Academic literature on the topic 'Northern Humboldt current ecosystem'
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Journal articles on the topic "Northern Humboldt current ecosystem"
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Cornejo, Rodolfo, Luis La Cruz, and Ramiro Castillo. "Distribución y biomasa de anchoveta (Engraulis ringens) y múnida (Pleuroncodes monodon) en el ecosistema marino de la Reserva Nacional de Paracas, región sur del Perú." Boletín de Investigaciones Marinas y Costeras 51, no. 1 (June 14, 2022): 99–116. http://dx.doi.org/10.25268/bimc.invemar.2022.51.1.1065.
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The present study determined the distribution and biomass of the Peruvian anchovy and pelagic red squat lobster related to the oceanographic characteristics in the marine protected area of the Paracas National Reserve in the Northern Humboldt Current System. Acoustic, biological, and oceanographic information was collected on the pelagic habitat in surveys carried out by the Peruvian Marine Research Institute during the summer and spring of 2018, 2019, and 2020. The results obtained indicated that the spatial occupation of the pelagic habitat of Peruvian anchovy and pelagic red squat lobster were influenced by the dynamics of upwelling, water masses, and a shallow and intense Oxygen Minimum Zone. Spatial overlap of high biomass of Peruvian anchovy and pelagic red squat lobster were recorded in the surface layer during the night. Although, with the presence of dense swarms of múnida in anoxic intermediate waters of the Oxygen Minimum Zone during the day. The Marine Protected Area off the Paracas National Reserve functions as a protection zone for the structure and functioning of the pelagic-neritic ecosystem and strengthens the fishery production of Peruvian anchovy stock in the Northern Humboldt Current System
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Gong, Yi, Yaxin Wang, Ling Chen, Yunkai Li, Xinjun Chen, and Bilin Liu. "Microplastics in different tissues of a pelagic squid (Dosidicus gigas) in the northern Humboldt Current ecosystem." Marine Pollution Bulletin 169 (August 2021): 112509. http://dx.doi.org/10.1016/j.marpolbul.2021.112509.
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Tam, J., S. Purca, L. O. Duarte, V. Blaskovic, and P. Espinoza. "Changes in the diet of hake associated with El Niño 1997−1998 in the northern Humboldt Current ecosystem." Advances in Geosciences 6 (January 9, 2006): 63–67. http://dx.doi.org/10.5194/adgeo-6-63-2006.
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Abstract. Hake (Merluccius gayi peruanus) predation plays an important role in the dynamics of the Humboldt Current ecosystem (HCE). Changes in the hake trophic habits associated with physical variability are expected to impact prey populations and to propagate through the food web. Time series (1995–2002) of (a) stomach contents of hake, (b) biomass estimations of fish prey species of hake, and (c) depth of the 15°C isotherm was analysed with the aim of exploring the impacts of El Niño 1997–1998 on the diet of hake. Biomass estimations of fish prey species were used to indicate resource availability, and depth of the 15°C isotherm to represent variability associated with the ENSO cycle in the physical environment of hake. The richness of prey species increased during the months when 15°C isotherm reached its deepest position, supporting the hypothesis of increased biodiversity (tropicalization) of the HCE during El Niño events. An increased variability in stomach fullness of hake was detected after 1999 which could indicate high heterogeneity in the food supply as a consequence of impacts of the warm event in the biotic community structure of the HCE, a physiological impairment of hake or an effect of the abrupt reduction in the mean total length of hake, postulated as a compensatory response to fishery pressure. Hake can be characterized as an opportunist predator according to the observed changes in its diet during 1995–2002. Overall, the diet of hake in the northern HCE exhibited transitory (e.g. increased richness of prey species in the stomach contents) and medium term (e.g. increased variability in feeding activity) responses associated with El Niño 1997–1998, which should be incorporated both in population dynamics and food web analyses.
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Joo, Rocio, Arnaud Bertrand, Marilu Bouchon, Alexis Chaigneau, Hervé Demarcq, Jorge Tam, Monique Simier, et al. "Ecosystem scenarios shape fishermen spatial behavior. The case of the Peruvian anchovy fishery in the Northern Humboldt Current System." Progress in Oceanography 128 (November 2014): 60–73. http://dx.doi.org/10.1016/j.pocean.2014.08.009.
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Tam, Jorge, Marc H. Taylor, Verónica Blaskovic, Pepe Espinoza, R. Michael Ballón, Erich Díaz, Claudia Wosnitza-Mendo, et al. "Trophic modeling of the Northern Humboldt Current Ecosystem, Part I: Comparing trophic linkages under La Niña and El Niño conditions." Progress in Oceanography 79, no. 2-4 (October 2008): 352–65. http://dx.doi.org/10.1016/j.pocean.2008.10.007.
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Alegre, Ana, Arnaud Bertrand, Marco Espino, Pepe Espinoza, Teobaldo Dioses, Miguel Ñiquen, Iván Navarro, Monique Simier, and Frédéric Ménard. "Diet diversity of jack and chub mackerels and ecosystem changes in the northern Humboldt Current system: A long-term study." Progress in Oceanography 137 (September 2015): 299–313. http://dx.doi.org/10.1016/j.pocean.2015.07.010.
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Taylor, Marc H., Jorge Tam, Verónica Blaskovic, Pepe Espinoza, R. Michael Ballón, Claudia Wosnitza-Mendo, Juan Argüelles, et al. "Trophic modeling of the Northern Humboldt Current Ecosystem, Part II: Elucidating ecosystem dynamics from 1995 to 2004 with a focus on the impact of ENSO." Progress in Oceanography 79, no. 2-4 (October 2008): 366–78. http://dx.doi.org/10.1016/j.pocean.2008.10.008.
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Grados, Daniel, Ronan Fablet, Michael Ballón, Nicolas Bez, Ramiro Castillo, Ainhoa Lezama-Ochoa, and Arnaud Bertrand. "Multiscale characterization of spatial relationships among oxycline depth, macrozooplankton, and forage fish off Peru using geostatistics, principal coordinates of neighbour matrices (PCNMs), and wavelets." Canadian Journal of Fisheries and Aquatic Sciences 69, no. 4 (April 2012): 740–54. http://dx.doi.org/10.1139/f2012-017.
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Upwelling ecosystems are particularly heterogeneous and present intense mesoscale (tens of kilometres) and submesoscale (hundreds of metres to kilometres) activity that are expected to drive the distribution of the organisms and thus their interactions. Here we addressed the impact of the physical forcing in the northern Humboldt Current system off Peru, which is characterized by the presence of an intense and shallow oxygen minimum zone and used the variability of the depth of the oxycline as a proxy of the physical forcing that impacts the epipelagic communities. We analyzed simultaneous high-resolution acoustic observations of the oxycline depth, the biomass in macrozooplankton, and the biomass in pelagic fish. Three complementary methodologies were considered: (i) geostatistical methods and correlation tests, (ii) principal coordinates of neighbour matrices, and (iii) wavelet analysis. Our results highlight the relevance of a multimethod framework to characterize the multiscale relationships between marine ecosystem components. We also provided evidence that the submesoscale-to-mesoscale variability of the oxycline depth drives the distribution of macrozooplankton, which further structures the distribution of forage fish in a bottom-up cascade.
