Characterization of bone pathologies in the ins2+/akita mouse, a new model for diabetes insulindependent: contribution for a better understanding of the disease in humans

Tese de Doutoramento, Ciências Biomédicas, Departamento de Ciências Biomédicas e Medicina, Universidade do Algarve, 2016

Reduction of elasmobranch by-catch in the hake semipelagic near-bottom longline fishery in the Algarve (Southern Portugal)

Elasmobranch fish, particularly deep-sea sharks, are the most important component of the by-catch of the hake semipelagic near-bottom 'pedra-e-bola' longline fishery in the Algarve (South Portugal) and most of these fish are discarded. The effects of the removal of the lower hooks were evaluated, in terms of target and by-catch reductions, by quantifying the catches of each hook relative to the distance from the bottom. The analysis showed that most European hake (Merluccius merluccius), the target species of this fishery, were caught in the middle range of the hooks, with very few individuals caught near the bottom, whereas for sharks the situation was the opposite, with most hooked near the bottom. The removal of the lower three pairs of hooks would result in a small reduction in the catch of the target species, but a much more significant reduction in elasmobranch by-catch. In the specific case of the blackmouth catshark (Galeus melastomus), discard mortality would be further minimized due to the fact that the lower hooks capture significantly smaller animals that are always discarded compared with hooks that are more distant from the bottom.

Age and growth of the smooth hammerhead shark, Sphyrna zygaena, in the Eastern Equatorial Atlantic Ocean, using vertebral sections

The smooth hammerhead shark Sphyrna zygaena (Sphyrnidae) is regularly caught as bycatch in pelagic longline fisheries, but is one of the least studied of all pelagic sharks. Recently, ICCAT (International Commission for the Conservation of Atlantic Tunas) issued recommendations underlining the need for more studies on the life history parameters of this and other pelagic shark species. To this end, the age and growth of S. zygaena were studied in the Eastern Equatorial Atlantic Ocean, in an area where growth parameters were not yet available for this species. Data from 139 specimens, caught between June and September 2009, ranging in size from 136 to 233 cm fork length (FL), were analysed. Preliminary trials were carried out to assess the most efficient growth band enhancement technique. These indicated that sectioning the vertebrae into 500 μm sections followed by staining with crystal violet produced the best results. Growth models were fitted using the traditional von Bertalanffy growth equation and a modification of this equation using a known size at birth. Growth models were compared using the Akaike information criterion (AIC). The von Bertalanffy growth equation seemed to be the most adequate model to describe growth in this species, with resulting growth parameters of L inf = 272 cm FL, k = 0.06 year for males and L inf = 285 cm FL, k = 0.07 year for females. In the first four years of life, S. zygaena grows 25 cm per year on average, but its growth slows down in later life. Future stock assessment models should incorporate these age and growth parameters for species management and conservation.