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Browsing by Author "Abecasis, David Maria Aguiar"

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  • 2007Master thesis Open access Show more
  • Multispecies spatial dynamics under different protection levels: an evaluation of the effects and optimal design of the Luiz Saldanha Marine Park
    Publication . Abecasis, David Maria Aguiar; Erzini, Karim
    The main objective of this study was to evaluate the potential benefits of the Luiz Saldanha Marine Park (LSMP) to three of the most important species for the local small scale artisanal fisheries: the white seabream, the Senegalese sole and the cuttlefish. Since this marine protected area (MPA) was implemented before the beginning of this study we also investigated if any changes had already occurred in the abundance or biomass of these species inside the MPA. High site fidelity was observed in white seabream with all individuals tagged with V9 acoustic transmitters being detected over 50% of the time (average of 85%). Although some Senegalese sole showed high site fidelity the majority of the individuals tagged were more transient. Cuttlefish demonstrated no site fidelity to the study area, spending a maximum of 39 days inside the monitored area. The home range areas (95% KUD) ranged between 0.43 and 1.28 km2 (average of 0.65 km2) for white seabream and between 0.54 and 2.22 km2 (average of 1.19 km2) for Senegalese sole. The results obtained for cuttlefish were not coherent given the low site fidelity presented by this species. White seabream demonstrated a clear preference for rocky bottoms habitats while Senegalese sole prefer sandy bottoms, especially medium grain size sand. The results of experimental fishing trials revealed no significant differences in the abundance or biomass of Senegalese sole or cuttlefish between the periods before and after the implementation of the LSMP. The species distribution models obtained with Maxent indicate that most of the LSMP presents suitable habitats for cuttlefish but only a small proportion is suitable for the Senegalese sole and white seabream. The Senegalese sole suitable habitats are mainly found in sandy areas facing south whereas the white seabream suitable habitats are restricted to the narrow rocky areas that border the coastline. Our results suggest that the existing marine reserve may offer appropriate protection for Senegalese sole and white seabream. However, given the low site fidelity and the large movements of cuttlefish the LSMP does not provide adequate protection for this species. According to the results of the different scenarios obtained with Marxan the design of the LSMP could be improved in order to offer more protection to habitats that are not sufficiently protected with the current design.
    2013Doctoral thesis Open access Show more