Establishing relationships between climatic variables and coastal fisheries of Portugal

• Autor(a) principal: Ullah, Hadayet
• Data de Publicação: 2012
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.1/5977
• topic: Recursos pesqueiros; Alterações climáticas; Descargas; Recursos marinhos; Produtividade; Variação espacial

The notion that climate change may impact coastal fish production suggests a need to understand how climate variables may influence fish catch on a small and large scale. The direct or indirect effects of climate change have been shown to affect catch in productive estuarine and coastal ecosystems. However, the effect of climatic variability and fishing effort on landing catches (as proxy of fish abundance) varied accordingly local and regional scale. Therefore, two studies were conducted. In the first study, an area with similar oceanographic environmental conditions, (Northwestern coast of Portugal) was selected, aiming to analyze the relationships between both climate and fishery variables on catch rates of important commercial and mostly short life cycle species (Alosa alosa, Alosa fallax, Engraulis encrasicolus, Sardina pilchardus, Sepia officinalis and Trachurus trachurus). In addition, particular emphasis was given to explore the effects of freshwater discharge from the three main rivers on the selected species landing trends. Therefore, time series of commercial landings of NW-Atlantic (northwestern Portugal) from 1989 to 2009 were analyzed using min/max autocorrelation factor analysis (MAFA) and dynamic factor analysis (DFA). These techniques were used to explore the relationships between the response variables (annual landings per unit effort) and explanatory variables [NAO index, sea surface temperature (SST), an upwelling (UPW) index, river discharge and fishing effort]. The results of the study confirmed that river discharge was the most important explanatory variables affecting coastal fisheries, followed by SST and UPW. In particular, seasonal river discharge became the explanatory variables that better explain the variability of the two most important small pelagic, Engraulis encrasicolus and Sardina pilchardus. Likewise, results also elucidated that change or reduction in river discharge during spawning event, might become detrimental for other species as well. The key finding of this study is that even within a small area with different rivers regimes and similar oceanographic conditions, the effect of environmental variables might be different on the same species/ population. In the other study, the sensibility of the species to climatic variability and fisheries was evaluated across regions: south, southwestern and northwestern Atlantic coast of Portugal. Similar statistical techniques were used for exploring data information that also includes the period from 1989 to 2009. The sensibility of the species studied to climatic variability differed accordingly the regions. However, results showed that wind and river discharge were the variables that mostly affect fishing trends, independently of different region. Thus, this study will significantly contribute to a better understanding of the relations between climate change and coastal fisheries variability, aspect that need to be considered for the integrated coastal management and development of new policies under the scope of climatic conditions.