Marine reserves have increasingly been recognised for their potential to address the pervasive problem of unsustainable harvest of fisheries worldwide. Biologists advocate the benefits of increased spawning biomass, larger modal sizes and greater densities of fish within marine reserves, and the possibility of spillover to adjacent fishable areas. Bioeconomic studies, however, find that pay-offs from stand-alone marine reserves rarely compete with sustainable yield management schemes, but that they can be beneficial when stocks are heavily exploited. Most of these bioeconomic models are analytical and deterministic in nature, and therefore ignore the redistribution of effort in response to closure and the inherent uncertainty of the marine environment. We present a bioeconomic analysis of a network of no-take areas around Stewart Island in New Zealand applied to the shellfish species paua (abalone) that incorporates both predicted redistribution and reduction in effort, as well as stochastic recruitment. A nested logit model is applied to spatially recorded catch and effort data by the Ministry of Fisheries between 1998 and 2003 to capture the two level decision-making process of divers. On any given day, divers decide whether to go diving at all, and if so, which of the 16 statistical areas around Stewart Island to visit. Weather conditions, spatially varying levels of catch per unit of effort and distance are used as explanatory variables to select areas for closure according to the �least economic impact� in terms of loss of diving trips. An age-structured biological model is developed with parameters specifically applied to paua stocks around Stewart Island. Virgin paua biomass as of 1974 is estimated on the basis of growth, survival, post-larval recruitment and egg production in the absence of fishing. Historic catch rates are then applied to find overall and area-specific levels of exploitation rates, spawning biomass, egg production, legal biomass and numbers of paua. In a final step, the economic model is linked to the biological model to simulate the imposition of no-take areas when taking account of the initial disproportional shift of harvest to fished areas in the first year, and the increase in overall pressure on legal biomass in the years thereafter. We contribute to the marine reserve debate by showing that in the very long run, the overall yield under closure of a relatively small area approaches and even slightly surpasses the yield under no closure for an assumed spillover gradient of 40% despite the redistribution of effort. The most important benefits of marine reserves emerge when stochastic recruitment is included in the recruitment function. In practice, predictions about the stock status and the impact of different harvest levels become much more difficult when acknowledging the inherent variability of the marine environment. The likelihood of stock collapse depends on the assumed value of two recruitment parameters, which highlights the effects of parameter uncertainty and emphasizes the role of marine reserves for population persistence. We also show that under uncertainty average yields under a management regime of a network of no-take areas in addition to the quota system can equal yields under no closure for an assumed spillover gradient of 40%, despite the increased pressure on areas adjacent to the closed areas. Our findings have significant implications for the management of the paua fishery at Stewart Island. For a heterogeneously abundant species, such as paua, spatial management in addition to quota limits could be vital in ensuring the long-term sustainability of the fishery given the inherent variability of the marine environment.

<p>The primary aim of the current study falls within the main framework of the Frontier Program (Pitcher 2005), namely to address aspects of &ldquo / Animal Husbandry&rdquo / . Within this research area, the determination of the effects of handling/grading and chemicals (anaesthetics) on the growth and survivorship of abalone are highlighted as key research areas and these are thus one of the focuses of this research.</p>

<p>The primary aim of the current study falls within the main framework of the Frontier Program (Pitcher 2005), namely to address aspects of &ldquo / Animal Husbandry&rdquo / . Within this research area, the determination of the effects of handling/grading and chemicals (anaesthetics) on the growth and survivorship of abalone are highlighted as key research areas and these are thus one of the focuses of this research.</p>

