No description available.

The two otolith organs (the saccule and utricle) are positioned perpendicular to each other and sense linear acceleration, head tilt, and gravity, with the primary role of providing input to the vestibulospinal reflex for postural stability. The vestibulospinal reflex serves to modulate posture via two descending pathways that aid in tonic contractions of the antigravity muscles in the arms and legs (lateral vestibulospinal tract) and activate neck motoneurons for the coordination of neck and eye movements (medial vestibulospinal tract). The lateral vestibulospinal tract receives the majority of its input from the otoliths and the cerebellum, whereas the medial vestibulospinal tract receives the majority of its input from the semicircular canals.

The focus of this work was on the use of otolith microchemistry and fish eye lens chemical profiles to measure fish movement and provided indirect support for the use of otolith microchemistry to examine exposure to crude oil. Chapter 1 provides an introduction to the applications of otolith microchemistry and eye lens isotopic profiles. In the second chapter, which examined associations between metal exposure and lesion formation in fishes collected after the Deepwater Horizon (DWH) oil spill, I did not observe any change in oil-associated metal concentrations in otoliths coinciding with the timing of the DWH oil spill. This suggests that either the technique used is not sensitive enough to detect any transient changes that may have occurred because of exposure to the oil spill or that the fish examined were not exposed to the oil spill. However, I did find that lesioned fish may have been exposed to a persistent source of trace-metals in the GoM prior to, during, and after the oil spill, and metal-induced immunomodulation may have occurred in these fish. These interactions between the physiological and environmental modulation of otolith element incorporation were explored further in Chapter 3 in which multiple tests demonstrated that physiology explained more of the variation in otolith chemical tags than ambient water chemistry. These findings suggest that the use of otolith microchemistry alone to track fish movement and potential exposure to harmful metals may be complicated by physiological control of otolith microchemistry. Thus, in Chapter 4, I pursued a novel method to evaluate the movement of fish across isoscapes of varying δ15N. I validated the use of fish eye lenses as potential lifetime recorders of isotopic histories and in Chapter 5 compared the use of fish eye lens δ15N profiles to otolith microchemistry profiles to examine fish movement. Both techniques suggested similar patterns of movement in Red Snapper from the northern GoM to the West Florida Shelf. This is the first study to use these complimentary techniques to track fish movement.

The resurgence of Texas' snook (Family Centropomidae) recreational fishery is coupled with an uncertainty as to what species occur in State waters, a limited understanding of life history, and habitat needs of its constituents. This study described species composition and early life history aspects of juvenile (< 100 mm SL) centropomids taken in bag seine collections in estuarine and freshwater habitats along the upper, middle, and lower coast of Texas during 2006 to 2010. Centropomus specimens (n = 548) captured from 41 locations across the Texas coast as well as congeners from Mexico (n = 24), Florida (n = 7), and Costa Rica (n = 3) were used in a genetics- and meristic-based determination of species composition, growth rates, range of hatching dates, geographic distribution, and habitat association. Genetic analyses of the mitochondrial DNA 16s ribosomal RNA gene and the mitochondrial control region (D - loop) validated the presence of smallscale fat snook (C. parallelus Poey, 1860, n = 333), common snook (C. undecimalis Bloch 1792, n = 212) and Mexican snook (C. poeyi Chavez, 1961, n = 3) in Texas, with the last of these validations representing the first known record of this species in Texas. AMOVA of 16s and D - loop sequences failed to detect genetic differentiation within Texas for C. parallelus and C. undecimalis. However, AMOVA for 16s and D - loop C. undecimalis sequences did yield significant genetic differences between Texas and Mexico against those from Florida and Costa Rica. Juvenile centropomids (< 100 mm SL) in Texas occupied backwater habitats with dissipated currents similar to those of Florida congeners (tidal sloughs, freshwater habitats, and structured shorelines). Coastal ranges of these species differed with C. parallelus taken from the Rio Grande to West Galveston Bay, whereas C. undecimalis was captured from the Rio Grande northward near Palacios. Three C. poeyi were captured at only two locations (Laguna Vista and Port Aransas). Daily growth rates varied between species and capture years, with these ranging from 0.22 to 0.97 mm d^-1. Analyses of hatch-date distribution suggest centropomids in Texas begin spawning in August and continue it through late September into mid-November.

