The growth rate of a fish is a fundamental function used in stock assessments to estimate the population size and the fishery pressure affecting the species. There has been recent debate within the stock assessment community regarding which type of growth model best represents the true growth rate of yellowfin tuna (Thunnus albacares), in the Atlantic Ocean; specifically, should assessments use a traditional von Bertalanffy growth curve or a so-called “two-stanza” growth curve, which combines one growth rate for smaller individual tuna and another for larger sizes. Using a simulated population created with the software R, both growth models were compared under different scenarios. The first part of this thesis examines the effect of different fisheries and their associated gear selectivity. Purse seine, baitboat and pelagic longline fisheries, which target yellowfin tuna in the Atlantic Ocean, were incorporated into the analysis. The second part looks at different sources of variability that occur either in nature (observation error) or in the process of analysis (process error). These include different growth variation, looking only at the fast growing young fish and using a set birth date versus a spawning period. These scenarios were used to determine if the sample, derived from a fishery-dependent sample, reflects the true population. Three populations of yellowfin tuna were created: an un-fished population, a fished population from stock assessment data, and a fished population from simulation software called ‘Population Simulator’. These populations were all analyzed for the different scenarios as well as the different fisheries. The final part of this thesis looks at three similar tuna species; skipjack (Katsuwonus pelamis), bigeye (Thunnus obesus ) and albacore (Thunnus alalunga). The same scenarios and gear selectivities were applied to these tuna species. The results of this study showed that the two-stanza growth curve was not a better fit for yellowfin tuna population in the Atlantic Ocean than the traditional von Bertalanffy growth curve. There were several scenarios that favored the two-stanza growth curve, but either it was a sample population not representative of the Atlantic Ocean population, or the two-stanza had no initial growth rate, making it the same as a traditional growth curve. Based on these results, it was evident that the traditional von Bertalanffy growth curve was the more accurate growth curve to use for yellowfin tuna in the Atlantic Ocean and it is recommended that this growth curve be used in the stock assessments going forward.

Les hétérogénéités de répartition de la matière organique (MO) du Crétacé de l'océan Atlantique central sont souvent liées à des facteurs d'ordre géodynamique et paléocéanographique. Or, la forte proportion de MO terrestre questionne l'hégémonie de ces mécanismes et appelle à mieux contraindre la dynamique sédimentaire des dépôts associés à cette MO. Par une approche source to sink couplant une étude géochimique de provenance à une étude de bassin à partir de données de subsurface, nous montrons une réorganisation du drainage sur les cratons ouest-africain et guyanais, caractérisée par une extension progressive des bassins versants vers les domaines internes pendant le Crétacé supérieur. En Afrique, ce processus s'accompagne d'un arrêt de la dynamique turbiditique dès le Turonien, et d'une diminution de celle-ci au Guyana Suriname. Dans les deux cas, ces changements ont été défavorables à l'accumulation de matière organique en domaine océanique profond. / The distribution heterogeneities of Cretaceous organic matter (OM) in the Central Atlantic Ocean are often related to geodynamic and paleoceanographic factors. However, the high proportion of terrestrial OM questions the hegemony of these mechanisms and shows the need to better constrain the sedimentary dynamics of organic-rich sediments. Using a source-to-sink approach coupling a geochemical provenance study with a basin study from subsurface data, we show a reorganization of drainage on the West African Craton and the Guyana Shield, characterized by a gradual extension of watersheds to the inner areas during the Upper Cretaceous. In the African deep basin, this process is coeval to a break of the turbiditic sedimentation from the Turonian and to its decrease in the Guyana-Suriname deep basin. In both cases, these changes were unfavorable to the enrichment of OM in the deep oceanic domain of the Central Atlantic.

