Abstract Taiwan is an island country, the topography of the adjacent territorial waters is diversified, multiple ocean currents converge here and there are rich basic production capabilities, all of which give birth to various marine organisms in Taiwan and help to form the favorable conditions for Taiwan to develop its offshore fishery. However, due to the lack of control of the production capabilities of offshore waters in the last few decades, plus the constant upgrading of fishing techniques and methods, as well as the lack of effective management, the fishery resources have been greatly impacted and the total fishery production continues to decline. Fishery resource management needs correct fishing location, fishing effort and catch totals as the scientific basis for fish stock assessment, in order to achieve effective management targets. The greatest problem for the offshore waters of Taiwan is that we could not obtain detailed information on the fishing location, operation time (fishing effort) and catch totals. At present, the above data were all obtained through investigations or by interviewing with captains to fill in report forms. However, out of fear of disclosing trade secrets and owing to omissions, the obtained data could not help in revealing the real fishery resource situation. The Coast Guard Administration of the Executive Yuan integrally established a coast radar system along the coast of Taiwan, which monitors all ships within the scanning area through 24-hour uninterrupted scanning, and digitally records the navigation data on ships. The data contains time, ship number, speed, course, latitude and longitude (location); by sorting out these data, we could discern the actual fishing location of the fishing boats. The objective of this study was to utilize the data collected by the coast radar system to determine the fishing location of the fishing boats, acquire the port entry and exit data of the fishing boats through the security examination system, work out the fishing effort, and by collecting the catch and sales data from five fishery harbors, derive the respective total amount of the 10 main fish species caught, in order to investigate the fishery dynamics of Southern Taiwan sea. Research results show that by applying the coast radar system along with the use of port entry and exit data on the fishing boats recorded in the security examination system, as well as the catch and sales data of the fishing boats, and through comparison of the above data, we could obtain proper estimations of fishing effort and fishing location of the fishing boats, as well as the catch per unit effort (CPUE) and the distribution of species composition. Keywords: coast radar, Tainan coastal and offshore fisheries, fishing effort, fishing location¡Acatch per unit effort

Commercial pelagic longline fishers within the U.S. Atlantic, Gulf of Mexico, and Caribbean are required to report all fishing interactions per each gear deployment to NOAA’s Vessel Logbook Program of the Southeast Fisheries Science Center to quantify bycatch, increase conservation efforts, and avoid jeopardizing the existence of vulnerable species listed under the Endangered Species Act (ESA). To provide additional accuracy, the Pelagic Observer Program (POP) of the SEFSC deploys professionally trained observers on longline vessels to produce a statistically reliable subset of longline fisheries data. A comparison of self-reported (“unobserved”) datasets versus observer-collected (“observed”) datasets showed a general consistency for most target species but non-reporting or under-reporting for a number of bycatch species and “lesser-valued” target species. These discrepancies between catch compositions and abundancies regarding targeted species, species of bycatch concern, and species of minimum economic value can provide insight into increased fisheries regulations, stricter requirements, or additional observer coverage.

A pesca artesanal de pequena escala (ou subsistência) tem sido historicamente pouco estudada. Poucos estudos buscam compreender os fatores que influenciam a pesca nessa escala. Populações humanas que dependem dos recursos naturais apresentam bom conhecimento sobre o ambiente e os recursos explorados. Barramentos de rios são uns dos principais impactos na pesca de águas interiores, e pouco se sabe sobre esses impactos ao longo do tempo. Portanto, informações das populações locais e da pesca de subsistência podem melhorar e complementar o conhecimento científico sobre a pesca e os impactos causados por barramentos. O objetivo desse estudo é analisar as características da dinâmica da pesca artesanal de subsistência no Baixo Rio Tocantins (Amazônia brasileira) através de entrevistas e desembarques pesqueiros. Testamos a eficiência do