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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Padrões na produtividade e na composição do pescado na pesca artesanal costeira e fluvial brasileira

Lima, Evelyn Gonçalves January 2012 (has links)
Os recursos pesqueiros estão sendo sobre-explotados mundialmente. A pesca pode conduzir ao efeito de cascata trófica e essa exploração pode ser insustentável. Por isso políticas de manejo são urgentes, mas faltam dados para subsidiar tais políticas e nesse sentido, estudos com pescadores artesanais através de entrevistas têm colaborado com o conhecimento sobre a dinâmica pesqueira. A pesca artesanal brasileira é a principal atividade econômica ou de subsistência e o pescado é a maior fonte de proteínas para populações caboclas ribeirinhas amazônicas e populações de caiçaras que vivem na área litorânea da Mata Atlântica. Esta pesquisa analisou padrões ecológicos espaciais e temporais na pesca artesanal brasileira em dois ecossistemas: a costa sudeste da Mata Atlântica e a Amazônia fluvial, tendo como base de dados entrevistas realizadas com pescadores ao longo de vários projetos de pesquisa. No capítulo 1 analisou-se a produtividade pesqueira no litoral sudeste. Foi testada a variação da biomassa média capturada citada pelos entrevistados em função de fatores temporais (idade do pescador e data em que ocorreu sua última pescaria) e espaciais (região aonde se localiza a comunidade do pescador entrevistado). Foram analisadas entrevistas com 423 pescadores, que indicaram que: a) houve uma diminuição na quantidade de peixes capturados ao longo do tempo; b) a biomassa capturada não foi influenciada pelo fator espacial; c) não houve influência da idade do pescador na biomassa capturada mencionada. O capítulo 2 abordou a costa sudeste da Mata Atlântica e a Amazônia fluvial. Foram analisadas a composição dos peixes, através dos nomes populares citados e seu nível trófico médio. Foram analisadas entrevistas com 658 pescadores da Amazônia fluvial (de 1987 a 2006) e 821 pescadores da costa sudeste da Mata Atlântica (de 1986 a 2009) (n=1479 entrevistados). Não houve variação do nível trófico segundo o tempo, porém o nível trófico variou de acordo com os fatores espaciais (ecossistema e região), sendo que o fator que mais influenciou essa variação foi região. Na costa sudeste da Mata Atlântica há possível substituição das espécies de nível trófico similar por outras espécies de mesmo valor econômico com o tempo. Na Amazônia fluvial esse padrão de substituição das espécies não foi observado. Conclui-se que a diminuição da biomassa capturada ao longo do tempo somada à substituição de determinadas espécies de peixes capturados na costa da Mata Atlântica, podem indicar que a pesca não está sendo sustentável. Medidas preventivas de manejo pesqueiro devem ser implementadas. / Fisheries resources are being over-exploited worldwide. Excessive fishing can lead to trophic cascades and this exploration may be unsustainable. Therefore, management policies are urgent, but data are lacking to support such policies. In this sense, studies addressing interviews with fishermen have collaborated with the knowledge about the dynamics of fishing. The Brazilian artisanal fishing is the main economic and subsistence activity and the main source of protein for riverine Amazonian Caboclo populations and caiçara populations, who live in the coastal area of the Atlantic Forest. This study examined spatial and temporal ecological patterns in Brazilian artisanal fisheries in two ecosystems: the southeast coast of the Atlantic Forest and the fluvial Amazon; the data was based in interviews with fishermen on the course of several research projects. In Chapter 1 it was analyzed the fishery productivity in the southeastern coast. It was checked the variation in the average biomass of fish captured according to the interviews with fishers, due to temporal factors (fishermen’s age and date of their last fishery) and spatial factors (the region where the community of fishermen interviewed is located). There were analyzed interviews with 423 fishers, indicating that: a) there was a decrease in the biomass of fish caught over time, b) the biomass of fish caught was not influenced by the spatial factor c) there was no influence of age of the fisherman on the biomass of fish caught that was mentioned by them. Chapter 2 addressed the southeast coast of the Atlantic Forest and the Inland freshwater Amazon. It was analyzed the composition of fish caught, through their popular names mentioned by fishers and their mean trophic level. There were analyzed interviews with 658 fishers in the Amazon Basin (from 1987 to 2006) and with 821 fishers in to the southeast coast of the Atlantic Forest (from 1986 to 2009) (n = 1479 fishers). There was no variation in trophic level according to the time since the last fishing trip, and according to the spatial factors (ecosystem and region), and the region was the factor that most influenced the variation in trophic level. On the southeast coast of the Atlantic Forest species with similar trophic levels have been probably replaced by species of similar economic value over time. However, in the freshwater Amazon this pattern of species replacement was not observed. It is concluded that the decrease in biomass captured over time and the replacement of species on the Atlantic coast, may indicate that the fishery has been not sustainable. Preventive fisheries management measures should thus be devised.
2