Abalone (Haliotis spp.) are marine broadcast spawners that inhabit temperate and tropical waters across the globe. Their importance as a fisheries resource has resulted in considerable research into key aspects of their biology, particularly around growth and reproduction. In addition, there has been ongoing interest regarding the genetic variation in both wild and hatchery populations. The majority of abalone dispersal probably occurs during a pelagic lecithotrophic larval stage. In general, oceanographic features, life history characteristics, and larval dispersal ability can manipulate dispersal and gene flow patterns of marine fauna. In the case of abalone, considerable research has examined the population genetic structure of a variety of species, and several papers implicate ocean currents and life history characteristics as important factors that define population genetic structure. In comparison to other abalone species, little information regarding the genetic structure of New Zealand's endemic H. iris exists. The goal of this thesis was to elucidate the genetic structure of H. iris using mitochondrial and nuclear markers in regards to two potential barriers to gene flow, the Cook Strait region and the gamete recognition protein, lysin. The genetic structure of H. iris was first examined in regards to a consistent pattern of genetic structure emerging in recent literature of coastal marine invertebrates around New Zealand: specifically, a north-south genetic split that occurs in the Cook Strait region (Chapter 2). Two regions of the mitochondria (totaling 1055 bp) were amplified across 477 individuals from 25 locations around New Zealand. A north-south split around the Cook Strait region was evident among H. iris samples. Unlike the other studies of New Zealand coastal marine invertebrates, the north-south split for H. iris was not located across regions of reported upwelling; instead the split was located across Cook Strait narrows. The north-south split was reflected in increased haplotype diversity for the northern samples. Genetic structure was also examined using microsatellite loci. After unsuccessful attempts at cross-species amplification using 8 loci developed for H. rubra and 11 loci developed for H. midae, 13 polymorphic loci were isolated de novo for H. iris (Chapter 3). Of these, three very polymorphic loci were optimized for population genetic analyses. These three loci were used to genotype 447–459 individuals from the same 25 locations examined with mitochondrial DNA (Chapter 4). Like the mitochondrial DNA, the microsattelites indicated population genetic structure around the Cook Strait region; however the split identified with microsatellites occurred in the greater Cook Strait region with two sample sites from the north of the South Island grouping with the North Island. Extrinsic barriers, like the Cook Strait region, are the primary focus of studies examining differentiation in marine invertebrate fauna. However, dispersal of an individual to a new population does not necessarily mean it can successfully reproduce with individuals of the new population. Potentially, populations may be diverging at genes essential for reproduction, i.e. gamete recognition proteins. The abalone egg recognition protein, lysin, is one of the best characterized gamete recognition proteins in marine broadcast spawners. Despite its well-understood function and structure, studies examining variation in lysin have been limited to small sample sizes (N ≤ 11) and have found very little variation. Here, lysin was screened across 287 individuals from 17 sampling sites around New Zealand to assess intraspecific variation and genetic structure across the Cook Strait region (Chapter 5). The majority of the variation in a 783 bp fragment spanning from exon 4 to 5, was located in the intron. The variability in this fragment detected no genetic structure among samples or across the Cook Strait region. The variation in lysin was considerably lower than the variation in either the mitochondrial DNA or the microsatellite loci. To determine whether this was an artifact of being a nuclear sequence, which, in general, have a lower mutation rates than microsatellite markers and mitochondrial DNA and a larger effective population size then mitochondrial DNA, or was a signature of a recent selective sweep, 857 bp of the Gα1 intron was assessed for genetic variation in 227 H. iris individuals from 14 sampling locations (Chapter 6). The Gα1 intron was considerably more diverse than the lysin fragment examined, suggesting that the relative lack of variation in the lysin fragment has resulted from a recent selective sweep. Additionally, the Gα1 intron was used to examine population genetic structure across the Cook Strait region and detected a weak but significant pattern of structure consistent with that detected using the microsatellite loci. Overall, the a priori tests of genetic structure based on mitochondrial DNA, microsatellite markers, and the across Gα1 intron all identified a north-south genetic split around the Cook Strait region; however, the patterns of this split was slightly inconsistent among molecular markers. When cluster analyses were applied the patterns of genetic structure became more similar: for the mitochondrial, microsatellite, and Gα1 intron data, cluster analyses indicate that only one sample from the north of the South Island groups with the North Island, while a few discrepancies existed in regards the grouping of samples from the east coast of the North Island.

