No description available.

L’objectiu d’aquesta tesi és millorar l’aplicació de mètodes de cromatografia de líquids acoblada a espectrometria de masses (LC-MS) per a l’estudi de toxines lipofíliques i emergents produïdes per microalgues en un ecosistema litoral mediterrani (Delta de l’Ebre, Catalunya, NO Mar Mediterrani). La primera contribució fou l’avaluació de diferents condicions per implementar el mètode de control de referència de toxines lipofíliques en bivalves, obtenint majors rendiments i complint amb els requeriments legals. Aquest mètode s’aplicà en l’estudi d’una floració de Dinophysis sacculus a la badia dels Alfacs, considerant diferents aproximacions per caracteritzar el risc: anàlisi de toxines en microalgues, dissoltes en aigua, i en bivalves. Els perfils toxínics de D. sacculus només presentaren àcid okadaic i pectenotoxina-2 (la toxina principal). El contingut de toxina total per cèl·lula s’incrementà cap al final de la floració, coincidint amb la màxima concentració d’àcid okadaic en musclos (fins a 3,7 vegades el màxim permès a Europa), la concentració de pectenotoxines fou menor. Els ostrons no acumularen toxines per sobre del nivell màxim permès. El mètode LC-MS permeté la detecció de les toxines emergents pinatoxina-g (primera detecció a Espanya) i espiròlid-1, les quals foren confirmades inequívocament mitjançant MS d’alta resolució, en concentracions baixes en marisc i mostrejadors passius. No es detectaren metabòlits acilats de pinatoxines i els falsos positius es descartaren amb informació ortogonal. Les toxines emergents denominades palitoxines també s’investigaren, i es descobriren dues noves palitoxines en cultius de noves soques d’Ostreopsis cf. ovata de Catalunya: l’ovatoxina-g (46-dehidroxi ovatoxina-a) i un isòmer de la palitoxina (anteriorment “palitoxina putativa”), igual que la palitoxina però hidroxilada en C-42 i entre l’extrem A y C-8, i deshidroxilada en C-17 i probablement en C-64. Els perfils toxínics contenien ovatoxines-a,-b,-c,-d i –e, amb concentracions per cèl·lula majors que les d’altres soques mediterrànies. / El objetivo de esta tesis es mejorar la aplicación de métodos de cromatografía de líquidos acoplada a espectrometría de masas (LC-MS) para el estudio de toxinas lipofílicas y emergentes producidas por microalgas en un ecosistema litoral mediterráneo (Delta del Ebro, Cataluña, NO Mar Mediterráneo). La primera contribución fue la evaluación de diferentes condiciones para implementar el método de control de referencia de toxinas lipofílicas en bivalvos, obteniendo mayores rendimientos y cumpliendo con los requerimientos legales. Este método se aplicó al estudio de una floración de Dinophysis sacculus en la bahía de Alfacs, considerando diferentes aproximaciones para caracterizar el riesgo: análisis de toxinas en microalgas, disueltas en agua, y en bivalvos. Los perfiles toxínicos de D. sacculus sólo presentaron ácido okadaico y pectenotoxina-2 (la más abundante). El contenido de toxina total por célula se incrementó hacia el final de la floración, coincidiendo con la máxima concentración de ácido okadaico en mejillones (hasta 3.7 veces el máximo permitido en Europa), la concentración de pectenotoxinas fue menor. Las ostras no acumularon toxinas por encima del nivel permitido. El método LC-MS permitió la detección de pinatoxina-g (primera detección en España) y espirólido-1 (toxinas emergentes), confirmadas inequívocamente mediante MS de alta resolución, en concentraciones bajas en bivalvos y muestreadores pasivos. No se detectaron metabolitos acilados de pinatoxinas, y los falsos positivos se descartaron con información ortogonal. Las toxinas emergentes denominadas palitoxinas también se investigaron, y se descubrieron dos nuevas palitoxinas en cultivos de nuevas cepas de Ostreopsis cf. ovata de Cataluña: ovatoxina-g (46-dehidroxi ovatoxina-a) y un isómero de la paltoxina (anteriormente “palitoxina putativa”), igual que la palytoxina pero hidroxilada en C-42 y entre el extremo A y C-8, y dehidroxilada en C-17 y probablemente en C-64. Los perfiles toxínicos contenían ovatoxinas-a,-b,-c,-d y –e, con concentraciones por célula mayores que las de otras cepas mediterráneas. / This thesis aims to improve the application of liquid chromatography coupled to mass spectrometry (LC-MS) methods for the study of lipophilic and emerging toxins produced by microalgae in a coastal Mediterranean environment (Ebro Delta, Catalonia, Spain, NW Mediterranean Sea). The first contribution was the evaluation of different conditions for the implementation of the official reference control method for lipophilic toxins in shellfish, in order to obtain higher sample throughput and meet legal requirements. This method was applied to study a bloom of Dinophysis sacculus in Alfacs Bay, considering different approaches to characterize risks: analysis of toxins in microalagae, dissolved in water and in shellfish. Toxin profiles of D. sacculus only included okadaic acid and pectenotoxin-2 (the most abundant). Toxin content per cell increased towards the end of the bloom, concomitant with the maximum okadaic acid concentration in mussels (up 3.7 times the maximum permitted level in