Padrões na produtividade e na composição do pescado na pesca artesanal costeira e fluvial brasileira

Lima, Evelyn Gonçalves January 2012 (has links)
Os recursos pesqueiros estão sendo sobre-explotados mundialmente. A pesca pode conduzir ao efeito de cascata trófica e essa exploração pode ser insustentável. Por isso políticas de manejo são urgentes, mas faltam dados para subsidiar tais políticas e nesse sentido, estudos com pescadores artesanais através de entrevistas têm colaborado com o conhecimento sobre a dinâmica pesqueira. A pesca artesanal brasileira é a principal atividade econômica ou de subsistência e o pescado é a maior fonte de proteínas para populações caboclas ribeirinhas amazônicas e populações de caiçaras que vivem na área litorânea da Mata Atlântica. Esta pesquisa analisou padrões ecológicos espaciais e temporais na pesca artesanal brasileira em dois ecossistemas: a costa sudeste da Mata Atlântica e a Amazônia fluvial, tendo como base de dados entrevistas realizadas com pescadores ao longo de vários projetos de pesquisa. No capítulo 1 analisou-se a produtividade pesqueira no litoral sudeste. Foi testada a variação da biomassa média capturada citada pelos entrevistados em função de fatores temporais (idade do pescador e data em que ocorreu sua última pescaria) e espaciais (região aonde se localiza a comunidade do pescador entrevistado). Foram analisadas entrevistas com 423 pescadores, que indicaram que: a) houve uma diminuição na quantidade de peixes capturados ao longo do tempo; b) a biomassa capturada não foi influenciada pelo fator espacial; c) não houve influência da idade do pescador na biomassa capturada mencionada. O capítulo 2 abordou a costa sudeste da Mata Atlântica e a Amazônia fluvial. Foram analisadas a composição dos peixes, através dos nomes populares citados e seu nível trófico médio. Foram analisadas entrevistas com 658 pescadores da Amazônia fluvial (de 1987 a 2006) e 821 pescadores da costa sudeste da Mata Atlântica (de 1986 a 2009) (n=1479 entrevistados). Não houve variação do nível trófico segundo o tempo, porém o nível trófico variou de acordo com os fatores espaciais (ecossistema e região), sendo que o fator que mais influenciou essa variação foi região. Na costa sudeste da Mata Atlântica há possível substituição das espécies de nível trófico similar por outras espécies de mesmo valor econômico com o tempo. Na Amazônia fluvial esse padrão de substituição das espécies não foi observado. Conclui-se que a diminuição da biomassa capturada ao longo do tempo somada à substituição de determinadas espécies de peixes capturados na costa da Mata Atlântica, podem indicar que a pesca não está sendo sustentável. Medidas preventivas de manejo pesqueiro devem ser implementadas. / Fisheries resources are being over-exploited worldwide. Excessive fishing can lead to trophic cascades and this exploration may be unsustainable. Therefore, management policies are urgent, but data are lacking to support such policies. In this sense, studies addressing interviews with fishermen have collaborated with the knowledge about the dynamics of fishing. The Brazilian artisanal fishing is the main economic and subsistence activity and the main source of protein for riverine Amazonian Caboclo populations and caiçara populations, who live in the coastal area of the Atlantic Forest. This study examined spatial and temporal ecological patterns in Brazilian artisanal fisheries in two ecosystems: the southeast coast of the Atlantic Forest and the fluvial Amazon; the data was based in interviews with fishermen on the course of several research projects. In Chapter 1 it was analyzed the fishery productivity in the southeastern coast. It was checked the variation in the average biomass of fish captured according to the interviews with fishers, due to temporal factors (fishermen’s age and date of their last fishery) and spatial factors (the region where the community of fishermen interviewed is located). There were analyzed interviews with 423 fishers, indicating that: a) there was a decrease in the biomass of fish caught over time, b) the biomass of fish caught was not influenced by the spatial factor c) there was no influence of age of the fisherman on the biomass of fish caught that was mentioned by them. Chapter 2 addressed the southeast coast of the Atlantic Forest and the Inland freshwater Amazon. It was analyzed the composition of fish caught, through their popular names mentioned by fishers and their mean trophic level. There were analyzed interviews with 658 fishers in the Amazon Basin (from 1987 to 2006) and with 821 fishers in to the southeast coast of the Atlantic Forest (from 1986 to 2009) (n = 1479 fishers). There was no variation in trophic level according to the time since the last fishing trip, and according to the spatial factors (ecosystem and region), and the region was the factor that most influenced the variation in trophic level. On the southeast coast of the Atlantic Forest species with similar trophic levels have been probably replaced by species of similar economic value over time. However, in the freshwater Amazon this pattern of species replacement was not observed. It is concluded that the decrease in biomass captured over time and the replacement of species on the Atlantic coast, may indicate that the fishery has been not sustainable. Preventive fisheries management measures should thus be devised.
3

