Changes in land cover and fish assemblage structure were assessed across two spatial and temporal scales in the Piedmont and Coastal Plain regions of the Chesapeake Bay watershed in Virginia. A long-term, local study (1953 to 2014) on the Tuckahoe Creek watershed used digitized aerial photography and satellite images (Landsat 5 TM and Landsat 8 OLI/TIRS) to quantify land cover change for five nested catchments in 1953, 1990, and 2014. Instream fish collections from 1958, 1990, and 2014 were utilized to assess a variety of fish assemblage metrics for each of the five catchments, and analyses were performed to assess associations between changes in land cover and changes in fish assemblage structure across all three time periods. A short-term, regional study assessed 21 catchments in the region using 1997 Landsat 5 TM satellite images and 2014 Landsat 8 OLI/TIRS satellite images to quantify land cover change. Fish collections from 1995-1999 and 2014 were utilized to assess a variety of fish assemblage metrics from samples taken at instream sites for each of the 21 catchments. Analyses were performed to discover any associations between changes in land cover and changes in fish assemblage structure from a regional perspective. This study found that there were significant changes in land cover over all study periods in the Tuckahoe Creek watershed and that land cover changes were correlated to changes in fish assemblage structure over the long-term study. Regionally, there were significant changes in land cover, with no correlation to changes in fish assemblage structure found. The data suggests that anthropogenic alterations to the landscape have had long-term effects on fish assemblage structure in Tuckahoe Creek, but the results from the short-term assessments did not detect a relationship between land cover changes and changes in fish assemblage structure. It is possible that the fish communities were already established in moderately degraded catchments by the 1990s due to previous anthropogenic stressors.

Made available in DSpace on 2017-07-10T14:38:21Z (GMT). No. of bitstreams: 1 Dhonatan Santos.pdf: 674044 bytes, checksum: 1cff602fb13d2c3e5d393019f4f174ab (MD5) Previous issue date: 2013-08-20 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This study evaluated the distribution and structure of the ichthyofauna of the Iguaçu River, in the stretch between downstream of the Iguaçu Falls to the mouth of the Paraná River. Were sampled monthly during the period of October 2010 to September 2012 using gillnets and longlines. Environmental variables showed no statistical differences between the sampled points. Were collected 10,996 fish belonging to 124 species, the Siluriformes had the greater values of richness, while Characiformes were the most abundant. Were recorded 17 species of longdistance migratory. In the lower portion were recorded high values of relative abundance for small species, while the upper portion, were recorded high values of biomass for large species. The evenness and Shannon diversity index showed significant differences between the points of the lower and upper portion, indicating that there could be some dominant species. The pattern increment longitudinal in richness was not detected, and the points of the upper portion were separated from others in multiple comparison test, suggesting a structuring for areas along the stretch sampled. These results indicate that the stretch of Iguaçu river, between Iguaçu Falls to the mouth with the Paraná River, the ichthyofauna presents differentiated structure along the spatial gradient, which may be related to differences in the physical structure of the sampled area / Este estudo avaliou a distribuição e estrutura da ictiofauna do rio Iguaçu, no trecho entre à jusante das Cataratas do Iguaçu até a foz com o rio Paraná. Foram realizadas amostragens mensais durante o período de outubro de 2010 a setembro de 2012, utilizando redes de espera e espinhel. As variáveis ambientais não apresentaram diferenças estatísticas entre os pontos amostrados. Foram coletados 10.996 peixes pertencentes a 124 espécies, os Siluriformes tiveram os maiores valores de riqueza, enquanto que Characiformes foram os mais abundantes. Foram registradas 17 espécies migradoras de longa distância. Na porção inferior foram registrados altos valores de abundância relativa para espécies de pequeno porte, enquanto que na porção superior foram registrados altos valores de biomassa para espécie de grande porte. A Equitabilidade e o índice de diversidade de Shannon apresentaram diferenças significativas entre os pontos da porção inferior e os pontos da porção superior, indicando que pode 8 haver dominância de algumas espécies. O padrão de incremento longitudinal na riqueza não foi detectado, e os pontos da porção superior foram separados dos demais no teste de comparações múltiplas, sugerindo uma estruturação por zonas ao longo da área amostrada. Esses resultados indicam que no trecho do rio Iguaçu compreendido entre as Cataratas do Iguaçu até a sua foz com o rio Paraná, a ictiofauna apresenta estrutura diferenciada ao longo do gradiente espacial, o que pode estar relacionado às diferenças na estruturação física da área amostrada

