Metodologías y herramientas para la planificación y gestión integrada de los recursos pesqueros en el estrecho de Gibraltar en un contexto de cambio climático

Abstract

The main objective of this Doctoral Thesis is to complement a tool to assess the short, medium and long term state of fisheries within a regime of rapid climate change in order to implement sustainable fisheries management, isolating and assessing the influence of environmental, political, social and economic factors on fisheries. To this end, a comprehensive study of the direct and indirect influence of environmental, socio-economic and legislative factors on the case of demersal fisheries of the genus Pagellus in the North Atlantic area has been carried out. Furthermore, the importance of environmental variability, from an oceanic and climatic perspective, on the state of a particular fishery of the genus Pagellus at a local scale, specifically the fishery of Pagellus bogaraveo in the Strait of Gibraltar, has been determined and quantified. The Thesis is divided into five chapters. The first chapter provides a contextualisation of the fishery of the genus Pagellus in FAO areas 27 and 34 from 1950 to 2014 based on reconstructed catch data. The applied analyses revealed the existence of historical variations and changes in catches, with the majority of the fisheries behaviour being downward with a progressive increase in fishing intensity on the stocks. The rest of the chapters are already focused on the Pagellus bogaraveo fishery in the Strait of Gibraltar. In chapter 2, the historical evolution of commercial landings of Blackspot seabream (Pagellus bogaraveo) from 1983 to 2016 is analysed. Patterns of change are evaluated from a univariate perspective and the environmental and legislative effect on landings is investigated. The use of univariate modelling techniques allowed us to establish possible factors associated with landings variability. In chapter 3, time-domain and time-frequency analyses provide an integrated view of climate-oceanographic variability with the historical dynamics of Blackspot seabream landings. It was determined that landings had two cycles (1990-2000 and 2005-2015) with 6-month and 12-month oscillations dominating, and that their dynamism is associated with climate and oceanographic variability. In chapter 4, a multivariate approach is carried out with the main objective of assessing the historical effects of an extensive battery of abiotic environmental factors on the production of Blackspot seabream from 1983 to 2015. The combination of different statistical techniques, mainly focused on the detection of common patterns and relationships between the fishing series and the different abiotic environmental variables, established the presence of these patterns and the existence of a significant influence of certain variables on landings. Finally, in chapter 5, the ARIMA models developed are implemented in a decision support system called "SFish SubClass 1.1", thanks to which the environmental and fishing effects on the stock are disaggregated. With "SFish SubClass 1.1", by integrating the simulated life cycles of the exploited species and the fishing component, the evolution of the biomass of the stock in the presence or absence of fishing activity is obtained. The importance of the environmental effect on the stock is assessed by means of two indices developed with the intention of improving the interpretation of the role played by this effect on the state of the stock. This methodology is applied to the Blackspot seabream fishery in the Strait of Gibraltar suggesting that the main factor responsible for the historical abundance-biomass changes is the fishing component.