Feeding trials were conducted to compare the nutritional requirements of juvenile marron (Cherax tenuimanus) under four different cultural environments. The rearing environments included aquaria under controlled laboratory conditions, cages in purpose-built commercial ponds, purpose-built earthen ponds and battery culture called the intensive crayfish culture system (ICCS).High levels of dietary cod liver oil in the semi-purified diet depressed the specific growth rates of juvenile marron under laboratory conditions. The dietary lipid levels were reflected in the lipid levels of the hepatopancreas of the marron. Dietary fatty acid profiles were also reflected in the fatty acid profiles of the hepatopancreas and subsequently in the tail muscles. Under cage environment in a purpose-built pond, dietary supplementation with cod liver oil (4%) plus sunflower oil (4%) increased the total biomass of juvenile marron. The specific growth rate under these condition had a strong positive correlation with all condition indices measured in the study (dry and wet hepatosomatic indices, dry and wet tail muscles to body weight ratio and moisture content of the hepatopancreas and tail muscles). The lack of protein in formulated practical diets, under commercial farm conditions, did not significantly influence the specific growth of juvenile marron but a diet containing fish protein source and fish oil resulted in a significantly higher survival. Feeding a diet containing fish protein and fish oil resulted in significantly higher wet tail muscles to body weight ratio than was observed with other diets. The inclusion of plant protein in formulated diets had an impact on the pond environment due to significantly higher ammonia levels that resulted in lower survival. Juvenile marron fed with a protein free diet and those fed with a plant protein diet had significantly lower protein ++ / levels in their hepatopancreas compared to those fed with diets containing animal protein. Juvenile marron in the battery culture environment tolerated long periods of starvation, utilising energy sources from the hepatopancreas and then from the tail muscles.Results from one rearing environment could not be directly transferred to another rearing environment. Environmental variables, particularly temperature, nitrogen metabolites and natural productivity of the ecosystem greatly influenced the nutritional requirements of the juvenile marron under culture. Ambient temperature and nitrogen metabolites may exert stronger control on the productivity, and thus profitability, of the commercial marron farms than the inclusion of micronutrients in the formulated diet.Specific growth rates, biomass, and wet and dry tail muscles to body weight ratios can be used as indicators of nutritional effectiveness of the diet. Further research is required to identify the interaction between the natural productivity of the ecosystem and the need to incorporate essential nutrients in formulated diets for the optimization of the marron production under commercial environment.

No description available.

Ce mémoire se concentre sur la fuite d’esclaves à la Nouvelle-Orléans entre 1816 et 1827. Plus de mille annonces de fuite des journaux Le Courrier de la Louisiane et La Gazette de la Louisiane sont analysées dans le but de mieux comprendre les diverses stratégies de résistance des esclaves louisianais à travers leur marronnage. En dépit des règlements qui sont censés contrôler les esclaves, comment parviennent-ils à s’enfuir? Comment parviennent-ils à s’octroyer une certaine liberté? Plusieurs lieux de fuite se dessinent à la Nouvelle-Orléans. Les bayous, les cyprières, les maisons de jeux, les marchés de viande à la levée sont tous des endroits susceptibles, parmi d’autres, de cacher des marrons. La journée du dimanche passée à la Place Congo reflète aussi une autre réalité des résistances. À cet endroit, esclaves et libres interagissent entre eux au su et au vu de tous. Des amitiés se tissent et l’entraide se développe de part et d’autre de la barrière raciale. Les nombreuses lois ne suffisent pas à contrôler adéquatement les gestes des esclaves. En dépit des contrôles, ils réussissent à se forger des micro-espaces de liberté dans une nouvelle géographie des résistances. Qui sont ces esclaves fugitifs ? Le profil type d’un esclave marron est un jeune homme d’environ 26 ans qui fuit seul. Par contre, mon mémoire démontre qu’il n’y a pas qu’un seul profil d’esclave fugitif. Enfants, femmes enceintes et personnes âgées peuvent décider de fuir. Quels sont les divers moyens utilisés pour réussir sa fuite? Ce mémoire tentera de répondre à tous ces questionnements.