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Ulloa, Raúl, Adolfo Vargas, Cristian Hudson, and Marcelo M. Rivadeneira. "Zoning of the Mejillones Peninsula marine protected coastal area of multiple uses, northern Chile." Latin American Journal of Aquatic Research 41, no. 3 (March 8, 2017): 506–18. http://dx.doi.org/10.3856/vol41-issue3-fulltext-14.
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Marine protected areas of multiple uses (MPA-MU), are an important management tool to protect biodiversity and regulate the use of coastal marine resources. However, robust conservation plans require an explicit consideration of not only biological but also social components, balancing the protection of biodiversity with a sustainable exploitation of marine resources. Here we applied the decision-making algorithm MARXAN to provide a zoning analysis at the Mejillones Peninsula MPA-MU in northern Chile, one of largest MPA’s of the Humboldt Current Marine Ecosystem. We set conservation goals for coarse and fine-filter conservation targets that were crossed out against different threats and pressure factors from human activities across the area. We identified a portfolio of sites for conservation, within the Mejillones Peninsula MPA-MU, representing different ecological systems with different levels of human impacts and vulnerability. These results may serve as a foundational guideline for the future administration of the MPA-MU.
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Segura-Cobeña, Eduardo, Joanna Alfaro-Shigueto, Jeffrey Mangel, Angel Urzua, and Konrad Górski. "Stable isotope and fatty acid analyses reveal significant differences in trophic niches of smooth hammerhead Sphyrna zygaena (Carcharhiniformes) among three nursery areas in northern Humboldt Current System." PeerJ 9 (April 22, 2021): e11283. http://dx.doi.org/10.7717/peerj.11283.
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Fishery pressure on nursery areas of smooth hammerhead in northern Peruvian coast have become a serious threat to sustainability of this resource. Even though, some management actions focused on conservation of the smooth hammerhead populations were proposed in recent years, their scientific foundations are often limited, and biomass of smooth hammerhead in Peruvian waters continues to decrease. To inform management and conservation, this study aims to evaluate the trophic niche of smooth hammerhead juveniles from three nursery areas in the northern Peruvian coast using stable isotope and fatty acid analyses. First, we compared the environmental characteristics of each nursery area (i.e., sea surface temperature and chlorophyll-a concentration) and concluded that nursery areas differed significantly and consistently in sea surface temperature. Subsequently, we evaluated isotopic composition of carbon and nitrogen and fatty acid profiles of muscle and liver tissues collected from juvenile smooth hammerhead from each nursery area. We found that juvenile smooth hammerhead captured in San José were enriched in heavier 13C and 15N isotopes compared to those captured in Máncora and Salaverry. Furthermore, the broadest isotopic niches were observed in juveniles from Máncora, whereas isotopic niches of juveniles from Salaverry and San José were narrower. This difference is primarily driven by the Humboldt Current System and associated upwelling of cold and nutrient rich water that drives increased primary production in San José and, to a less extent, in Salaverry. Compared to smooth hammerhead juveniles from Máncora, those from San José and Salaverry were characterised by higher essential fatty acid concentrations related to pelagic and migratory prey. We conclude that smooth hammerhead juveniles from three nursery areas in the northern Peruvian coast differ significantly in their trophic niches. Thus, management and conservation efforts should consider each nursery area as a unique juvenile stock associated with a unique ecosystem and recognize the dependence of smooth hammerhead recruitment in San José and Salaverry on the productivity driven by the Humboldt Current System.
Dissertations / Theses on the topic "Northern Humboldt current ecosystem"
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Luján, Paredes Doris Criscely. "Dealing with uncertainty in complex models ˸ an application to the OSMOSE ecosystem model of the northern Humboldt current system." Thesis, université Paris-Saclay, 2022. http://www.theses.fr/2022UPASB013.
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L'augmentation de la complexité des modèles permet d'obtenir une représentation plus réaliste des systèmes naturels. Cela peut également conduire à la création d'outils très complexes, dont il est nécessaire d'étudier les sources d'incertitudes, ainsi que le degré de confiance que nous pouvons accorder à leurs prédictions. Cette thèse porte sur l'étude de l'incertitude dans le modèle d'écosystème marin OSMOSE appliqué à l'écosystème nord du courant de Humboldt. Ce travail explore les différentes méthodes et outils disponibles pour les études d'incertitude. Nous avons mis en œuvre une analyse d'incertitude, dont les principaux résultats ont montré que l'incertitude d'un modèle complexe dépend de l'incertitude de quelques paramètres d'entrée, qu'elle se propage dans le temps et que, selon les sorties du modèle sélectionnées, celles-ci peuvent atténuer ou amplifier le niveau d'incertitude de ses résultats. Nous présentons également un protocole basé sur le critère de fiabilité des paramètres.Cela nous permet de classer les paramètres du modèle en fonction de la source d'information utilisée pour estimer leurs valeurs et d'attribuer un niveau d'incertitude aux paramètres du modèle. Enfin, nous proposons une série de recommandations pour les futures études d'incertitude utilisant des modèles complexesModels of increasing complexity help achieve a more realistic representation of natural systems. This can also lead to the creation of very complex tools, which sources of uncertainty must be studied, as well as the degree of confidence we can place in their predictions. This thesis focuses on studying the uncertainty of the OSMOSE marine ecosystem model applied to the northern Humboldt current ecosystem. This work explores several methods and tools available for uncertainty studies. We implemented an uncertainty analysis, where our main results show that the uncertainty in a complex model depends on the uncertainty in a few inputs, which propagates in time, and depending on the model outputs selected, these may dampen or amplify the level of uncertainty in model results. We also propose a protocol based on the parameter reliability criterion. This allows classifying model parameters according to the source of information used to estimate their values and assigning a level of uncertainty to model parameters. Finally, we provide a series of recommendations for future uncertainty studies using complex models
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Alegre, Norza Sior Ana Renza Paola. "Trophic ecology of jumbo squid and predatory fishes in the Northern Humboldt Current System." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS223/document.
