Bacterial histamine formation in mackerel and albacore was studied by inducing histamine in the muscles under controlled storage conditions. The optimum temperature for histamine formation was 25°C. The highest level of histamine detected was 283 mg/100 g in the 2-day stored mackerel; and 67.1 mg/100 g in the 6-day stored albacore. To identify the bacteria crucial to histamine formation, histamine formers were isolated using the conventional culture method. Enteric bacteria were most frequently isolated from the fish. Weak histamine formers were found in the gill and skin of fresh fish, and they required the enrichment step. Prolific histamine formers were mostly isolated from the decomposed muscles during storage at 25°C. Morganella morganii was the most prolific histamine former, producing >3,000 ppm in culture broth. M. morganii was the most prevalent histamine former in mackerel. In albacore, however, the most prevalent species was Hafnia alvei, a weak histamine former, resulting in less histamine accumulation than mackerel. Weak histamine formers, identified as natural bacteria in the marine environment, were found in mackerel during storage at 4°C after fish became unsuitable for human consumption. At 0°C, neither histamine-forming bacteria nor histamine was detected in fish. M. morganii formed significant amounts of histamine (>200 mg/100 g) in artificially contaminated fresh and frozen mackerel, albacore, and mahi-mahi when the fish were improperly stored at ambient temperatures (25°C). Growth of M. morganii was controlled by storage of fish at 4°C or below, but histamine formation was controlled only during frozen storage. For rapid detection of M. morganii, a PCR assay was developed by designing 16S rDNA targeted primers. Unique primers found for M. morganii were: the forward primer, 5'-CTCGCACCATCAGATGAACCCATAT-3'; and the reverse primer, 5'-CAAAGCATCTCTGCTAAGTTCTCTGGATG-3'. Nine CFU/ml of M. morganii inoculated in albacore homogenate were detected with a 6 h-enrichment of samples in TSB at 37°C. It would be necessary to monitor the presence of M. morganii in fish during handling and storage due to its high histamine-producing capability and prevent its contamination and proliferation after capture. The PCR assay developed in this study would be helpful to routinely monitor its presence in fish. / Graduation date: 2002

To clarify the spatiotemporal distribution of the winter and spring larval fish assemblage in the coastal waters off Kaohsiung and Pingtung, Taiwan, larval fishes were collected during four research cruises by conducting 35 tows of the larval net in coastal waters off Zuoying, Linyuan, Linban and Fangliao in January and March 2009 and in coastal waters off Linyuan adjacent to the Kaoping River estuary in January and March 2010. Water temperature, salinity and dissolved oxygen were measured during the sampling of the fish larvae. Seawater samples were also collected for analyzing concentrations of nutrient salts. In 2009, a total of 2,023 fish larvae, representing 38 families and 74 species, were collected. The fish larvae assemblage exhibited seasonal variation in both abundance and species composition. The abundance (460 ind./1000m3) and the number of species (34 families and 66 species) of the fish larvae collected in March were higher than those (28 ind./1000m3, 14 families and 27 species) collected in January. Fish larvae also exhibited spatial variation in species composition. In January, the most dominant families of fish larvae were: Myctophidae off Linyuan, Sparidae off Linban and Nomeidae off Fangliao. In March, in the northward coastal waters off Linyuan Scombridae was the most dominant family, and in the southward coastal waters off Linyuan, Clupeidae and Sillaginidae were the dominant families. No significant differences existed in the abundance of fish larvae among the sampling areas, but the abundance of fish larvae in the sampling sites off Linyuan and Linban tended to be strongly influenced by tide. In 2010, a total of 1,959 fish larvae, representing 39 families and 59 species, were collected. These fish larvae showed diurnal and seasonal variations in abundance and in species composition. The abundance (767 ind./1000m3) and the number of species (39 families and 55 species) of the fish larvae in March were higher compared with those (26 ind./1000m3, 16 families and 25 species) in January. Moreover, the abundance of fish larvae in the nighttime was higher than that in the daytime. In March, the most dominant family in the daytime was Serranidae, whereas the most dominant family in the nighttime was Myctophidae, indicating the diurnal migration of Myctophidae these larvae. Cluster analysis indicated that the abundance and species composition of the fish larvae differed between January and March in 2009. The difference in species composition among the four sampling areas was only found significant for the fish larvae collected in the coastal waters off Fangliao in winter, and the most influenced families were Nomeidae and Myctophidae. In 2010, seasonal variations were found in the abundance and species composition of the fish larvae, and the abundance of the fish larvae showed the difference between nearshore and inshore sampling sites in the nighttime in winter. In spring, the fish larvae were all inshore fishes, but the species composition had annual variation. The temperature and salinity data obtained in the sampling sites conformed to the surface seawater of South China Sea, indicating that the occurrence of the dominant family Scombridae may be related to the seawater of South China Sea.

Made available in DSpace on 2014-12-17T14:33:07Z (GMT). No. of bitstreams: 1 RodrigoXS_DISSERT.pdf: 1797294 bytes, checksum: f032295b5b46cf49baf85e9aff88c766 (MD5) Previous issue date: 2012-04-27 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Cytogenetic studies in fish have been contributed significantly to a better understanding of the marine biodiversity, presenting information related to characterization, evolution and conservation of species e fisheries stocks. Among the marine species which cytogenetic data are less well known pelagic forms are detached, that despite the economic importance and conservation efforts have been suffering great pressure from the artisanal and industrial fisheries. The present work characterized cytogenetically six species of large pelagic fish in the Atlantic, belonging to the Order Perciformes, among them, four species of Scombridae, Thunnus albacares, T. obesus, Scomberomorus brasiliensis and Acanthocybium solandri and two Coryphaenidae, Coryphaena equiselis and C. hippurus using Classical cytogenetic methods as conventional staining, C-banding and Ag-NORs and molecular through staining fluorochromes AT and GC-specific and mapping of ribosomal multigene families, 18S and 5S. The identification of phylogenetic patterns and cytotaxonomic markers between the species and the presence of sex chromosomes in at least one species of Coryphaenidae, are particularly useful in the formulating of phylogenetic hypotheses, as well as comparisons between groups and populations / Os estudos citogen?ticos em peixes v?m contribuindo significantemente para um melhor conhecimento sobre a biodiversidade marinha, apresentando informa??es voltadas ? caracteriza??o, evolu??o e conserva??o de esp?cies e estoques pesqueiros. Entre as esp?cies marinhas cujos dados citogen?ticos s?o menos conhecidos se destacam as formas pel?gicas, que apesar da import?ncia econ?mica e de esfor?os conservacionistas v?m sofrendo grande press?o da pesca artesanal e industrial. O presente trabalho caracterizou citogeneticamente seis esp?cies de grandes peixes pel?gicos no Atl?ntico, pertencentes ? Ordem Perciformes, dentre elas, quatro esp?cies de Scombridae, Thunnus albacares, T. obesus, Scomberomorus brasiliensis e Acanthocybium solandri e duas de Coryphaenidae, Coryphaena equiselis e C. hippurus utilizando m?todos citogen?ticos cl?ssicos, como colora??o convencional, bandamento C e Ag-RONs, e moleculares, atrav?s da colora??o com fluorocromos AT e GC-espec?ficos e mapeamento de fam?lias multig?nicas ribossomais 18S e 5S. A identifica??o de padr?es filogen?ticos e marcadores citotaxon?micos entre as esp?cies e a presen?a de cromossomos sexuais em pelo menos uma esp?cie de Coryphaenidae, s?o particularmente ?teis na formula??o de hip?teses filogen?ticas, bem como em compara??es entre grupos e popula??es

Aquest treball es centra en el coneixement de l'estructura poblacional de tres espècies piscícoles de la família Scombridae, el bonítol (Sarda sarda), la bacora (Thunnus alalunga) i la tonyina (Thunnus thynnus) en la seva distribució de l'atlàntic i el mediterrani. / This work focuses on understanding the population structure of three fish species of the family Scombridae, bonito (Sarda sarda), the figs (Thunnus alalunga) and bluefin tuna (Thunnus thynnus) distribution in the Atlantic and the Mediterranean.

Les recherches en halieutique ont pour objectif d’améliorer les connaissances sur le fonctionnement des populations de poissons afin de transférer celle-ci vers des outils de gestion. Ce travail de thèse repose sur un ensemble d’expériences et de modélisations destinées à approfondir notre compréhension générale du comportement associatif de poissons grands pélagiques avec des objets flottants à la surface de l’océan. Notre objectif est de tester si les milliers d’objets flottants artificiels déployés par les pêcheurs (DCP - Dispositifs de Concentration de Poissons) constituent des pièges écologiques pour les thons tropicaux. <p><p>Pour mener à bien ce travail, nous avons dans le premier chapitre caractérisé le comportement individuel de thons dans un réseau de DCP ancrés. L’analyse de données de marquage acoustique de 96 thons albacores (Thunnus albacares) (30-96 cm) à Hawaii montre que les thons présentent une plasticité comportementale forte face aux DCP qu’ils rencontrent mais également que le temps de résidence sous les DCP diminue avec la taille des individus. Afin de quantifier l’impact de l’augmentation de la densité de DCP il est essentiel de comprendre les mécanismes et les facteurs qui influencent les temps de résidences sous les DCP. Dans le second chapitre, des expériences de choix binaires suggèrent un rôle de la biomasse agrégée dans la formation, la maintenance et la dispersion des agrégations que forment les thons sous les objets flottants. La quantification de la dynamique des arrivées et des départs des poissons aux DCP permettra de valider les hypothèses que nous proposons concernant les mécanismes sociaux sous-jacents d’une part et d’autre part de tester l’influence de la qualité de l’environnement et de la densité de DCP sur les temps de résidences individuels et la distribution spatiale des populations. Dans le troisième chapitre, la comparaison de facteurs de condition de listaos (Katsuwonus pelamis) matures capturés en bancs libres et sous objets flottants dans une zone naturellement riche en objets flottants, et relativement peu impactée par le déploiement de DCP (Le Canal du Mozambique), nous a permis d’établir un point de référence essentiel pour estimer les effets des perturbations actuelles. Plus généralement, les résultats obtenus dans les différents chapitres tendent à conforter l’hypothèse d’un rôle social et non trophique des objets flottants dans l’écologie de thonidés. Les résultats obtenus durant cette thèse amènent à poser un regard nouveau sur l’hypothèse du piège écologique. <p><p>Notre travail s’est principalement intéressé à un modèle biologique de choix, les thons tropicaux. Cependant le cadre théorique des questions abordées, les outils d’observations et les méthodes d’analyses développées sont assez génériques pour être appliqués aux autres espèces rencontrées sous les objets flottants. Cette recherche s’intègre plus généralement dans les problématiques visant à mieux comprendre les stratégies comportementales et la distribution des populations dans des environnements multi-sites.<p> / Doctorat en Sciences agronomiques et ingénierie biologique / info:eu-repo/semantics/nonPublished