<p>The rationale of this study is to apply light stable isotope chemistry towards investigations that require temporally high-resolution data. High-resolution (or high sampling frequency) data sets, are critical for testing environmental and/or paleoenvironmental hypotheses that seek to explain processes occurring over rapid or short time intervals. The investigation of climate variation (e.g., seasonality, El Niño, deglaciation), animal migration and physiology, and disturbance ecology (e.g., fire, flooding) benefits from the recovery of proxy information at decadal to subannual resolutions. The type of material used also dictates a spatial scale. Herein are presented four studies that utilize high-resolution light stable isotope profiles with contrasting temporal and spatial scales. The first study employs advances in three-dimensional computer-controlled micromilling to recover ~daily to weekly deposited carbonate from small (~1 cm) mollusc shells. Stable oxygen isotope values from freshwater mollusc shells are predictably related to the local environment of growth using previously published temperature-fractionation relationships, providing a paleoclimate record of temperature and precipitation. The second study investigates variation in stable carbon isotope values from Aplodinotus grunniens otoliths, for which high-resolution patterns were critical in assessing metabolic rate as the governing control. The third study employs high-resolution stable oxygen and carbon isotope values to determine chinook salmon (Oncorhynchus tshawytscha) seasonal and ontogenetic migration in Lake Ontario and its tributaries. Lastly, high-resolution stable hydrogen and carbon isotope values of chitin derived from Mexican free-tailed bat (Tadarida brasiliensis) guano are presented, providing a record of abrupt climate change. Thus, this thesis reports on promising new research avenues for paleoclimatology, paleoecology, and modern ecology.

<p>The rationale of this study is to apply light stable isotope chemistry towards investigations that require temporally high-resolution data. High-resolution (or high sampling frequency) data sets, are critical for testing environmental and/or paleoenvironmental hypotheses that seek to explain processes occurring over rapid or short time intervals. The investigation of climate variation (e.g., seasonality, El Niño, deglaciation), animal migration and physiology, and disturbance ecology (e.g., fire, flooding) benefits from the recovery of proxy information at decadal to subannual resolutions. The type of material used also dictates a spatial scale. Herein are presented four studies that utilize high-resolution light stable isotope profiles with contrasting temporal and spatial scales. The first study employs advances in three-dimensional computer-controlled micromilling to recover ~daily to weekly deposited carbonate from small (~1 cm) mollusc shells. Stable oxygen isotope values from freshwater mollusc shells are predictably related to the local environment of growth using previously published temperature-fractionation relationships, providing a paleoclimate record of temperature and precipitation. The second study investigates variation in stable carbon isotope values from Aplodinotus grunniens otoliths, for which high-resolution patterns were critical in assessing metabolic rate as the governing control. The third study employs high-resolution stable oxygen and carbon isotope values to determine chinook salmon (Oncorhynchus tshawytscha) seasonal and ontogenetic migration in Lake Ontario and its tributaries. Lastly, high-resolution stable hydrogen and carbon isotope values of chitin derived from Mexican free-tailed bat (Tadarida brasiliensis) guano are presented, providing a record of abrupt climate change. Thus, this thesis reports on promising new research avenues for paleoclimatology, paleoecology, and modern ecology.