Marine reserves have increasingly been recognised for their potential to address the pervasive problem of unsustainable harvest of fisheries worldwide. Biologists advocate the benefits of increased spawning biomass, larger modal sizes and greater densities of fish within marine reserves, and the possibility of spillover to adjacent fishable areas. Bioeconomic studies, however, find that pay-offs from stand-alone marine reserves rarely compete with sustainable yield management schemes, but that they can be beneficial when stocks are heavily exploited. Most of these bioeconomic models are analytical and deterministic in nature, and therefore ignore the redistribution of effort in response to closure and the inherent uncertainty of the marine environment. We present a bioeconomic analysis of a network of no-take areas around Stewart Island in New Zealand applied to the shellfish species paua (abalone) that incorporates both predicted redistribution and reduction in effort, as well as stochastic recruitment. A nested logit model is applied to spatially recorded catch and effort data by the Ministry of Fisheries between 1998 and 2003 to capture the two level decision-making process of divers. On any given day, divers decide whether to go diving at all, and if so, which of the 16 statistical areas around Stewart Island to visit. Weather conditions, spatially varying levels of catch per unit of effort and distance are used as explanatory variables to select areas for closure according to the �least economic impact� in terms of loss of diving trips. An age-structured biological model is developed with parameters specifically applied to paua stocks around Stewart Island. Virgin paua biomass as of 1974 is estimated on the basis of growth, survival, post-larval recruitment and egg production in the absence of fishing. Historic catch rates are then applied to find overall and area-specific levels of exploitation rates, spawning biomass, egg production, legal biomass and numbers of paua. In a final step, the economic model is linked to the biological model to simulate the imposition of no-take areas when taking account of the initial disproportional shift of harvest to fished areas in the first year, and the increase in overall pressure on legal biomass in the years thereafter. We contribute to the marine reserve debate by showing that in the very long run, the overall yield under closure of a relatively small area approaches and even slightly surpasses the yield under no closure for an assumed spillover gradient of 40% despite the redistribution of effort. The most important benefits of marine reserves emerge when stochastic recruitment is included in the recruitment function. In practice, predictions about the stock status and the impact of different harvest levels become much more difficult when acknowledging the inherent variability of the marine environment. The likelihood of stock collapse depends on the assumed value of two recruitment parameters, which highlights the effects of parameter uncertainty and emphasizes the role of marine reserves for population persistence. We also show that under uncertainty average yields under a management regime of a network of no-take areas in addition to the quota system can equal yields under no closure for an assumed spillover gradient of 40%, despite the increased pressure on areas adjacent to the closed areas. Our findings have significant implications for the management of the paua fishery at Stewart Island. For a heterogeneously abundant species, such as paua, spatial management in addition to quota limits could be vital in ensuring the long-term sustainability of the fishery given the inherent variability of the marine environment.

Magister Scientiae - MSc (Biodiversity and Conservation Biology) / South Africa

Inadequate information of the nutritive physiology and the dietary requirements of abalone are the principle factors that currently limit the development of a formulated feed for the commercial culture of Haliotis midae. The need to develop a method to determine apparent digestibility co-efficient's for abalone in order to facilitate further applied nutritional research was identified. Animals between 50 and 80 mm were collected from natural stocks along the east Cape coast of South Africa at Port Alfred and Great Fish point, and acclimated to laboratory conditions. Initial trials demonstrated that H. midae accepted and preferred a semi-purified diet to the seaweed Plocamium corallorhiza, one of the main components of it's natural diet. A technique of determining apparent digestibility co-efficient's (ADC) using the indirect method with chromic oxide as an inert marker was developed. Digestibility trials yielded higher dry matter (DMADC) and crude protein apparent digestibility co-efficient's (CPADC) for the semi-purified diet than for two species of algae, Gelidium amanzii and P. corallorhiza (83.7% and 95.6%, 70.7% and 80.0%, and 29.9% and 57.3% respectively). The ability of the animals to utilize terrestrial animal and plant ingredients efficiently makes it feasible to use conventional feed ingredients in formulated feeds for H. midae. Trials to determine the effect of different temperatures (15°C, 18°C and 22°C) on DMADC and CPADC of the semipurified diet showed that peak digestibility occurred at 18°C. There was also a positive relationship between temperature and consumption rate. Although no enzyme studies with H. midae have been conducted, the peak ADC's at 18°C is attributed to an increase in enzyme activity at this temperature. Transit time, an inverse function of temperature and consumption, is considered to be responsible for the decrease in the ADC' s at 22°C in conjunction with a possible decrease in enzyme activity at this temperature. A photoperiod trial to investigate the effect of darkness on DMADC and CPADC of the semi-purified diet revealed that digestive efficiency decreased with increasing hours of darkness. There was also a positive relationship between duration of darkness and the rate of consumption. The decrease in ADC's is attributed to decreased transit times as the duration of darkness increased . The contribution of this project to the understanding of abalone nutrition, the development of a formulated abalone feed and systems design for abalone farms is discussed.