Le débit saisonnier du Mékong joue un rôle central dans la structuration amont/aval des communautés aquatiques. Cette étude examine les dynamiques de la structure spatiale et temporelle des communautés de poissons dans le bassin inférieur du Mékong, comprenant le Mékong aval et ses principaux affluents. L'application de méthodes statistiques univariées et multivariées, sur des bases de données spatiales et temporelles piscicoles et environnementales, met en évidence : * Le rôle prépondérant des débits dans l'explication de la dynamique spatiale et temporelle des patrons de diversité et de structure des assemblages piscicoles dans la bassin aval du Mékong. * Les effets de la pêche non sélective dans l'un des plus grands systèmes de production halieutique tropicale au monde, le lac le Tonlé Sap, avec la mise en évidence d'une production globalement durable marquée néanmoins par une composition altérée des communautés de poissons. * Les réponses des assemblages de poissons face aux fluctuations saisonnières et à la stabilité des débits dans les rivières non régulées et régulées du bas Mékong. Les résultats obtenus lors de cette thèse contribuent à la connaissance du fonctionnement des peuplements piscicoles et apportent une aide à la conception de plans de gestion et de conservation des ressources halieutiques et des autres ressources aquatiques dans le bassin du Mékong et au-delà. Cette étude suggère que : * Le maintien de la dynamique saisonnière des débits et de la connectivité des habitats est impératif afin d'assurer la dispersion longitudinale et latérale des poissons vers des habitats vitaux pour leur reproduction, leur alimentation et leur protection. * L'établissement d'une réglementation appropriée basée sur la connaissance des pics migratoires de poissons aux différentes échelles spatio-temporelles permettrait aux poissons migrateurs de franchir les rivières pour accéder à leurs habitats nécessaires à l'accomplissement de leur cycle de vie. Aussi, faire respecter et opérationnaliser de façon efficace les mécanismes officiels de gestion halieutique aux échelles locales, nationales et régionales, mais aussi allouer suffisamment de moyens pour le secteur de la pêche afin de lutter contre les pratiques de pêche illégale et pour la mise en œuvre de mesures de conservation contribuerait à résoudre les problèmes de surexploitation des ressources aquatiques. * La mimique des variations naturelles des débits par les barrages hydroélectriques devrait être priorisées et appliquées comme une des mesures permettant d'atténuer leurs impacts sur les peuplements aquatiques du bassin du Mékong. / The Mekong seasonal flow plays a pivotal role in structuring up- and downstream aquatic communities. The thesis investigates the dynamics of spatial and temporal fish community structure in the Lower Mekong system, i.e. the Lower Mekong River and its major tributaries. Using spatial and time-series datasets and univariate as well as multivariate statistical approaches, the thesis highlights: * The importance of flow and other environmental factors in explaining spatial and temporal dynamics of fish diversity patterns and assemblage structure in the Lower Mekong system. * The effects of indiscriminate fishing in one of the world's largest tropical inland fisheries, the Tonle Sap, with the finding of, despite overall stationary catch per unit effort (CPUE), strong alterations in assemblages composition, with decreasing trends in catches of large-sized species, and increasing trends in the catches of some small-sized species. * Contrasted responses of fish assemblages to a gradient of disruption of flow seasonality and predictability due to dams in the Lower Mekong system. The results obtained through this thesis contribute to the ecological understanding of fish assemblages and to the design of applications for long-term planning, monitoring, management and conservation of fisheries in the Mekong Basin and beyond. The thesis suggests that: * Maintaining the Mekong robust and predictably seasonal flood pulse dynamics and habitat connectivity is imperative to ensure fish longitudinal and lateral dispersal ability among critical habitats for breeding, feeding and seeking refuge. * Setting appropriate regulations based on known peak fish migrations at various spatiotemporal scales would allow migratory fish species to pass through rivers, access critical habitats and complete their life cycles. Also, enforcing and operationalizing the existing formal fisheries management mechanisms effectively at local, national and regional levels as well as allocating sufficient resources to the fishery sector to combat illegal fishing practices and implementing fisheries conservation measures in critical habitats would help deal with the problem of overharvesting. * Hydropower-related pulsed flows that can mimic as far as possible the natural pulsed flows are critical to reduce downstream effects on aquatic organisms, and, thus, should be prioritized and applied as one of the measures to mitigate the impacts from existing and planned hydropower dams in the Mekong Basin.

