Thesis (MBA)--Stellenbosch University, 1998. / ENGLISH ABASTRACT: The techniques for animal reproduction and husbandry for both abalone and sea turtle farming have been well established and researched over the last decade. Although market related data seems to be scarce, marketing analysis reviewed and conducted as part of this study suggests that extensive markets exist for live cocktail size abalone and sea turtle products, especially in the East Asian countries. A decline in natural resources and increased demand resulted in a fast expanding niche market for these products. This study shows that development of an abalone farm in South Africa for the production of cocktail size (±80 mm; ±100 g) is a highly profitable venture. Economic feasibility analysis indicated that the development of an abalone farm capable of producing 150 tons annually should result in a rate of return in excess of 50% over a seven-year investment period. On the other hand, sea turtle farming is a less profitable investment with Green turtle farming yielding a return of approximately 25% and Hawksbill farming yielding a return closer to 30% over a seven-year investment period. According to the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), all sea turtle species have been listed as endangered or threatened. Currently all countries who are members of CITES are prohibited from international trade in sea turtles or sea turtle products. Prospective entrepreneurs wishing to establish a sea turtle farming venture have to adhere to stringent regulatory and control measures, a major obstacle in the development of a profitable enterprise. Both abalone and sea turtle farming have long payback periods, due to the slow growth-rates of the investigated species. In order to produce animals in a time frame that is economically viable, artificially formulated feeds have to be used. The usage of artificially formulated feeds proved to be a major expense, especially in the case of sea turtle farming. / AFRIKAANSE OPSOMMING: Die tegnieke vir die reproduksie, onderhoud en groei van beide perlemoen en seeskilpad akwakultuur boerderye is goed gevestig en nagevors oor die afgelope dekade. Alhoewel mark verwante data skaars is, dui bemarking analises aan dat 'n enorme mark bestaan vir lewendige "cocktail" grootte perlemoen en seeskilpadprodukte, veral in Oos Asie. 'n Afname in natuurlike hulpbronne en 'n toename in aanvraag, het 'n vinnige "nis" mark vir die produkte tot gevolg gehad. Die ontwikkeling van 'n perlemoen boerdery vir die produksie van "cocktail" grootte (±80 mm; ±100 g) perlemoen kom voor as 'n hoogs winsgewende onderneming. 'n Ekonomiese winsgewindheidsanalise het getoon dat die ontwikkeling van 'n perlemoenplaas, met 'n produksie van sowat 150 ton perlemoen jaarliks, 'n opbrengs van oor die 50% oor 'n sewe jaar investeringsperiode teweeg sal bring. Seeskilpad boerdery, aan die ander kant, kom as 'n minder winsgewende belegging voor, waar Groen seeskilpad boerdery 'n opbrengs van ongeveer 25% en Hawksbill boerdery 'n opbrengs van min of meer 30% oor 'n sewe jaar beleggings periode toon. Volgens CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) is alle seeskilpaaie gelys as bedreig. Alle lande wat huidiglik lede is van CITES, word van die reg voorbehou om internasionale handel te dryf in seeskilpaaie of seeskilpadprodulcte. Voorgenome entrepeneurs met die begeerte om 'n seeskilpadboerdery te begin, sal voor streng maatreels en beheer- maatstawwe te staan kom, wat 'n groot stuikelblok is in die ontwikkeling van 'n winsgewende seeskilpadplaas. Beide perlemoen- en seeskilpadboerderye het lang terugbetalingsperiodes, 'n waameming wat verduidelik kan word aan hand van die stadige groei-tempo's van die bestudeerde spesies. In orde om diere in 'n spesifieke tydsperiode te produseer wat ekonomies winsgewend is, moet daar van artifisieel geformuleerde voeding gebruik gemaak word. Die gebruik van geformuleerde voeding. is egter duur, veral in die geval van seeskilpadboerderye.

Thesis (Ph. D.)--University of California, Riverside, 1995. / Includes bibliographical references (leaves 342-367).