Thesis (M.S.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1999. / Includes bibliographcial references (p. 117-118). / This thesis describes an attempt to build a box model of the circulation in the eastern North Atlantic and to use it with transient tracer data to infere rates of ventilation in the subtropcial thermocline. The starting point is the analysis of former studies on box models, transient tracer data and the combination of both. The advantages and pitfalls associated with the tracer age approach on the one hand and the inventory approach on the other hand are weighed and the choice set upon the inventory approach is justified. Next the data used is presented and processed, and the results are compared with the known circulation patterns of the basin. The estimates computed fall in the expected and acceptable range. The uncertainties, in particular on the boundary conditions, are acknowledged to be a crucial factor on the following analysis yet only rough estimates can be produced. In particular, the geostrophic velocities at the boundaries can only be determined lest an unknown constant. No internally consistent model can be found that satisfies the linear conservation balances, geostrophy and steadiness assumptions and the boundary conditions imposed. The circulation generated only satisfies mass balance and the boundary conditions to a certain extent. Experience suggests that there are incompatibilities among the various constraints. Two different numerical methods fail to find an acceptable solution. Using the default circulation obtained, the forward problem is formulated and investigated. The resulting tracer distribution and time history is incompatible with the observed field. As a consequence, an attempt is made at the inverse problem in the hope that relaxation of the boundary conditions will provide some insight into the general failure of the model. As there appears to be no feasible solution though, the circulation is further inspected and it is concluded that given its flaws, no boundary condition will be able to generate a tracer field even in partial agreement with the observations. It is finally concluded that transient tracers can be used to dismiss grossly wrong circulation models. / by Gwenaëlle C. Jeunhomme. / M.S.

Thesis: Ph. D., Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 163-174). / The Gulf Stream and Deep Western Boundary Current (DWBC) shape the distribution of heat and carbon in the North Atlantic, with consequences for global climate. This thesis employs a combination of theory, observations and models to probe the dynamics of these two western boundary currents. First, to diagnose the dynamical balance of the Gulf Stream, a depth-averaged vorticity budget framework is developed. This framework is applied to observations and a state estimate in the subtropical North Atlantic. Budget terms indicate a primary balance of vorticity between wind stress forcing and dissipation, and that the Gulf Stream has a significant inertial component. The next chapter weighs in on an ongoing debate over how the deep ocean is filled with water from high latitude sources. Measurements of the DWBC at Line W, on the continental slope southeast of New England, reveal water mass changes that are consistent with changes in the Labrador Sea, one of the sources of deep water thousands of kilometers upstream. Coherent patterns of change are also found along the path of the DWBC. These changes are consistent with an advective-diffusive model, which is used to quantify transit time distributions between the Labrador Sea and Line W. Advection and stirring are both found to play leading order roles in the propagation of water mass anomalies in the DWBC. The final study brings the two currents together in a quasi-geostrophic process model, focusing on the interaction between the Gulf Stream's northern recirculation gyre and the continental slope along which the DWBC travels. We demonstrate that the continental slope restricts the extent of the recirculation gyre and alters its forcing mechanisms. The recirculation gyre can also merge with the DWBC at depth, and its adjustment is associated with eddy fluxes that stir the DWBC with the interior. This thesis provides a quantitative description of the structure of the overturning circulation in the western North Atlantic, which is an important step towards understanding its role in the climate system. / by Isabela Astiz Le Bras. / Ph. D.

No description available.

No description available.