conhecimento ecológico local de pescadores através de entrevistas no diagnóstico da dinâmica da pesca e de mudanças ambientais decorrentes de barragens em grandes rios (1º capítulo). Também analisamos o rendimento pesqueiro e as variáveis que influenciam na captura de peixes em cinco comunidades de pescadores artesanais do Baixo Rio Tocantins (2º capítulo). Foram realizadas 300 entrevistas com pescadores de nove comunidades ribeirinhas e registrados 606 desembarques pesqueiros em cinco destas comunidades, em 67 dias de amostragem. Através das entrevistas é possível identificar os peixes mais capturados, as artes de pesca e tamanhos de malhas de redes mais utilizadas pelos pescadores, além da sazonalidade da abundância dos peixes. Houve mudança na composição dos desembarques pesqueiros, 22 anos após o barramento. Através das entrevistas com os pescadores, foi possível identificar também quais espécies de pescado aumentaram (Plagioscion squamosissimus), quais diminuíram (Characidae, várias espécies de pacu), bem como quais desapareceram (Semaprochilodus brama) após o barramento. A produção anual e o rendimento financeiro da pesca foram reduzidos em cerca de 55% após o barramento do rio. A maior parte da variação da biomassa de peixes capturada é explicada pelas variáveis ligadas ao esforço e comportamento do pescador: tempo de pesca (35%), número de pescadores (30%) e a distância até local de pesca (20%). Entrevistas demonstraram ser um método rápido, confiável e de baixo custo para obter importantes informações sobre a pesca e os impactos à jusante de uma hidrelétrica em um grande rio amazônico. O conhecimento ecológico local pode complementar pesquisas ecológicas de longa duração de uma maneira rápida e eficiente. Considerar os pescadores, seu conhecimento e seu comportamento na elaboração de planos de manejo pesqueiro adequados com a realidade local, parece ser a maneira mais promissora de garantir a manutenção da biodiversidade, conservação dos recursos pesqueiros e manutenção da pesca artesanal como atividade econômica. / Small-scale artisanal (or subsistence) fisheries have been little studied. Few studies have attempted to understand the factors that influence the fisheries on this scale. Human populations that depend upon natural resources show good knowledge about the environment and the exploited resources. Dams are among the main impacts affecting inland fisheries and there is little knowledge about the impacts of dams on fisheries over time. Information from local populations and subsistence fishing may improve and complement the scientific knowledge on fisheries and dam’s impacts. The aim of this study is to analyze the dynamics of subsistence fishing in the Lower Tocantins River (Brazilian Amazon) through interviews and fish landings. We tested the efficiency of recording fishermen’s local ecological knowledge through interviews for assessment of the fisheries dynamics and environmental changes caused by dams in large rivers (1st chapter). We also analyzed the fishing income and the variables that influence the biomass of fish caught in five fishing communities of the Lower Tocantins River (2nd chapter). We conducted 300 interviews with fishermen in nine riverine communities and recorded 606 fish landings in five of these communities in 67 sampling days. Through interviews it is possible to identify the most caught fish species, the fishing gear and gillnet mesh sizes used by most of the fishermen, and the seasonal fish abundance patterns. The composition of fish landings changed 22 years after the dam’s closure. Through interviews with fishermen, also it was possible to identify the species of fish that increased (Plagioscion squamosissimus), decreased (Characidae, several species of pacu) and even disappeared (Semaprochilodus brama) after the dam’s closure. The annual production and financial income of fishing have been reduced by about 55% after the dam’s closure. Most of the variation in the biomass of fish caught is explained by variables related to the fishing effort and to the fisherman’s behavior , such as fishing time (35%), number of fishermen (30%) and distance to fishing grounds (20%). Interviews with fishermen showed to be fast, reliable and inexpensive methods to obtain important information about the fisheries and the impacts downstream from a dam in a large Amazonian river. The local ecological knowledge of resource users can complement long-term ecological research efficiently. The fishermen, their knowledge and their behavior should be considered when developing fisheries management plans appropriate to local realities. This seems to be the most promising way to ensure the maintenance of biodiversity, conservation of fishing resources, and maintenance of artisanal fisheries as an economic activity.

