In the northeastern Ionian Sea, two populations of dolphins, the short-beaked common dolphin and the common bottlenose dolphin, have been studied since 1993 by the Tethys Research Institute, Italy. Results show a low density of bottlenose dolphins, and a rapid decline in common dolphin numbers and encounter rates. I constructed an ecosystem model using Ecopath with Ecosim for the northeastern Ionian Sea to explain the two different abundance trends of these species of dolphins, and the trophic interactions with their prey and with the fisheries. The Ecopath model was built for the year 1964, adding data on biomass, P/B, Q/B and diet for each functional group of the ecosystem, fisheries landings and discards. Ecosim was used to generate simulated trajectories to fit with the ‘observed’ trends (e.g., biomass, CPUE and catches) for the most important groups of the ecosystem. The results of the fitting underline a clear decline of common dolphins caused by reduced prey availability. In particular, sardine and anchovy stocks, the main prey of common dolphins, have decreased sharply since the late 1970s due to intensive fishing pressure in the area until the end of 1990s. On the other hand, the population of bottlenose dolphins has increased through time; a positive correlation was observed between this species of dolphin and the development of the fish farm industry in the study area. Ecosim was used to simulate three fishing policy scenarios within the study area. Three different fishing closures were investigated: the closure of purse seiners; the closure of the industrial fisheries (purse seiners, trawlers and beach seiners); and the closure of the entire fishing fleets. According to Ecosim predictions, sardines and anchovies would benefit from all three management strategies. Common dolphins showed a significant increase only when the entire study area was closed to fishing. The creation of MPAs was explored using Ecospace. In particular, two different scenarios were evaluated: a MPA1 that closed the entire area to fisheries, and a MPA2 that allowed the small and big artisanal fisheries to operate. The results obtained using this spatial model agreed with similar scenarios simulated in Ecosim.

In the northeastern Ionian Sea, two populations of dolphins, the short-beaked common dolphin and the common bottlenose dolphin, have been studied since 1993 by the Tethys Research Institute, Italy. Results show a low density of bottlenose dolphins, and a rapid decline in common dolphin numbers and encounter rates. I constructed an ecosystem model using Ecopath with Ecosim for the northeastern Ionian Sea to explain the two different abundance trends of these species of dolphins, and the trophic interactions with their prey and with the fisheries. The Ecopath model was built for the year 1964, adding data on biomass, P/B, Q/B and diet for each functional group of the ecosystem, fisheries landings and discards. Ecosim was used to generate simulated trajectories to fit with the ‘observed’ trends (e.g., biomass, CPUE and catches) for the most important groups of the ecosystem. The results of the fitting underline a clear decline of common dolphins caused by reduced prey availability. In particular, sardine and anchovy stocks, the main prey of common dolphins, have decreased sharply since the late 1970s due to intensive fishing pressure in the area until the end of 1990s. On the other hand, the population of bottlenose dolphins has increased through time; a positive correlation was observed between this species of dolphin and the development of the fish farm industry in the study area. Ecosim was used to simulate three fishing policy scenarios within the study area. Three different fishing closures were investigated: the closure of purse seiners; the closure of the industrial fisheries (purse seiners, trawlers and beach seiners); and the closure of the entire fishing fleets. According to Ecosim predictions, sardines and anchovies would benefit from all three management strategies. Common dolphins showed a significant increase only when the entire study area was closed to fishing. The creation of MPAs was explored using Ecospace. In particular, two different scenarios were evaluated: a MPA1 that closed the entire area to fisheries, and a MPA2 that allowed the small and big artisanal fisheries to operate. The results obtained using this spatial model agreed with similar scenarios simulated in Ecosim.

In the northeastern Ionian Sea, two populations of dolphins, the short-beaked common dolphin and the common bottlenose dolphin, have been studied since 1993 by the Tethys Research Institute, Italy. Results show a low density of bottlenose dolphins, and a rapid decline in common dolphin numbers and encounter rates. I constructed an ecosystem model using Ecopath with Ecosim for the northeastern Ionian Sea to explain the two different abundance trends of these species of dolphins, and the trophic interactions with their prey and with the fisheries. The Ecopath model was built for the year 1964, adding data on biomass, P/B, Q/B and diet for each functional group of the ecosystem, fisheries landings and discards. Ecosim was used to generate simulated trajectories to fit with the ‘observed’ trends (e.g., biomass, CPUE and catches) for the most important groups of the ecosystem. The results of the fitting underline a clear decline of common dolphins caused by reduced prey availability. In particular, sardine and anchovy stocks, the main prey of common dolphins, have decreased sharply since the late 1970s due to intensive fishing pressure in the area until the end of 1990s. On the other hand, the population of bottlenose dolphins has increased through time; a positive correlation was observed between this species of dolphin and the development of the fish farm industry in the study area. Ecosim was used to simulate three fishing policy scenarios within the study area. Three different fishing closures were investigated: the closure of purse seiners; the closure of the industrial fisheries (purse seiners, trawlers and beach seiners); and the closure of the entire fishing fleets. According to Ecosim predictions, sardines and anchovies would benefit from all three management strategies. Common dolphins showed a significant increase only when the entire study area was closed to fishing. The creation of MPAs was explored using Ecospace. In particular, two different scenarios were evaluated: a MPA1 that closed the entire area to fisheries, and a MPA2 that allowed the small and big artisanal fisheries to operate. The results obtained using this spatial model agreed with similar scenarios simulated in Ecosim. / Science, Faculty of / Zoology, Department of / Graduate