Recent advances in otolith microchemistry have established that trace element composition can be used to chemically reconstruct fish life history and serve as a stock identification tool. In modern fisheries practices, these two applications are especially pertinent to wild salmon populations, which are difficult to track over large spatial scales and nearly impossible to identify in mixed populations. This project has applied a novel method using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to anadromous sockeye salmon (Oncorhynchus nerka) otoliths from four separate watersheds in Sitka, Alaska. Spatial distributions of Li, Mg, Mn, Zn, Sr, and Ba were determined via continuous lateral ablation scans across the diameter of transversely sectioned sagittal otoliths. Time-series data generated from line scan analysis were used to chemically reconstruct sockeye life history, and examine elemental signatures in the core, freshwater, and marine growth regions of otoliths for stock identification purposes. Chemical profiles of life history showed that Sr, Ba, and to a lesser degree Mg, reflected ambient chemistry, and were effective for tracking sockeye migration from fresh to marine water. Manganese was also effective for determining migration to fresh and marine water; however, it is believed that diet more than ambient chemistry is the factor controlling uptake. Elements such as Zn and Li provided information related to fish physiology, such as growth and changes in osmoregulation during transitions from low to high salinity environments. Results also showed that several elements were either enriched or depleted in the core of sockeye otoliths. Maternal investments and spatial differences in crystal structure are believed to significantly affect element uptake in otoliths during incubation and early development. Elemental signatures in the otolith core may therefore be inaccurate as an indicator of stock origin. This problem was investigated by isolating core, freshwater, and marine signatures and evaluating individually their ability to correctly classify sockeye otoliths to their natal watersheds using step-wise discriminant function analysis. This demonstrated that freshwater signatures provided the greatest accuracy (91%) for stock ID. Core signatures, which have been used in past stock ID studies, showed poor classification results (68%) for sockeye salmon otoliths. Trace element signatures from the marine growth regions of sockeye otoliths displayed the poorest classification accuracy (52.5%) of the three growth regions. Thus, freshwater signatures are the most effective tool for identifying the origin of wild salmon, even when they far removed from their natal watersheds.