Master of Science / Department of Biology / Craig Paukert / We investigated spatial variation in fish assemblage and food web structure in the Kansas River, USA in relation to habitat changes. Fishes were collected at ten sites throughout the Kansas River for assessing assemblage structure in summer 2007 using fish community metrics and at 3 sites in 2006 for food web structure using stable isotope analysis. Satellite imagery indicated riparian habitat on the Kansas River was dominated by agriculture in the upper reaches (>35%) and tended to increase in urban land use in the lower reaches (>58%). Instream habitat complexity also decreased with increased urban area (<25%) becoming more channelized. Jaccard's similarity and percent similarity indices suggested that large-bodied fishes show changes in species presence and composition longitudinally within the river. Also, reaches directly above Bowersock Dam in Lawrence, Kansas and below the Johnson County Weir, near Kansas City, Kansas had low percent similarity compared to other reaches, suggesting the dam and the weir affect community composition. Canonical correspondence analysis indicated that species that prefer high velocity flows and sandy substrate (blue sucker and shovelnose sturgeon) are associated with the upper river reaches. Also, there was a higher abundance of omnivorous and planktivorous fish species in the lower more channelized river. The lower reaches contain more tolerant, macrohabitat generalist species and the upper river contained more intolerant, fluvial specialist species. Fish, macroinvertebrates, and detritus were collected at three river reaches classified as the heterogeneous instream habitat (>40% grass islands and sand bars) intermediate (22% grass islands and sand bars), and homogeneous (6% grass islands and sand bars) instream habitat reaches in June 2006. Riparian land use (proportion as agricultural and urban) was related to instream habitat with homogeneous areas having more urban riparian area compared to the heterogeneous and intermediate reaches. The heterogeneous habitat reach had higher variability in [Delta][superscript]13C for fish classified as piscivores/invertivores (P=0.029) and macroinvertebrates (P=0.004) suggesting the complex habitat in the heterogeneous habitat reach provided more variable food sources. The [Delta}15N values also indicated that ten of the twelve fish species tended to consume prey at higher trophic levels in the heterogeneous habitat reach suggesting a more complex food web. Land use practices are leading to homogenization of instream habitat and this homogenization of habitats may be related to food web diversity and trophic position of fishes. Conserving intolerant, native species in the Kansas River may require maintaining suitable habitat for these species and restoration of impacted areas of the river.

Fish assemblages from 54 oxbow lakes in the Mississippi Alluvial Valley were sampled to identify relationships among environmental variables and fish biodiversity in floodplain lake ecosystems. Environmental variables deterministic over fish biodiversity showed a hierarchical organization and were classified as primary or secondary depending on if one variable was considered to govern another. Primary variables included depth, surface area, surrounding land use, and degree of lake-river interconnectedness. Secondary variables included suites of water quality and primary productivity variables. Maximum depth and percentage of agricultural land surrounding lakes showed strongest relationships with other ecosystem components, significantly influencing water quality, primary productivity, and fish biodiversity. I found contrasting results regarding effect of lake-river interconnectedness on fish biodiversity, but maintain that connectivity is nonetheless an important floodplain lake ecosystem component and suggest that floodplain lake management efforts focus on depth, percentage of agricultural land, and restoration of connectivity.

