Transcriptomics and gene expression profiling enables the elucidation of the genetic response of an organism to various environmental cues. Transcriptomics enables the deciphering of differences between two closely related organisms to the same environment and in contrast, enables the elucidation of genetic responses of the same organism to different environmental cues. Two major methods are utilized for the study of transcriptomes, high-throughput sequencing and microarray analysis. High-throughput sequencing technologies such as the Illumina platform are relatively new and protocols must be developed for the analyses of transcriptomes (RNA-sequencing). A RNA-seq protocol was developed and refined for the Illumina sequencing platform. This protocol was then utilized for the de novo sequencing of the steelhead salmon transcriptome. Hatchery steelhead exhibit a reduced fitness compared to wild steelhead that has been shown to be genetically based. Consequently, the steelhead transcriptome was assembled, annotated, and used to identify gene expression differences between hatchery and wild fish. We uncovered many differentially expressed genes involved in metabolic processes and growth and development. This work has created a better understanding of the genetic differences between hatchery and wild steelhead salmon. Brachypodium distachyon is a monocot grass important as a model for cereal crops and potential biofuels feedstocks. To better understand the genetic response of this plant to different environmental cues, a comprehensive assessment of the transcriptomic response was conducted under a variety of conditions including diurnal/circadian light/dark/temperature environments and different abiotic stress conditions. Using a whole-genome tiling DNA microarray, we identified that the majority of transcripts in Brachypodium exhibit a daily rhythm in their abundance that is conserved between rice and Brachypodium. We also identified numerous cis-regulatory elements dictating these rhythmic expression patterns. We also identified the genetic response to abiotic stresses such as salinity, drought, cold, heat, and high light. We uncovered a core set of genes which responds to all stresses, indicating a core stress response. A large number of transcription factors were uncovered as potential nodes for regulating the abiotic stress response in Brachypodium. Moreover, promoter elements that drive specific responses to discrete abiotic stresses were uncovered. Altogether, the transcriptome analyses in this work furthers our understandings of how particular organisms respond to environmental cues and better elucidates the relationship between genes and the environment. / Graduation date: 2012 / Access restricted to the OSU Community at author's request from Oct. 5, 2011 - April 5, 2012.

There is growing realisation world wide that the attainment of environmental sustainability is contingent upon reinstatement of community authority over management of natural resources. In acknowledgement of this imperative the government of Mozambique has formulated policies and enacted legislation to promote Community-Based Natural Resource Management. The research reported here considers the prospects for achieving CBNRM in a fishery located in a remote part of the country on the border between Mozambique and Tanzania. The central hypothesis addressed is that the fishery in historical terms was operated under a common property regime and that, under a number of forces , this has changed to an open access regime. The challenge facing government is to return the fishery to a common property regime. A conceptual framework which illustrates transformation of the fishery was developed. This was used to structure the research. Central question posed includes: what evidence is there that the fishery may have operated as common property system? what evidence is there that it now operates as an open access system? • what forces promoted such change, if indeed change has occurred? The findings are that the fishery has changed and now has the characteristics of the prospects for a return to CBNRM. Three issues are considered: who is the community? • what are the resources? and what are the management issues? It is concluded that definition of the 'community' is difficult because of historical precedents of access and use. The resource is shown to be complex including fish, water, land and plants; it also varies in tenure and space. Quite different rights of tenure issues accompany different resources. And management is complicated by international issues and apparent weaknesses in organisational structures, legislation and resources (human and financial). Evidence indicates that the people involved in the fishery are concerned about the state of the fishery and the lack of controls. They express a need for CBNRM. This study exposes the very complex nature of the fishery and suggests that failure to appreciate and understand this complexity encourages simplistic approaches to introduction of CBNRM. These are likely to fail. It is recommended that in light of the complexity elucidated by this research, the government should engage a strategic planning process with the intention of designing and implementing a process for introducing CBNRM which is constructed in the context of what is a very complex system. / Thesis (M.Env.Dev.)-University of Natal, Pietermaritzburg, 2000.