Commercial capture-based aquaculture of the Atlantic bluefin tuna (ABT), Thunnus thynnus (L.), has been prominent in the Mediterranean for over a decade. Owing to several limitations encountered in working with the species, including its high commercial value, there has been little research carried out relating to this species. The objective of this study was to examine several health parameters of captive ABT. These included an examination of coronary artery lesions, haematology, plasma biochemistry, assessment of immune function and changes in fatty acid (FA) flesh content through the on-growing period. Arteriosclerosis in fish is a pathologic condition of uncertain etiology and involves the main coronary artery in teleosts. Apart from reports of their widespread occurrence in salmonids, they have been described from a restricted number of wild ABT specimens but have not received further attention. This investigation analysed the effect of size and period of net-pen rearing on the prevalence and severity of arteriosclerotic lesions in ABT. Coronary arteries from wild and captive fish were investigated and prevalence was 100 %, but increasing structural degradation was observed with increasing fish size, suggesting that lesions progress throughout the life of the fish. Due to the limited availability of wild specimens, the effect of captivity on arteriosclerosis in ABT could not be adequately quantified, although observations suggest that the farming process has no major effect on arteriosclerotic lesions in ABT. Studies on the haematology, plasma biochemistry and immunology of ABT are limited. Haematological and plasma biochemical indices are useful in animal health assessment but use of these requires the establishment of species-specific ranges. Blood was collected from captive ABT specimens of varying weight (61-361 kg) and the major haematological (n = 45), plasma biochemical (n = 30) and immunological parameters (n = 45) were quantified. Size-based differences were found in haematological indices between experimental sub-groups including increased erythrocyte number and haemoglobin level in smaller ABT. No differences were found in immunological parameters except for total IgM levels, which were higher in the smaller individuals. Preliminary investigations indicated that disease prevalence in captive ABT is very low. Epidermal mucus is an important interface between fish and their environment and comprises immunological components which act as a first barrier against pathogen entry or colonisation. Mucus was collected from captive ABT and analysed for innate immune components. The presence of IgM was detected in the mucus of ABT by an enzyme-linked immunosorbent assay and several different enzymes were detected with an API-ZYM kit assay. Zymography experiments confirmed the presence of protease-like enzymes in the mucus, while enzyme assays quantified alkaline phosphatase, protease, esterase and cathepsin B activities. Lysozyme levels were high. The mucus agglutinated sheep erythrocytes but did not demonstrate complement or bacteriolytic activity. There is restricted information on the fatty acid composition of farmed ABT or how this is influenced when the fish are held under commercial aquaculture conditions. This study investigated the FA composition of farmed ABT, its variation by dorsal muscle region and the correlation between dietary FA composition with that of the fish. Analysis of flesh samples retrieved from farmed ABT did not reveal significant differences in the FA composition of experimental sub-groups irrespective of size, time held in captivity or diet. These results indicate that FA metabolism in ABT is substrate-selective. Gene expression measurements from several organs of ABT showed that expression of Δfad5 and elovl5, genes involved in FA metabolism, were highest in the brain followed by the liver but no expression of these genes was detected in the spleen. The findings of this research address aspects of health evaluation and nutritional status in farmed ABT and are discussed in terms of farming practice. Conclusions from some of these studies suggest that the practice of holding wild-captured stock in cages for periods of up to 18 months does not result in significant impact on ABT.

This study aimed at complementing studies of sperm whale social and vocal behaviour that were restricted to the Pacific Ocean. The characteristic multi-pulsed structure of sperm whale clicks allows for estimation of whales' size from measurements of the inter-pulse intervals (IPI). I have developed two new automatic methods for IPI estimation from clicks recorded during foraging dives. When compared to other previously developed methods, the newly developed method that averages several clicks' autocorrelation function showed the best performance amongst the automatic methods. Previous studies did not support individual identity advertisement among social unit members as the function for the sperm whale communication signals called codas. I tested within coda type variation for individual specific patterns and found that, while some coda types do not allow for individual discrimination, one did so. This variation suggests that different coda types may have distinct functions. Analysis of social structure in the Azores found that, similar to the Eastern Tropical Pacific, sperm whales form long term social units of about 12 individuals. Unlike the Pacific Ocean, Azorean social units do not form temporary groups with other units, suggesting differences in the costs and benefits of group formation. I argue that these are due to differences in terms of predation pressure and intraspecific competition between the Azores and the Pacific study sites. The variation of coda repertoires in the Atlantic also showed a pattern dissimilar to that previously documented in the Eastern Tropical Pacific. In the North Atlantic, coda repertoire variation is mostly geographic, which is parsimoniously explained by random drift of culturally transmitted coda repertoires. No sympatric vocal clans with distinct dialects were found as has been noted in the Pacific. Drawing upon the differences found in social structure I argue that selection for maximization of differences between units with similar foraging strategies may have led to the Pacific vocal clans. The differences between oceans suggest that sperm whales may adaptively adjust their behaviour according to experienced ecological conditions.

