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Assessing fisheries sustainability status using different classification systems : using snapper and grouper as case studies
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Abstract(s)
Esta dissertação forneceu uma visão global do estado de sustentabilidade das pescarias de lucianos1 e garoupas. Os lucianos e garoupas são recursos essenciais para o sector da pesca de "pequena-escala" a nível global, com um papel fundamental na subsistência e segurança alimentar de muitas comunidades costeiras em todo o mundo. Em termos globais, os desembarques destes recursos têm vindo a aumentar ao longo dos anos, com quase um milhão de toneladas reportadas em anos recentes. O estado de sustentabilidade de muitas pescarias de lucianos e garoupas é usualmente desconhecido, particularmente para as pescarias de "pequena-escala" em países em desenvolvimento, onde o sistema estatístico é normalmente ausente ou insuficiente, e onde existe uma capacidade limitada de investigação e monitorização para a realização de avaliações do estado do stock complexas e exigentes ao nível de informação necessária. Esta tese desenvolveu, aplicou e testou metodologias inovadoras, para avaliar o estado de pescarias de lucianos e garoupas com informação limitada, as quais podem igualmente ser aplicadas a um vasto número de pescarias a nível global. Os três principais pilares deste trabalho foram: 1) realizar um diagnóstico do conhecimento existente sobre a pescaria; 2) avaliar a sustentabilidade das pescarias através de metodologias adaptadas aos melhores dados disponíveis; 3) avaliar o estado dos recursos através de novas metodologias usando dados de frequência de comprimento da pesca comercial. O Indicador Genérico de Conhecimento (IGC) desenvolvido nesta tese permite identificar as principais lacunas de conhecimento e destacar áreas onde o desenvolvimento da investigação é fundamental para informar a gestão sustentável dos recursos pesqueiros. Este novo indicador realçou que 70% das pescarias de lucianos e garoupas apresenta um baixo nível de conhecimento e têm informação limitada. A análise do estado de sustentabilidade das pescarias de lucianos e garoupa mostraram que cerca de 50% destas pescarias foram classificadas como "sobre-explorada", 30% como "não-explorada" e 19% em "plena exploração". Além disso, o número de pescarias sobre-exploradas tem vindo a aumentar ao longo dos anos. Devido à limitação de dados quantitativos, foram investigadas fontes de informação alternativas e o Index de Desenvolvimento Humano (IDH) salientou-se como indicador do estado da biomassa. A modelação categórica revelou um alto nível de correspondência (72%) entre o estado do stock original e estimado, fazendo este procedimento bastante promissor para ser aplicado a outras pescarias com informação limitada. Para regiões específicas, o estado de pescarias de lucianos e garoupa foi analisado com base em dados da composição de comprimentos das capturas, mas adoptando abordagens distinctas. Uma abordagem metodológica aplicou diferentes métodos baseados em dados de comprimentos e simulou os diferentes efeitos dos parâmetros biológicos (crescimento) nas estimativas do estado do stock para as principais espécies de lucianos e garoupa capturadas no Mar de Java (Indonésia). Foram encontradas diferenças no estado dos recursos, consoante a arte de pesca utilizada, tendo o palangre apresentado bons indicadores do estado do stock para todas as espécies estudadas. Efeitos dos parâmetros biológicos foram testados: Linf e, secundariamente, M/K têm uma forte influência nos indicadores do estado do stock. Métodos baseados na frequência de comprimentos também foram aplicados, pela primeira vez, para avaliar o estado de sustentabilidade das principais espécies de serranídeos na região dos Açores, cobrindo seletividade de artes e padrões espaciais (ilhas) distintos. A garoupa (Serranus atricauda) apresenta uma pior condição do estado do stock do que o mero (Epinenhelus marginatus), em particular, para estimativas baseadas em desembarques na ilha de São Miguel. Estes resultados apontam para a necessidade de desenvolvimento de medidas de gestão que tenham em consideração as diferentes artes de pesca e padrões espaciais. Esta dissertação contribui com metodologia nova e análises para melhorar a compreensão do estado de pescarias para as quais existe pouca informação, em particular para pescarias de lucianos e garoupa. Este trabalho também fornece directrizes para apoiar a concepção de medidas de gestão para garantir a sustentabilidade destes recursos e destaca áreas onde melhorias são críticas.