Com a Constituição Federal do Brasil de 1988, as comunidades remanescentes de quilombos adquiriram direito legal às áreas tradicionalmente ocupadas e o Estado passou a implementar Políticas Públicas visando seu desenvolvimento. Estas Políticas atualmente têm como foco a agroecologia, no sentido de manejo ecológico dos recursos naturais por meio de ação social coletiva. Porém, mesmo os projetos com tal enfoque não têm alcançado os resultados esperados, priorizando apenas a substituição de insumos sintéticos e práticas degradadoras. Considerou-se que o território pode ser um importante instrumento de análise de projetos de agroecologia e que projetos agroecológicos que abrangem as diferentes perspectivas do território têm maiores chances de resultados efetivos para comunidades quilombolas. Assim, o objetivo deste trabalho foi avaliar os Projetos Agroecológicos desenvolvidos na comunidade quilombola Mandira, em Cananéia/SP/Brasil. O trabalho foi realizado entre 2011 e 2014 através de técnicas qualitativas, com entrevistas, observação participante, história oral e análise de documentos. Os projetos analisados foram os relativos à criação da Reserva Extrativista do Mandira e manejo de recursos marinhos, e à implantação de sistemas agroflorestais. O projeto de manejo de recursos marinhos proporcionou inicialmente maior sustentabilidade à atividade e agregação de valor a partir da criação de uma Cooperativa, porém tem mostrado indícios de redução dos estoques naturais, segundo a percepção dos moradores, além da especialização na atividade e redução da produção para autoconsumo. O projeto de sistemas agroflorestais, de abrangência territorial, proporcionou maior diversidade de produtos, tanto para consumo quanto para comercialização, realizada em uma feira agroecológica. As famílias que trabalham com manejo de recursos marinhos possuem maior dependência do mercado, tanto para comercialização, quanto para obtenção de alimentos, diferentemente do outro projeto, que proporcionou maior autonomia, formação de capital social e alimentação saudável. Esses resultados podem confirmar a hipótese de que a perspectiva territorial se constitui um importante instrumento de avaliação de Projetos e também pode contribuir na implementação de ações de Políticas Públicas agroecológicas. / With the Federal Constitution of Brazil of 1988 the remaining maroon communities acquired statutory right to traditionally occupied areas and the Govern started to implement Public Policies aimed at their development. These policies currently are focused on agroecology, in the sense of ecological management of natural resources through collective social action. However, even projects with this approach have not achieved the expected results, just prioritizing the substitution of synthetic inputs and degrading practices. Whereas that the territorial approach involves endogenous and exogenous issues of the relationship between the community and the society, and would offer a greater opportunity of success in the implemented agroecological actions, the objective of this study was to evaluate Public Policies in Mandira maroon community in Cananéia, São Paulo State, Brazil, on these two different perspectives, agroecological and territorial. The study was conducted between 2011 and 2014 using qualitative techniques, including interviews, participant observation, oral history and document analysis. The analyzed projects were those concerning to the establishment of the Mandira Extractive Reserve and management of marine resources, and the implementation of agroforestry systems. The management project of marine resources initially provided greater sustainability to activity and adding value through the creation of a Cooperative, but it has shown signs of stock reduction, as perceived by residents, besides the specialization in the activity and reduction of production for self-consumption. The project of territorial coverage agroforestry systems, provided greater diversity of products, both for consumption and for sale, held in an agroecological fair. Families working with the marine resources management have greater dependence on the market, either for marketing as for obtaining food, unlike the other project, which provided greater autonomy, social capital formation and healthy eating, indicating that the territorial approach in Public Policy agroecological actions can contribute to more effective and sustainable results.

