Author(s): Baeta, Ana Filipa Ribeiro, 1980-
Date: 2009
Persistent ID: http://hdl.handle.net/10451/1650
Origin: Repositório da Universidade de Lisboa
Subject(s): Pescas; Impacto ambiental; Sustentabilidade; Gestão; Biologia marinha; Teses de doutoramento - 2009
Tese de doutoramento, Biologia (Biologia Marinha), Universidade de Lisboa, Faculdade de Ciências, 2009
Assess fishing impacts on marine ecosystem and fisheries sustainability is essential to achieve proper management of the sector and for the conservation of resources and marine ecosystem. The main fishing impacts (bycatch, namely of protected species, discards, and impacts on habitats and on marine trophic web) of seven Portuguese fisheries were assessed. The ecological impact requiring more urgent attention was bycatch, which in some cases led to significant amounts of discards. In particular, it was analyzed the elasmobranchs bycatch in trammel nets fishery, which constituted an important part of the total biomass caught and of the individuals discarded, and the impact of nets loss in the marine environment, which continue to fish for a relatively long periods of time, especially in rocky bottom. We also observed changes in the marine trophic web of Portuguese waters by analysis of the mean trophic level of national landings. The analysis of the sustainability of the national fisheries sector has shown that, in general, it has increased in recent years, although at a higher rate in economic and institutional dimensions than in ecological and social dimensions. The traditional fisheries of the Tagus estuary showed an intermediate sustainability, making clear the need for intervention. The Portuguese fisheries management measures were assessed considering their effects on commercial species, verifying that in general they have not the desired effects and that the current management model should be changed. Marine protected areas have been suggested as a tool for fisheries management. A methodology to assess their effectiveness in the small fisheries sustainability was developed and applied to the marine area of the Natural Park of Arrábida, for which there is only improvements in ecological and management areas.
Assess fishing impacts on marine ecosystem and fisheries sustainability is essential to achieve proper management of the sector and for the conservation of resources and marine ecosystem. The main fishing impacts (bycatch, namely of protected species, discards, and impacts on habitats and on marine trophic web) of seven Portuguese fisheries were assessed. The ecological impact requiring more urgent attention was bycatch, which in some cases led to significant amounts of discards. In particular, it was analyzed the elasmobranchs bycatch in trammel nets fishery, which constituted an important part of the total biomass caught and of the individuals discarded, and the impact of nets loss in the marine environment, which continue to fish for a relatively long periods of time, especially in rocky bottom. We also observed changes in the marine trophic web of Portuguese waters by analysis of the mean trophic level of national landings. The analysis of the sustainability of the national fisheries sector has shown that, in general, it has increased in recent years, although at a higher rate in economic and institutional dimensions than in ecological and social dimensions. The traditional fisheries of the Tagus estuary showed an intermediate sustainability, making clear the need for intervention. The Portuguese fisheries management measures were assessed considering their effects on commercial species, verifying that in general they have not the desired effects and that the current management model should be changed. Marine protected areas have been suggested as a tool for fisheries management. A methodology to assess their effectiveness in the small fisheries sustainability was developed and applied to the marine area of the Natural Park of Arrábida, for which there is only improvements in ecological and management areas.