A pesca artesanal de pequena escala (ou subsistência) tem sido historicamente pouco estudada. Poucos estudos buscam compreender os fatores que influenciam a pesca nessa escala. Populações humanas que dependem dos recursos naturais apresentam bom conhecimento sobre o ambiente e os recursos explorados. Barramentos de rios são uns dos principais impactos na pesca de águas interiores, e pouco se sabe sobre esses impactos ao longo do tempo. Portanto, informações das populações locais e da pesca de subsistência podem melhorar e complementar o conhecimento científico sobre a pesca e os impactos causados por barramentos. O objetivo desse estudo é analisar as características da dinâmica da pesca artesanal de subsistência no Baixo Rio Tocantins (Amazônia brasileira) através de entrevistas e desembarques pesqueiros. Testamos a eficiência do conhecimento ecológico local de pescadores através de entrevistas no diagnóstico da dinâmica da pesca e de mudanças ambientais decorrentes de barragens em grandes rios (1º capítulo). Também analisamos o rendimento pesqueiro e as variáveis que influenciam na captura de peixes em cinco comunidades de pescadores artesanais do Baixo Rio Tocantins (2º capítulo). Foram realizadas 300 entrevistas com pescadores de nove comunidades ribeirinhas e registrados 606 desembarques pesqueiros em cinco destas comunidades, em 67 dias de amostragem. Através das entrevistas é possível identificar os peixes mais capturados, as artes de pesca e tamanhos de malhas de redes mais utilizadas pelos pescadores, além da sazonalidade da abundância dos peixes. Houve mudança na composição dos desembarques pesqueiros, 22 anos após o barramento. Através das entrevistas com os pescadores, foi possível identificar também quais espécies de pescado aumentaram (Plagioscion squamosissimus), quais diminuíram (Characidae, várias espécies de pacu), bem como quais desapareceram (Semaprochilodus brama) após o barramento. A produção anual e o rendimento financeiro da pesca foram reduzidos em cerca de 55% após o barramento do rio. A maior parte da variação da biomassa de peixes capturada é explicada pelas variáveis ligadas ao esforço e comportamento do pescador: tempo de pesca (35%), número de pescadores (30%) e a distância até local de pesca (20%). Entrevistas demonstraram ser um método rápido, confiável e de baixo custo para obter importantes informações sobre a pesca e os impactos à jusante de uma hidrelétrica em um grande rio amazônico. O conhecimento ecológico local pode complementar pesquisas ecológicas de longa duração de uma maneira rápida e eficiente. Considerar os pescadores, seu conhecimento e seu comportamento na elaboração de planos de manejo pesqueiro adequados com a realidade local, parece ser a maneira mais promissora de garantir a manutenção da biodiversidade, conservação dos recursos pesqueiros e manutenção da pesca artesanal como atividade econômica. / Small-scale artisanal (or subsistence) fisheries have been little studied. Few studies have attempted to understand the factors that influence the fisheries on this scale. Human populations that depend upon natural resources show good knowledge about the environment and the exploited resources. Dams are among the main impacts affecting inland fisheries and there is little knowledge about the impacts of dams on fisheries over time. Information from local populations and subsistence fishing may improve and complement the scientific knowledge on fisheries and dam’s impacts. The aim of this study is to analyze the dynamics of subsistence fishing in the Lower Tocantins River (Brazilian Amazon) through interviews and fish landings. We tested the efficiency of recording fishermen’s local ecological knowledge through interviews for assessment of the fisheries dynamics and environmental changes caused by dams in large rivers (1st chapter). We also analyzed the fishing income and the variables that influence the biomass of fish caught in five fishing communities of the Lower Tocantins River (2nd chapter). We conducted 300 interviews with fishermen in nine riverine communities and recorded 606 fish landings in five of these communities in 67 sampling days. Through interviews it is possible to identify the most caught fish species, the fishing gear and gillnet mesh sizes used by most of the fishermen, and the seasonal fish abundance patterns. The composition of fish landings changed 22 years after the dam’s closure. Through interviews with fishermen, also it was possible to identify the species of fish that increased (Plagioscion squamosissimus), decreased (Characidae, several species of pacu) and even disappeared (Semaprochilodus brama) after the dam’s closure. The annual production and financial income of fishing have been reduced by about 55% after the dam’s closure. Most of the variation in the biomass of fish caught is explained by variables related to the fishing effort and to the fisherman’s behavior , such as fishing time (35%), number of fishermen (30%) and distance to fishing grounds (20%). Interviews with fishermen showed to be fast, reliable and inexpensive methods to obtain important information about the fisheries and the impacts downstream from a dam in a large Amazonian river. The local ecological knowledge of resource users can complement long-term ecological research efficiently. The fishermen, their knowledge and their behavior should be considered when developing fisheries management plans appropriate to local realities. This seems to be the most promising way to ensure the maintenance of biodiversity, conservation of fishing resources, and maintenance of artisanal fisheries as an economic activity.