Europe), pectenotoxins were accumulated at lower concentrations. Oysters did not accumulate toxins over the maximum permitted level. The optimized method allowed the detection of the emerging toxins pinnatoxin-g (first report in Spain) and spirolide-1, which were unequivocally confirmed by High Resolution MS at low concentrations in shellfish and passive samplers. Acyl ester metabolites of pinnatoxins were not detected, and false positives were discarded by orthogonal information. The emerging toxins named palytoxins were also investigated in the study area, and two new palytoxins were discovered in cultures of new strains of Ostreopsis cf. ovata from Catalonia: ovatoxin-g (46-dehydroxy ovatoxin-a) and isomeric palytoxin (formerly “putative palytoxin”), like palytoxin but hydroxylated at C-42 and in the segment from the A-side terminal to C-8, and dehydroxilated at C-17 and most likely at C-64. Toxin profiles also contained ovatoxin-a, -b, -c, -d and –e, at concentrations per cell higher than toxin quotas reported for other Mediterranean strains.

The use of adaptive feeding systems to deliver feed remotely to Atlantic salmon (Salmo salar) cages has the potential to improve the localised environment through a reduction in particulate waste. This can be achieved through improved growth and lower Feed Conversion Ratio (FCR). The aim of this project was to assess whether adaptive feeding systems confer any environmental benefit at salmon farms through by comparing two fish farm sites, one that uses a Computer Aided System (CAS) adaptive feeding system (AKVAsmart UK limited, Inverness, Scotland) (Portavaide fish farm) and one using hand feeding (Rubha Stillaig). This investigation comprised of 3 elements: 1) a comparative assessment of the quantity and nutrient composition of particulate waste material emanating from the cages; 2) collection of benthic samples plus a video survey along transects at each site including a reference station, with an analysis of differences in benthic fauna, sediment grain size and sediment nutrient composition; and 3) comparison of the distribution of waste under each feeding regime using a GIS-based modelling approach. Particulate waste was collected via sediment traps. Uneaten feed was caught in only 3 out of 184 separate collections and thus no estimate of feed loss for each feeding system could be made. Samples were analyzed for total solids (TS), faecal solids (FS), faecal carbon (FC), faecal nitrogen (FN) content and faecal sedimentation rate (FSR). The highest deposition occurred under the cages and decreased with increased distance from the cage centre. Maximal deposition of TS at Portavadie was higher than at Rubha Stillaig when feed was included, although average TS, FS, Fe and FN per tonne of production did not significantly vary between sites. Carbon sedimentation rate was analyzed using regression analysis and a General Linear Model Factorial ANOVA on faecal waste only and showed no significant differences between sites and, therefore, no difference between feeding methods . There were no differences observed in the diversity and abundance of benthic species under the two feeding systems. By the end of the production period all stations out to 25m from the cage edge were dominated by Capitella capitata at both sites, this species proving a useful indicator of the impact of nutrient deposition. The analysis suggested that Heteromastus filiformis and Corophium sp. provided useful indicators of the onset of nutrient enrichment. Measurement of carbon and nitrogen levels and particle size in sediment showed no difference between sites. Variations between sites in species abundance and diversity and sediment carbon and nitrogen levels reflected the different sediment conditions prevalent at the start of the sampling period. Univariate and multivariate analysis showed there was no difference in species diversity and abundance between the sites as a result of using adaptive feeding systems. Horizontal cage movement, measured at up to 10m, reduced the predicted settlement under the cage by 23% and 11 % for feed and faecal distribution respectively. There was no significant difference in the predicted settlement of waste particulates under adaptive and hand feeding. The GIS model prediction of carbon flux (g C m-2 15-days-1) was validated for faecal settlement using sediment trap data where predictions agreed well with observations from Portavadie fish farm, with an accuracy of ± 53.1 % when all stations were included, improving to ± 27.6% when deposition under the cage was excluded. Overall, the approaches used did not identify specific differences between sites that used adaptive feeding and hand feeding methods. The growth period using the adaptive feeding system was approximately nine weeks shorter than under hand feeding, however, which could be used constructively to increase the fallowing period whilst maintaining current levels of production. This would benefit the localised benthos by increasing the time available for recovery before further production takes place and thus the CAS Adaptive Feeding System could be used as part of a broader sustainable farming strategy for fish culture.