Padrões na produtividade e na composição do pescado na pesca artesanal costeira e fluvial brasileira

Lima, Evelyn Gonçalves January 2012 (has links)
Os recursos pesqueiros estão sendo sobre-explotados mundialmente. A pesca pode conduzir ao efeito de cascata trófica e essa exploração pode ser insustentável. Por isso políticas de manejo são urgentes, mas faltam dados para subsidiar tais políticas e nesse sentido, estudos com pescadores artesanais através de entrevistas têm colaborado com o conhecimento sobre a dinâmica pesqueira. A pesca artesanal brasileira é a principal atividade econômica ou de subsistência e o pescado é a maior fonte de proteínas para populações caboclas ribeirinhas amazônicas e populações de caiçaras que vivem na área litorânea da Mata Atlântica. Esta pesquisa analisou padrões ecológicos espaciais e temporais na pesca artesanal brasileira em dois ecossistemas: a costa sudeste da Mata Atlântica e a Amazônia fluvial, tendo como base de dados entrevistas realizadas com pescadores ao longo de vários projetos de pesquisa. No capítulo 1 analisou-se a produtividade pesqueira no litoral sudeste. Foi testada a variação da biomassa média capturada citada pelos entrevistados em função de fatores temporais (idade do pescador e data em que ocorreu sua última pescaria) e espaciais (região aonde se localiza a comunidade do pescador entrevistado). Foram analisadas entrevistas com 423 pescadores, que indicaram que: a) houve uma diminuição na quantidade de peixes capturados ao longo do tempo; b) a biomassa capturada não foi influenciada pelo fator espacial; c) não houve influência da idade do pescador na biomassa capturada mencionada. O capítulo 2 abordou a costa sudeste da Mata Atlântica e a Amazônia fluvial. Foram analisadas a composição dos peixes, através dos nomes populares citados e seu nível trófico médio. Foram analisadas entrevistas com 658 pescadores da Amazônia fluvial (de 1987 a 2006) e 821 pescadores da costa sudeste da Mata Atlântica (de 1986 a 2009) (n=1479 entrevistados). Não houve variação do nível trófico segundo o tempo, porém o nível trófico variou de acordo com os fatores espaciais (ecossistema e região), sendo que o fator que mais influenciou essa variação foi região. Na costa sudeste da Mata Atlântica há possível substituição das espécies de nível trófico similar por outras espécies de mesmo valor econômico com o tempo. Na Amazônia fluvial esse padrão de substituição das espécies não foi observado. Conclui-se que a diminuição da biomassa capturada ao longo do tempo somada à substituição de determinadas espécies de peixes capturados na costa da Mata Atlântica, podem indicar que a pesca não está sendo sustentável. Medidas preventivas de manejo pesqueiro devem ser implementadas. / Fisheries resources are being over-exploited worldwide. Excessive fishing can lead to trophic cascades and this exploration may be unsustainable. Therefore, management policies are urgent, but data are lacking to support such policies. In this sense, studies addressing interviews with fishermen have collaborated with the knowledge about the dynamics of fishing. The Brazilian artisanal fishing is the main economic and subsistence activity and the main source of protein for riverine Amazonian Caboclo populations and caiçara populations, who live in the coastal area of the Atlantic Forest. This study examined spatial and temporal ecological patterns in Brazilian artisanal fisheries in two ecosystems: the southeast coast of the Atlantic Forest and the fluvial Amazon; the data was based in interviews with fishermen on the course of several research projects. In Chapter 1 it was analyzed the fishery productivity in the southeastern coast. It was checked the variation in the average biomass of fish captured according to the interviews with fishers, due to temporal factors (fishermen’s age and date of their last fishery) and spatial factors (the region where the community of fishermen interviewed is located). There were analyzed interviews with 423 fishers, indicating that: a) there was a decrease in the biomass of fish caught over time, b) the biomass of fish caught was not influenced by the spatial factor c) there was no influence of age of the fisherman on the biomass of fish caught that was mentioned by them. Chapter 2 addressed the southeast coast of the Atlantic Forest and the Inland freshwater Amazon. It was analyzed the composition of fish caught, through their popular names mentioned by fishers and their mean trophic level. There were analyzed interviews with 658 fishers in the Amazon Basin (from 1987 to 2006) and with 821 fishers in to the southeast coast of the Atlantic Forest (from 1986 to 2009) (n = 1479 fishers). There was no variation in trophic level according to the time since the last fishing trip, and according to the spatial factors (ecosystem and region), and the region was the factor that most influenced the variation in trophic level. On the southeast coast of the Atlantic Forest species with similar trophic levels have been probably replaced by species of similar economic value over time. However, in the freshwater Amazon this pattern of species replacement was not observed. It is concluded that the decrease in biomass captured over time and the replacement of species on the Atlantic coast, may indicate that the fishery has been not sustainable. Preventive fisheries management measures should thus be devised.
4