In the late 1980's abalone culturalists noticed reduced growth rate and shell deformities in some abalone stocks. These problems were the result of infestations by a shell boring polychaete, Terebrasabella heterouncinata. Under intensive abalone culture conditions the level of infestation can reach epidemic proportions and there are often severe consequences for the host abalone. Heavy sabellid infestation levels have placed the economic viability of several South African farms under threat. This study formed part of an ongoing project that is aimed at investigating the basic biology of Terebrasabella heterouncinata. The majority of abalone farmers in South Africa feed their abalone either naturally occurring kelp (Ecklonia maxima) or the formulated abalone feed, Abfeed. Farmers have suggested that the use of Abfeed is associated with higher sabellid infestation levels and changing the abalone diet from Abfeed to kelp helps reduce sabellid infestation. Speculation has arisen indicating that older, slower growing abalone are more susceptible to sabellid infestation. The effect of host abalone diet history and their growth on sabellid settlement success, morphometries and reproduction was quantified. To better understand the plasticity of the expression of life history traits the variability of morphometric and reproductive characteristics was compared between different farm environments. And more...

Global growth in aquaculture, referred to as the blue revolution, is seen by many to be the solution to future food scarcity. However, this growth has been accompanied by disease emergence. Disease emergence is inevitable when host populations are concentrated and densities exceed the threshold value for occurrence of outbreaks. Abalone farming is a relatively recent development and diseases of abalone are not well characterised. There have been relatively few systematic surveys of abalone diseases in the world. Much of the available information resulted from investigations of specific disease outbreaks, such as withering syndrome in California. The outstanding example of a formal survey of abalone health was conducted in Australia. A methodical survey of abalone health, encompassing all farms and including wild abalone, has never been done in South Africa. However, South Africa has for many years had a herd health program for abalone producers and this has generated the largest body of data on abalone disease occurrence in the world. Although these data have some shortcomings, it was felt that analysis could provide insights into the epidemiology of parasites in farmed Haliotis midae, as well as informing better surveillance techniques for the future. Data for abalone submitted from nine farms as part of the herd health management program during the period 1 January 2000 to 31 December 2004 were analysed. No wild abalone were included in these data and the only abalone species considered was the South African abalone or perlemoen, Haliotis midae. Data on the age of the abalone and their diet were obtained from the farms. The abalone originated from either flow through or recirculation systems. Each animal was weighed and measured at the laboratory. A standard set of tissue sections was fixed and processed for histology. Presence of parasites was recorded, as well as the sex and degree of gonad development. Once data had been captured in Excel, a series of tables was constructed from counts of infected and non infected abalone for all host and environmental factors contained in the data set. Charts of the tables were drawn. Where host and environmental factors appeared to interact, these data were also tabulated and charted. Statistical analyses of the data in Excel followed. All analyses were performed for sessile ciliates, renal coccidia, gut protozoa, digestive gland PAGE 2 OF 137 protozoa and rickettsia like prokaryotes. The rarity of trematode infections made meaningful analyses difficult. The chi square test, effect sizes and odds ratios were used to seek significant associations. When confounding and interaction were suspected, stratum specific odds ratios were calculated. The summary odds ratio used in this study was the Mantel Haenszel summary odds ratio. The Breslow Day test for interaction was performed when necessary. Confidence intervals were determined using the method of Woolf. The overall prevalence of the various parasites was very variable. Sessile ciliates were the most common, with a prevalence of 68.3%. Rickettsia like prokaryotes were found in 13.1% of animals. The other gut associated parasites were more scarce, with prevalences under five percent. Renal coccidia affected less than two percent of animals. Trematode infections were extremely rare, at a prevalence of 0.05%. The results of the chi square test showed a significant association between age and parasite prevalence for all parasites tested. Odds ratios were calculated comparing animals of 24 months and younger to those older than 24 months. In all cases, except trematode and left kidney coccidian infections, risk of parasite infection tended to increase with increasing age. For left kidney coccidian infections, risk of infection decreased with increasing age. Trends for body mass were similar to those for age, which is expected, as animals generally become larger with increasing age. A significant association between growth rate and parasite prevalence existed for some parasites. The chi square test showed a significant association between condition index and parasite prevalence for all parasites tested. A significant association between sex and parasite