Marine ranching has been identified as an alternative to traditional aquacultural rearing and growing organisms for consumption. In the Eastern Cape, abalone ranching is a new and experimental industry. The aims of the research were to: first develop a GIS model to assist management in site selection for abalone seeding; and secondly to develop and standardize the sampling methodology in order to ground truth the sites, and assist in the monitoring and habitat identification of abalone. The GIS model developed in Chapter 3 was created using an unsupervised classification and fuzzy logic approach. Both vector and raster datasets were utilized to represent 7 different layers. Predominantly satellite imagery was used to classify the different substrate groups according to pixel colour signatures. The basic process was to apply a fuzzy rule set (membership) to rasters which gave an output raster (Fuzzification). The membership output rasters were overlaid which creates a single model output. It was found that model accuracy increased significantly as more layers were overlaid, due to the high variability within each of the individual layers. Model ground-truthing showed a strong and significant correlation (r2 = 0.91; p < 0.001) between the model outputs and actual site suitability based on in situ evaluation. Chapter 4 describes the investigation towards the optimal sampling methods for abalone ranching habitat assessments. Both destructive sampling methods and imagery methods were considered as methods of data collection. The study also evaluated whether quadrat and transects were going to be suitable methods to assess sites, and what size or length respectively they should be to collect the appropriate data. Transect length showed great variation according to the factor assessed. A transect of 15 metres was found to be optimal. Abalone counts showed no significant (p = 0.1) change in the Coefficent of Variance (CV) for transect lengths greater than 15m, and had a mean of 0.2 abalone per metre. Quadrat size showed a significant difference in functional group richness between quadrat sizes of 0.0625m2, and 0.25m2 but no difference between 0.25m2 and 1m2 quadrats for both scape and photographic quadrats. It was also found that between 5 and 10 replicates (p = 0.08) represents the functional groups appropriately using quadrats and that a 0.25m2 quadrat is most suitable for sampling. Chapter 5 describes the benthic community structure of Cape Recife shallow water reefs. Using the standardized methodology previously mentioned, 45 sites were assessed to identify the community structure. These sites were grouped into 5 different groups influenced by depth and substrate, as well as functional group composition according to a Wards classification. The community structure showed that depth and substrate play a significant role (p < 0.05) in the community type. There is also a significant relationship (p < 0.05) between complexity, rugosity, abalone presence and substrate. During this study the basic protocols for site selection and benthic community monitoring have been developed to support the abalone ranching initiative in the Cape Recife area. It has also provided a baseline of the benthic community in the ranching concession area which will be used as a benchmark for future monitoring efforts. The site selection, sampling, and monitoring methods developed during the course of this work have now been rolled out as Standard Operating Procedures for the ranching programme in this area.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Nearly all South African abalone farms function on an intensive pump-ashore, flow-through system. Large volumes of sea water that are pumped ashore flow through abalone or kelp harvesting tanks and finally gravitate back to the ocean. If the effluent from an abalone farm can be desalinated without permanent membrane fouling, then sea water reverse osmosis (SWRO) technology can be integrated effectively with established abalone farms without having to increase the farms’ intake system capacities. Without the need to construct and maintain an intake system, the overall cost of desalination can be reduced. Therefore, the aim of this study was to determine the feasibility and viability of integrating a SWRO desalination plant with a typical South African abalone farm. The project focused on four areas of concern, namely: - characterisation of typical South African abalone