Orientador: Alpina Begossi / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-11T02:56:17Z (GMT). No. of bitstreams: 1 Lopes_PriscilaFabianaMacedo_D.pdf: 4700329 bytes, checksum: bbc9137dcc5a651ed9a7ac7fd9349c6d (MD5) Previous issue date: 2008 / Resumo: O enfoque deste estudo está centrado na dinâmica da pesca artesanal de caráter comercial da Praia do Perequê, Guarujá, SP, sob a perspectiva da ecologia comportamental humana e da análise do processo de decisão por parte dos pescadores. Assim, o objetivo geral foi avaliar a dinâmica da pesca artesanal local, comparando-a a outras pescarias artesanais brasileiras, levando em conta seus aspectos sócio-econômicos, ecológicos e comportamentais, a fim de fornecer subsídios básicos, mas essenciais, para o manejo dos recursos pesqueiros locais. Os resultados de quatorze meses de estudos de campo são integrados ao longo de três capítulos através de conceitos derivados da ecologia evolutiva, tais como otimização e territorialidade, e conceitos que provêm da Teoria dos Comuns, como regimes de propriedade. Os métodos utilizados incluem entrevistas semi-estruturadas para o levantamento sócio-econômico (n=51), acompanhamento de desembarques (n=424) e de viagens de pesca (n=21) e mapeamento (pontos georreferenciados) e etnomapeamento (identificação pelos pescadores) dos principais pontos de pesca. O primeiro capítulo traz uma caracterização sócio-econômica da comunidade, analisando as similaridades e diferenças entre os dois principais grupos de pescadores: os pescadores de camarão (camaroeiros) e os pescadores de peixes. Foram registradas as principais e poucas espécies de camarão (n=2) e peixe (n=5) de interesse para a pesca, os equipamentos utilizados (e.g.: arrasto de fundo e rede de espera), a influência da migração de pescadores de outros estados para o local, especialmente os vindos da região Sul, e as interrelações econômicas e familiares que direcionam a vida local (e.g: economia centrada na pesca e comércio do camarão). O segundo capítulo aborda a pesca e o processo decisório por parte do pescador. O esforço de pesca é analisado sob a perspectiva temporal, mostrando a influência de fatores sazonais (e.g.: vento) em decisões que governam, por exemplo, o simples fato de ir ou não pescar diariamente. Além disso, é uma área de livre acesso, onde nem regras locais nem o poder público fiscalizam e limitam a exploração dos recursos, contribuindo para que o processo de decisão se dê apenas em nível individual e não comunitário. Apesar disto, alguns conflitos em função da sobreposição entre as áreas de pesca de camaroeiros e demais pescadores podem ser observados. O ultimo capítulo traz uma análise a partir da Teoria do Forrageio Ótimo, testando-se se o pescador obtem a maximização (otimização) calórica e financeira. Foram encontradas evidências de sobre-exploração de peixes, já que o pescador precisa ir cada vez mais longe para conseguir espécies que normalmente são pescadas próximas à costa. Além disso, o fato de ambos os grupos de pescadores obterem a otimização de seus ganhos calóricos e financeiros sugere um comportamento que visa somente o retorno a curto prazo, uma estratégia claramente não conservacionista. O levantamento de alguns pontos principais ao longo deste estudo no que concerne à pesca no Perequê (como migração de pescadores, conflitos sobre o direito de acesso às áreas de pesca, exploração não controlada, intensa dependência de poucos recursos) subsidia e mostra a relevância de se adotar medidas de manejo imediatas, que visem coibir ou diminuir o impacto ambiental e social que uma eventual crise dos recursos locais poderia causar. Entre tais medidas de manejo, cita-se a aplicação efetiva da legislação existente, o desenvolvimento de acordos locais próprios que visem diminuir conflitos e tornar a exploração mais sustentável, e principalmente a reforma das instituições formais e informais, as quais facilitariam a efetivação de tais medidas / Abstract: This study focus on the dynamics of the commercial, but still artisanal fisheries in Perequê Beach, Guarujá, SP, under the perspective of human behavioral ecology and decision-making processes analyses by local fishermen. Its main goal was to evaluate the conditions of the local fisheries, comparing it to other artisanal fisheries in Brazil, taking into account social-economic, ecological and behavioral factors, in order to provide basic but essential information to local fisheries management. The results of 14 months of fieldwork are integrated throughout three chapters using concepts from evolutionary ecology, such as optimization and territoriality, and concepts from the Commons Theory, such as property regimes. The methods used include semi-structured interviews applied to the social-economic characterization, fish landings samplings (n=424), participant observations in some fishing trips (n=21) and fishing spots mapping (georeferenced spots) and ethnomapping (identified by the local fishermen). The first chapter brings up a socialeconomic portrait of the community, showing the similarities and differences between the two fishing systems: shrimp trawl and gillnet fishery. Few targeted shrimp (n=2) and fish (n=5) species were identified. The kinds of equipment used (bottom otter trawl and gillnet), the importance of fishermen migration from other Brazilian states to the place, especially from the south region, and the economic and family based interrelations that lead the local life (economy based on fishing and commerce of shrimp) were also studied. The second chapter addresses the local fisheries and fishermen¿s decision-making processes. Fishing effort is analyzed under a temporal perspective, investigating the