prevalence was found for all parasites tested. A significant association also existed between parasite prevalence and gonad development for sessile ciliates, renal coccidia and gut protozoa. There were significant differences in parasite prevalences between farms for all parasites tested. The South and West coasts were next compared using the chi square test. There were significant differences in parasite prevalences between coasts for only three of the parasites tested, namely renal coccidia, gut protozoa and rickettsia. Crude odds ratios showed that, with the exception of left kidney coccidia and trematodes, there was a greater risk of parasite infection on the West than the South coast. For left kidney coccidia, the risk was greater on the PAGE 3 OF 137 South coast. A chi square test was performed to examine the relationship between parasite prevalence in Hermanus and other areas. A significant difference was found for renal coccidia and gut associated parasites. The crude odds ratios for parasite prevalence in other areas compared to Hermanus were calculated. With the exception of sessile ciliates and trematodes, there was a greater risk of parasite infection in areas other than Hermanus. In the case of sessile ciliates, there was a greater risk within Hermanus than in other areas. Unfortunately, it was almost impossible to determine whether a seasonal effect exists for parasite prevalence from the available data. This was shown to be partly due to the effect of prevalence on individual farms. Significant differences in parasite prevalences between diets for all parasites tested were shown using the chi square test. To further test the strength of the association, odds ratios were calculated comparing only kelp and artificial feed. For right kidney coccidia and gut associated parasites, the odds ratios indicated a significantly increased risk of infection in animals receiving kelp compared to those on artificial feed. There was no difference in risk for sessile ciliates and left kidney coccidia. The majority of animals originated in flow through systems. The chi square test showed significant differences in parasite prevalences between systems for sessile ciliates, renal coccidia and rickettsia like prokaryotes. Odds ratios showed a significantly greater risk of sessile ciliate infections, but a smaller risk of left kidney coccidia, in animals in flow through systems when comparing only kelp fed animals. Age is likely to lead to increased prevalences if the risk of infection is constant over time and also if infections are retained. Physiological changes in the animals may also affect their risk of infection. A further important aspect of age in abalone relates to changes in husbandry. Increasing age may be the underlying reason for some of the prevalence patterns seen with mass and sex. The origin of the sample population was considered in terms of farm of origin as well as geographic area. Abalone production in the study area was highly concentrated, with approximately two thirds coming from six farms situated within ten kilometres of each another on the South coast and almost forty percent from Hermanus alone. The present study found no PAGE 4 OF 137 evidence of increased parasite prevalence in areas where abalone farming is concentrated. It was felt that this study could not generate much insight into seasonal occurrence, due to uneven distribution of variables between months. The relationship between diet and parasite prevalence was perhaps the most interesting aspect of this study and possible reasons for the association are explored. Lastly, the results indicated that parasite buildup in recirculation systems was not as problematical as may be expected. It is possible that the increased prevalence of left kidney coccidia in recirculation systems is linked to the resistance of the host population rather than to the dynamics of the actual system. The very low prevalence of sessile ciliates in recirculation systems could not be explained by examination of any other variable considered in this study. Overall, the prevalences of soft tissue parasites in Haliotis midae compared favourably with those found for parasites of other abalone species abroad. Measures which would tend to reduce parasite prevalence include separation of age groups and maintaining a relatively young population on the farm. Culling of underperforming animals is recommended. Kelp should not be used in animals of two years or younger. In older animals, there was still a greater risk associated with kelp than with artificial feed, but it was not as marked. Recirculation systems proved to be less associated with increased parasite prevalence than one may expect. The other major findings of this study did not lend themselves to practical application. / Dissertation (MSc)--University of Pretoria, 2010. / Production Animal Studies / unrestricted