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Ce travail est une contribution à l'étude de l'écologie trophique d'importants prédateurs de la partie Nord du système du Courant de Humboldt (NSCH), le chinchard (Trachurus murphyi), le maquereau (Scomber japonicus) et le calmar géant (Dosidicus gigas). Nous avons caractérisé la variabilité des modes d'alimentation de ces espèces à différentes échelles spatiotemporelles et fourni de nouvelles connaissances sur le comportement alimentaire de ces espèces, définies comme opportunistes par des travaux antérieurs. Pour ce faire, nous avons appliqué une variété de méthodes statistiques à un vaste jeu de données comprenant 27188 estomacs non vides. Sur cette base nous avons décrit l'organisation spatiale de la faune fourrage de ces prédateurs et documenté les changements dans la composition des proies en fonction de la taille de prédateurs et des conditions environnementales. Nos résultats indiquent que l'oxygène dissous jour un rôle clef dans ces processus. Nous avons également résolu un paradoxe sur l'alimentation du calmar géant: pourquoi ils ne se nourrissent guère sur l'immense biomasse d'anchois (Engraulis ringens) présente le long de la côte du Pérou? Nous avons montré que la présence d'une zone de minimum d'oxygène (ZMO) superficielle devant le Pérou pourrait limiter la cooccurrence entre calmars géant et anchois. Pour synthétiser ces résultats, nous avons proposé un modèle conceptuel de l'écologie trophique du calmar géant tenant compte du cycle ontogénétique, de l'oxygène et de la disponibilité des proies. Par ailleurs, nous avons montré que le chinchard et le maquereau se nourrissent des espèces les plus accessibles comme par exemple la galathée Pleurocondes monodon ou les larves zoea. Ces deux prédateurs présentent un chevauchement trophique mais, contrairement à ce qui avait été décrit dans d'autres études, le chinchard n'est pas aussi vorace que le maquereau. Le régime alimentaire de ces poissons est caractérisé par une forte variabilité spatio-temporelle et le talus continental s'avère être une importante frontière biogéographique. La composition du régime alimentaire des poissons prédateurs étudiés n'est pas nécessairement un indicateur cohérent de l'évolution de la biomasse des proies. Les événements El Niño ont eu un faible effet sur le taux de remplissage des estomacs et sur le régime alimentaire du chinchard et du maquereau. Par ailleurs les changements en diversité des proies à échelle décennale contredisent le classique paradigme de corrélation positive entre diversité et température. Finalement, les patrons globaux décrits dans ce travail, illustrent le comportement alimentaire opportuniste, les stratégies de vie et le haut degré de plasticité de ces espèces. Un tel comportement permet de s'adapter aux changements de l'environnementThis work provides a contribution to a better understanding of the trophic ecology of important predators in the Northern Humboldt Current System, the jack mackerel (Trachurus murphyi), the chub mackerel (Scomber japonicus) and the jumbo squid (Dosidicus gigas) by the characterization of the highly variable feeding patterns of these species at different spatiotemporal scales. We provided new knowledge on the comparative trophic behaviour of these species, defined as opportunistic in previous investigations. For that purpose we applied a variety of statistical methods to an extensive dataset of 27,188 non-empty stomachs. We defined the spatial organization of the forage fauna of these predators and documented changes in prey composition according to predators' size and spatiotemporal features of environment. Our results highligh the key role played by the dissolved oxygen. We also deciphered an important paradox on the jumbo squid diet: why do they hardly forage on the huge anchovy (Engraulis ringens) biomass distributed of coastal Peru? We showed that the shallow oxygen minimum zone present off coastal Peru could hamper the co-occurrence of jumbo squids and anchovies. In addition, we proposed a conceptual model on jumbo squid trophic ecology including the ontogenetic cycle, oxygen and prey availability. Moreover we showed that the trophic behaviour of jack mackerel and chub mackerel is adapted to forage on more accessible species such as for example the squat lobster Pleurocondes monodon and Zoea larvae. Besides, both predators present a trophic overlap. But jack mackerel was not as voracious as chub mackerel, contradictorily to what was observed by others authors. Fish diet presented a high spatiotemporal variability, and the shelf break appeared as a strong biogeographical frontier. Diet composition of our fish predators was not necessarily a consistent indicator of changes in prey biomass. El Niño events had a weak effect on the stomach fullness and diet composition of chub mackerel and jack mackerel. Moreover, decadal changes in diet diversity challenged the classic paradigm of positive correlation between species richness and temperature. Finally, the global patterns that we described in this work, illustrated the opportunistic foraging behaviour, life strategies and the high degree of plasticity of these species. Such behaviour allows adaptation to changes in the environment
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Uumati, Martha. "Acoustic investigations on bearded goby and jellyfish in the northern Benguela ecosystem." Thesis, University of St Andrews, 2013. http://hdl.handle.net/10023/4469.
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Historically the nutrient rich Benguela ecosystem supported large stocks of commercially important fish which sustained the Namibian fishing sector. Recently, non-exploited species i.e. bearded goby (Sufflogobius bibarbatus) and jellyfish (Chrysaora fulgida and Aequorea forskalea) have become more apparent and are described as key-species in this ecosystem. Empirical evidence for understanding the stock abundance and dynamics of S. bibarbatus and jellyfish are still sparse, as research focus has been mainly on commercially important fish. The abundance of these non-exploited species in relation to the environment and commercial species are also not well understood. Lack of methods to effectively assess jellyfish and S. bibarbatus have furthermore limited our knowledge. Acoustics can cover large water volumes and observe many trophic groups and interactions simultaneously hence currently proposed as the most reliable observation tool available to remotely study multiple species that are overlapping and widely distributed in marine ecosystems. For acoustic assessments using echo sounders, the ability to detect, identify and distinguish targets from each other and the echo ability (target strength: TS) of individual targets is pivotal to convert acoustic data from a calibrated system into significant biological measures. The lack of effective acoustic identification (ID) techniques and knowledge about TS of species may limit the application of acoustics. The swimbladder generally contributes more than 90% to the backscattered energy from fish, which makes knowledge of the swimbladder vital for understanding the acoustic properties of a fish. Prior to this study, the presence or absence of a swimbladder within S. bibarbatus has been uncertain. This thesis is an exploratory study addressing 1) the acoustic identification challenge of species in aggregating in mixed assemblages and 2) the acoustic characteristics of the target species. The latter two are of essence to assess the biomass, distributions and ecological interactions of these non-exploited. The multiple frequency data (18, 38, 70, 120 and 200 kHz) and trawl data used in this study were collected on a survey conducted by the RV G.O.Sars during April 2008 in the northern Benguela. Fifteen validated assumed to be ‘single species' trawl and acoustic datasets were selected and used in the application and developing of ID techniques. Traditional acoustic identification techniques (Sᵥ-differencing and relative frequency response r(f)) were adopted and found ineffective as standalones to discriminate the species under study. The overlaps in the Sᵥ differences of the three species complicated separation. A multivariate statistical approach, Linear Discriminant Analysis (LDA) was applied to predict which of the variables s[subscript(A)], S[subscript(A)], Δs[subscript(A)] and r(f) discriminated the three species groups from each other with a higher accuracy. It was found that by combining backscattering strength S[subscript(A)] and r(f) a correct classification accuracy of up to 95% could be obtained. Limitation is that the LDA technique as any classification method is not applicable in “real time” during surveys. A new technique, here within referred to as the Separator Technique, which incorporates the standard techniques, LDA results, a novel r(f) similarity comparison technique and a threshold s[subscript(A)] response technique was established. The effectiveness of the Separator Technique is in the recognition of similarities and stability in frequency response by simple correlation of the observed frequency response at systematic Sᵥ-threshold levels. Accurate acoustic classification depends on good and valid training datasets and there has so far not been a simple way of acoustically detecting if the selected assumed “pure” datasets is contaminated or not. Only available reliable source are the trawl samples. The r(f) similarity comparison method showed that some of the assumed ‘single species' trawls were mixed and that presence of <1% of strong scatterers could mask a weaker scatterer. By evaluating the threshold s[subscript(A)] frequency response, the proportion of thresholded backscattering could be quantified. A frequency which is more appropriate for the acoustic assessment of the respective species in mixed aggregations could also be identified. Further improvements of the Separator Technique are required in terms of the precise Sᵥ-cut levels. The presence of S. bibarbatus' swimbladder was confirmed from two thawed specimens. From further investigations on 26 dissections of sampled S. bibarbatus, the swimbladder was identified as a physoclist (closed swimbladder) with an extensive gas gland, and its morphology was roughly described as prolate spheroid shaped and with about 5ᴼ negatively tilted compared fish vertebra. This means that the strongest echo from a goby will be found when the fish is at about 5ᴼ head down relative to the horizontal. The in situ TS of 8 cm sized S. bibarbatus and the two jellyfish species: C. fulgida [umbrella diameter: 21.7 cm] and A. forskalea [16 cm] at multiple frequencies (18, 38, 70, 120 and 200 kHz) was estimated. At 38 kHz, the TS was -53 dB for S. bibarbatus, -58 dB for A. forskalea and -66 dB for C. fulgida. The single echo detection (SED) approach which is assumed to be a more accurate method for estimating TS than the previously applied methods for jellyfish. The TS results for S. bibarbatus are of similar magnitude to other published TS values of C. fulgida. This suggests that estimates of jellyfish may be overestimated due to inaccuracies in target identification. This thesis established the acoustic characteristics of jellyfish and S. bibarbatus within the northern Benguela which makes it possible to acoustically assess and monitor jellyfish and/or fish. The identification technique though still in early phases of development, can be applied to enhance quality of training datasets (samples) used in classification. This piece of work can reduce variability in biomass estimates that arises from masking or misclassification of echoes.
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Field, John C. "Application of ecosystem-based fishery management approaches in the Northern California Current /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/5279.
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Joo, Arakawa Rocío. "A behavioral ecology of fishermen : hidden stories from trajectory data in the Northern Humboldt Current System." Thesis, Montpellier 2, 2013. http://www.theses.fr/2013MON20224/document.
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Ce travail propose une contribution originale à la compréhension du comportement spatial des pêcheurs, basée sur les paradigmes de l'écologie comportementale et de l'écologie du mouvement. En s'appuyant sur des données du 'Vessel Monitoring System', nous étudions le comportement des pêcheurs d'anchois du Pérou à des échelles différentes: (1) les modes comportementaux au sein des voyages de pêche (i.e. recherche, pêche et trajet), (2) les patrons comportementaux parmi les voyages de pêche, (3) les patrons comportementaux par saison de pêche conditionnés par des scénarios écosystémiques et (4) les patrons spatiaux des positions de modes comportementaux, que nous utilisons pour la création de cartes de probabilité de présence d'anchois. Pour la première échelle, nous comparons plusieurs modèles Markoviens (modèles de Markov et semi-Markov cachés) et discriminatifs (forêts aléatoires, machines à vecteurs de support et réseaux de neurones artificiels) pour inférer les modes comportementaux associés aux trajectoires VMS. L'utilisation d'un ensemble de données pour lesquelles les modes comportementaux sont connus (grâce aux données collectées par des observateurs embarqués), nous permet d'entraîner les modèles dans un cadre supervisé et de les valider. Les modèles de semi-Markov cachés sont les plus performants, et sont retenus pour inférer les modes comportementaux sur l'ensemble de données VMS. Pour la deuxième échelle, nous caractérisons chaque voyage de pêche par plusieurs descripteurs, y compris le temps passé dans chaque mode comportemental. En utilisant une analyse de classification hiérarchique, les patrons des voyages de pêche sont classés en groupes associés à des zones de gestion, aux segments de la flottille et aux personnalités des capitaines. Pour la troisième échelle, nous analysons comment les conditions écologiques donnent forme au comportement des pêcheurs à l'échelle d'une saison de pêche. Via des analyses de co-inertie, nous trouvons des associations significatives entre les dynamiques spatiales des pêcheurs, des anchois et de l'environnement, et nous caractérisons la réponse comportementale des pêcheurs selon des scénarios environnementaux contrastés. Pour la quatrième échelle, nous étudions si le comportement spatial des pêcheurs reflète dans une certaine mesure la répartition spatiale de l'anchois. Nous construisons un indicateur de la présence d'anchois à l'aide des modes comportementaux géo-référencés inférés à partir des données VMS. Ce travail propose enfin une vision plus large du comportement de pêcheurs: les pêcheurs ne sont pas seulement des agents économiques, ils sont aussi des fourrageurs, conditionnés par la variabilité dans l'écosystème. Pour conclure, nous discutons de la façon dont ces résultats peuvent avoir de l'importance pour la gestion de la pêche, des analyses de comportement collectif et des modèles end-to-endThis work proposes an original contribution to the understanding of fishermen spatial behavior, based on the behavioral ecology and movement ecology paradigms. Through the analysis of Vessel Monitoring System (VMS) data, we characterized the spatial behavior of Peruvian anchovy fishermen at different scales: (1) the behavioral modes within fishing trips (i.e., searching, fishing and cruising); (2) the behavioral patterns among fishing trips; (3) the behavioral patterns by fishing season conditioned by ecosystem scenarios; and (4) the computation of maps of anchovy presence proxy from the spatial patterns of behavioral mode positions. At the first scale considered, we compared several Markovian (hidden Markov and semi-Markov models) and discriminative models (random forests, support vector machines and artificial neural networks) for inferring the behavioral modes associated with VMS tracks. The models were trained under a supervised setting and validated using tracks for which behavioral modes were known (from on-board observers records). Hidden semi-Markov models performed better, and were retained for inferring the behavioral modes on the entire VMS dataset. At the second scale considered, each fishing trip was characterized by several features, including the time spent within each behavioral mode. Using a clustering analysis, fishing trip patterns were classified into groups associated to management zones, fleet segments and skippers' personalities. At the third scale considered, we analyzed how ecological conditions shaped fishermen behavior. By means of co-inertia analyses, we found significant associations between fishermen, anchovy and environmental spatial dynamics, and fishermen behavioral responses were characterized according to contrasted environmental scenarios. At the fourth scale considered, we investigated whether the spatial behavior of fishermen reflected to some extent the spatial distribution of anchovy. Finally, this work provides a wider view of fishermen behavior: fishermen are not only economic agents, but they are also foragers, constrained by ecosystem variability. To conclude, we discuss how these findings may be of importance for fisheries management, collective behavior analyses and end-to-end models
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Espinoza, Pepe. "Trophic dynamics in the northern Humboldt Current system : insights from stable isotopes and stomach content analyses." Thesis, Brest, 2014. http://www.theses.fr/2014BRES0066/document.
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Le nord du système du Courant de Humboldt (NHCS), le long des côtes péruviennes, est l'une des régions océanique les plus productives au monde. Il représente moins de 0.1% de la surface des océans mondiaux mais contribue actuellement à plus de 10% des captures mondiales en poissons, avec l’anchois Engraulis ringens comme espèce emblématique. Comparé aux autres systèmes d’upwelling de bord Est, la forte productivité en poissons ne peut être expliquée par une productivité primaire plus élevée. Par contre, le NCHS est la région où El Niño, et la variabilité climatique en général est la plus notable. D’autre part, les eaux de surface oxygénées recouvrent une zone de minimum d’oxygène extrêmement intense et superficielle. L’objectif principal de ce travail est de mieux comprendre les relations trophiques au sein du NHCS en combinant l'analyse de contenus stomacaux et d'isotopes stables. Cette étude se focalise sur une variété d’organismes allant des bas niveaux trophiques comme le zooplancton aux prédateurs supérieurs (oiseaux et les otaries à fourrure). Elle combine des études de contenus stomacaux ponctuelles et sur le long terme d’espèces clés telles que l’anchois et la sardine Sardinops sagax et une analyse plus globale, basée sur l'utilisation d'isotopes stables et considérant l’ensemble du réseau trophique dans les années récentes (2008 – 2012). Les analyses des contenus stomacaux d'anchois et de sardine ont permis de revisiter l'écologie de ces espèces. En effet, bien que le phytoplancton domine largement les contenus stomacaux en termes d’abondance numérique, le zooplancton est de loin la composante alimentaire la plus importante pour ces deux espèces en termes de carbone. Dans le cas de l’anchois, les euphausiacés contribuent à plus de 67.5% du carbone ingéré, suivis par les copépodes (26.3%). Sélectionner les proies les plus grandes telles que les euphausiacés procure un avantage énergétique pour l’anchois dans cet écosystème où les carences en oxygène imposent de fortes contraintes métaboliques aux poissons pélagiques. La sardine se nourrit de zooplancton plus petit que l’anchois (copépodes plus petits et moins d’euphausiacés). Ainsi, la compétition trophique entre les sardines et les anchois est minimisée dans le NSCH par le partage de la ressource zooplancton selon sa taille, comme cela a déjà été montré dans d’autres écosystèmes. Ces résultats remettent en question la compréhension première de la position des petits poissons pélagiques (zooplanctonophage et non phytoplanctonophage) dans la chaine trophique ce qui implique de reconsidérer le fonctionnement et les modèles trophiques du NCHS. Afin d’obtenir une compréhension plus globale de la position trophique relative des principaux composants du NHCS une approche basée sur des analyses d’isotopes stables (δ13C et δ15N) a été utilisée. Pour ce faire, la signature isotopique d'échantillons de 13 groupes taxonomiques (zooplancton, poissons, calmars et prédateurs supérieurs) prélevés entre 2008 et 2011 a été déterminée. Les valeurs de δ15N obtenues sont fortement impactées par l’espèce, la taille et la latitude. Le long de la cote péruvienne, la zone de minimum d’oxygène devient en effet plus intense et plus superficielle au sud de ~7.5ºS impactant fortement la valeur de δ15N de la ligne de base. Nous avons donc utilisé un modèle linéaire à effet mixte prenant en compte les effets latitude et taille afin de prédire la position trophique relative des composants clés de l’écosystème. Ces analyses isotopiques confirment les résultats issus des contenus stomacaux sur le régime alimentaire de l’anchois et mettent en évidence l’importance potentielle d’une composante souvent négligée de l’écosystème, la galathée pélagique Pleuroncodes monodon. En effet, nos résultats supportent l’hypothèse selon laquelle cette espèce s’alimenterait en partie sur les oeufs et larves d’anchois, menaçant ainsi les premiers stades de vie des espèces exploitées. [...]The northern Humboldt Current system (NHCS) off Peru is one of the most productive world marine regions. It represents less than 0.1% of the world ocean surface but presently sustains about 10% of the world fish catch, with the Peruvian anchovy or anchoveta Engraulis ringens as emblematic fish resource. Compared with other eastern boundary upwelling systems, the higher fish productivity of the NHCS cannot be explained by a corresponding higher primary productivity. On another hand, the NHCS is the region where El Niño, and climate variability in general, is most notable. Also, surface oxygenated waters overlie an intense and extremely shallow Oxygen Minimum Zone (OMZ). In this context, the main objective of this study is to better understand the trophic flows in the NHCS using both stomach content and stable isotope analyses. The study focuses on a variety of organisms from low trophic levels such as zooplankton to top predators (seabirds and fur seals). The approach combines both long-term and specific studies on emblematic species such as anchoveta, and sardine Sardinops sagax and a more inclusive analysis considering the 'global' food web in the recent years (2008 –2012) using stable isotope analysis.Revisiting anchovy and sardine we show that whereas phytoplankton largely dominated anchoveta and sardine diets in terms of numerical abundance, the carbon content of prey items indicated that zooplankton was by far the most important dietary component. Indeed for anchovy euphausiids contributed 67.5% of dietary carbon, followed by copepods (26.3%).Selecting the largest prey, the euphausiids, provide an energetic advantage for anchoveta in its ecosystem where oxygen depletion imposes strong metabolic constrain to pelagic fish. Sardine feed on smaller zooplankton than do anchoveta, with sardine diet consisting of smaller copepods and fewer euphausiids than anchoveta diet. Hence, trophic competition between sardine and anchovy in the northern Humboldt Current system is minimized by their partitioning of the zooplankton food resource based on prey size, as has been reported in other systems.These results suggest an ecological role for pelagic fish that challenges previous understanding of their position in the foodweb (zooplanktophagous instead of phytophagous), the functioning and the trophic models of the NHCS.Finally to obtain a more comprehensive vision of the relative trophic position of NHCS main components we used stable isotope analyses. For that purpose we analyzed the δ13C and δ15N stable isotope values of thirteen taxonomic categories collected off Peru from 2008 - 2011, i.e., zooplankton, fish, squids and air-breathing top predators. The δ15N isotope signature was strongly impacted by the species, the body length and the latitude. Along the Peruvian coast, the OMZ get more intense and shallow south of ~7.5ºS impacting the baseline nitrogen stable isotopes. Employing a linear mixed-effects modelling approach taking into account the latitudinal and body length effects, we provide a new vision of the relative trophic position of key ecosystem components. Also we confirm stomach content-based results on anchoveta Engraulis ringens and highlight the potential remarkable importance of an often neglected ecosystem component, the squat lobster Pleuroncodes monodon. Indeed, our results support the hypothesis according to which this species forage to some extent on fish eggs and larvae and can thus predate on the first life stages of exploited species. However, the δ13C values of these two species suggest that anchoveta and squat lobster do not exactly share the same habitat. This would potentially reduce some direct competition and/or predation
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Passuni, Saldana Giannina Paola. "A bird-eye view on the spatio-temporal variability of the seasonal cycle in the Northern Humboldt Current System : the case of Guanay cormorant, Peruvian booby and Peruvian pelican." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT161/document.
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Le Système Nord du Courant de Humboldt (SNCH) est le lieu d’une forte activité biologique due à un upwelling côtier intense. Il abrite l’une des plus grandes populations de l’anchois du Pérou soumis à la plus grande pêcherie monospécifique au monde. Le SNCH héberge aussi de grandes et variables, populations d’oiseaux, composées de trois espèces sympatriques productrices de guano : le cormoran guanay (Phalacrocorax bougainvillii), le fou péruvien (Sula variegata) et le pélican péruvien (Pelecanis thagus), qui se nourrissent principalement d’anchois. Dans ce travail, nous examinons les fluctuations de ces trois populations d’oiseaux marins, en nous concentrant sur le cycle saisonnier de leur reproduction, pour aborder les questions suivantes : Dans quelle mesure les saisonnalités de reproduction diffèrent elles entre espèces ? Dans quelle mesure sont-elles plastiques dans le temps et dans l’espace ? Qu’est ce qui, des conditions environnementales et des activités anthropogéniques affecte le plus la reproduction des oiseaux marins ? Nous abordons ces questions en utilisant des données de présence de reproducteurs (1) dans 30 sites péruviens répartis entre 06°S-18°S (2003-2014) ; et (2) dans un site, pendant trois périodes (1952-1968, 1972-1989, 2003-2014). Nous utilisons des covariables environnementales décrivant les conditions océanographiques, l’abondance, l’accessibilité et la condition des proies, ainsi que des covariables décrivant la pression de pêche. Nous utilisons des modèles d’occupation multi-saisonniers pour caractériser la saisonnalité de la reproduction et la relier aux covariables environnementales. Nous utilisons aussi des analyses en composantes principales fonctionnelles pour classifier les différences de saisonnalité entre sites, et des forêts aléatoires de régression pour analyser la contribution relative des covariables à la variabilité de la saisonnalité de reproduction.Nous mettons en évidence qu’en moyenne, la reproduction démarre au cours de l’hiver austral / début de printemps et prend fin en été / début d’automne, ce patron étant plus marqué chez les fous et pélicans que chez les cormorans. La reproduction est calée dans le temps de telle sorte à ce que les jeunes prennent leur indépendance lorsque les conditions de production primaire, d’abondance et d’accessibilité des proies sont maximales. Ce patron est unique en comparaison avec les autres écosystèmes d’upwelling et peut être expliqué par les fortes abondances absolues de proies disponibles tout au long de l’année dans le SNCH.La saisonnalité de reproduction diffère entre les sites de nidification. Les oiseaux se reproduisent plus tôt et avec de plus fortes probabilités lorsque les colonies sont plus grandes, situées sur des îles à moins de 20 km des côtes, aux plus basses latitudes, et présentant une production primaire plus élevée. Alors, la saisonnalité de la reproduction est davantage influencée par les conditions environnementales locales que par les gradients environnementaux de grande échelle.Les oiseaux marins adaptent aussi la saisonnalité de leur reproduction aux changements drastiques causés dans l’écosystème par les changements de régime. Les cormorans font preuve de la plus grande plasticité, en modulant la date te l’amplitude de la saisonnalité de leur reproduction, cela est probablement permis par leur plus grande flexibilité de fourragement. Les dates et amplitudes fixes observées chez les fous peuvent être liées aux spécificités de leur stratégie de fourragement et à des changements de proies lorsque le stock d’anchois est bas. Les différences spécifiques dans les adaptations de la saisonnalité de reproduction permettent aux oiseaux de profiter différemment des conditions locales de proies, et de faire face aux changements de régime avec des stratégies différentes. Une méthodologie de capture-recapture en parallèle des comptages mensuels est proposée pour élargir les horizons de l’évaluation des dynamiques d’une populationThe Northern Humboldt Current System (NHCS) is a place of a high biological activity due to an intense coastal upwelling. It supports one of the biggest forage fish populations, the Peruvian anchovy, and the world-leading monospecific fishery in terms of landings. The NHCS also hosts large, although variable, seabird populations, composed among others by three guano-producing sympatric species: the Guanay cormorant (Phalacrocorax bougainvillii), the Peruvian booby (Sula variegata) and the Peruvian pelican (Pelecanus thagus), which all feed primarily on anchovy.In this work we reviewed the fluctuations of these three seabird populations, focusing on the seasonal cycle of their breeding, to address the following questions: How different are the seasonality of reproduction among species? To what extent may they be plastic in space and time? What from the natural environment and the anthropogenic activities impact more the breeding of seabirds?We addressed these questions using the monthly occupancy of breeders (1) in >30 Peruvian sites between 06°S and 18°S and from 2003 to 2014; and (2) in one site during three decadal periods (1952-1968, 1972-1989, 2003-2014). We also used environmental covariates from satellite and at-sea monitoring such as oceanographic conditions, prey abundance, availability and body conditions, and fisheries pressure covariates. We used multiseason occupancy models to characterize the seasonality of breeding and relate it with environmental covariates. We also used functional principal component analysis for classifying the differences in seasonality among sites, and random forest regression for analyzing the relative contribution of covariates in the variability of the seasonal breeding.We found that in average seasonal breeding mainly started during the austral winter/ early spring and ended in summer/ early fall, this pattern being stronger in boobies and pelicans than in cormorants. The breeding onset of seabirds is timed so that fledging independence occurs when primary production, prey conditions and availability are maximized. This pattern is unique compared with other upwelling ecosystems and could be explained by the year-round high abundances of anchovy in the NHCS.The average seasonal breeding may differ among nesting sites. Seabirds breed earlier and are more persistent when colonies are larger, located on islands, within the first 20km of the coast, at lower latitudes and with greater primary production conditions. These results suggest that in the NHCS, the seasonality of breeding is more influenced by local environmental conditions than by large-scale environmental gradients. These results provides critical information to a better coordination of guano extraction and conservancy policies.Seabirds may also adapt the seasonality of their breeding to drastic ecosystem changes caused by regime shifts. We found that the three study species exhibited a gradient of plasticity regarding the seasonality of their breeding. Cormorants showed a greater plasticity, modulating the timing and magnitude on their breeding seasonality. This is probably authorized by the greater foraging flexibility offered its great diving capacities. Fixed onset and magnitudes of breeding in boobies may be related to their specific foraging strategy and/or to changes of prey items when anchovy stock was low. We also suggested that boobies may adapt other fecundity traits as growth rate of chicks to lower abundance of anchovy.The specific differences in the adaptation of seasonal breeding allow seabirds to take profit differently from local prey conditions or to face differently regime shifts. Further researches, implementing a large-scale capture-recapture methodology in parallel with monthly census, are proposed in order to fulfill gaps in the basic knowledge on vital traits (adult survival, first age at reproduction, and juvenile recruitment) which are critical parameters to evaluate the dynamic of a population
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Iitembu, Johannes Angala. "Trophic relationships of hake (Merluccius capensis Castelnau, 1851 and M. paradoxus Franca 1960) from the Northern Benguela current ecosystem (Namibia) : inferences from stable isotopes and fatty acids." Thesis, Rhodes University, 2014. http://hdl.handle.net/10962/d1020296.
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Two species of hake (Merluccius capensis and Merluccius paradoxus) account for most of Namibia’s fisheries catch, and they are important secondary consumers in the Benguela Current ecosystem. Inferences on their trophic relationships have been based mainly on stomach content analyses. However, such data are limited temporally because they represent only snapshots of recent feeding, and are quantitatively biased because of variation in the digestion rates of different prey. The principal aim of the thesis was to understand the trophic relationships of two hake species relative to each other, their known prey and top predators (demersal sharks) in the northern Benguela Current ecosystem (Namibia), using time-integrating trophic biomarkers. By using stable isotope (carbon and nitrogen) and fatty acid signatures of their muscle tissues, my overall objectives were to produce new knowledge about 1) hake ontogenic trophic relationships, 2) the contributions of different prey to hake diets, 3) hake dietary differences, and 4) some aspects of hake’s trophic relationships with demersal sharks. Tissues of hake (n=358), their potential prey (n=455), and demersal sharks (n=42) were collected between 2008 and 2012 during demersal bottom trawl surveys off Namibia, for stable isotope and fatty acid analyses. And more...