A pesca artesanal de pequena escala (ou subsistência) tem sido historicamente pouco estudada. Poucos estudos buscam compreender os fatores que influenciam a pesca nessa escala. Populações humanas que dependem dos recursos naturais apresentam bom conhecimento sobre o ambiente e os recursos explorados. Barramentos de rios são uns dos principais impactos na pesca de águas interiores, e pouco se sabe sobre esses impactos ao longo do tempo. Portanto, informações das populações locais e da pesca de subsistência podem melhorar e complementar o conhecimento científico sobre a pesca e os impactos causados por barramentos. O objetivo desse estudo é analisar as características da dinâmica da pesca artesanal de subsistência no Baixo Rio Tocantins (Amazônia brasileira) através de entrevistas e desembarques pesqueiros. Testamos a eficiência do conhecimento ecológico local de pescadores através de entrevistas no diagnóstico da dinâmica da pesca e de mudanças ambientais decorrentes de barragens em grandes rios (1º capítulo). Também analisamos o rendimento pesqueiro e as variáveis que influenciam na captura de peixes em cinco comunidades de pescadores artesanais do Baixo Rio Tocantins (2º capítulo). Foram realizadas 300 entrevistas com pescadores de nove comunidades ribeirinhas e registrados 606 desembarques pesqueiros em cinco destas comunidades, em 67 dias de amostragem. Através das entrevistas é possível identificar os peixes mais capturados, as artes de pesca e tamanhos de malhas de redes mais utilizadas pelos pescadores, além da sazonalidade da abundância dos peixes. Houve mudança na composição dos desembarques pesqueiros, 22 anos após o barramento. Através das entrevistas com os pescadores, foi possível identificar também quais espécies de pescado aumentaram (Plagioscion squamosissimus), quais diminuíram (Characidae, várias espécies de pacu), bem como quais desapareceram (Semaprochilodus brama) após o barramento. A produção anual e o rendimento financeiro da pesca foram reduzidos em cerca de 55% após o barramento do rio. A maior parte da variação da biomassa de peixes capturada é explicada pelas variáveis ligadas ao esforço e comportamento do pescador: tempo de pesca (35%), número de pescadores (30%) e a distância até local de pesca (20%). Entrevistas demonstraram ser um método rápido, confiável e de baixo custo para obter importantes informações sobre a pesca e os impactos à jusante de uma hidrelétrica em um grande rio amazônico. O conhecimento ecológico local pode complementar pesquisas ecológicas de longa duração de uma maneira rápida e eficiente. Considerar os pescadores, seu conhecimento e seu comportamento na elaboração de planos de manejo pesqueiro adequados com a realidade local, parece ser a maneira mais promissora de garantir a manutenção da biodiversidade, conservação dos recursos pesqueiros e manutenção da pesca artesanal como atividade econômica. / Small-scale artisanal (or subsistence) fisheries have been little studied. Few studies have attempted to understand the factors that influence the fisheries on this scale. Human populations that depend upon natural resources show good knowledge about the environment and the exploited resources. Dams are among the main impacts affecting inland fisheries and there is little knowledge about the impacts of dams on fisheries over time. Information from local populations and subsistence fishing may improve and complement the scientific knowledge on fisheries and dam’s impacts. The aim of this study is to analyze the dynamics of subsistence fishing in the Lower Tocantins River (Brazilian Amazon) through interviews and fish landings. We tested the efficiency of recording fishermen’s local ecological knowledge through interviews for assessment of the fisheries dynamics and environmental changes caused by dams in large rivers (1st chapter). We also analyzed the fishing income and the variables that influence the biomass of fish caught in five fishing communities of the Lower Tocantins River (2nd chapter). We conducted 300 interviews with fishermen in nine riverine communities and recorded 606 fish landings in five of these communities in 67 sampling days. Through interviews it is possible to identify the most caught fish species, the fishing gear and gillnet mesh sizes used by most of the fishermen, and the seasonal fish abundance patterns. The composition of fish landings changed 22 years after the dam’s closure. Through interviews with fishermen, also it was possible to identify the species of fish that increased (Plagioscion squamosissimus), decreased (Characidae, several species of pacu) and even disappeared (Semaprochilodus brama) after the dam’s closure. The annual production and financial income of fishing have been reduced by about 55% after the dam’s closure. Most of the variation in the biomass of fish caught is explained by variables related to the fishing effort and to the fisherman’s behavior , such as fishing time (35%), number of fishermen (30%) and distance to fishing grounds (20%). Interviews with fishermen showed to be fast, reliable and inexpensive methods to obtain important information about the fisheries and the impacts downstream from a dam in a large Amazonian river. The local ecological knowledge of resource users can complement long-term ecological research efficiently. The fishermen, their knowledge and their behavior should be considered when developing fisheries management plans appropriate to local realities. This seems to be the most promising way to ensure the maintenance of biodiversity, conservation of fishing resources, and maintenance of artisanal fisheries as an economic activity.