Aquatic polyculture has been recognised as a potential way of increasing the costeffectiveness of farming marron (Cherax tenuimanus), as it can lower average costs of production, increase system yields, and reduce economic risks associated with monoculture operations. Polyculture also increases ecological stability and assists recycling processes, which can result in synergistic benefits to participating species. In aquaculture, this synergism can result in increased profitability through advanced growth rates and/or reduced feed input. However, many of the inherent advantages of aquatic polyculture rely on cohabitants occupying distinct ecological niches within the system. In Western Australia, opportunities to multi-crop aquatic species are limited by species choice due to low natural diversity and strict translocation policies. This creates a situation where available aquaculture species exhibit overlaps in occupied niches. Effects of this overlap can include direct predation, increased intraspecific conflict, and competition for resources such as shelter and food. Prior to this study, silver perch (Bidyanus bidyanus) were identified as a prime candidate for duoculture with marron, based on favourable schooling and feeding characteristics, and preliminary trials demonstrated commercial benefits, including synergistic growth advantages to marron. However, investigations also showed that silver perch will predate on both small and moulting crayfish under certain conditions, and that growth of silver perch was inhibited when held in cages to prevent predation. The work reported in this thesis was undertaken to address the niche overlap existing between marron and silver perch, and therefore assist the marron industry in Western Australia in implementing appropriate management strategies for diversification. / Research focussed on investigating the ecological issues underlying interspecific interactions in marron polysystems, with the eventual aim of presenting information that could assist system managers in determining optimal conditions required to reduce antagonistic relationships and maximise synergism, ultimately leading to higher yields. Seven trials were conducted in three culture systems (54L aquaria, 250L aquaria and 720m2 experimental ponds) examining the ability of marron to detect, recognise and respond to a range of information cues (chemical, visual, tactile) from two potential predators (silver perch and Murray cod), with and without competition from conspecific and heterospecific crayfish (Cherax albidus). The ability of marron to interpret and respond appropriately to these variables was tested under a range of system-specific conditions, including stocking density, stocking size, shelter/habitat complexity, food availability, light intensity and life stage. Cage culture conditions were also examined to determine if the addition of shelter would mediate growth inhibition previously recorded, and to determine the desired stocking regime to return market sized fish in one growth season (8 months). Results from laboratory research and field-based trials did not support the free-range culture of marron and silver perch, even where turbidity and habitat complexity is high. Although both male and female marron (various sizes) demonstrated an ability to detect and differentiate between chemical and visual cues from potential predators, avoidance responses were only displayed upon attack from predators, or following predation of conspecifics; and avoidance strategies employed by marron were relatively ineffective. / Although marron showed some capacity to recognise an impending predatory threat, high initial mortalities and growth inhibition due to reduced foraging, would greatly reduce system yields. In addition, intraspecific competition between marron is likely to increase as avoidance responses would lead to high relative densities within shelters. The lack of avoidance behaviour displayed by marron when only visual and chemical cues from predators are present strongly supports cage culture of silver perch in marron ponds. As marron did not appear to alter their general behaviour (e.g. foraging) based on cues associated with silver perch held in cages they stand to benefit from cohabitation. Field-trials examining the pond culture of marron and caged silver perch demonstrated synergistic growth advantages to marron, compared to monoculture, and also identified several system variables that appear to improve polyculture production. The addition of bank shelters (within 1m of waters edge) was suggested to give marron a competitive advantage when moulting, expressed through growth and survival. Survival of marron was also increased in caged polyculture ponds, compared to monoculture, most likely due to increased health status (due to improved recycling) and/ or increased habitat complexity owing to the presence of fish cages. Growth inhibition previously reported when silver perch are held in cages was mediated to some degree by cage shelters, which appeared to increase feeding behaviour, reduce general anxiety and resulted in increased growth. The introduction of advanced silver perch fingerlings in order to produce market-sized fish in one growth season was also supported. However, it is recommended that cage culture dynamics require further elucidation if silver perch are to be commercially successful as a stand-alone crop using this growout strategy. / Significantly, the synergistic growth advantages experienced by marron when grown with fish demonstrate value from polyculture even if fish are not depended on as a secondary income. In this case, other species may also provide similar advantages, and a native candidate such as freshwater cobbler (Tandanus bostocki) would also redress problems associated with translocation laws restricting the use of silver perch in some areas of Western Australia. As no density effects were recorded in any of the trials conducted for either species, further investigation into increased system loads is required. In addition, as nutrient loads, and thus phytoplankton density, usually increases proportionately with pond biomass it is recommended that an additional herbivorous species, for example white eye mullet (Mugil cephalus), be examined in conjunction with increased density trials. Field research reported in this thesis was carried out in earthen ponds utilising remediated water from a acidified mine lake. Over a three-year period water quality parameters were maintained within optimal ranges for marron and silver perch, and survival and growth of both species was comparable to industry levels. These results validate the effectiveness of mine-water treatment technology; and accordingly, results support commercial viability of crayfish polyculture utilising remediated acid mine water. The large water resources offered by the numerous artificial lakes created from open cut mining has the potential to sustain a large successful aquaculture industry for Collie (Western Australia), and in other areas with extension of water treatment technology. / The incorporation of caged silver perch into marron ponds not only takes advantage of the inherent economic and risk-spreading benefits from a diversified management strategy, but also incorporates a number of within-system benefits due to synergism between species. The ecological approach to aquatic polyculture research reported in this thesis has elucidated key communication factors underlying interactions within crayfish polysystems, which is critical to a knowledge-based approach to system management.