Cette thèse porte sur l'étude de l’efficacité d’une Aire Marine Protégée (AMP) comme outil de restauration des ressources marines et de gestion des stocks halieutiques en zone tropicale ouest africaine. L’étude concerne trois AMP. Il s’agit de l’AMP de Bamboung située en zone estuarienne (sous influence marine), à l'intérieur d'un delta et fermée à l’exploitation halieutique depuis 2004. La deuxième AMP est celle des îles d’Urok créée en 2005 et située dans la réserve de biosphère de l’archipel des Bijagos dans la partie littorale de la Guinée-Bissau. Elle est divisée en trois zones et la pêche y est autorisée avec une pression de pêche de plus en plus forte de la zone centrale vers la zone périphérique. La troisième AMP est le Parc National du Banc d’Arguin situé le long de la côte mauritanienne. Il a été créé en 1976 et les activités de pêche y sont pratiquées de façon réglementée. Beaucoup d’AMP ont été évaluées à travers le monde et les résultats obtenus sont dans la majeure partie des cas positifs. Dans les milieux tropicaux, les variabilités interannuelles et intra-annuelles des paramètres environnementaux influent sur l’organisation spatio-temporelle des peuplements de poissons. Par conséquent, la mise en place d’AMP dans une zone tropicale a suscité des interrogations quant à leur efficacité en rapport avec l’influence des paramètres de l’environnement. Selon l’AMP étudiée, une approche spatiale ou temporelle sera utilisée pour répondre aux questions posées. Les méthodes d’analyse utilisées sont de type comparatif. L’analyse des données biologiques est précédée par celle des paramètres physico-chimiques qui a mis en évidence des variabilités saisonnières dans chaque AMP. Ce résultat justifie le choix d’analyser les données biologiques par saison afin de minimiser au mieux l’influence des variations environnementales. En ce qui concerne l’AMP de Bamboung, les résultats de l’analyse suivant une approche globale ont clairement montré son rôle positif dans la restauration des ressources marines. L’approche saisonnière a mis en évidence ce rôle de restauration mais en saison froide et non en saison chaude et humide. En 9 années de protection, l'AMP de Bamboung a contribué au retour de gros poissons dans le bolon de Bamboung. Son rôle dans l’enrichissement de la zone proximale à travers le phénomène de «Spillover» n’a pas pu être mis en évidence. Une tendance à la baisse des indicateurs biologiques en fonction de la distance à l'AMP a été observée surtout en saison chaude et en saison humide. De même l’analyse des indicateurs liés à la reproduction ne montre pas que l’AMP de Bamboung améliore la reproduction des poissons. Concernant, l’AMP des îles d’Urok et le Parc National du Banc d’Arguin, les analyses n’ont pas donné de résultats clairs quant à leur rôle dans l’amélioration des rendements de pêche et de la reproduction des poissons. Cependant, pour l’AMP des îles d’Urok, les tendances observées semble montrer une forte concentration de biomasse dans la zone centrale, un rôle d’équilibre joué par la zone intermédiaire et un rôle de pourvoyeur de biomasse de poisson de la zone périphérique. Pour le PNBA, le secteur intérieur semble contribuer à l’enrichissement du secteur extérieur par un transfert de biomasse. La faible quantité de données récoltées dans les AMP pourrait être à l’origine des résultats négatifs. Ainsi, l’idée d'effectuer des suivis biologiques à court terme et d'analyser les indicateurs liés à la reproduction au niveau population ont été envisagés pour les trois AMP afin de trouver des résultats clairs quant à leur rôle dans la gestion des stocks halieutiques. / This thesis focuses on the study of the effectiveness of Marine Protected Areas (MPAs) as restoration tools of marine resources and fish stocks management in tropical West Africa. The study involves three MPAs. The first one is the Bamboung MPA, a marine reserve located in estuarine areas (with marine influence), closed to fishing since 2004. The second is the Urok Islands MPA established in 2005 and located in the biosphere Reserve of Bijagos archipelago in the coastal part of Guinea-Bissau. It is divided into three areas and fishing is allowed there with a fishing pressure becoming stronger from the central area to peripheral area. The third MPA is the Banc d‟Arguin National Marine Park located along the coast of Mauritania. It was created in 1976 and fishing activities are restricted. Many AMP were evaluated worldwide and the results are in the main part positive. In tropical zones, the variability of environmental parameters affects the spatial and temporal organization of fish assemblage. Therefore, the MPA establishment in a tropical zone has raised questions about their effectiveness inrelation to the influence of environmental