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The decline of Haliotis midae (perlemoen) populations together with the ensuing collapse of commercial abalone fisheries in South Africa have shifted the responsibility to abalone farms to meet the demand for perlemoen. Attention has recently turned to the genetic enhancement of cultured abalone in order for the farms to remain competitive in the international aquaculture market. To develop a successful breeding programme it is imperative to draw on a good foundation of high levels of genetic diversity and to successfully maintain these levels in order to create an enhanced strain of cultured abalone. A Performance Recording Scheme (PRS) was established as the first breeding programme for Haliotis midae to utilise molecular tools. This programme was aimed at enhancing the growth rate of abalone in order to shorten the production times on farms. The current study made use of 12 species-specific microsatellite markers to assign parentage to a group of faster-growing PRS animals, as selected by the abalone farms, in order to select a diverse on-farm generation of broodstock. Additionally, the influence of standard selection practises on the genetic diversity of a population compared to genotypic selection was investigated. This data was also used to study the differentiation and levels of genetic diversities within and between cultured and wild populations. Selection based on genotypic traits successfully retained genetic diversity while some diversity was lost in phenotypically selected populations. These phenotypic populations differed significantly from each other and wild populations, while the genotypic populations were similar in genetic composition to each other and wild populations of the West coast. The broodstock populations used in the PRS spawning event were representative of the wild populations from where they were sourced, with no significant differentiation between the broodstock and West coast population. When these broodstock populations were compared to their corresponding offspring populations, only two populations displayed a significant loss in diversity; although all of the offspring populations showed significant differentiation with their corresponding broodstock populations. This was attributed to the differential contribution of broodstock and the effect of artificial selection. It was established that the cultured populations of the participating abalone farms should be used with caution in ranching and reseeding programmes. These populations differed significantly from both the East and West coast wild populations. This study concluded that it is possible to retain genetic diversity by selecting breeding animals based on genotypic traits. The loss of diversity in some cultured populations and significant differentiation from the wild populations indicate that animals are exposed to different selection pressures in the cultured environment. The results found in this study highlight the need for the effective management of hatchery practices and the genetic monitoring of the breeding animals. / AFRIKAANSE OPSOMMING: Die afname in Haliotis midae (perlemoen) populasies en die daaropvolgende ineenstorting van die kommersiële perlemoen bedryf in Suid-Afrika het die verantwoordelikheid om in die aanvraag na perlemoen te voorsien, na perlemoen plase verskuif. Die genetiese verbetering van verboude perlemoen geniet tans aandag in ‘n poging om kompeterend te bly in die internasionale mark. Dit is noodsaaklik vir die sukses van ‘n broeiprogram om gebruik te maak van ‘n goeie genetiese basis met hoë vlakke van genetiese diversiteit en die suksesvolle behoud van die vlakke om so ‘n verbeterde lyn te skep. ‘n Groeiprestasie aanteken stelsel [Performance Recording Scheme (PRS)] is gestig as die eerste broeiprogram vir Haliotis midae wat gebruik maak van molekulêre tegnieke. Die doel van hierdie program was om die groeitempo van verboude perlemoen te verbeter om produksie tye te verkort. Die huidige studie het gebruik gemaak van 12 spesie-spesifieke mikrosatelliet merkers om ouerskap toe te ken aan ‘n groep vinnig-groeiende PRS-diere, soos geselekteer deur die perlemoen plase, om ‘n diverse generasie gekultiveerde diere te selekteer wat as broeidiere kan dien. Die invloed van standaard seleksie metodes op die genetiese diversitiet van ‘n populasie in vergelyking met genotipiese seleksie is ook ondersoek. Die ouerskap data is ook gebruik om differensiasie en vlakke van genetiese diversiteit tussen verboude perlemoene en wilde populasies vas te stel. Seleksie gebasseer op genetiese eienskappe het daarin geslaag om genetiese diversiteit te behou, terwyl diversiteit verlore gegaan het in die fenotipies geselekteerde populasies. Hierdie fenotipiese populasies het ook beduidend met mekaar sowel as met die wilde populasies verskil, terwyl genotipiese populasies soortgelyk was in hul genetiese samestelling en nie van die wilde populasies van die Weskus verskil het nie. Die broeidiere wat in die PRS broeiprogram gebruik is, was verteenwoordigend van die wilde populasies vanwaar hulle oorspronlik gekom het, met geen beduidende differensiasie tussen die broeidiere en die Wes kus populasies nie. Met die vergelyking van die broeidiere en hul ooreenstemmende nageslag, het dit geblyk dat slegs twee populasies ‘n beduidende verlies aan genetiese diversiteit getoon het, alhoewel al die nageslag beduidende populasie differensiasie met hul ouers getoon het. Hierdie bevindinge is toegeskryf aan oneweredige bydraes van die broeidiere tydens gameetvrystelling en die invloed van kunsmatige seleksie. Hierdie studie het ook vasgestel dat die verboude perlemoen populasies met sorg gebruik moet word om wilde populasies te herstel, aangesien hierdie populasies beduidend verskil het van wilde populasies van beide die Oos en Wes-kus. Hierdie studie het gevind dat dit moontlik is om genetiese diversiteit te behou deur diere te selekteer op grond van genotipiese eienskappe. Die verlies van diversiteit in sommige van die verboude perlemoen populasies en die beduidende verskil met die wilde populasies dui daarop dat diere in die gekultiveerde omgewing blootgestel word aan verskillende tipes seleksiedruk. Hierdie bevindinge beklemtoon die belang vir effektiewe bestuur van broeiery praktyke en genetiese monitering van broeidiere.