influence of seasonal factors (e.g.: wind) in decisions that rule, for example, the simple daily act of going fishing or not. In addition to that, Perequê represents an open access area, where neither local rules nor government enforces the existing laws or curtails the resource exploitation, which makes the decision making processes be solely at the individual level and not at the community level. Despite that, some conflicts due to the overlap of fishing areas between trawlers and gillnetters can be observed. The last chapter bringsup an analysis based on Optimal Foraging Theory, testing if a fisherman tries to maximize (optimization process) his caloric and financial returns. Pieces of evidence concerning fish overexploitation were found, as the fisherman needs to go further to fish species that are usually caught close to the coast. Moreover, the fact that both fishing groups aims at maximizing their financial and caloric return suggests a kind of behavior that is directed towards the short term return, a strategy clearly non-conservationist. The main points showed by this study concerning Perequê¿s fishing (fishermen¿s migration, conflicts over the rights to use the fishing spots, non regulated exploitation, intense dependence on a few fishing resources, etc.) ground and show the need of adopting immediate management measures, aiming at restricting and decreasing the environmental and social impacts caused by an eventual resource crises. Among them, it is suggested the fleet control, the effective enforcement of existing regulations, the development of local agreements that aim to decrease conflicts and to make resource exploitation more sustainable, and mainly the restructuring of formal and informal institutions, which would make the application of such measures easier / Doutorado / Ecologia / Doutor em Ecologia

Une ZEE de près de 230000 km², avec un plateau continental d’environ 39000 km², balayée par l’intense upwelling présent pratiquement toute l’année dans cette zone de l’Atlantique centre est, expliquent la richesse biologique des eaux mauritaniennes et leur potentiel élevé en ressources halieutiques, avec des espèces diversifiées et de valeur marchande élevée.Plusieurs décennies d’efforts s’appuyant sur des politiques centrées sur la conservation des ressources halieutiques et l’intégration de la pêche à l’économie nationale, ont permis au pays d’impulser le développement d’un secteur national dynamique de pêche.Le développement des institutions nationales et de la réglementation a permis d’asseoir la souveraineté de l’Etat sur la ZEE, de codifier le droit régalien de l’Etat sur les ressources halieutiques, de déterminer les mécanismes d’allocation des droits de pêche et leurs supports physiques, et d’organiser les structures chargées de la mise en œuvre des ces institutions. Avec une contribution moyenne au cours des dernières décennies, de 4-10% du PIB, de 20-30% des recettes budgétaires, les recettes en devises générées par l’exportation des produits et les redevances de pêche versées par les armements étrangers, qui constituent un soutien important au budget national, la pêche mauritanienne joue, depuis quelques décennies, un rôle clef dans la réalisation des objectifs des politiques économiques du pays.La Mauritanie a toujours été un pays habité en majorité par des nomades qui ne connaissaient pas la mer auparavant, à l’exception de la tribu Imraguen qui pratiquait la pêche traditionnelle depuis des générations. Il est aujourd’hui tourné vers la mer par nécessité et commence à se rendre compte de ses ressources aussi bien bénéfiques pour sa population que pour son développement économique. Cependant, l’avenir du secteur de la pêche sera surtout dessiné avec la mise en place des plans d’aménagement efficaces, qui vont constituer le cadre de gestion du secteur de la pêche pour les prochaines années. / An EEZ of nearly 230,000 square kilometers, with a continental shelf of about 39000 km ², swept by the intense upwelling that is present during almost the whole year in this area of the East Middle Atlantic, explain the biological richness of Mauritanian waters and their high potential in fish resources, with diverse species and high market value. Several decades of effort based on policies that focus on the conservation of fishery resources and the integration of fisheries to national economy, have enabled the country to boost the development of a dynamic national sector of fishery. The development of national institutions and the regulation has helped to underpin the State's sovereignty over the EEZ, to codify the sovereign right of the State on fisheries resources, to determine the mechanisms for allocating fishing rights and their physical media, and organize the structures responsible for the implementation of these institutions. With an average contribution over the past decades, over 4-10% of GDP, 20-30% of fiscal revenue, foreign exchange earnings generated by exports of goods and royalties paid by the fishing foreign arms, which constitute an important support to the national budget, the Mauritanian fishing plays in recent decades, a key role in achieving the objectives of economic policy of the country. Mauritania has always been a country inhabited mostly by nomads, who does not know the sea, except the tribe Imraguen who practice the traditional fishery for generations. It is now facing the sea through necessity and begins to realize its resources as beneficial for its people as its economic development. However, the future of fisheries will be especially designed with the introduction of effective management plans, which will provide the framework for management of fisheries in the coming years.

This study focused on the management of the red sea urchin Loxechinus albus fishery in Chile. The main objective was to design, construct, implement and assess a computer-based simulation model to analyse the biological effects, socio-economic consequences and spatial dynamics resulting from coastal management plans applied to this resource under the system of AMEBR. This was accomplished by using systems dynamics (SD) and geographical information systems (GIS) modelling, in a process of model development, run, optimisation, sensitivity analysis and risk management, and a series of field-based activities carried out at the cove of Quintay. The GIS model developed for allocating sea urchins restocking sites offered a flexible, cost-effective, user-friendly and descriptive technique for support decision-making on management of this species and other benthic resources. Final site selection for restocking was based on the identification, quantification and selection of higher suitability¦availability combinations (site categories). This map showed 16 different suitability¦availability combinations or site categories, ranging from 4¦100 to 8¦100 (suitability points¦availability %). These had an average of 6.44¦69.37 (covering an area of 82.5 Ha overall equivalent to 81.21% of the study area. This site classification demonstrated high heterogeneity between options, and revealed the full variety of alternatives for decision-making. More importantly, the generally high suitability indexes as well as available area emphasised the prospects for restocking sea urchins in this study area. Over and above of the quantitative outcomes obtained from running the GISRM (suitable and available restocking sites) and the BSESM (alternative strategic management plans), the case study-based analysis made it possible to disclose the wider issues related to the red sea urchin coastal management. These results demonstrated the biological inefficiency of traditional size/seasonal restriction-based approach (macro-scenario 1) for sustainable management of the target species. More importantly, final outcomes strongly suggested that a combination of adaptive restocking-based enhancement activities and flexible exploitation constituted a highly attractive approach (macro-scenario 3) for stock management of this fishery in terms of harvestable stock and related incomes. However from the economic analysis, stocking was also found to be economically unfeasible, being a rather cost intensive exercise negatively affected by high natural mortality rates. A single-variable optimisation analysis demonstrated that a higher survival rate is needed to generate sufficient profits to cover major restocking costs and a positive payment, or a cost reduction is essential to make up for the loss. On top to these practical constraints, based on the distinctive modest economic situation prevailing for most Chilean coves and hence their limited capacity to pay for stocking material, unless adequate and constant funding is available to support artisanal associations, they are very unlikely to develop mass release programmes. Given the economic (i.e.: high operating costs) and technical (i.e.: low survival rates) limitations conditioning stocking-based management cost-effectiveness and applicability, wide implementation of mass releases as a major approach for management of the red sea urchin fishery is very unlikely to take place in Chile. This study presents a methodology and offers a tool to design, evaluate and optimise coastal management plans for the red sea urchin in a dynamic, interactive, systematic, integrated and flexible way. The optional strategic management plans proposed on this study may not be applied equally to any AMEBR, as they are the outputs arising from a single cove-specific analysis. Still, the complete methodological framework and analysis procedures developed may be applied to run the BSESM and optimise management of a red sea urchin fishery at any other AMEBR case of study.

The mechanisms of mortality during critical life stages of fish are not well-understood and, for many species, it is not clear if the mechanisms are similar for naturally and artificially propagated individuals. For Chinook salmon (Oncorhynchus tshawytscha), natural fish potentially face negative interactions, such as competition, and survival disadvantages, such as smaller size, that may limit survival when in association with hatchery fish. To better understand the mechanisms of mortality for hatchery and natural Chinook salmon during the critical early marine residence stage, I: (1) developed a model to discriminate between hatchery and natural juveniles using otolith structure; (2) directly compared migratory patterns of hatchery and natural juveniles; and (3) determined if there was evidence for selective mortality during early marine residence. I followed two cohorts through space and time by collecting juveniles from May-September in the Columbia River estuary and off the coast in September of 2010 and 2011. I compared attributes of those juveniles when they firstentered marine waters with those of survivors after their first summer at sea. I used a combination of genetic stock identification, otolith chemistry and structure, and physical tags to determine stock of origin, size at and timing of freshwater emigration, marine growth, and production type (hatchery or natural). I focused on the subyearling life history of a federally managed genetic stock group (upper Columbia River summer and fall Chinook salmon, UCR Su/F) because: 1) it is an abundant stock group; 2) subyearlings may be more vulnerable to size-selective mortality than yearlings; and 3) it is currently impossible to assess impacts