Este trabalho se ocupa dos usos espaciais das preposições para e em nos contextos aqui chamados de locativos e direcionais produzidos com o verbo estar pleno de sentido de locação e o verbo ir de movimento. A análise parte dos pressupostos da Semântica Cognitiva, especificamente da teoria dos esquemas imagéticos (JOHNSON, 1987; LAKOFF, 1987) e as operações de transformações entre esses esquemas (PEÑA, 2008; DEWELL, 2005; LAKOFF, 1987). O corpus utilizado é composto por entrevistas de fala espontânea coletadas em comunidades quilombolas dos estados do Maranhão e São Paulo. Os contextos analisados são aqueles nos quais as duas preposições parecem alternar, como em: Eles estão pro Maranhão ou Eles estão no Maranhão, como também em: Foram pro cinema e Foram no cinema. Argumenta-se que tal alternância se dê pelas transformações entre esquemas imagéticos, nomeadamente os esquemas ORIGEM-PERCURSO-DESTINO e CONTÊINER. Para fundamentar a argumentação, são apresentados os pressupostos teóricos que embasam este trabalho, a problemática e algumas questões de cunho metodológico são discutidos. Por fim, apresenta-se uma proposta de análise semântico-cognitiva que considere a representação do espaço para as duas preposições em foco. / This study deals with the spatial uses of the prepositions em (in) and para (to) in the contexts here called locative and directional produced with the verb estar (to be) for locations and the verb ir (to go) in the movement sense. The analysis is based on the Cognitive Semantics framework, specifically the theory of image schemas (JOHNSON, 1987; Lakoff, 1987) and the transformation processes of those schemas (PEÑA, 2008; DEWELL, 2005; Lakoff, 1987). The corpus is made of interviews of spontaneous speech collected in comunidades quilombolas (maroon communities) from the states of Maranhão and São Paulo. The contexts examined are those in which the two prepositions appear to switch, as in: \"Eles estão pro Maranhao\" (They are to Maranhão) or \"Eles estão no Maranhao,\" (They are in Maranhão) also in: \"Eles foram pro cinema\" (They went to the cinema) and \"Eles foram no cinema.\" (They went in the cinema). It is argued that this alternation is given by image schema transformations, mainly the SOURCE-PATH-GOAL and the CONTAINER image schema. To support this argument, the theoretical assumptions are presented. The problem of this work and some methodological issues are as well discussed. Finally, a proposal in the Cognitive Semantic framework analysis is suggested for analyzing the spatial representation of both prepositions in focus in this work.