parameters. According to the AMP, spatial or temporal approach will be used to answer questions. Comparison analysis will be used. The analysis of biological data comes after those of the physicochemical parameters that show strong seasonal variability in each MPA. This result justifies the choice of seasonal analysis of biological data in order to minimize the influence of environmental variations.Regarding the Bamboung MPA, the results of global approach clearly confirm that it is an effective tool for restoring marine resources. The seasonal approach shows this role in cold season, but not in hot and wet seasons. In 9 years of protection, the Bamboung MPA contributed to attract big fish in the Bamboung bolon. The spillover effect in Bamboung MPA is not clearly demonstrated according to our results. A downward trend of biological indicators according to the distance to the MPA has been observed especially in hot season and wet season. Similarly, the analysis of indicators related to reproduction does not show that the Bamboung MPA improve fish reproduction. Regarding Urok Islands MPA and Banc d’Arguin National marine Park, the results do not confirm that these AMP are fish stock management tools (improved yields of fishing activities and fish reproduction). However, for Urok islands MPA the observed trends suggest a biomass concentration in the central area, an equilibrium role played by the intermediate area and a role of fish biomass provider of the peripheral area. For Banc d’Arguin National Marine Parc, the inside area seems to contribute to the enrichment of the external area by transferring fish biomass. Non-specific results could be explained by the small data collected in the MPAs. So the idea to conduct a short-term biological monitoring and to analyze reproduction indicators in population level has been considered for the three MPA to find clear results on their role in the management of fish stocks.

Made available in DSpace on 2014-07-29T16:21:21Z (GMT). No. of bitstreams: 1 Camila Leite Pereira.pdf: 1087738 bytes, checksum: 510e1b512e1fe3b15b02211035e90619 (MD5) Previous issue date: 2010-03-26 / The synchrony concept can be defined like the degree that different biologics systems show similar temporal evolution. Synchronies fluctuations in species are attributed to influence of ambient factors or individuals dispersion (distance of ambient). Thus, the objective this study was measured the ichthyofauna similarity among six environment of Parana River floodplain in responses to these different mechanisms. The biotic (ichthyofauna abundance) and abiotic (limnology gradients) dates was provided by NUPELIA. The statistical analyses supported in multivariate analyses applied in abundance matrices of fish species, limnology variables and connectivity distance among habitats. In such case the ichthyofauna dynamic varied asynchronous over time and space on the periods of 1987 to 19988 and 2006 to 2008. The period of greatest assemblage significant synchronies corresponded to intermediary period. The main reason of this synchrony was explain by the fluviometric quota, since the dynamic of this variable affected similarly the species abundance among locations. Altogether this study confirmed the theoretical support of Niche as a mechanism of assemblage synchrony in stable ecosystems. The neutral process wasn t a good model to explain the assemblage similarity between locations. / O conceito de sincronia pode ser definido como o grau em que diferentes sistemas biológicos mostram evoluções temporais similares. Flutuações sincrônicas nas espécies são atribuídas à influência de fatores ambientais ou dispersão de indivíduos (distância entre ambientes). Nesse contexto o objetivo deste estudo foi quantificar a similaridade da ictiofauna entre seis ambientes da planície de inundação do rio Paraná, em respostas a estes diferentes mecanismos. Os dados bióticos (abundância da ictiofauna) e abióticos (variáveis limnológicas) foram gentilmente cedidos pelo NUPELIA. Através de análises multivariadas aplicadas à matrizes de abundância de espécies de peixes, variáveis limnológicas e distância de conectividade entre ambientes, verificou-se que em dois períodos (1987 a 1988 e 2006 a 2008) a dinâmica da ictiofauna variou de forma assincrônica entre ambientes. O período de maiores sincronias significativas na assembléia correspondeu ao período intermediário avaliado. O principal motivo desta sincronicidade foi explicado pela cota fluviométrica, já que a dinâmica dessa variável entre os ambientes afetou de forma similar a abundância das espécies. De modo geral este estudo confirmou as bases teóricas do nicho de Hutchinson, em detrimento aos processos neutros, como mecanismo de sincronia da assembléia em ecossistemas estáveis.