| Summary: | [eng] Aphanopus carbo (Lowe, 1839), the black scabbardfish, is a benthopelagic teleost with high commercial value in the NE Atlantic, especially in Madeira Archipelago and mainland Portugal. Given its commercial interest and high susceptibility to overfishing, as a consequence of low fecundity and low growth rate, improving the knowledge on its life cycle and population dynamics is of uttermost importance for improving fisheries management and advice. Although some questions persist, the agreed assumption is that there is a unique stock that undergoes a clockwise migration around the NE Atlantic driven by feeding and reproduction. The available information that supports the hypothetical migratory cycle of A. carbo was reviewed in this Thesis and different methodological approaches were proposed to explore its life history traits and relate them with the migratory cycle, in order to increase information on the species for a sustainable knowledge-based fishery management, and to assess its population dynamics and spatial pattern in the NE Atlantic. Differences in fatty acids and stable isotopes concentrations in the muscle tissue of specimens from different areas supported the species hypothetical migratory cycle. Mature specimens showed a prevalence of polyunsaturated fatty acids (PUFA) which are related with high energetic demands, supporting the hypothesis that the black scabbardfish continues to feed during the spawning period. PUFA associated with a response to stress were high in specimens from the southernmost areas which might be related with the expected long-distance migrations. The analysis of sex steroids in blood serum confirmed their role as intrinsic triggers for gonadal maturation and spawning in black scabbardfish. Based on estradiol (E2) and testosterone (T) concentrations, some developing females from Madeira were clustered with females from mainland Portugal, giving evidence that not all developing females will have the ability to mature and reproduce during the current spawning season. The ...
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