farm water - SWRO desalination plant pilot study and membrane fouling behaviour - general operation of a typical abalone farm and its implications for desalination - cost estimates and implications for the integration of an SWRO desalination plant with an abalone farm During a nine-month on-site investigation, sea water turbidity was reduced by up to 43% from a mean value of 0.82 NTU in the influent stream to 0.47 NTU in the combined effluent stream from the abalone tanks. Even with spikes in the influent turbidity, the turbidity of the combined effluent from all abalone tanks (excluding tank flush water) remained below 1 NTU. Dissolved organic carbon (DOC) in both the influent and combined effluent remained below 1 mg/litre. Ultrafiltration (UF) was selected as pre-treatment to the reverse osmosis (RO) in order to minimise potential fouling of the RO membranes. Membrane compaction of both the UF and RO membranes contributed significantly to initial flux losses – as much as 18% for the polyethersulfone (PESM) UF membranes and 20% for the thin film composite (TFC) polyamide RO membrane. However, this is comfortably in line with typical compaction values quoted in the literature. Without pre-flocculation, the UF was able to operate at a specific flux between 45 and 55 litre/m2/h (LMH) and recoveries ranging between 60 and 75%. Corresponding trans-membrane pressure (TMP) ranged between 0.59 and 0.76 bar. With ferric chloride pre-flocculation at a concentration of 3 mg/litre (as Fe3+) the UF could be operated at notably lower TMP values between 0.11 and 0.36 bar. These results indicate that provision should definitely be made for pre-flocculation when using UF as pre-treatment, despite the fact that the DOC concentrations and turbidity of the abalone farm effluent are quite low (DOC <1 mg/litre, NTU <1). It furthermore highlights the inability of DOC and turbidity alone to predict the membrane fouling potential of water. A better indicator of membrane fouling potential, albeit not perfect, is the modified fouling index (MFI0.45). This index follows a linear trend with foulant concentration and serves as a good indicator of the filterability of water. On-site measurements showed an increase in mean MFI0.45 values from 29 s/litre2 for the influent to 48 s/litre2 for the effluent from the abalone tanks, thereby confirming the need for pre-flocculation as part of UF pre-treatment. Chemically enhanced backwashing (CEB) of the UF membrane at least every 24 hours was found to be essential for its stable operation. Therefore, UF with pre-flocculation (3 mg/litre Fe3+) and regular CEB can be used effectively as pre-treatment method for the desalination of abalone farm effluent water. An RO ‘feed-and-bleed’ system was used to simulate the typical performance of the last membrane in a full-scale RO membrane bank. This RO membrane performed well with no signs of extreme fouling. The membrane produced a good quality permeate – for the last membrane in a membrane bank – reducing the TDS of the RO feed from 33 493 mg/litre to 969 mg/litre. These results compared well with simulated values by Reverse Osmosis System Analysis (ROSA; an RO simulator by DOW), indicating a TDS reduction from 33 271 mg/litre to 1 409 mg/litre at a feed pressure of 56 bar, and overall recovery of 44%. A steady performance of the RO membrane during the pilot study indicated that it is possible to desalinate abalone effluent water without notable permanent membrane fouling. A stable normalised flux rate of 8 LMH was achieved and RO membrane integrity remained intact with a salt rejection that ranged from 98.0 to 98.5%. No sudden reduction in permeate flux was observed as a result of fouling by unknown constituents present in the UF permeate. DBNPA (a non-oxidising disinfectant) was dosed once per week at a concentration of 10 – 30 mg/litre for 30 minutes. Scaling was controlled effectively by means of an antiscalant dosed at a concentration of 11 – 12 mg/litre in the feed stream. The CIP frequency was not optimised but a CIP frequency of once every 6 – 8 weeks appeared to be more than adequate to prevent permanent membrane fouling Advantages of integrating an SWRO desalination plant with a South African abalone farm include: - no lengthy and costly environmental impact assessment (EIA) is required to build a new intake system - shared capital and operational cost of intake system - dual incentive to keep constant good quality