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Geist, Simon Joscha [Verfasser], Werner [Akademischer Betreuer] Ekau, and Ulrich [Akademischer Betreuer] Saint-Paul. "Early life history traits of coastal pelagic fishes in the northern Benguela Current ecosystem off Namibia / Simon Joscha Geist. Gutachter: Ulrich Saint-Paul ; Werner Ekau. Betreuer: Werner Ekau." Bremen : Staats- und Universitätsbibliothek Bremen, 2013. http://d-nb.info/1072078228/34.
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Taylor, Marc Hollis [Verfasser]. "The Northern Humboldt current ecosystem and its resource dynamics : insights from a trophic modeling and time series analysis / by Marc Hollis Taylor." 2008. http://d-nb.info/989375226/34.
Full textBooks on the topic "Northern Humboldt current ecosystem"
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Wintersteen, Kristin. Fishmeal Revolution: The Industrialization of the Humboldt Current Ecosystem. University of California Press, 2018.
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Wintersteen, Kristin. Fishmeal Revolution: The Industrialization of the Humboldt Current Ecosystem. University of California Press, 2017.
Find full textBook chapters on the topic "Northern Humboldt current ecosystem"
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Tam, Jorge, Adolfo Chamorro, and Dante Espinoza-Morriberón. "Modelling the Northern Humboldt Current Ecosystem: From Winds to Predators." In Marine Coastal Ecosystems Modelling and Conservation, 55–76. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-58211-1_3.
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Chevallier, Adrien, Wolfgang Stotz, Marcel Ramos, and Jaime Mendo. "The Humboldt Current Large Marine Ecosystem (HCLME), a Challenging Scenario for Modelers and Their Contribution for the Manager." In Marine Coastal Ecosystems Modelling and Conservation, 27–51. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-58211-1_2.
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"A Deep History of the Humboldt Current Ecosystem." In The Fishmeal Revolution, 15–29. University of California Press, 2021. http://dx.doi.org/10.2307/j.ctv1ns7mgc.7.
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"1. A Deep History of the Humboldt Current Ecosystem." In The Fishmeal Revolution, 15–29. University of California Press, 2021. http://dx.doi.org/10.1525/9780520976825-005.
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Thiel, Martin, Erasmo Macaya, Enzo Acu√±a, Wolf Arntz, Horacio Bastias, Katherina Brokordt, Patricio Camus, et al. "The Humboldt Current System of Northern and Central Chile." In Oceanography and Marine Biology, 195–344. CRC Press, 2007. http://dx.doi.org/10.1201/9781420050943.ch6.
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Francis, R. C., J. Field, D. Holmgren, and A. Strom. "Historical Approaches to the Northern California Current Ecosystem." In The Exploited Seas, 123–40. Liverpool University Press, 2001. http://dx.doi.org/10.5949/liverpool/9780973007312.003.0006.
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R. C. Francis, J. Field, D. Holmgren and A. Strom traces the historical record of the west coast North American marine ecosystem through historical, paleoclimatological, and environmental disciplines in order to understand its development over centuries of change. The results show that large-scale climate forcing is a core factor in the fluctuating stock of coastal species over the eighteenth, nineteenth, and twentieth centuries.
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Nasri, Ahmed, Takoua Mhadhbi, Mohamed Allouche, Amel Hannachi, Hary Demey, Patricia Aïssa, Hamouda Beyrem, and Ezzeddine Mahmoudi. "Persistent Organic Pollutants in the Bizerte Lagoon Ecosystem: Occurrence, Distribution, and Ecotoxicological Assessment Using Marine Organism." In Environmental Sciences. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.100549.
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Marine ecosystem represents an ecologically and economically important water bodies for human and animal living. Their increasing pollution by persistent organic pollutants has represented a major environmental alarm during the last years. In the current study, we examined the occurrence, local distribution and ecotoxicological menace of organic pollutants, comprising brominated flame retardants (BFR), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and organochlorine pesticides (OCPs) in different matrices from the Northern Tunisian Coastal Ecosystem (Bizerte lagoon). The pollutant existence in this biome is related with a negative impact on the biocenosis health. Many approach including (i) chemical analyses; (ii) taxonomic structure and ecological indices analyses; (iii) and biochemical experimental studies, were investigated to determine the ecosystem quality and the contaminant effects. Our chapter introduces the baseline information on the organic contaminations extent and toxicological impact, as well as, it contribute to evaluate the ecological quality of this marine coastal ecosystem.
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B. Makhado, Azwianewi, Rodney Braby, Bruce M. Dyer, Jessica Kemper, Alistair M. McInnes, Desmond Tom, and Robert J.M. Crawford. "Seabirds of the Benguela Ecosystem: Utilisation, Long-Term Changes and Challenges." In Birds - Challenges and Opportunities for Business, Conservation and Research. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.96326.
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The Benguela Current is used by c. 82 seabird species, of which seven are endemic to it. Eggs and guano of formerly abundant seabirds were heavily harvested in the 19th and 20th centuries but decreases in seabird populations led to cessation of these industries at islands. Guano is still scraped from platforms. Seabird ecotourism has grown. There were large recent decreases in numbers of African Penguins Spheniscus demersus, Cape Gannets Morus capensis and Cape Phalacrocorax capensis and Bank P. neglectus Cormorants and redistributions of these other species away from the centre of the Benguela ecosystem towards its northern or eastern boundaries. In 2020, seabirds endemic to the Benguela ecosystem and albatrosses and petrels migrating into it had high proportions of globally Near Threatened or Threatened species. The primary threat to four Endangered endemic birds was scarcity of forage resources. A Vulnerable endemic damara tern was susceptible to habitat degradation and disturbance. The principal threat to visiting albatrosses and petrels was by-catch mortality. Identification and effective protection of Important Bird Area breeding and marine foraging and aggregation sites, and a suite of complementary measures, are needed to conserve the seabirds and ensure continuation of their economic and ecosystem benefits into the future.
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Caviedes, César N. "Impacts of El Niño-Southern Oscillation on Natural and Human Systems." In The Physical Geography of South America. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195313413.003.0028.
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Off the coasts of northern Perú and southern Ecuador, warm equatorial waters meet the cold Humboldt Current. Variations in sea temperatures and associated fauna have been known to fishing folk since colonial times. They noticed that toward the end of every year tepid waters appeared between the Gulf of Guayaquil (Ecuador) and Point Pariñas (Perú) and persisted until late February, causing tropical species to be added to the fish they commonly caught. Coupled with the arrival of warm waters was a surge in air humidity and an increase in summer showers. Since this environmental phenomenon occurred around Christmas, the local fishermen called it El Niño, or Child Jesus. Early scientific observations on the nature and extent of these phenomena revealed that they were not regionally restricted to coastal Perú and Ecuador, but extended over the whole tropical Pacific, involving pressure fields and wind flows across the basin. Thus, when referring to this coupled ocean-atmospheric system, both variations of sea temperature across the tropical Pacific and changes of the atmosphere in contact with the ocean must be considered (Neelin et al., 1998). Normally, the tropical Pacific Ocean, from the coast of Ecuador and Perú to longitude 120°W, is dominated by westward- flowing cold waters, which are the prolongation of the Humboldt Current. Near longitude 120°W, sea surface temperatures approach normal equatorial values of ~28°C. When the flow reaches the western Pacific, it creates a sealevel rise of nearly 40 cm, which is maintained by the wind shear of the equatorial easterlies. The thermocline, which marks the lower boundary of the sun-heated water layer, runs at a depth of 40 m between Perú and the Galápagos Islands, but on the Asian side of the Pacific it dips to 120 m, revealing a marked asymmetry in the thickness of the sunheated layer across the Pacific. During El Niño years, the westward flow of cooler waters is weak because there is less wind shear from the easterly winds, and the thermocline plunges to 80 m in the eastern equatorial Pacific.