La compréhension de la connectivité entre les nourriceries estuariennes et les habitats marins est fondamentale pour l'étude de la dynamique des peuplements et des populations de poissons et pour la conception de stratégies efficaces de conservation et de gestion des pêches. Le but de ce travail était donc de fournir une première référence faunistique et écologique des poissons des estuaires et du lagon de l'île de Socotra (Nord-Ouest de l'Océan Indien) pour les gestionnaires de la zone côtière, avec un accent particulier sur le fonctionnement des populations d'une espèce sentinelle: Terapon jarbua. Dans cette étude, une approche multidisciplinaire a été développée afin de comprendre le fonctionnement et l'importance des estuaires (TOCE's : Temporarily Open / Closed Estuaries) et du lagon de l'île de Socotra pour les poissons marins. Différents outils de la biologie et de la chimie (taxonomie, écologie, phylogéographie, génétique des populations, microstructure et microchimie des otolithes) ont été utilisés et les principales conclusions de ce travail sont les suivantes: 1) Les estuaires de Socotra sont composés de 64 espèces dans 30 familles, un chiffre élevé par rapport aux normes régionales. La comparaison avec les inventaires faunistiques d'Afrique du Sud et du Yémen suggère que Socotra joue le rôle de tremplin biogéographique, en permettant la connexion d'une grande variété de groupes taxonomiques provenant de différentes unités biogéographiques. De plus 33 des 64 espèces recensées sont considérées comme importantes pour l'économie locale, soulignant l'importance primordiale des estuaires comme sites de fraie et nourriceries, pour le fonctionnement durable des services écosystémiques. 2) La phylogéographie et la structure génétique des populations de T. jarbua ont été analysées considérant des marqueurs de type Cytochrome c Oxydase sous-unité I et microsatellites. Une différenciation génétique élevée et significative a été observée à l'échelle de l'Indo-Ouest Pacifique. Trois groupes de populations ont pu être identifiés, le groupe du Nord-Ouest de l'Océan Indien (Socotra, Yémen et Iran), le groupe de l'Ouest de l'Inde et le groupe de la Mer de Chine. Cependant, les grandes différences nucléotidiques observées soulèvent certaines questions concernant l'identification de l'espèce et suggèrent que T. jarbua pourrait être en réalité un complexe d'espèces, en dépit du fait que la coloration caractéristique de T. jarbua facilite son identification. A l'échelle plus restreinte du Nord-Ouest de l'Océan Indien, une expansion récente de la population de T. jarbua après des extinctions locales au cours des glaciations du Pléistocène pourrait expliquer la faible mais significative différenciation génétique. Le génotypage des marqueurs microsatellites souligne une différenciation génétique relativement élevée et significative entre les estuaires, sur le secteur Socotra-Yémen. Si la distance géographique n'est pas un facteur structurant majeur des populations de T. jarbua dans la région du Golfe d'Aden, le lien étroit entre les juvéniles T. jarbua et les TOCE, ainsi que les phénomènes d'ouverture associés à de possibles goulots d'étranglement démographiques dans ces systèmes côtiers, peuvent expliquer la mise en place d'une différenciation génétique locale significative entre les estuaires. Bien que l'environnement dynamique de la région puisse limiter la différenciation génétique, la courte durée du stade larvaire de cette espèce (25 jours estimés par la lecture des microstructures de l'otolithe) et la possible rétention des larves dans certains secteurs peuvent réduire l'homogénéisation à plus grande échelle géographique. 3) Les analyses de la composition élémentaire des nucleus d'otolithes suggèrent l'existence de plusieurs zones de fraie marines ; ces données confrontées aux résultats des investigations en génétique des populations suggèrent un modèle régional de métapopulation composée de sous-populations ouvertes… / Understanding connectivity between estuarine nurseries and marine habitats is fundamental to explore fish population dynamics and to the design of effective conservation and fisheries management strategies. The aim of this work was to provide the first faunistic and ecological baseline of Socotra Island (North-Western Indian Ocean) estuaries and lagoon fishes for governmental coastal managers and decision makers, with a particular focus on the population functioning of a sentinel species: Terapon jarbua. In this study, a multidisciplinary approach was developed to understand the functioning and importance of Socotra estuaries (TOCE's: Temporarily Open / Close Estuaries) and lagoons for marine fishes. Several biological and chemical tools (taxonomy, ecology, phylogenetics, population genetics, otolith microstructure, otolith microchemistry) were used and the main findings of this work are as follows: 1) Socotra estuaries are composed of 64 species in 30 families, a high figure by regional standards. The comparison with faunistic records from South Africa and Yemen mainland provides further support to Socotra's function as a biogeographic "stepping stone" for certain species. Moreover 33 out of the 64 recorded species were considered as relevant species for the local economy. This underscores the paramount importance of these coastal water bodies as spawning and nursery sites and for the sustainability of vital provisioning ecosystem services. 2) The phylogeography and the genetic structure of T. jarbua populations were analyzed considering Cytochrome c Oxidase subunit I and microsatellites and underlined two patterns of genetic structure. A high and significant genetic differentiation was observed at the scale of the Indo-West Pacific. Three population clusters could be drawn, the North-Western Indian Ocean cluster (Socotra, Yemen and Iran), the West Indian Shelf cluster and the Chinese Sea cluster. However, the large number of nucleotide differences raised some issues concerning the species identification as T. jarbua might be a species complex, despite the fact that it shows a characteristic color pattern easily identifiable. At the restricted scale of the North-Western Indian Ocean, recent population expansion after local extinctions during the Pleistocene glaciations might explain small but significant genetic differentiation. Considering microsatellites, genotyping highlighted a relatively high and significant genetic differentiation between estuaries, over the Socotra-Yemen region. Geographical distance is not a major structuring factor for T. jarbua populations in the wider Gulf of Aden region. The strict link between juvenile T. jarbua and TOCE's, and the opening/closing associated with possible demographic bottlenecks, could increase the local differentiation among estuaries. Although the dynamic environment of the region driven by the monsoon system could reduce the genetic differentiation between populations, the short larval stage duration and potential larval retention in particular sectors might reduce homogenization over larger geographical scale. 3) The analysis of otolith nucleus elemental composition suggested the existence of several marine spawning grounds, thus confirming the population genetics approach suggesting a regional model of metapopulation composed of open subpopulations (i.e. multiple sources and more or less pronounced mixtures of larval flows displaying a spatio-temporal variability). In addition, transect Sr:Ba ratio analysis along the otolith growth axis showed clear pattern of post larval migrations into estuarine nurseries where individuals remain for two years. Finally, otolith edges elemental fingerprint assignation tests to nurseries were highly accurate and could conduct in the future to the assessment of the contribution level of a particular nursery to the adult population of T. jarbua as well as others ecologically or economically important species.