water flowing through the farm - early warnings regarding occurrences such as algal bloom and red bait - shared operational and management cost to keep pipelines clean - electricity saved (pumps for intake system) Disadvantages of integrating an SWRO desalination plant with a South African abalone farm include: - will require diverting of the abalone tank wash water from regular effluent - possible water ‘down-times’ due to maintenance operations on abalone farm Based on information from the literature the fixed capital cost depreciation rate (FCCDR) typically contributes approximately 40% and the operation and maintenance (O&M) cost typically contributes 60% to the unit production cost (UPC) of desalinated water. Furthermore, a SWRO desalination plant’s intake system can contribute between 5% and 33% to the FCCDR, depending on the nature and design of the plant. Consequently, the intake system can contribute between 2% and 13% of the UPC of desalinated sea water. This implies possible cost savings of between R0.15/m3 and R2.37/m3 for the production of fresh water (depending on site-specific design factors) when desalinating sea water effluent from on-shore abalone tanks. Integration of an SWRO desalination plant with a South African abalone farm is feasible and viable, provided that the necessary steps and precautions are taken to ensure a smooth and stable operation of the SWRO desalination plant. Cost savings on the part of all the stakeholders are possible if the correct contract can be negotiated. / AFRIKAANSE OPSOMMING: Byna alle Suid Afrikaanse perlemoenplase funksioneer op ‘n seewater deurvloeistelsel. Groot volumes seewater word aan wal gepomp en vloei deur die perlemoen of kelp-oes tenks. Hierdie water vloei dan uiteindelik terug na die oseaan as gevolg van swaartekrag. Indien die afvalwater van die perlemoenplase ontsout kan word sonder permanente membraanbevuiling kan seewater tru-osmose (SWTO)-tegnologie effektief met gevestigde perlemoenplase geïntegreer word sonder om die plase se water inname-stelsels se kapasiteite te vergroot. Sonder die behoefte aan uitbreiding en instandhouding van ‘n water inname-stelsel by so ‘n plaas behoort die totale koste van ontsouting aansienlik minder te wees. Die doel van hierdie studie was dus om die uitvoerbaarheid en lewensvatbaarheid van ‘n integrasie van ‘n SWTO ontsoutingsaanleg met ‘n tipiese Suid Afrikaanse perlemoenplaas te ondersoek. Ten einde dit te doen, het die projek op vier areas van belang gefokus, naamlik: - karakterisering van tipiese Suid-Afrikaanse perlemoenplaas water - SWTO ontsoutingsaanleg loodsstudie en membraan bevuilingsgedrag - algemene bedryf van ‘n tipiese perlemoenplaas en die implikasies vir ontsouting - kosteberamings en koste-implikasies met betrekking tot die integrasie van ‘n SWTO ontsoutingsaanleg met ‘n perlemoenplaas Gedurende ‘n nege maande op-perseel ondersoek is seewater troebelheid verminder met tot 43% van 'n gemiddelde waarde van 0.82 NTU in die invloeistroom tot 0.47 NTU in die gekombineerde afvalwaterstroom wat die tenks verlaat. Selfs met skerp wisseling in die invloeistroom troebelheid, bly afvalwaterstroom troebelheid deurgaans onder 1 NTU met die uitsondering van tenk spoelwater. Opgeloste organiese koolstof (OOK) in beide die invloeistroom en die gekombineerde afvalwaterstroom het deurgaans onder 1 mg/liter gebly. Ultrafiltrasie (UF) is gebruik as voorbehandeling vir die tru-osmose (TO) om sodoende potensiële bevuiling van TO membrane te minimaliseer. Membraan kompaksie van beide die UF en TO het merkbaar bygedra tot aanvanlike deurvloeiverliese – so veel as 18% vir die poli-etersulfoon (PESM) UF membrane en 20% vir die dun film saamgestelde (DFS) poli-amied TO membraan. Hierdie is egter gerieflik binne die tipiese kompaksiewaardes soos aangehaal in die literatuur. Sonder flokkulasie was die UF in staat tot temperatuur aangepaste deurvloeitempo van tussen 45 en 55 liter/m2/h (LMH) teen herwinningstempo’s tussen 60 en 75%. Ooreenstemmende trans-membraandrukkings (TMD) het gewissel tussen 0.59 en 0.76 bar. Met ysterchloried voor-flokkulasie teen 'n konsentrasie van 3 mg/liter (as Fe3+) kon die UF teen merkbaar laer TMD waardes bedryf word – tussen 0.11 en 0.36 bar. Hierdie resultate dui daarop dat daar beslis voorsiening vir pre-flokkulasie gemaak moet word wanneer UF as voorbehandeling gebruik word, ten spyte van die feit dat die OOK konsentrasie en troebelheid van die afvalwater van die