Karenia brevis dinoflagellate blooms off the west coast of Florida can create devastating effects on marine communities when they release a neurotoxin known as a brevetoxin. These blooms, informally referred to as red tides, can cause massive fish kills, necessitate closures of shellfish fisheries, and can even leave lingering toxins that impact shelf communities long after the bloom has dissipated. As a result, much effort has been put into studying K. brevis bloom initiation and dynamics. However, how K. brevis blooms impact Florida's fisheries is not fully understood because the relationship between K. brevis cell counts and fish mortality is poorly described. To study this relationship and the ecosystem response to K. brevis blooms, Ecopath with Ecosim (EwE) modeling is used to force K. brevis bloom mortality on the shelf ecosystems by using a recently developed time series that indexes K. brevis bloom severity. This index dynamically drives K. brevis bloom mortality in EwE in a historical reconstruction scenario from 1980 to 2009. Three hypotheses on ecosystem response are explored using Gag grouper as a case study. We postulate a) that K. brevis blooms impose bottom-up and top-down effects on the food web, b) that episodic perturbations by these blooms shape the community structure and c) that fishing pressure exacerbates those effects. Results support the hypothesis that K. brevis blooms pose top-down food web pressures, which is seen by evidence of trophic cascading. Changes in community structure with bloom mortality are also evidenced by changes seen in biodiversity and richness. An exacerbation of those effects as a result of heavy fishing pressure is evident, however, is only seen during severe bloom events. Little to no changes were found in the mortality from K.brevis blooms during blooms of average severity, and less mortality was imposed on the system during blooms of particularly low severity. However, this may be an artefact of the mode of action of K. brevis in EwE. Investigation of bloom effects on Gag showed that natural mortality rates of Gag appear to be largely influenced by mortality incurred during K. brevis blooms relative to the low rate of predation on Gag. Moreover, consumption rates of Gag on its prey were found to increase under a realistic schedule of these blooms. This may be due to a combination of effects, including increased mortality on competitors (making more prey available for Gag) and a lowering of the mean age of the Gag stock, which increases population productivity.

Understanding the interaction of multiple drivers and their compounded effects on ecosystem dynamics is a key challenge for marine resource management. The Baltic Sea is one of the world’s seas most strongly impacted by effects from both human activities and climate. In the late 1980’s changes in climate in combination with intensive fishing initiated a reorganization of the Central Baltic Sea (CBS) food web resulting in the current sprat-dominated state. In the future, climate change is projected to cause drastic changes in hydrodynamic conditions of the world oceans in general, and the Baltic Sea in particular.   In this thesis, CBS food web responses to the combined effects of fishing, nutrient loads and climate were tested for the past (1974-2006) and projected into the future (2010-2098). A new food web model for the CBS (BaltProWeb) was developed using extensive monitoring data across trophic levels. This model described the past food web dynamics well, and was hence also used for future (2010-2098) projections. Different ensemble modeling approaches were employed when testing the food web response to future scenarios. The results show that regardless the climate change, the management of nutrient loads and cod fishing are likely to determine the food web dynamics and trophic control mechanisms in the future Baltic Sea. Consequently, the variation in the food web projections was large, ranging from a strongly eutrophied and sprat-dominated to a cod-dominated CBS with eutrophication levels close to today’s values. The results also suggest a potential risk of abrupt ecosystem changes in the future CBS, particularly if the nutrient loads are not reduced. Finally, the studies illustrate the usefulness of the ensemble modeling approach, both from the perspective of ecosystem-based management as well as for studying the importance of different mechanisms in the ecosystem response. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: In press. Paper 5: Submitted.</p>