No description available.

La daurade royale (Sparus aurata, L.) est une espèce migratrice, connue pour coloniser les lagunes côtières, fortement anthropisées, du printemps à l'automne. Identifier les lagunes clés pour l'accomplissement du cycle de vie doit donc permettre de mieux gérer et protéger les populations de daurades du Golfe du Lion. Dans ce cadre, la microchimie de l'otolithe est un outil précieux. Au cours de sa croissance, cette concrétion de l'oreille interne incorpore des éléments chimiques prélevés dans le milieu. Piégés dans le réseau cristallin, ils sont une image des conditions environnementales rencontrées par le poisson à une date donnée ce qui rend possible, en théorie, de reconstituer ses migrations. Néanmoins, pour cela, il faut (i) connaître précisément la croissance du poisson et de ses otolithes, (ii) mettre en évidence des différences chimiques entre les zones clés pour le cycle de vie en identifiant les outils statistiques appropriés pour la discrimination des habitats. Ainsi, (i) la comparaison objective de modèles de croissance, associée à l'analyse d'un spécimen exceptionnellement âgé a permis de remettre en cause les données classiquement acceptées sur la croissance de la daurade et le schéma de croissance de ses otolithes a été établi ; (ii) la comparaison de 4 méthodes statistiques de discrimination a permis de sélectionner la méthode du random forest pour différencier les signatures chimiques des otolithes de S.aurata de différentes lagunes. Ces avancées ont permis de confirmer le schéma migratoire précédemment décrit, tout en révélant une variabilité des comportements entre les individus et au cours de la vie du poisson. Les juvéniles semblent préférer les lagunes dessalées, suggérant un rôle de nurserie pour ces habitats, alors que les adultes préfèrent des lagunes profondes comme l'étang de Thau. Le maintien de la diversité des caractéristiques des différentes lagunes est donc nécessaire, afin d'assurer la pérennité de la population de S.aurata dans le Golfe du Lion. / The Gilthead seabream (Sparus aurata L.) is a migratory species, known to colonize coastal lagoons with high anthropogenic load, from spring to autumn. It is necessary to identify key lagoons for the seabream life cycle to allow better management and protection of gilthead seabream populations in the Gulf of Lions. For this, otolith microchemistry is a powerful tool. As it grows, this inner ear concretion absorbs chemical elements taken in its surrounding. Traped in the crystal net, these elements are an image of the environmental conditions met by the fish individual. It is then possible to rebuild fish past migrations. For this it is necessary to (i) precisely know the fish and otoliths growth calendars and (ii) identify chemical differences between the key habitats for the life cycle by choosing statistical methods for habitat discrimination.(i) The objective comparison of many growth models, combined to the analysis of an exceptionally old specimen allowed to propose a new scheme for the gilthead seabream growth and its otolith growth pattern was established ; (ii) the comparison of 4 statistical discrimination methods allowed to select the random forest method to differentiate the otolith chemical signatures of gilthead seabreams from various lagoons. These insights confirmed the already described migration pattern and emphasized a behavioural variability between individuals and between periods of life. The juveniles seem to prefer brackish lagoons, suggesting a nursery rôle for these habitats, whereas the adults prefer deeper lagoons as the Thau lagoon. The maintenance of the lagoons diversity is thus necessary for the preservation of the Gilthead seabream population in the Gulf of Lions.