perlemoenplaas redelik laag is (OOK <1 mg / liter, troebelheid <1 NTU). Verder lig dit die onvermoë uit om OOK en troebelheid alleen te gebruik om membraanbevuilingspotensiaal van water te voorspel. ‘n Beter aanwyser van membraanbevuilingspotensiaal, alhoewel nie perfek nie, is die aangepaste bevuilingsindeks (MFI0.45). Hierdie bevuilingsindeks volg ‘n lineêre neiging met die konsentrasie van onsuiwerhede en dien as ‘n goeie aanwyser van die filtreerbaarheid van water. Op-perseel metings het getoon dat ‘n toename in gemiddelde MFI0.45 waardes van 29 s/litre2 vir die invloeistroom tot 48 s/litre2 vir die afvalstroom van die perlemoentenks die behoefte vir voor-flokkulasie as deel van UF voorbehandeling bevestig. Chemies versterkte terugspoeling (CVT) van die UF membrane ten minste elke 24 uur is noodsaaklik gevind ten einde bestendige werking te verseker. Dus kan UF met voor-flokkulasie (3 mg/liter Fe3 +) en gereelde CVT effektief as voorbehandeling metode vir die ontsouting van perlemoenplaas afvalwater gebruik word. ‘n TO ‘voer-en-bloeistelsel’ is gebruik om die tipiese prestasie van die laaste membraan in ‘n volskaalse TO membraanbank te simuleer. Hierdie TO membraan het goed presteer sonder tekens van buitensporige membraanbevuiling. Vir die laaste membraan in ‘n membraanbank het die membraan goeie gehalte finale water gelewer – ‘n vermindering van die totaal opgeloste stowwe (TOS) van die TO voerwater van 33 493 mg/liter tot 969 mg/liter is behaal. Hierdie resultate het goed vergelyk met gesimuleerde waardes deur Reverse Osmosis Analysis System (ROSA, ‘n TO simulator deur DOW) wat ‘n TOS vermindering van 33 271 mg/liter tot 1 409 mg/liter by ‘n voerdruk van 56 bar en ‘n algehele herwinningstempo van 44% aandui. ‘n Bestendige werking van die TO membraan tydens die loodsstudie het getoon dat dit moontlik is om perlemoenplaas afvalwater te ontsout sonder merkwaardige permanente membraanbevuiling. 'n Stabiele genormaliseerde deurvloeitempo van 8 LMH is bereik en TO membraan integriteit het ongeskonde gebly met 'n sout verwerping wat gewissel het van 98.0 tot 98.5%. Geen skielike afname in finale water deurvloeitempo is waargeneem as gevolg van bevuiling deur onbekende onsuiwerhede in die UF finale water nie. DBNPA (‘n nie-oksiderende ontsmettingsmiddel) is een keer per week teen ‘n ‘n konsentrasie van 10 – 30 mg / liter vir 30 minute gedoseer. Mineraal skaalvorming is effektief beheer deur die dosering van ‘n anti-skaalmiddel teen 11 – 12 mg/liter in die TO voerstroom. Die skoonmaak-in-plek (SIP) frekwensie is nie ge-optimeer nie, maar ‘n SIP een keer elke 6 – 8 weke is meer as voldoende gevind om mikrobiese bevuiling te voorkom. Voordele van die integrasie van 'n SWTO ontsoutingsaanleg met 'n Suid-Afrikaanse perlemoenplaas sluit die volgende in: - geen lang en duur omgewings impak ontleding (OIO) is nodig vir die bou van ‘n nuwe inname-stelsel nie - gedeelde kapitaal en operasionele koste van inname-stelsel - tweeledige aansporing om konstant goeie gehalte watervloei deur die plaas te verseker - vroegtydige waarskuwings ten opsigte van gebeurtenisse soos rooigety - gedeelde bedryfs- en bestuurskoste om voerpype skoon te hou Nadele van die integrasie van 'n SWTO ontsoutingsaanleg met 'n Suid-Afrikaanse perlemoenplaas sluit die volgende in: - vereis herleiding van perlemoentenk spoelwater weg van gereelde afvalwater - moontlike watervloei-aftye weens instandhoudingsbedrywighede op die perlemoenplaas Gebaseer op inligting uit die literatuur dra die vaste kapitaal koste waardeverminderings-koers (VKKWK) gewoonlik ongeveer 40% en die bedryfs- en instandhoudingskoste (B&I) ongeveer 60% by tot die produksiekoste per eenheid (PKE) van ontsoute water.Verder kan ’n SWTO ontsoutingsaanleg se inname-stelsel tussen 5% en 33% tot die VKKWK bydra afhangende van die aard en ontwerp van die aanleg. Gevolglik kan die inname-stelsel tussen 2% en 13% tot die PKE van ontsoute seewater bydra. Dit impliseer ‘n moontlike kostebesparing van tussen R0.15/m3 en R2.37/m3 vir die produksie van vars water wanneer die afvalwater van perlemoentenks ontsout word. Integrasie van 'n SWTO ontsoutingsaanleg met 'n Suid-Afrikaanse perlemoenplaas is uitvoerbaar en lewensvatbaar indien die nodige stappe en voorsorgmaatreëls geneem is om ‘n vlot en bestendige werking van die SWTO ontsoutingsaanleg te verseker. Kostebesparings vir alle belanghebbendes (beleggers) is moontlik indien daar oor die korrekte kontrak onderhandel kan word.