Climate change impacts on production and dynamics of fish populations

Hedström, Per January 2016 (has links)
Ongoing climate change is predicted to increase water temperatures and export of terrestrial dissolved matter (TDOM) to aquatic ecosystems influencing ecosystem productivity, food web dynamics and production of top consumers. Ecosystem productivity is mainly determined by the rates of primary production (GPP) in turn controlled by nutrients, light availability and temperature, while temperature alone affect vital rates like consumption and metabolic rates and maintenance requirements of consumers. Increased level of TDOM causes brownification of water which may cause light limitation in algae and decrease GPP and especially so in the benthic habitat. Temperature increase has a been suggested to increase metabolic rates of consumers to larger extent than the corresponding effect on GPP, which suggest reduced top consumer biomass and production with warming. The aim of this thesis was to experimentally study the effects of increased temperature and TDOM on habitat specific and whole ecosystem GPP and fish densities and production. In a replicated large-scale pond experiment encompassing natural food webs of lotic ecosystems I studied population level responses to warming and brownification in the three- spined stickleback (Gasterosteus aculeatus). Results showed overall that warming had no effect on whole ecosystem GPP, likely due to nutrient limitation, while TDOM input decreased benthic GPP but stimulated pelagic GPP. In fish, results first of all suggested that recruitment in sticklebacks over summer was negatively affected by warming as maintenance requirements in relation to GPP increased and thereby increased starvation mortality of young-of-the-year (YOY) sticklebacks. Secondly, brownification increased mortality over winter in YOY as the negative effect on light conditions likely decreased search efficiency and caused lower consumption rates and starvation over winter in sticklebacks. Third, seasonal production of YOY, older, and total stickleback production was negatively affected by warming, while increased TDOM caused decreased YOY and total fish production. The combined effect of the two was intermediate but still negative. Temperature effects on fish production were likely a result of increased energy requirements of fish in relation to resource production and intake rates whereas the negative effect of TDOM likely was a result of decreased benthic resource production. Finally, effects of warming over a three-year period caused total fish density and biomass and abundance of both mature and old fish to decrease, while proportion of young fish increased. The main cause behind the strong negative effects of warming on fish population biomass and changes in population demographic parameters were likely the temperature driven increased energy requirements relative to resource production and cohort competition. The results from this thesis suggest that predicted climate change impacts on lentic aquatic ecosystems will decrease future densities and biomass of fish and negatively affect fish production and especially so in systems dominated by benthic resource production.
5

Socio-ecological drivers of fish biomass on coral reefs : the importance of accessibility, protection and key species / Les déterminants socio-écologiques de la biomasse en poissons sur les récifs coralliens : importance de l'accessibilité, de la protection et des espèces clés