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-07-17T13:22:24Z No. of bitstreams: 1 AnaHelenaVarellaBevilacqua_TESE.pdf: 4834986 bytes, checksum: ffaa031d5941bd3e8c15b66a0e5cb8d6 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-07-19T13:46:10Z (GMT) No. of bitstreams: 1 AnaHelenaVarellaBevilacqua_TESE.pdf: 4834986 bytes, checksum: ffaa031d5941bd3e8c15b66a0e5cb8d6 (MD5) / Made available in DSpace on 2017-07-19T13:46:10Z (GMT). No. of bitstreams: 1 AnaHelenaVarellaBevilacqua_TESE.pdf: 4834986 bytes, checksum: ffaa031d5941bd3e8c15b66a0e5cb8d6 (MD5) Previous issue date: 2017-02-23 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Os recursos pesqueiros marinhos det?m grande import?ncia econ?mica, social e ecol?gica garantindo a gera??o de renda e a seguran?a alimentar para trabalhadores ligados direta e indiretamente ao setor pesqueiro. A din?mica ecol?gica destes recursos determina a atividade pesqueira que por sua vez, provoca mudan?as nos estoques explorados. Estas mudan?as atingem todo o ecossistema e n?o apenas as esp?cies mais comercializadas, devido ? pesca acidental, ao descarte e a remo??o de presas ou predadores. Contudo, em pa?ses em desenvolvimento, o uso de recursos marinhos ? pouco ou nada regulamentado o que acarreta na falta de manejo adequado. Assim, a gest?o desta atividade requer uma avalia??o ecossist?mica com foco n?o apenas nos recursos, mas tamb?m na pesca e nos usu?rios dos recursos. Assim, neste trabalho s?o utilizadas abordagens ecossist?mica e econ?mica para gerar informa??es que possam ser utilizadas para subsidiar pol?ticas de manejo ecossist?mico da atividade pesqueira. O primeiro cap?tulo alia o conhecimento cient?fico e o conhecimento tradicional dos pescadores na modelagem ecossist?mica da pesca, abrindo caminho para a utiliza??o da metodologia para a elabora??o de planos de manejo de pesca voltados para o ecossistema. Neste cap?tulo, conclui-se que os pescadores podem ser fontes confi?veis de informa??es sobre a biologia e ecologia das principais esp?cies alvo da atividade pesqueira, contribuindo para a cria??o de modelos sobre a din?mica pesqueira que possam subsidiar a??es efetivas de manejo ecossist?mico. O segundo cap?tulo traz a modelagem da cadeia de valores da pesca de pequena escala, identificando a participa??o dos atores e como os benef?cios econ?micos s?o distribu?dos ao longo da cadeia. Neste estudo de caso, concluiu-se que a seguran?a alimentar da comunidade pesqueira exerce uma import?ncia maior no recebimento do pescado em compara??o ?s comunidades tur?sticas do entorno. Assim, o turismo deixa de ser observado como o receptador de boa parte da produ??o local. No terceiro cap?tulo analisamos a combina??o de indicadores de produ??o, econ?micos e do pescador (sociais) entre as comunidades com maior e menor grau de depend?ncia do turismo. O turismo pode ser visto como fonte alternativa de rendimento em comunidades costeiras desde que bem manejado. O quarto cap?tulo traz uma an?lise que visa descrever as caracter?sticas da composi??o de esp?cies desembarcadas, visando uma melhor compreens?o da din?mica do sistema sociocultural que influenciam nas capturas de recursos naturais. Sob o cen?rio de pesca sem dados e turismo em crescimento, s?o urgentemente necess?rias a??es para projetar com cuidado o turismo gerenciado e a pesca comercial bem regulada para toda a ?rea costeira. O quinto e ?ltimo cap?tulo aborda a pesca praticada em ambientes recifais. O principal objetivo deste estudo foi identificar os principais impulsionadores da pesca de recifes para o setor de pequena escala ao longo de um gradiente de press?o de pesca em oito comunidades do nordeste brasileiro. As comunidades estudadas foram divididas em categorias de press?o de pesca para explorar se as caracter?sticas das esp?cies est?o relacionadas ?s condi??es socioecon?micas e comparar suas caracter?sticas de pesca. Os resultados sugerem que fatores econ?micos s?o as vari?veis que explicam a variabilidade dos desembarques de esp?cies de recifes entre as comunidades. Este conhecimento pode ser ?til para o desenvolvimento de planos de gest?o eficazes que possam beneficiar economicamente os pescadores. / Marine fishing resources have great economic, social and ecological importance, guaranteeing the generation of income and food security for workers directly and indirectly linked to the fishing industry. The ecological dynamics of these resources determines the fishing activity which, in turn, causes changes in the exploited stocks. These changes affect the entire ecosystem and not only the most commercialized species due to by-catch, discarding and the removal of prey or predators. However, in developing countries, the use of marine resources is little or nothing regulated which leads to a lack of adequate management. Thus, the management of this activity requires an ecosystem assessment focusing not only on resources, but also on fishing and users of resources. Thus, in this work, ecosystemic and economic approaches are used to generate information that can be used to subsidize policies of ecosystem management of the fishing activity. The first chapter combines the scientific knowledge and the fishers? traditional knowledge for the ecosystemic modeling of fishing, opening the way for the use of the methodology for the elaboration of fishery management plans focused on the ecosystem. In this chapter, we conclude that fishermen can be reliable sources of information on the biology and ecology of the main target species of the fishing activity, contributing to the creation of models on the fishing dynamics that can subsidize effective actions of ecosystem management. The second chapter provides modeling of the small-scale fishing value chain, identifying stakeholder participation and how economic benefits are distributed along the chain. In this case study, it was concluded that the food security of the fishing community is of greater importance in receiving the fish compared to the surrounding tourist communities. Thus, tourism is no longer seen as the recipient of much of the local production. In the third chapter we analyze the combination of production, economic and fishermen indicators (social) between communities with a degree of dependence on tourism. Tourism can be seen as an alternative source of income in coastal communities since well managed. The fourth chapter presents an analysis that aims to describe the characteristics of the composition of landed species, aiming at a better understanding of the dynamics of the socio-cultural system that influence the capture of natural resources. Under the dwindling and growing tourism landscape, action is urgently needed to carefully design managed tourism and well-regulated commercial fishing for the entire coastal area. The final chapter deals with fishing practiced in reef environments. The main objective of this study was to identify the main drivers of reef fishing for the small-scale sector along a fishing pressure gradient in eight communities in northeastern Brazil. The studied communities were divided into fishing pressure categories to explore whether species characteristics are related to socioeconomic conditions and to compare their fishing characteristics. The results suggest that economic factors are the variables that explain the variability of the landings of reef species among communities. This knowledge can be useful for the development of effective management plans that can economically benefit fishermen.