The Roe’s abalone (Haliotis roei) fishery near Perth, Western Australia, is uniquely accessible, and highly vulnerable to overexploitation. The sustainability of this intensively utilized fishery requires robust assessment. To facilitate an assessment, this research aimed to provide rigorous and detailed biological information with appropriate interpretation. Four critical aspects of the species’ biology and population dynamics were investigated: (1) the stock structure; (2) the recreational catch; (3) an appropriate growth curve and description of size at age; and (4) abundance measures against which to assess the impact of fishing mortality. Allozyme electrophoresis was used to investigate stock structure across the species’ distribution. Standardized variance in allelic frequencies between 10 sites in south-western Australia indicated high levels of gene flow across the 3000 km sampled (mean FST = 0.009). An isolation-by-distance was evident when pairwise measures of GST were related to geographic distance (r=0.45, P<0.001). The area of complete genetic mixing was estimated from samples within the Perth fishery to be less than the distance between the two nearest sites, or 13 km. Consequently, the Perth fishery comprises numerous discrete stocks, each requiring independent assessment. A possible mechanism for this population structure is the retention of larvae in the wind driven currents oscillating in the near-shore lagoons, with rare pulses of long distance dispersal via the southerly Leeuwin current, running further offshore. The presumed impact of intensive recreational fishing, combined with substantial commercial quotas for the Perth fishery, had led to tight restrictions on fishing effort, without any quantitative measure of the recreational catch. A stratified creel survey was adapted to estimate the effort, catch rate and mean weight of abalone harvested by the recreational sector. Catches were estimated for reef complexes, or stocks, of less than 10 nautical miles (18.5 km) of coast. Between 1997 and 2000 the recreational catch varied from 30 to 45 tonnes whole weight, approximately equivalent to the commercial quota of 36 tonnes. On average 88% of the recreational catch came from two stocks, while 98% of the commercial catch came from these two, and one additional, stocks. The incidental mortality from recreational fishing, measured as the number of abalone left dead on the reef as a proportion of the estimated catch, was approximately 7% and 20% at two sites surveyed. Spatial and temporal patterns of growth were examined on the west coast of Western Australia. Growth increments were measured for abalone larger than about 30 mm from tagging studies at five sites in the Perth fishery, a site at the northern extent of the species’ distribution and a site in the southwest. Mean annual growth increments of the 0+ year class were obtained by fitting components to length frequencies from five sites in the Perth fishery, and combined with growth increments from each Perth tag site for model fitting. A von Bertalanffy growth curve provided a slightly better fit to the tag data, but a Gompertz growth curve was a much better fit when the mean increment from the 0+ to 1+ cohort was included, with the inflection occurring at about 40 mm, the size at sexual maturity. There was no difference in annual growth between the two years studied. There was significant variation in growth between the reef platform and adjacent sub-tidal reef, but this variation was site specific and faster growth rates were not consistently associated with either habitat. There was no latitudinal trend in growth rate. Growth at the Perth sites was the fastest and similar at all five sites with growth increments greater in summer than in winter. Size and abundance of abalone were measured using fixed transects and quadrats. Abalone densities were highest on the outer edge of the platform, intermediate in the middle of the reef platform, and lowest on both the inner platform and the sub-tidal reef. The pattern of mean lengths of abalone was the inverse of the density. Mean length and abundance were driven by the presence of post-settlement juveniles on the outer and middle reef habitats. There was a high spatial variation in abundance, with densities varying between transects at the same site, but the trend between years for each transect at a site was not significantly different. Abalone abundances, by size class, were examined from sites sampled between 1996 and 2002. A low density of post-settlement juveniles at all sites in 1997 was reflected in low densities of the 1+ and 2+ year classes in subsequent years. Abalone abundances at an unfished site were steady over the seven years. Two sites were located within each of the main stocks utilised by the recreational fishery. Abundance was stable or increasing in one stock, corresponding to a stable total catch. In the second stock the total catch increased over time and abundances declined. Perth is the focus of the Roe’s abalone fishery, with recreational and commercial fishers take about equal shares of the annual catch. Stocks are highly subdivided, with most of this catch coming from only 3 stocks occupying about 20 nautical miles of coast. Growth rates were found to be lower than previous estimates, and more similar to other commercial species of abalone. All life history stages are highly habitat specific, particularly the recruits, and the distribution and abundance through time indicate that the main stocks are near, or slightly over, the limit of sustainable fishing.