Le propos de cette thèse est d’étudier le rift de l’Atlantique sud au Congo, en se focalisant sur (1) la dynamique des reliefs amont du rift (les épaulements de rift), (2) l’architecture stratigraphique du remplissage sédimentaire et (3) le routage sédimentaire ante- à syn-rift. L’etude de terrain a permis de reconstituer la géométrie des paléovallées, le cadre sédimentaire et stratigraphique du remplissage sédimentaire et de discuter des implications géodynamiques de ces paleovalleys en termes de dynamique du rift et de contrôle des systèmes sédimentaires. Ces paléovallées ont été incisées dans le substratum précambrien du Mayombe par des rivières alluviales pendant la phase d'étirement du rifting et remplies par des sédiments d’âge Aptien moyen de la Formation de Chéla. Le remplissage sédimentaire de ces paléovallées consiste en des faciès gravitaires sousaquatiques interdigités dans les argiles lacustres riches en matière organique, recouvrant en discordante le socle Précambrien du Mayombe. Ces depôts s'organisent en une séquence transgressive, caractérisée par l’empilement des séquences élémentaires de type finning-up . L’analyse sédimentologique de carottes a permis de caractériser les environnements de dépôts des Formations de Pointe-Noire, Pointe-indienne et de Chéla, correspondant à la phase d’hyperextension (sag) de l’evolution du rift. La Formation de Pointe-Noire d’âge Barrémien moyen est constituée des faciès gravitaires de cônes sous-lacustres profonds à dominance argileux et riches en matière organique dans lesquels s’intercalent localement des faciès carbonatés de plate-forme peu profonde et gravitaires resédimentés du membre de Toca, accumulés au cours d'une importante transgression associée à un évènement anoxique général. La Formation de Pointe-indienne d’âge Barrémien supérieur à Aptien inferieur est caracterisée par variations latérales et verticales de faciès. Elle comprend des faciès gravitaires gréso-argileux (membre Mengo) de cônes sous-lacustres profonds, surmontés par des faciès mixtes silicoclastiques et carbonatés de rampe interne à moyenne dominée par des vagues de tempêtes (Membre des Argiles vertes) passant progressivement vers le haut à des faciès deltaïques de Tchibota. La formation de Chéla d’âge Aptien moyen se caractérise par des variations latérales et verticales de faciès. Elle comprend des faciès sous-aquatiques de delta alluvionnaire passant latéralement aux faciès gravitaires sous-lacustres, suivi par des faciès de baies mixtes lacustres -marine, surmontés par des faciès de sabkha (membre Vembo) recourvets par les evaorites de Loémé. Les facies de sebkha au sommet de la Formation de Chéla témoignent d’une incursion marine avant la mise en place des évaporites. Les corrélations stratigraphiques entre puits ont permis de subdiviser la succession sédimentaire de la phase d’hyper-extension (sag) en trois principales séquences de dépôt montrant respectivement des tendances rétrogradante, progradante et rétrogradante. La datation des zircons et apatites détritiques a permis de reconstituer le routage sédimentaire ante- à syn-rift et l’évolution de reliefs en amant du rift. Les résultats montrent des changements spatio-temporels de sources de sediments et deux régions de provenance de sédiments. Les sédiments ante-rift (Formation de Vandji) d’age Berriasien proviennent des sources lointaines, confirmant l’existence d’un système pre-rift – et donc d’un bassin antérieur au système rift du segment central de l’Atlantique sud, alimenté de l’ouest à sud-ouest par des sources angolaise et brésilienne. Les sédiments syn-rift (Formation de Djéno) d’age Barremien inférieur et Sag (Formation de chéla) d’age Aptien moyen proviennent des sources locales (massif du Mayombe), ce qui implique un changement majeur de sources et de reliefs entre les phases pre-rift et syn-rift et l’existance des reliefs en amont de la faille bordière pendant les phases d’étirement et d’hyper-extension du rift. / The purpose of this thesis was to study the South Atlantic rift system in Congo by focusing on (1) the dynamic of the upstream paleoreliefs (rift shoulders), (2) the stratigraphic architecture and (3) sediment routing of the pre to syn-rift sedimentary infilling. Detailed field mapping allows to characterize the geometry of the incised valleys, sedimentary environments of thier sediment infilling and to discuss the geodynamic implications of these incised valleys in terms of rift dynamic and control of sedimentary systems. These incised valleys were cut through the