of hatchery production due to low rates of marking the hatchery fish within this stock group. The classification model included two metrics, the presence or absence of a previously unreported transfer check associated with hatchery rearing and variability in otolith increment width, and predicted production type with a 92% jack-knifed accuracy. Overall, timing of marine entry was similar for hatchery and natural UCR Su/F juveniles, which entered marine waters from May-September with a peak in July and August in both years. Estuarine residence times were brief: 80% of the individuals captured in the estuary had resided in saline waters for < 3 days and mean estuarine residence was significantly greater (7 ± 1.3 d) in 2010 than 2011 (1 ± 0.3 d). The only clear difference was that natural individuals captured in the estuary in 2011 migrated to saline waters earlier (July 13th ± 4 d) than hatchery conspecifics (August 10th ± 6 d). However, the timing of marine entry was similar (July 27th ± 1 d) between hatchery and natural fish collected later in the ocean. This observation could be due to differential survival related to the timing of marine entry. Alternatively, estuarine collections may not have adequately represented the emigrating population due to rapid emigration. I documented clear spatial overlap between production types during early marine residence but no difference in median size at marine entry (100 ± 3.5 mm), size at capture (152 ± 4.0 mm), or marine growth (0.94 ± 0.1 %b l d-1). There were also no significant differences in size at marine entry between estuary and ocean collections, which indicates that size-selective mortality had not occurred. Based on both external tags and the otolith classification model, the mean percentage of natural fish in ocean collections was 17% (± 4.8) greater than in the Columbia River estuary; this finding may indicate that estuarine collections are biased to hatchery fish or, more likely, that natural fish survived at higher rates than hatchery fish. Increased survival of natural fish may be related to greater selection pressure during freshwater rearing and prior experience with predators. This study provides the first direct stock-specific comparison of juvenile migratory behavior in natural and hatchery juvenile Columbia River Chinook salmon during early marine residence. Further research is needed to determine if natural fish consistently survive better than hatchery conspecifics and, if so, determine the specific traits and behaviors that afford a survival advantage. / Graduation date: 2013

Orientador: Fernando Fernandes Mendonça / Resumo: A atividade pesqueira desempenha um importante papel ambiental e socioeconômico, pois é fonte de renda e alimento para milhões de pessoas no mundo. Entretanto, falhas em sua gestão e lacunas nos dados biológicos para muitas espécies, tem resultado na sobreexplotação de seus estoques, o que pode impactar diversos ecossistemas marinhos. Neste contexto, os peixes-de-bico, grupo formado pelas famílias Xiphiidae e Istiophoridae, são considerados valiosos recursos pesqueiros, porém ainda não há consenso sobre o número e a validade das espécies da família Istiophoridae e também há incertezas sobre a avaliação atual de seus estoques. Sendo assim, o objetivo deste estudo é o de delimitar as espécies da família Istiophoridae e os estoques genéticos do agulhão-vela Istiophorus platypterus no Oceano Atlântico utilizando marcadores moleculares mitocondriais. Entre os resultados dos testes de delimitação de espécies, o número variou entre 6 e 12 táxons possíveis, dependendo do teste aplicado. Em relação a delimitação dos estoques genéticos de I. platypterus no Atlântico, assumindo-se apenas uma espécie no gênero Istiophorus, nossos resultados apontam a existência de alta diversidade genética, componde um único estoque genético no Atlântico (ΦST=0,01121, p=0,02438), apresentando um alto fluxo gênico. Porém, pela análise da rede de haplótipos e da inferência bayesiana observa-se a existência de diferentes linhagens mitocondriais simpátricas, que divergiram durante o Mioceno Superior e foram ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Fishing activity plays an important environmental and socio-economic role, as it is a source of income and food for millions of people worldwide. Although, shortcomings in management and gaps in biological data for many species resulted in the overexploitation of their stocks, which may impact several marine ecosystems. In this context, billfishes, a group compounded by the Xiphiidae and Istiophoridae families, are considered valuable fish resources, but there is still no consensus on the number and validity of the species of Istiophoridae family and there are also uncertainties about the current fisheries stocks assessments. Thus, the main objectives of this study are to delimit the species of the Istiophoridae family and the genetic stocks of the sailfish, Istiophorus platypterus, in the Atlantic Ocean using mitochondrial molecular markers. Among the species delimitation tests results, the number ranged from 6 to 12 possible taxa depending on the test applied. In order to determine the genetic stock of I. platypterus in the Atlantic Ocean, assuming only one species in the genus Istiophorus, our results point to the existence of high genetic diversity, comprising a single genetic stock in the Atlantic (ΦST = 0.01121, p = 0.02438), presenting a high gene flow. However, the analysis of the network of haplotypes and Bayesian inference shows the existence of different sympatric mitochondrial lines, which diverged during the Upper Miocene and were re-approximated, interrupting th... (Complete abstract click electronic access below) / Doutor