No description available.

En la presente Tesis Doctoral se ha estudiado la presencia y bioacumulación de compuestos organoclorados en la piscicultura del Mediterráneo occidental, así como en el entorno marino circundante. La investigación realizada se estructura en tres partes diferenciadas. En la primera parte se ha utilizado la técnica GC-MS para el estudio de la presencia de los contaminantes organoclorados en productos de la acuicultura marina, investigándose el comportamiento de los mismos a lo largo del ciclo biológico de la dorada (Sparus aurata), y comparando los resultados obtenidos en ejemplares salvajes y cultivados. Además, se ha realizado un estudio específico sobre la transferencia maternal de organoclorados a los ovocitos de doradas salvajes y cultivadas. En la segunda parte se han determinado las relaciones entre isótopos estables de carbono y nitrógeno con el objetivo de estudiar las diferentes características alimentarias de las doradas salvajes y cultivadas, relacionándolas con el comportamiento de los compuestos organoclorados en las cadenas tróficas estudiadas. Por último, se ha desarrollado metodología analítica para la determinación de Dioxin-Like PCBs mediante GC-MS/MS (trampa iónica), en muestras procedentes de la acuicultura marina, estudiando en detalle las etapas de purificación de los extractos y el fraccionamiento de los analitos previamente a la determinación analítica.

tesis por compendios / El objetivo de esta tesis doctoral es investigar los ritmos diarios de comportamiento alimentario e indicadores de bienestar en la dorada. Este objetivo general se aborda en 3 áreas temáticas interrelacionadas: selección dietaria, sincronización al horario de alimentación e indicadores de bienestar. El nexo común gira en torno al estudio de los ritmos de alimentación en la dorada, mediante el empleo de comederos a demanda en los cuales el pez es capaz de elegir libremente la cantidad y el momento en el cual desea alimentarse, y si dispone de más de un comedero a demanda, realizar selección dietaria y decidir el tipo de alimento; o bien mediante comederos automáticos que permiten estudiar el efecto sincronizador del horario de alimentación. La alimentación además juega un papel clave en el bienestar de los peces, cuya evaluación requiere considerar los ritmos de indicadores fisiológicos de estrés y el comportamiento alimentario de los peces.

Für einen sicheren Herdenschutz in Gebieten mit frei lebenden Wölfen ist der Einsatz von Herdenschutzhunden in Kombination mit Elektrozäunen zu empfehlen. Der Umgang mit Herdenschutzhunden erfordert Sachkenntnis und Verantwortungsbewusstsein. Die Broschüre erläutert Unterschiede zum Hütehund, beschreibt Grundlagen der Sozialisierung und die wichtigsten Rassen. Im zweiten Teil werden Untersuchungsergebnisse zu verschiedenen Varianten der Elektro-Umzäunung dargestellt, insbesondere zur benötigten Arbeitszeit beim Aufbau der Netze. Im Ergebnis der Analyse wird eine übersprungsichere Variante empfohlen, die mit vertretbarem Zeitaufwand aufgebaut werden kann und den Herdenschutz gewährleistet.

La creixent importància de l'aqüicultura fa necessària la recerca per a la millora i abaratiment de les dietes per a la piscicultura, amb l'objectiu d'optimitzar el desenvolupament del sector de forma sostenible.Cal buscar alternatives a la farina i l'oli de peix, matèries primeres cada vegada més limitants, que s'han utilitzat tradicionalment en la formulació de pinsos per a peixos carnívors.S'han testat dietes experimentals amb diferents percentatges de reemplaçament de la farina de peix per fonts proteiques vegetals per a orada (Sparus aurata) i truita irisada (Oncorhynchus mykiss). Amb la finalitat d'ajustar la composició aminoacídica del pinso al perfil requerit per les espècies, es van utilitzar en les dietes de substitució, mescles d'ingredients vegetals i suplementació amb aminoàcids lliures. En experiències de creixement de dotze setmanes, el reemplaçament de la farina de peix va disminuir l'activitat total de les proteases digestives, suggerint la presència a la dieta de factors antinutricionals. En ambdues espècies, però, van aparèixer mecanismes de compensació, com l'increment de la longitud intestinal relativa, l'increment d'algunes activitats proteasa específiques, o el desplaçament de la capacitat d'absorció des de l'intestí proximal cap a zones intestinals distals. Aquests mecanismes compensatoris van permetre obtenir bones taxes de creixement amb substitucions de fins a un 75% de la farina de peix. Els animals alimentats amb dietes de substitució total van presentar una funció digestiva deteriorada i un creixement al voltant d'un 20% menor al dels animals alimentats amb la dieta basada en farina de peix.En l'orada es testà la substitució simultània de la farina de peix (75%) i de diferents percentatges d'oli de peix (33, 66 i 100%). L'administració de les dietes experimentals amb un 66% i un 100% d'oli vegetal durant deu setmanes va disminuir l'activitat enzimàtica digestiva, però la capacitat d'absorció d'aminoàcids no es va veure afectada. Només la dieta de doble substitució amb el reemplaçament total de l'oli de peix va afectar negativament el creixement. Es va estudiar l'efecte de la inclusió total d'oli vegetal en dietes amb diferent percentatge (50% i 75%) i origen de fonts proteiques vegetals. Les orades presentaren diferents patrons de regionalització de la capacitat d'absorció de nutrients al llarg del tracte intestinal segons les fonts proteiques utilitzades. El grup de menor substitució de la farina de peix presentà una activitat proteolítica digestiva més elevada i superior taxa de creixement.El síndrome d'hivern, malaltia que afecta a les orades en cultiu de la costa Nord-Mediterrània, té un origen multifactorial, i pot ocasionar importants pèrdues econòmiques en els mesos freds.S'han testat en orades pinsos comercials amb diferent percentatge de lípids (14 i 22%) com a dietes de preparació per a l'hivern. L'engreix durant 75 dies amb les dietes estudiades no afectà l'absorció de nutrients a nivell intestinal o els índexs de creixement. L'exercici moderat tampoc afectà aquests paràmetres. Es descarta que a baixes temperatures els animals rebutgin l'aliment degut a una incapacitat en l'absorció de nutrients, ja que tots els grups d'orades van respondre de manera similar a una situació prolongada de fred. / Fish meal and fish oil have traditionally been used in the diets for carnivorous fish species. This primary sources are now limited so alternatives need to be found. Experimental diets with different percentages of fish meal replacement by plant sources were tested in sea bream and rainbow trout. Feeds contained a mixture of ingredients that matched species amino acid requierements and were supplemented with free amino acids to avoid nutritional imbalances. In a 12-week growth trial, when up to 75% of the fish meal was replaced digestive protease activity fell and histological changes occurred, suggesting that antinutritional factors were present in the diets. However, compensation mechanisms (relative intestinal length increase, increase in some specific protease activities, or increased absorption in distal intestinal regions) appeared in both species, enabling good growth rates.The use of plant ingredients as the sole source of protein affected the efficiency of the digestive processes in both species. Fish showed a final weight decrease of around 20%.Replacement of 75% fish meal and different percentages of fish oil (33, 66 and 100%) was studied in sea bream. After 10 weeks the inclusion of over 66% of plant oil provoked a decrease in enzymatic activities, amino acid absorption capacities were not affected and only total fish oil replacement affected growth performance.Replacement of all the fish oil when 50 and 75% of fish meal was replaced by different plant sources was also tested. Sea bream showed different absorption patterns depending on the protein source used. In the group of low fish meal replacement digestive proteolytic activities were higher and growth rates were better.Sea bream can be affected by winter syndrome in some regions of the north mediterranean coast. Commercial diets with different percentages of lipids as diets to prevent it, did not affect intestinal nutrient absorption or growth performance. Moderate exercise did not affect the parameters. The refusal of feed at low temperatures is not related to nutrient absorption impairments, since all sea bream groups showed similar responses to a long, cold-induced situation.

Submitted by Elaine Aparecida Mani (elainea.mani@hotmail.com) on 2018-05-17T17:56:27Z No. of bitstreams: 1 Dissertação Elaine - Revisada ENCADERNAÇÃO.docx: 12214593 bytes, checksum: b5f564f214526ecacc264ad51586fa00 (MD5) / Approved for entry into archive by Jacqueline de Almeida null (jacquie@franca.unesp.br) on 2018-05-18T19:53:16Z (GMT) No. of bitstreams: 1 Mani_EA_me_fran.pdf: 4687027 bytes, checksum: a64cedf4cfa312164073533f2ee8ffa1 (MD5) / Made available in DSpace on 2018-05-18T19:53:16Z (GMT). No. of bitstreams: 1 Mani_EA_me_fran.pdf: 4687027 bytes, checksum: a64cedf4cfa312164073533f2ee8ffa1 (MD5) Previous issue date: 2018-03-23 / A Lei 10.639, assinada pelo presidente Luiz Inácio Lula da Silva em 2003, corresponde à alteração da Lei de Diretrizes de Bases da Educação, de 1996 (Lei 9.394/96) e torna obrigatório o ensino da temática de História e Cultura da África e dos Afro-brasileiros nos estabelecimentos de ensino fundamental e médio do país. A questão que nos motiva a empreender uma pesquisa sobre esta temática consiste em saber se, após quinze anos da sanção desta Lei, as escolas estão aplicando-a e traduzindo-a em práticas pedagógicas efetivas. Portanto, o objetivo geral que norteia esta pesquisa consiste em analisar o grau de implementação e enraizamento da Lei 10.639/03, a partir de práticas pedagógicas realizadas em uma escola pública de Ensino Médio e Técnica do interior de São Paulo, assim como identificar as principais dificuldades e os desafios encontrados pelos professores e gestores para a sua implementação. Trata-se de uma pesquisa qualitativa por pretender verificar o grau de implementação e o enraizamento de uma política pública educacional através de pesquisa bibliográfica e estudo de caso. Os dados foram coletados através dos documentos escolares: Plano Plurianual de Gestão, Projeto Político-Pedagógico; Planos de Trabalho, diários de classe e Proposta de Currículo por Competência para o Ensino Médio do Centro Paula Souza (2012); de observação e registro em diário de campo e registro fotográfico; de entrevistas semiestruturadas com os professores e com a equipe gestora e grupo de discussão com alunos do Ensino Médio. À luz da análise sobre as dificuldades de implementação adquiridas deu-se a construção de uma proposta de intervenção que pudesse servir de modelo de ação para a escola avaliada e para as demais escolas que ainda não conseguiram implementar a Lei 10.639/03 ou que a implementam com dificuldade. / The Law No. 10,639/2003, signed by the President Luiz Inácio Lula da Silva, corresponds to the amendment of the Guidelines and Bases of National Education (Law No. 9,394/1996.) and makes it mandatory for Brazilian basic education schools the teaching of Afro-Brazilian and African History and Culture. This study aims at investigate whether fifteen years after being sanctioned the Law 10,639/2003 is still being applied at Brazilian schools and being translated into effective pedagogical practices. The general purpose of this study is to analyze the degree of implementation and rooting of the Law No. 10,639/2003, based on pedagogical practices carried out at a Public and Technical High School in the interior of São Paulo State. This study also intends to identify the main difficulties and challenges faced by the school staff during the period of the law implementation. It is a qualitative research because it seeks to verify the degree of implementation and the rooting of an educational public policy through bibliographical research and case study. The data were collected from the school documents such as the Multiannual Management Plan, Political-Pedagogical Project; Lesson Plans, Class Register Book, and Curriculum for high school students at Paula Souza Center (2012). The data were gathered both from observation and from written and photographic records; from semi-structured interviews with teachers, coordinators and principals and from discussion group with high school students. Taking the implementation difficulties analysis into consideration, an intervention proposal will be suggested to the evaluated school and for other schools that have not yet been able to implement the Law No. 10,639/2003 as well as those which have implemented it with difficulty.

Bacillary Necrosis of Pangasius (BNP) caused by Edwardsiella ictaluri is considered to be the most serious disease occurring in farmed striped catfish (Pangasianodon hypophthalmus) in Vietnam. This disease has had an increasing impact over the last ten years and has been reported to cause 50-90% mortality of stocks during a single outbreak. Data obtained from natural outbreaks of E. ictaluri in striped catfish showed the role of environmental factors in the establishment and progression of this disease. At present, factors affecting the virulence and transmission of E. ictaluri in striped catfish are poorly understood. The central hypothesis of this thesis focuses on the complex picture of the environmental factors and infectivity of E. ictaluri in striped catfish. In this study, 80 isolates of E. ictaluri recovered from natural clinical disease outbreaks occurring in striped catfish farms between 2002 and 2011 located in 4 distinct geographical areas within Vietnam were characterised using a variety of methods. The biochemical profiles showed that E. ictaluri isolates from striped catfish in Vietnam have similar phenotypic characteristics to other E. ictaluri isolates from other infected fish species. These data showed high levels of phenotypic homogeneity between the E. ictaluri isolates investigated. The status of isolates recovered from natural infections over time and from geographically distinct farms was evaluated using pulsed-field gel electrophoresis (PFGE), plasmid profile identification and antibiotic sensitivity tests. The PFGE results showed 6 main groups with a similarity of 82% and the corresponding genotypes of the prevalent isolates illustrated annual differences. Three plasmid groups were identified distributed among the isolates investigated, in which high molecular weight plasmids of approximately 35 and 140 kb were found in two of the groups. Plasmid profiles of the present study did not show any trend of geographical region or year of isolation. The 140 kb plasmid has been considered as a multi-antibiotic resistance plasmid which confers resistance to tetracycline, trimethoprim and sulphonamides. All Vietnamese isolates showed a high level of resistance to Oxolinic acid, Sulfadimethoxine/Ormetoprim (Romet), Oxytetracycline and Amoxicillin. A reproducible bacterial immersion challenge model was developed and the LD60 estimated prior to performing subsequent experimental challenge studies. Fish were exposed to 107 cfu ml-1 of E. ictaluri by immersion for up to 30 seconds, resulting in a cumulative percentage mortality of 63%. Edwardsiella ictaluri was recovered and identified from all the dead and moribund fish during these experiments and affected fish showed similar clinical signs and pathology to those reported from natural E. ictaluri infections. The present study resulted in a successful experimental immersion challenge model for E. ictaluri infection in healthy striped catfish. Cohabitation challenges were also developed and produced 15-40% mortality, typical clinical signs and pathology, and successful recovery of the challenge organism demonstrating horizontal transmission of E. ictaluri in striped catfish. Experimental studies were then conducted to investigate the association between pH or salinity of water and susceptibility to E. ictaluri infection in striped catfish. The first experiments were performed in in vitro conditions in which E. ictaluri isolates were cultured in a variety of pH and salt concentrations. In vivo experiments were then designed where striped catfish were exposed to 107 cfu ml-1 of E. ictaluri for 30 seconds and then held at 4 different water pHs (5.5, 6.5, 7.5 and 8.5) or NaCl concentrations (0, 0.5, 1 and 1.5%). The results of in vitro experiments showed that a pH value between 5.5 to 6.5 and salt concentration between 0-0.5% were optimal for the growth of E. ictaluri. The in vivo experiments demonstrated that the cumulative mortality of striped catfish in water at pH 5 and pH 6 was significantly higher than that of fish maintained in more alkaline water (p<0.05). By contrast, the cumulative mortality of the striped catfish maintained in 0.5% salt concentration was significantly lower than those kept in 0%, 1% and 1.5% salt concentration (p<0.05). Clinical signs, lesions and histopathological changes in the affected fish were consistent with those reported in natural infections. This study highlighted the use of pH 8.5 and salinity of 0.5% NaCl as a means of decreasing the susceptibility of striped catfish to E. ictaluri. In conclusion, this study used a variety of methods in order to enhance the understanding of the biochemical, biophysical characteristics, plasmid profile and antibiotic resistance as well as the relatedness of E. ictaluri isolates recovered from farmed striped catfish in Vietnam. This study provided two reliable and reproducible bacterial challenge models (immersion and cohabitation) and emphasised the link between pH and salinity with the infectivity and pathogenicity of E. ictaluri in striped catfish.