ABSTRACT: This dissertation provided a global overview of the sustainability status of snapper and grouper fisheries. Snapper and grouper are essential resources for the small-scale fisheries sector globally, with a critical role in the livelihoods and food security of many coastal communities worldwide. On a global scale, the reported landings of these resources have been increasing over the last decade reaching almost 1 million tonnes in recent years. The sustainability status of many snapper and grouper fisheries is often unknown, particularly for small-scale fisheries in developing countries where the reporting system is usually absent or insufficient, and there is a limited capacity for research and monitoring to carrying out complex and high data-demanding stock assessments. This work developed, applied and tested innovative methodologies to assess the status of snapper and grouper data-limited fisheries, which could as well be applied to a broader range of fisheries. The three main pillars of this work were to: 1) undertake a diagnosis of the existing knowledge of the fishery; 2) evaluate the sustainability status of the fisheries through methodologies adapted to the best available data; and 3) assess the status of the fisheries through new methodologies using length-frequency data from the commercial fisheries. The Generic Knowledge Indicator (GKI) framework developed in this thesis allows the identification of the main gaps in knowledge and highlights areas where research improvements are critical to inform the sustainable management of the fishing resources. This new indicator highlighted that 70% of the snapper and grouper fisheries worldwide exhibited low-knowledge and are data-limited. The analyses of the sustainability status of snapper and grouper fisheries showed that about 50% of these fisheries were classified as overexploited, while 30% as non-fully exploited, and 19% as fully exploited. The analysis also showed that the number of overexploited fisheries has been increasing over recent years. Due to the limitation of quantitative data, alternative sources of information were explored and the Human Development Index (HDI) emerged as a proxy for the status of biomass. The multinomial modelling approach revealed a high level of correspondence (72%) between the original and estimated status, making this procedure very attractive to be applied to other data-limited fisheries. Also, analyses on the status of snapper and grouper fisheries were conducted for specific regions based on length-frequency data available, with distinct approaches being adopted. A methodologic approach, applying different length-based methods and simulating different effects of the life-history parameters on the estimations, was carried out for the most important species caught in the snapper and grouper fishery in the Java Sea (Indonesia). Differences in the status of the resources were found depending on the gear used, with the longline fishery presenting good indicators for all species studied. Bias in the life-history parameters was tested: Linf and, secondarily, M/K parameters have a stronger influence in the stock indicators outputs. Length-based methods were also applied to assess the sustainability status of the main serranid species in the Azores region, covering distinct gear selectivity and spatial (islands) patterns. Black tail comber (Serranus atricauda) is in worse sustainability status than dusky grouper (Epinenhelus marginatus), in particular, for estimates based on landings from São Miguel island. These results support the need for the development of management measures that take into account different gears and spatial patterns. This dissertation contributes with new methodology and analyses to improve the understanding of the status of data-limited fisheries, in particular for snapper and grouper fisheries. This work also provided information to support the design of management measures aimed at guaranteeing the sustainability of these resources and highlights areas where improvements are critical.
ABSTRACT: This dissertation provided a global overview of the sustainability status of snapper and grouper fisheries. Snapper and grouper are essential resources for the small-scale fisheries sector globally, with a critical role in the livelihoods and food security of many coastal communities worldwide. On a global scale, the reported landings of these resources have been increasing over the last decade reaching almost 1 million tonnes in recent years. The sustainability status of many snapper and grouper fisheries is often unknown, particularly for small-scale fisheries in developing countries where the reporting system is usually absent or insufficient, and there is a limited capacity for research and monitoring to carrying out complex and high data-demanding stock assessments. This work developed, applied and tested innovative methodologies to assess the status of snapper and grouper data-limited fisheries, which could as well be applied to a broader range of fisheries. The three main pillars of this work were to: 1) undertake a diagnosis of the existing knowledge of the fishery; 2) evaluate the sustainability status of the fisheries through methodologies adapted to the best available data; and 3) assess the status of the fisheries through new methodologies using length-frequency data from the commercial fisheries. The Generic Knowledge Indicator (GKI) framework developed in this thesis allows the identification of the main gaps in knowledge and highlights areas where research improvements are critical to inform the sustainable management of the fishing resources. This new indicator highlighted that 70% of the snapper and grouper fisheries worldwide exhibited low-knowledge and are data-limited. The analyses of the sustainability status of snapper and grouper fisheries showed that about 50% of these fisheries were classified as overexploited, while 30% as non-fully exploited, and 19% as fully exploited. The analysis also showed that the number of overexploited fisheries has been increasing over recent years. Due to the limitation of quantitative data, alternative sources of information were explored and the Human Development Index (HDI) emerged as a proxy for the status of biomass. The multinomial modelling approach revealed a high level of correspondence (72%) between the original and estimated status, making this procedure very attractive to be applied to other data-limited fisheries. Also, analyses on the status of snapper and grouper fisheries were conducted for specific regions based on length-frequency data available, with distinct approaches being adopted. A methodologic approach, applying different length-based methods and simulating different effects of the life-history parameters on the estimations, was carried out for the most important species caught in the snapper and grouper fishery in the Java Sea (Indonesia). Differences in the status of the resources were found depending on the gear used, with the longline fishery presenting good indicators for all species studied. Bias in the life-history parameters was tested: Linf and, secondarily, M/K parameters have a stronger influence in the stock indicators outputs. Length-based methods were also applied to assess the sustainability status of the main serranid species in the Azores region, covering distinct gear selectivity and spatial (islands) patterns. Black tail comber (Serranus atricauda) is in worse sustainability status than dusky grouper (Epinenhelus marginatus), in particular, for estimates based on landings from São Miguel island. These results support the need for the development of management measures that take into account different gears and spatial patterns. This dissertation contributes with new methodology and analyses to improve the understanding of the status of data-limited fisheries, in particular for snapper and grouper fisheries. This work also provided information to support the design of management measures aimed at guaranteeing the sustainability of these resources and highlights areas where improvements are critical.
Description
Tese de Doutoramento, Ciências do Mar (Recursos Marinhos), 26 de maio de 2021.
Keywords
Ecologia Marinha Garoupa Lutjanidae (família) Pesca Sustentável Serranidae (família) Sustentabilidade Marinha Data-limited Fisheries Grouper Small-scale Fisheries Snapper Stock Status
Citation
Amorim, Patrícia Alexandra da Silva (2021). "Assessing fisheries sustainability status using different classification systems: using snapper and grouper as case studies", 219 p.. Doutoramento em Ciências do Mar (Recursos Marinhos). Horta: Universidade dos Açores. [Consult. Dia Mês Ano]. Disponível em www:<http://hdl.handle.net/10400.3/6148>.