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"Propagated Fish in Resource Management." In Propagated Fish in Resource Management, edited by GARY E. WHELAN. American Fisheries Society, 2004. http://dx.doi.org/10.47886/9781888569698.ch26.
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<em>Abstract.</em>—Michigan’s fish hatcheries were originally developed in the 1870s in response to rapidly declining commercial fish stocks caused by massive overharvest and habitat degradation. While the writings of early fish culturists decried the waste from the commercial fishery and the destruction of critical habitat, there was little political will to do anything but stock fish, so for nearly 50 years, hatcheries became the only fishery management tool to address these problems. In the 1920s and 1930s, fishery managers recognized that more than hatcheries were needed to restore fish populations. Efforts were initiated to improve habitat and strictly control harvest. Hatcheries were still the primary focus of fisheries management, but culture policy changed to the production of fingerling rather than fry. This philosophy held sway until 1950 when a combination of research on fingerling returns and social demand for instant recreation forced the start of the legal-size trout program along with a reduction in the coolwater culture program in Michigan. In 1964, a complete shift in thought occurred. The legal-size trout program was discontinued, habitat rehabilitation was emphasized, and a policy of a 1:1 return to the creel as stocked was instituted. Propagated fish also became a tool for ecosystem change and Great Lakes salmonid stocking started in earnest to balance these prey dominated systems. In the 1970s and 1980s, coolwater fisheries programs were re-examined as water quality improvements from the Clean Water Act opened up new habitat for the re-establishment of these species. Large-scale culture operations for fingerling walleye, northern pike, muskellunge, and lake sturgeon culture operations were reinitiated. In the 1980s and 1990s, public concern over hatchery programs forced managers to review fish culture and stocking practices, and hatcheries became one of many biological, legal, and sociological tools to rehabilitate fish populations. Current Fisheries management philosophy in Michigan uses cultured fish to meet four objectives: (1) reestablish extirpated species, (2) rehabilitate degraded fish populations, (3) provide for ecosystem balance, and (4) create new sportfishing opportunities.
Conference papers on the topic "Northern Humboldt current ecosystem"
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Aparco, Luis Angel La Cruz, Ramiro Castillo, Jhon Robles, Carlos Valdez, and Rodolfo Cornejo. "Pelagic species identification using multifrequency acoustic in the Northern Humboldt Current System off Peru." In 2017 IEEE/OES Acoustics in Underwater Geosciences Symposium (RIO Acoustics). IEEE, 2017. http://dx.doi.org/10.1109/rioacoustics.2017.8349744.
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Kitazawa, Daisuke, and Jing Yang. "Numerical Study on Circulation and Thermohaline Structures With Effects of Icing Event in the Caspian Sea." In ASME 2010 29th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2010. http://dx.doi.org/10.1115/omae2010-20667.
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A hydrostatic and ice coupled model was developed to analyze circulation and thermohaline structures in the Caspian Sea. The northern part of the Caspian Sea freezes in the winter. Waters start icing in November and ices spread during December and January. The northern part of the Caspian Sea is covered by ices in severe winters. Ice-covered area is at its maximum during January and February, and then ices begin melting in March and disappear in April. The occurrence of ices must have significant effects on circulation and thermohaline structures as well as ecosystem in the northern Caspian Sea. In the present study, formation of ices is modeled assuming that ices do not move but spread and shrink on water surface. Under the ices, it is assumed that the exchange of momentum flux is impeded and the fluxes of heat and brine salt are given at sea-ice boundary. The ice model was coupled with a hydrostatic model based on MEC (Marine Environmental Committee) Ocean Model developed by the Japan Society of Naval Architect and Ocean Engineers. Numerical simulation was carried out for 20 years to achieve stable seasonal changes in current velocity, water temperature, and salinity. The fluxes of momentum, heat, and salt were estimated by using measurement data at 11 meteorological stations around the Caspian Sea. Inflow of Volga River was taken into account as representative of all the rivers which inflow into the Caspian Sea. Effects of icing event on circulation and thermohaline structures were discussed using the results of numerical simulation in the last year. As a result, the accuracy of predicting water temperature in the northern Caspian Sea was improved by taking the effects of icing event into account. Differences in density in the horizontal direction create several gyres with the effects of Coriolis force. The differences were caused by differences in heat capacity between coastal and open waters, differences in water temperature due to climate, and inflow of rivers in the northern Caspian Sea. The water current field in the Caspian Sea is formed by adding wind-driven current to the dominant density-driven current, which is based on horizontal differences in water temperature and salinity, and Coriolis force.
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Menéndez, Jaime, Jorge Fernández, and Andrés Araujo. "Assessing Sustainability Strategies in the Oil and Gas Sector through the Sustainable Development Goals. A Case Study of a Multi-Stakeholder Innovation Ecosystem." In International Petroleum Technology Conference. IPTC, 2022. http://dx.doi.org/10.2523/iptc-22272-ms.
Full textAbstract:
Abstract Developing effective sustainability strategies by oil and gas (O&G) companies requires that they embrace the global call to incorporate the United Nations’ Sustainable Development Goals (SDGs) into their business strategies and operations. However, more attention is needed in the academic literature regarding the analysis of the linkage between O&G companies and the SDGs. A previous study by the authors proposed an analysis process in order to assess sustainability strategies in the O&G sector, based on the combination of two sources of information provided by relevant international organizations in the energy field. This initial research focused on a small number of SDGs, which may not reflect the complexity of the approach to sustainability by an O&G company. Therefore, an extension of the analysis is introduced in this paper following a research with two stages. The first stage is based on case study methodology (taking a refinery in the Basque Country, in Northern Spain). This yields a qualitative identification of different avenues that the O&G company under study can follow to contribute to targeted SDGs with its own technological and industrial resources and current research and innovation projects. Building on this, the second stage of this line of research focuses on identifying which business relationships are the result of the activities and projects that contribute to SDGs. As a whole, the universe of business and non-business relationships constitute a growing multi-stakeholder innovation ecosystem on which the company relies to achieve its sustainability objectives. This innovation network around the refinery's operations encompasses a variety of stakeholders (companies, technology and research centers, universities and others) working on innovative projects related to hydrogen and synthetic fuels production, circular economy, electric vehicles, energy storage, renewable energy communities or digitalization, among other technologies and energy carriers. This ecosystem is supported by a web of public-private cooperation schemes at different government levels. The outcome of this approach to innovation reflects how, by adopting a multi-energy strategy, the analyzed company can act as a catalyst for innovation spillovers and synergies in the whole Basque Country region, which has implications that go beyond energy and climate issues.