SALEMA, SARPA SALPA LINNAEUS 1758: STOCK STRUCTURE IN THE EASTERN ATLANTIC AND BIOLOGICAL CHARACTERIZATION OFF THE PORTUGUESE COAST

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Salema, Sarpa salsa (Linnaeus 1758) : stock structure in the eastern atlantic and biological characterizatin off the portuguese coast

Publication . Paiva, Rafaela Barros; Gordo, Leonel Serrano, 1957-; Costa, Maria José, 1947-

This thesis comprises the first multidisciplinary study of Sarpa salpa in the southern Northeast Atlantic Ocean because it analyzes its stock structure and characterizes the biological parameters of the specimens off the Portuguese coast. To achieve those goals, specimens from three areas of mainland Portugal and Madeira were collected and supplementary samples from Mediterranean Sea were obtained for genetic analysis. Considering the analysis of the stock structure, the body geometric morphometric techniques and the elliptical Fourier analysis indicated some overlap in the mainland specimens, especially between the central and south areas, and a clear separation of Madeira individuals. Both techniques indicated that at least two stocks may occur, one in Madeira and the other in mainland waters but were not clear regarding to the existence of an additional stock in mainland waters, separating the northern region from the central and south areas. Evidence of stocks through morphometric analysis indicated that individuals have been underlying some genetic divergence or adaptation to local conditions, being the latter the most applicable to the present case. Regarding genetics, the analysis of mitochondrial and nuclear data of S. salpa support the hypothesis that: a) there is no evidence of stock structure between Atlantic and Mediterranean samples; b) exists a reduction of the current gene flow among sampling sites; c) there is a clear expansion signal from the possible refuges in the coast of Africa with accumulation of mutation in situ; d) the mitochondrial and nuclear DNA introgression detected seems to be ancient, probably existing before the expansion took place. For the analysis of age, growth and reproduction new information was given for the Portuguese continental coast, where no information was available. This new information is particularly valuable because life history parameters of S. salpa were estimated and that can be used to provide baseline data to be applied in ecological modelling, to inform, improve and assess the fisheries towards a sustainable management. The information determined on S. salpa life history parameters, captured in the Portuguese waters, included: the duration of the spawning season (from September to November); the determination of growth pattern (medium-slow); the estimation of L50 for males (25 cm); the clarification of the fecundity type (determinate) and its estimation. Cystic structures have been documented in S. salpa ovaries and the results indicated that the cysts may be part of the species reproductive strategy.

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Fundação para a Ciência e a Tecnologia

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SFRH/BD/80268/2011