Precambrian Mayombe basement by alluvial processes shaping pediments during the stretching period of the rift and filled with middle Aptian siliciclastic sediments of the Chéla formation. The sediment filling consists of flood-generated sublacustrine gravity flow deposits interbedded with organic-rich lacustrine shales, overlying unconformably the basement. These deposits are organized into an overall transgressive depositional sequence, characterized by stacked of elementary fining upward facies sequences. Detailled facies analysis of cores permits to determine the sedimentary environments of the Pointe-Noire, Pointe-Indienne and Chéla Formation, developed during the hyper-extended (sag) rift phase. The middle Barremian Pointe-Noire Formation consists of organic-rich shale-prone deep-lacustrine fan facies intertonguing locally with shallow-water platform carbonate facies and gravity-flow resedimented carbonate facies of the Toca Member that were deposited in an anoxic deep-lake. The Late Barremian–early Aptian Pointe-Indienne Formation is characterized by facies heterogeneity. This Formation consists of sand-rich sublacustrine-fan gravity facies of Mengo member overlain by storm influenced mixed siliciclastic-carbonate ramp facies (Argiles vertes Member) passing upward to deltaic facies of Tchibota member. The middle Aptian Chéla Formation represents a widespread transgressive unit, characterized by lateral and vertical changes in facies and a variety of depositional environnements. It is made up of interbedded coarse-grained alluvial bedload facies and sub-lacustrine gravity facies at the base, overlain by lacustrine-marine mixed bay facies passing upward to sabkha facies, which in turn are capped by evaporites of the Loémé Formation. The sebkha facies records the late middle Aptian marine transgression on the Congo basin prior to the deposition of Upper Aptian evaporites of Loémé Formation. Well-log stratigraphic correlations permit subdivision of the middle Barremian to middle Aptian syn-hyper-extended rift-related deposits into three major depositional sequences that display retrogradation, progradation, and retrogradation stacking pattern, respectively. Detrital zircon and apatite provenance analyses provide a better understanding of sediment routing systems of the pre to syn-rift infilling, and paleorelief and tectonic evolutions during the Early Cretaceous times. The results show changes in sediment provenances and two different source areas. The Berriasian-Valanginian Pre-rift sediments of the Vandji Formation were derived from multiple and relatively distant source areas, located either in the South America and southern of Africa plate, thus supporting the existence of large intracratonic basin prior to the rifting, fed by prominent large-scale drainage system. located toward the southwest. In contrast to the Pre-rift sediments, the Barremian syn-stretched rift sediments of the Djeno Formation and the Aptian syn- hyper-extended rift sediments of the Chela Formation were derived from adjacent Precambrian Mayombe belt that underwent phases of tectonic uplift during the rifting. Consequently, this implies an abrupt change in sediment provenance and relief between the pre-rift phase and the Syn-rift phase and indicate the persistence of local sources, i.e. from rift shoulders, from the stretching rift phase to the hyper-extended (sag) rift phase.

Two sympatric species of dolphins (Atlantic spotted dolphins, Stenella frontalis and Atlantic bottlenose dolphins, Tursiops truncatus) have been long-term residents to Little Bahama Bank. This study assessed whether there was a change in residence patterns or diurnal foraging depths of bottlenose dolphins following a large emigration event in the resident spotted dolphin community on this sandbank. Photo-identification was used to identify individual bottlenose dolphins and compare pooled years before (2010-2012) and after (2013-2015) the spotted dolphin emigration. The identified community size and overall residency of the bottlenose dolphins remained similar, although two bottlenose dolphins emigrated over deep water to the site spotted dolphins emigrated. Bottlenose dolphins diurnally fed in shallower water but remained in the same geographic foraging locations. Reasons remain unknown for this depth change, but potential changes in the productivity of primary bottlenose dolphin foraging habitats or reduction of spotted dolphins from shallower depths remain possibilities. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection