exploited. Commercial farms are currently producing 750 tons per annum, making this an economically viable enterprise. Increasing world demand and dwindling natural populations have, however, necessitated the adoption of genetic management practices on South African abalone farms to remain sustainable. This can be done by means of DNA markers, which are employed to investigate various phenomena from genetic diversity parentage and brood-stock contributions to linkage mapping and marker-assisted selection for genetic enhancement of the commercial species. The use of microsatellite markers for various abalone aquaculture applications is highlighted in this review. [ABSTRACT FROM AUTHOR]

Abstract: Compensatory density-dependent processes in fish stocks are critical for the sustainability of fisheries, yet the implications of different mechanisms of density dependence in populations are seldom considered. We examine a size-structured matrix model of an abalone population subject to compensatory density-dependent processes at various life-stages. Matrix elements governing transitions amongst seven length classes are derived from growth, fecundity and mortality data for abalone populations in Australia, employing a probabilistic Gompertz growth model that accurately represents tag-recapture data for these populations. The resulting transition matrix is then modified to take account of density-dependent fecundity, survival and growth processes at various life stages. Equilibrium states of these models are obtained in the absence of fishing. Hypothetical populations at these equilibria are then subjected to fishing pressure and their responses examined. We find that density-dependent fecundity, survival and growth are each sufficient to stabilize these populations under harvesting. Density-dependent fecundity and survival lead to altered population structures after short time delays, while density-dependent growth stabilizes populations over longer time scales. Some forms of density-dependent growth lead to a false recovery from the initial fishing impact, followed by a decline to a lower stable level. The varied response to fishing under different compensatory mechanisms implies that simple stock–recruitment models may not capture key aspects of the dynamics of fishery stocks, nor predict their response to fishing correctly. Since density-dependent growth has been demonstrated for many species, its implications for fisheries deserve further theoretical investigation. [Copyright &y& Elsevier]

Approximately 1–2% of the tropical abalone Haliotis asinina inhabiting Heron Island Reef are infected with opecoelid digeneans. These largely inhabit the haemocoel surrounding the cerebral ganglia and digestive gland–gonad complex, and infected abalone typically have significantly reduced or ablated gonads. Observations of infected abalone reveal two distinct cercarial emergence patterns, one which correlates tightly with the abalone’s highly regular and synchronous fortnightly spawning cycle, and the other which occurs in a circadian pattern. The former appears to be a novel emergence strategy not previously observed in digeneans. While the cercariae in all abalone are morphologically indistinguishable, comparison of sequences from the internal transcribed spacer 2 (ITS 2) region of the ribosomal DNA reveals a 5.7% difference between cercariae displaying different emergence patterns, indicating these are two distinct species that probably belong to the same genus. The ITS 2 sequences of the species with the daily emergence pattern are identical to that of an undescribed adult opecoelid from the gut of the barramundi cod, Cromileptes altivelis. Combined molecular, morphological and emergence data suggest that while these opecoelid cercariae use the same first intermediate host and are closely related species—members of the genus Allopodocotyle—they fill different ecological niches that are likely to include different definitive hosts. [ABSTRACT FROM AUTHOR]

This study documents the genetic population relationships between Ezo-awabi Haliotis discus hannai and Kuro-awabi H. discus discus by means of the microsatellite technique with an emphasis on the extent of genetic difference between Ezo- and Kuro-awabi populations. Eight markers were employed to screen five populations each collected from Ezo- and Kuro-awabi habitats. All eight loci showed polymorphisms in all populations (number of alleles per locus, 11.1–14.1; averaged expected heterozygosity, 0.64–0.70). The number of loci that yielded significant genetic heterogeneities (allele frequency distribution and/or pairwise θ) between Ezo- and Kuro-awabi populations was larger than that generated in comparisons between populations within Ezo- and Kuro-awabi habitats. According to the bootstrap neighbor-joining trees constructed on the basis of two genetic distance measures ( DA and DST), the 10 populations fell into two clusters of populations (Ezo-awabi and Kuro-awabi habitat groups), and the results of hierarchical amova testing also supported the neighbor-joining clustering. The outcomes presented here suggest that the microsatellite markers used in this study are potentially an efficient means to differentiate Ezo- and Kuro-awabi populations. [ABSTRACT FROM AUTHOR]

Discusses the facets of abalone biology for the sustainable management of fisheries. Details on the decline in global abalone production; Implications for the management of wild stocks of abalone; Accounts on the scale of functional units of abalone stocks.

Populations of abalone have precipitously declined in California over the past several decades, largely as a result of fishing pressure and disease. Because of these declines, farmed seed abalone have been planted in an attempt to research and restore dwindling populations. Withering syndrome is a chronic disease responsible for mass mortalities of wild black abalone, Haliotis cracherodii , in southern and central California and is caused by the bacterium "Candidatus Xenohaliotis californiensis". This bacterium has been observed in wild populations of black and red (Haliotis rufescens ) abalone south of Carmel and in farmed red abalone throughout the state. In an effort to elucidate the distribution and source of the bacterium in northern California, the presence or absence of the disease and bacterium was verified at 15 locations north of Carmel. This research revealed that both the bacterium and withering syndrome are present in abalone populations south of San Francisco. In addition, the bacterium (but not withering syndrome) is present at two locations in northern California, both associated with outplants of hatchery-reared abalone, suggesting a link between restoration efforts and the present distribution of this pathogen. These data highlight the need for careful assessment of animal health before restocking depleted populations. [ABSTRACT FROM AUTHOR]

A dynamic model that links biokinetics and consumer–resource dynamics for describing zinc (Zn) accumulation in abalone Haliotis diversicolor supertexta has been developed and then applied to Zn data from real abalone farms. The biokinetic parameters used in this study, uptake and depuration rate constants of abalone and their food source, red alga Gracilaria tenuistipitata var. liui, were obtained from a laboratory 14-d exposure experiment. We carried out a sensitivity analysis of the model by using the fractional factorial design technique, taking into account the influence of consumer–resource-related parameters such as growth and death rates and biomass and biokinetic parameters characterized by bioconcentration factor. Results indicate that the response time of biomagnification dynamics of Zn accumulation in abalone was influenced mainly by the growth rate of algae and biomass and the death rate of abalone and by interactions algae biomass and abalone death rate and abalone and algae biomass. New algae production results in substantially higher values of biomagnification factor. The linked model was then applied to field observations from a real-life situation of variable Zn concentrations occurring in abalone farms. Simulation results show that the predicted values are within a factor of 2 of the measured values (% errors range from 5.3±4% to 44.1±8%). Both model analysis and model application to the abalone farms suggest that the linking influences between biokinetics and consumer–resource dynamics support Zn accumulation in H. diversicolor supertexta and in G. tenuistipitata var. liui as functions of Zn concentration in water and abundance of food occurring in abalone farms. [Copyright &y& Elsevier]

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]