Dinâmica das pescas e gestão participativa do polvo vulgar (Octopus vulgaris) capturado pela frota de covos e alcatruzes no sul de Portugal

Tese de Doutoramento, Ciências do Mar, da Terra e do Ambiente, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2015

The following PhD dissertation presents information on biological, ecological, socioeconomical and governmental aspects of the fishery of the common octopus (Octopus vulgaris), captured by pot and trap fishing fleets in the region of Algarve (Portugal), in the southwest of the Iberian Peninsula. The thesis work has been divided into two parts, Part One and Part Two. Part One addresses the fishery dynamics of the common octopus and its relationship with the life cycle of the species, especially those aspects concerning key reproductive stages such as spawning, para-larvae and fishing recruitment, and also its relationship with the environment. Part Two analyses the management of the fishery of the common octopus currently in force in Portugal, particularly in the Algarvian region. A series of workshops were held with stakeholders from this fishery, such as fishermen, scientists and government officials, with the purpose of discussing management approaches aimed to improve this fishery, for example the implementation of a seasonal closure in order to protect the reproduction of the species. Part One is sub-divided into two chapters, Chapter Two and Chapter Three, which precede the introduction or Chapter One. Chapter One gives an overview of the octopus fisheries around the world, the life cycle of the species and how it affects the management of the fishery, and challenges faced by the fishers and industry. Chapter Two emerges from the necessity of the fishermen to establish the time of the year that is deemed most suitable for implementing a ban on the fishery of the common octopus, in order to protect its reproduction and recruitment. This chapter aims to explain the relationship between the dynamics of the fishery and the octopus's life cycle. By means of multivariate statistical analysis of the last 25 years of data from fishing landing records at 12 main ports of the region, the most important factors linking the fishery dynamics of the octopus and its biology were identified. The results were used to construct an life cycle figure that can be used by fishermen, scientists, students, government officials, among others as a quick reference guide. Chapter Three investigate fishing landing data from the Port of Santa Luzia, one of the most important octopus ports in the Algarvian region. The use of statistical techniques such as Dynamic Factor Analyses (DFA) specifically intended for the analysis of time series including local oceanographic and environmental data is explored in order to find common trends and its relationship with environmental variables relevant to the selected fishing area. The results of these analyses reveal factors that affect the recruitment of the species in the Algarve. Part Two is sub-divided also into two chapters, Chapter Four and Chapter Five. Chapter Four begins with a description of the current socio-economic situation and governance model of the pot and trap octopus fisheries in the country. Using a time line approach, a retrospective of the evolution of this fishery during the last 50 years was developed. Common challenges associated with the steady increase of this fishery were identified. Chapter Five analyses ideas debated at seven participatory workshops, held between 2014 and 2015, on the management of the pot and trap octopus fishery in the Algarvian region. In these meetings, stakeholders (fishermen, marine biology researchers, scientists, representatives of government bodies and public institution, university students, among others) discussed proposals aimed to address current challenges, improve the management of the fishery of this resource, and develop a comanagement model that benefits all parties involved in the activity. These proposals were summarized in a handbook that is included as an annex at the end of this PhD dissertation. This paper concludes in Chapter Six with a general discussion about previous chapters and future research that are considered necessary as a result of this work.