Este trabalho se ocupa dos usos espaciais das preposições para e em nos contextos aqui chamados de locativos e direcionais produzidos com o verbo estar pleno de sentido de locação e o verbo ir de movimento. A análise parte dos pressupostos da Semântica Cognitiva, especificamente da teoria dos esquemas imagéticos (JOHNSON, 1987; LAKOFF, 1987) e as operações de transformações entre esses esquemas (PEÑA, 2008; DEWELL, 2005; LAKOFF, 1987). O corpus utilizado é composto por entrevistas de fala espontânea coletadas em comunidades quilombolas dos estados do Maranhão e São Paulo. Os contextos analisados são aqueles nos quais as duas preposições parecem alternar, como em: Eles estão pro Maranhão ou Eles estão no Maranhão, como também em: Foram pro cinema e Foram no cinema. Argumenta-se que tal alternância se dê pelas transformações entre esquemas imagéticos, nomeadamente os esquemas ORIGEM-PERCURSO-DESTINO e CONTÊINER. Para fundamentar a argumentação, são apresentados os pressupostos teóricos que embasam este trabalho, a problemática e algumas questões de cunho metodológico são discutidos. Por fim, apresenta-se uma proposta de análise semântico-cognitiva que considere a representação do espaço para as duas preposições em foco. / This study deals with the spatial uses of the prepositions em (in) and para (to) in the contexts here called locative and directional produced with the verb estar (to be) for locations and the verb ir (to go) in the movement sense. The analysis is based on the Cognitive Semantics framework, specifically the theory of image schemas (JOHNSON, 1987; Lakoff, 1987) and the transformation processes of those schemas (PEÑA, 2008; DEWELL, 2005; Lakoff, 1987). The corpus is made of interviews of spontaneous speech collected in comunidades quilombolas (maroon communities) from the states of Maranhão and São Paulo. The contexts examined are those in which the two prepositions appear to switch, as in: \"Eles estão pro Maranhao\" (They are to Maranhão) or \"Eles estão no Maranhao,\" (They are in Maranhão) also in: \"Eles foram pro cinema\" (They went to the cinema) and \"Eles foram no cinema.\" (They went in the cinema). It is argued that this alternation is given by image schema transformations, mainly the SOURCE-PATH-GOAL and the CONTAINER image schema. To support this argument, the theoretical assumptions are presented. The problem of this work and some methodological issues are as well discussed. Finally, a proposal in the Cognitive Semantic framework analysis is suggested for analyzing the spatial representation of both prepositions in focus in this work.

Made available in DSpace on 2016-04-27T19:30:23Z (GMT). No. of bitstreams: 1 Antonio Carvalho Costa.pdf: 1354540 bytes, checksum: 97b3841aef4ee9474f0fab1d77c09497 (MD5) Previous issue date: 2011-10-06 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / This work is about the process of forming identities in Ivaporunduva (Eldorado-SP) as a result of their struggle and recognition them as a remnant of Quilombo. In early 1990, communities in the Ribeira Valley (SP / PR) faced with the 'Article 68' ADCT as a possibility to stop the advancement of the interests that sought to install hydroelectric projects in the course of the Rio Ribeira de Iguape. Ivaporunduva starts composing his quilombola (maroon) identity as it articulated their struggle to oppose to the dams and in recognition of its territory through the Grupo de Mulheres de Eldorado (Women's Eldorado Group), Movimento dos Ameaçados por Barragens MOAB, (Movement of People Affected by Dams) and Associação Quilombola (maroon association). This movement mobilized universities, government agents and non-governmetal organization with the same purpose. With the work development, we tried to emphasize the new social roles that emerged within the community Ivaporunduva, as well as the readings from residents about the process that culminated in the public record of its Quilombola territory in 2010 / Disserta-se sobre o processo de constituição de identidades em Ivaporunduva (Eldorado-SP) em decorrência de suas lutas e reconhecimento como remanescente de quilombo. No início dos anos de 1990, as comunidades do Vale do Ribeira (SP/PR) se depararam com o artigo 68 do ADCT como uma possibilidade de frear o avanço dos interesses que visavam instalar empreendimentos hidroelétricos no curso do Rio Ribeira de Iguape. Ivaporunduva passa a compor sua identidade quilombola na medida em que articulava sua luta de oposição às barragens e pelo reconhecimento de seu território através do Grupo de Mulheres de Eldorado, Movimento dos Ameaçados por Barragens (MOAB) e associação quilombola. Esse movimento mobilizou universidades, agentes do poder público e organizações não governamentais com o mesmo propósito. Com o desenvolvimento do trabalho, procurou-se dar ênfase aos novos papéis sociais surgidos no interior da comunidade de Ivaporunduva, bem como às leituras dos moradores acerca do processo que culminou com o registro cartorial de seu território quilombola em 2010