L'objectif principal de cette thèse était d'étudier la dynamique spatiale et temporelle de la structure des communautés de poissons du fleuve Mékong en aval et du grand lac Tonlé Sap au Cambodge. Les deux systèmes sont fortement liés et caractérisés par les systèmes d'inondation pulsés. À l'aide d'approches multivariées sur des bases de données piscicoles, environnementales et des traits fonctionnels des taxons étudiés, j'ai pu mettre en évidence : * les gradients longitudinaux des caractéristiques physicochimiques des eaux et l'importance relative des facteurs environnementaux dans la structuration des communautés de poissons à large échelle ; * la structure temporelle des communautés de poissons qui est fortement liée aux traits fonctionnels des taxons et déclenchée par les crues occasionnées du système * la structure de base du réseau trophique et l'état écologique du système d'inondation pulsé qui est perturbé par la pression anthropique. Ces résultats ont démontré leurs valeurs quant à leurs potentiels de transferts vers la compréhension écologique et la gestion durable des ressources de pêches dans le système d'inondation pulsé en Asie tropicale en relevant que : * la connectivité entre le fleuve Mékong et le lac Tonlé Sap est indispensable pour les poissons pour compléter leurs cycles de vie, et la conservation devrait prioritairement s'effectuer au milieu du Mékong où se trouve la plus forte diversité. * dans le système d'inondation pulsé, la structure temporelle des communautés dépend des dynamiques des crues, donc l'aménagement des cours d'eau est à éviter au maximum. * la compréhension bioécologique complète des communautés et leurs relations trophiques sont primordiales pour la mise en place des plans de gestion et de conservation à long terme. / The main objective of the thesis was to study the spatial and temporal dynamics of fish community structure in Lower Mekong river basin and Tonle Sap Great Lake in Cambodia. These two systems are strongly connected to each other and characterised by flood pulse system. By using the multivariate approaches on the fish, environmental and fish functional traits data sets, I am able to highlight: * the longitudinal gradients of physicochemical characteristics of water and the relative importance of environmental factors in explaining the large scale patterns of fish community; * the temporal structure of fish community, which is strongly linked to functional traits of fish and trigged by the pulse dynamics of the system; * the baseline trophic structure model and ecological health assessment of flood pulse system, which is disturbed by anthropogenic pressure. These results have demonstrated their values as well as their potentials to transfers toward an ecological understanding and sustainable fisheries resource management of the flood pulse system in tropical Asia by suggesting: * the connectivity between Mekong river and Tonle Sap lek is essential for fish to complete their life cycle and also the conservation should be done in the middle part of Lower Mekong river where containing the highest diversity; * in flood pulse system, the temporal structure of fish community strongly depend on the dynamics of pulses; therefore any river development must be strictly prohibited; * complete bio-ecological understanding of communities and their trophic relationships are crucial to the establishment of long-term management and conservation plans.

No description available.