Maire, Eva 28 September 2018 (has links)
Les récifs coralliens hébergent la plus grande biodiversité sur Terre et fournissent la nourriture, le revenu économique, la protection côtière et les valeurs culturelles pour des millions de personnes. L'accessibilité des écosystèmes via les réseaux routiers est un déterminant majeur de leurs conditions, les écosystèmes les plus accessibles étant les plus menacées. Longtemps, l’estimation de l'accessibilité par l’Homme s’est limitée à l'utilisation de la distance linéaire qui ignore l’irrégularité des côtes maritimes et les réseaux routiers, facteurs influençant le temps nécessaire pour atteindre les lieux de pêche. Cette thèse présente un double enjeu : (i) développer des indices d'accessibilité intégrant l’hétérogénéité du milieu marin pour quantifier les impacts humains sur les récifs ; (ii) évaluer l'importance de ces nouveaux indices, en interaction avec les mesures de protection, pour expliquer les variations de la biomasse de poissons. Dans un premier temps, j’ai caractérisé la proximité des hommes aux récifs, en tenant compte des surfaces rencontrées (routes, chemin, eau) qui influencent le temps de trajet jusqu’aux récifs. Le temps de trajet a permis de calculer un indice de gravité, défini comme la population humaine divisée par le temps de trajet au carré, pour évaluer le niveau de pression humaine de n'importe quel récif au monde. J'ai trouvé que le temps de trajet et la gravité sont des déterminants majeurs de la biomasse de poissons à l’échelle globale. Dans un second temps, trois applications utilisant ces nouveaux indices ont permis de montrer que (i) la gravité permet de révéler l’efficacité des actions de conservation : les réserves placées là où les impacts humains sont modérés à forts fournissent des gains de conservation élevés pour la biomasse de poissons, mais elles sont peu susceptibles de protéger les prédateurs supérieurs, qui sont uniquement présent dans les réserves soumises à de faibles impacts humains ; (ii) en utilisant un cas d'étude réalisé dans le Nord-Ouest de Madagascar, j'ai illustré comment la proximité du marché peut affecter les communautés de pêcheurs et, finalement, engendrer des changements dans l'exploitation des ressources marines ; (iii) j’ai développé une nouvelle approche, le Community-Wide Scan (CWS), pour identifier les espèces de poissons qui contribuent de manière significative à la biomasse et à la couverture corallienne des récifs de l’Indopacifique, celles-ci pouvant constituer des espèces cibles à protéger. Dans le contexte de changements globaux et de perte de biodiversité, la mesure d’accessibilité constitue un outil puissant et permet de relancer le défi de gestion durable et efficace des socio-écosystèmes coralliens. / Coral reefs have the greatest biodiversity of any ecosystem on the planet and support ecosystem goods and services to million people who depend directly on them for food, economic income, coastal protection and cultural values. Ecosystem accessibility, through road networks, is the main driver of their conditions, with the most accessible ecosystems being most at risk of resource depletion. To date, measuring accessibility to humans was strictly limited to examining the linear distance which ignores ragged coastlines and road networks that can affect the time required to reach fishing grounds. This thesis presents a double challenge: (i) developing new metrics of accessibility that account for seascape heterogeneity to better assess human impacts on coral reefs; (ii) evaluating the importance of coral reef accessibility, in interactions with their management, to explain variations of fish biomass. First, I developed novel metrics of reef proximity to human populations and markets based on the friction distance which is related to transport surfaces (paved road, dirt road, water) influencing the effective reach of human settlements. Travel time was used to build the gravity index, defined as human population divided by the squared travel time, to assess the level of human pressure on any reef of the world. I found that both travel time and gravity are strong predictors of fish biomass globally. Second, three applications using these new metrics highlighted that (i) gravity identified critical ecological trade-offs in conservation since reserves placed with moderate-to-high impacts may provide substantial conservation gains for fish biomass while reserve locations with low human impacts were more likely to support higher-order predation, (ii) using a study case in Northwest Madagascar, I illustrated how market proximity can affect fishermen communities and, ultimately, trigger changes in marine resources exploitation, and (iii) I implemented a new Community-Wide Scan (CWS) approach to identify fish species that significantly contribute to the biomass and coral cover on Indo-Pacific reefs and which provided tractable conservation targets. Within the context of global changes and biodiversity loss, the thesis challenges the sustainable and efficient management of coral reef socio-ecological systems with accessibility being the cornerstone.
6

Hodnocení stability rybničního ekosystému v Národní přírodní rezervaci Řežabinec / The assessment of the NPR Řežabinec pond ecosystem stability.

ŠRÁMEK, Pavel January 2014 (has links)
The first part is characterized by a pond ecosystem and National Nature Reserve Řežabinec in terms of its historical development and creation. Are mentioned methods , the method and system of protection of the site. The paper describes a method of fish farming during the period of the individual plans of care farming in the last five years and the water conditions in the area . The ecosystem is assessed on the basis of available data in the literature to me In our own work we focus on monitoring water chemistry and state recovery tank , especially in terms of development and biomass of zooplankton species representation in the course of one growing season. He also details the fishing and agricultural management and water management conditions in the locality. Marginally judging submerged and littoral vegetation and the presence of water birds. This work demonstrated the dependence of the size of the fish stock on the frequency of a generic representation of zooplankton and the positive impact of lower stocking on the development and stability of the entire ecosystem. Contributes to the stability and sensitive farming in the last period.

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