Seconde espèce de mollusque bivalve la plus exploitée au monde, la palourde japonaise Venerupis philippinarum représente un intérêt économique majeur. A l’échelle du bassin d’Arcachon, la maladie du muscle marron ou BMD (pour Brown Muscle Disease), pathologie émergente découverte en 2005 inquiète tout particulièrement le secteur de la pêche. Cette pathologie affecte le muscle adducteur postérieur de la palourde et perturbe l’ouverture-fermeture des valves. Cette perturbation entraine la remontée des individus à la surface du sédiment et la mort.Ces travaux de thèse ont porté d’une part sur l’épizootiologie de la maladie et son impact sur l'hôte et d’autre part sur l’identification de l’agent responsable de la maladie.Une étude sur la distribution des palourdes dans le bassin d’Arcachon (littoral Atlantique français) montre que la prévalence de la BMD a diminué entre 2010 et 2012. Toutefois cette baisse ne concerne pas les individus ayant atteint la taille légale de pêche (> 35mm). De plus, la maladie semble apparaitre chez des individus de plus en plus petit et risque donc d’accroitre la mortalité aux plus jeunes stades. L’analyse des facteurs environnementaux impliqués dans la distribution de la maladie souligne la corrélation entre la prévalence de la BMD et un hydrodynamisme relativement « calme ».La BMD affecte tout particulièrement le métabolisme énergétique de l’hôte, les mécanismes de réponse au stress oxydant et également le système immunitaire. De nombreuses fonctions sont surexprimées chez les hôtes malades mais d’autres voies comme celle de l’apoptose sont régulées négativement par l’agent infectieux.Si l’origine virale est maintenant une hypothèse solide (microscopie électronique, transcriptomique), la nature exacte de l’agent étiologique (famille virale) ne peut à ce jour être déterminée avec certitude. Des particules virales ont bien été observées dans les tissus malades mais pas dans les tissus sains, et ont pu être purifiées sur gradient de sucrose. Toutefois, les essais pour provoquer la maladie chez des individus sains ont échoué. / The Manila clam Venerupis philippinarum is the second most exploited mollusk bivalve in the world and represents a major economic interest. At the scale of Arcachon bay, the Brown Muscle Disease or BMD, an emergent pathology discovered in 2005, concerns fishing activity. This pathology affects the posterior adductor muscle of the clam and disrupts the valve opening and closing process. It induces the migration of clams to the surface and their death.This thesis concerns on the one hand the epizootiology of the disease and its impact on host and on the other hand the identification of the causal agent of the disease. A study of the clam distribution in Arcachon bay (French Atlantic coast) shows that prevalence of BMD decreased between 2010 and 2012. However this decrease doesn't affect clams of the legal harvesting size (> 35mm). Furthermore, the disease seems to appear in individuals with increasingly smaller size and thus risks to increase mortality in the youngest stages. The analysis of the environmental factors that are involved in the disease distribution highlights the correlation between prevalence of the BMD and relatively "quiet" hydrodynamism.BMD particularly affects the energy metabolism of the host, the oxidative stress response mechanisms and the immune system.Many functions are up-regulated in the BMD-affected hosts but other ways, as the apoptosis, are down-regulated by the infectious agent.Although viral origin of BMD is now a convincing hypothesis (electronic microscopy, transcriptomic), the nature of the etiological agent (viral family) cannot so far be determined with certainty. Viral particles were observed in tissues of BMD-diseased hosts but not in tissues of healthy host. They have been purified on sucrose gradient. However, the attempt to provoke the disease in healthy individuals failed.

Seconde espèce de mollusque bivalve la plus exploitée au monde, la palourde japonaise Venerupis philippinarum représente un intérêt économique majeur. A l'échelle du bassin d'Arcachon, la maladie du muscle marron ou BMD (pour Brown Muscle Disease), pathologie émergente découverte en 2005 inquiète tout particulièrement le secteur de la pêche. Cette pathologie affecte le muscle adducteur postérieur de la palourde et perturbe l'ouverture-fermeture des valves. Cette perturbation entraine la remontée des individus à la surface du sédiment et la mort.Ces travaux de thèse ont porté d'une part sur l'épizootiologie de la maladie et son impact sur l'hôte et d'autre part sur l'identification de l'agent responsable de la maladie.Une étude sur la distribution des palourdes dans le bassin d'Arcachon (littoral Atlantique français) montre que la prévalence de la BMD a diminué entre 2010 et 2012. Toutefois cette baisse ne concerne pas les individus ayant atteint la taille légale de pêche (> 35mm). De plus, la maladie semble apparaitre chez des individus de plus en plus petit et risque donc d'accroitre la mortalité aux plus jeunes stades. L'analyse des facteurs environnementaux impliqués dans la distribution de la maladie souligne la corrélation entre la prévalence de la BMD et un hydrodynamisme relativement " calme ".La BMD affecte tout particulièrement le métabolisme énergétique de l'hôte, les mécanismes de réponse au stress oxydant et également le système immunitaire. De nombreuses fonctions sont surexprimées chez les hôtes malades mais d'autres voies comme celle de l'apoptose sont régulées négativement par l'agent infectieux.Si l'origine virale est maintenant une hypothèse solide (microscopie électronique, transcriptomique), la nature exacte de l'agent étiologique (famille virale) ne peut à ce jour être déterminée avec certitude. Des particules virales ont bien été observées dans les tissus malades mais pas dans les tissus sains, et ont pu être purifiées sur gradient de sucrose. Toutefois, les essais pour provoquer la maladie chez des individus sains ont échoué.

Interactions between non-native yabbies (Cherax albidus) and indigenous marron (Cherax tenuimanus) in the south-west of Western Australia are not well understood. While there is abundant evidence to suggest that invasive freshwater crayfish are detrimental to native species, the nature and degree of impact on marron populations by exotic yabbies remains unclear. Researchers have hypothesized that invasive species make faster and more appropriate use of information about their environment than native species. This greater behavioural plasticity can result in displacement of indigenous species, successful colonisation by invaders, and subsequent disturbance to natural ecosystems and representative biodiversity. / The research presented in this thesis examines the behavioural responses of an indigenous crayfish (C. tenuimanus) and an invasive crayfish (C. albidus) to waterborne odours derived from food, alarm sources and finfish predators. This study was undertaken to assist in the understanding of predatory and competitive interactions between indigenous and non-indigenous crayfish and fish predators, with particular relevance to Western Australia. Predation and competition are major forces influencing community structure in ecosystems; therefore knowledge of competitive and predatory interactions will be of benefit when considering future translocation policies. / Behavioural trials were conducted in two culture systems (54 L aquaria and a 70,000 L mesocosm), where marron and yabbies were exposed to a range of water-borne odours from finfish predators (silver perch and Murray cod), with and without competition from conspecific and heterospecific crayfish. A number of variables likely to influence crayfish behaviour were investigated: strength of chemical odour; crayfish size, gender, diurnal and nocturnal activity patterns; predator size; prior-residence; suitable habitat/shelter; and feed availability. / A key innovation in this research was the high replication in the aquarium-based observation trials using a Latin Cube design, which resulted in greater statistical strength and lower variability. More importantly, this research deviated from the tradition of exclusively using the ‘individual crayfish’ approach for odour-detection experiments and tested these results in a 70,000 L communal observation tank. This was an important development in crayfish behavioural experimentation, particularly as several key findings from the individual crayfish approach were confirmed in a multi-species environment. / Results from this study supported the hypothesis that invasive crayfish species make more appropriate use of a wider range of information about their environment than native crayfish species. Yabbies were found to possess behavioural characteristics not present in marron, such as clearer behavioural modifications to food and heterospecific odour, and cautionary behaviour in the presence of odour from a finfish predator. During simulated daylight conditions, marron displayed behaviours conducive to predation that were not present in yabbies, including less time spent in shelter and more time spent in locomotory activity. However, during specialised night-time observational studies developed during this research, these differences were not evident. This would not seem to be an unusual result, given that crayfish naturally forage at night and become more active; however, it may have important implications for future behavioural studies of crayfish, indicating a bias associated with day-time approaches. Crayfish size also played a role in behavioural modifications to water-borne odours. Larger marron displayed clearer changes in behaviour and were more responsive to heterospecific alarm odour than juveniles. Furthermore, juveniles of both species were more active than adults and sub-adults. / The expansion of the yabby population into Western Australian habitats occupied by marron has been facilitated through translocation for aquaculture, and biological characteristics of the species, some of which are typical of other invasive crayfish species including: tolerance of a variety of conditions; rapid growth; early sexual maturity; burrowing to escape drought and predation; capable of multiple spawns in a growth season; and aggressiveness. Another characteristic of invasive crayfish species also shared by yabbies, as supported by the results of this study, is high behavioural plasticity. / Although marron do not share the same level of behavioural plasticity found in yabbies, their larger body size increases their success in competitive interactions. The comparatively smaller body size of yabbies may be the major factor limiting their population expansion in the presence of marron, especially in water-bodies where shelter is a limited resource. / Marron are an important endemic species in Western Australia, but their conservation is threatened by competition and predation from exotic species. The research presented in this thesis indicates that invasive yabbies are more receptive to chemical stimuli and better equipped to respond to predation risk than marron. This information will be of benefit when considering future translocation policy in Western Australia and highlights the need for a cautious approach to species introductions.