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SST fronts and the summer sperm whale distribution in the north-west Mediterranean Sea

Journal of the Marine Biological Association of the UK (Impact Factor: 1.13). 02/2007; 87:187-193. DOI: 10.1017/S0025315407054689
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    Journal of the Marine Biological Association of the UK 02/2007; 87(01). · 1.13 Impact Factor
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    ABSTRACT: The Marine Strategy Framework Directive (Directive, 2008/56/EC of the European Parliament and of the Council of 17 June 2008) establishes a framework for community action in the field of marine environmental policy. The MSFD overall objective is to achieve the “Good Environmental Status” (GES) in the marine environment, by the year 2020, based on 11 qualitative descriptors. Moreover, the MSFD requires the assessment of the functioning of each objective in relation to pressures and based on this knowledge the definition of appropriate program of measures to control the pressures that significantly affect the marine environmental status. This highlights the critical step of defining what is “Good Environmental Status”. The potential use of large marine vertebrates in determining the environmental status of pelagic marine ecosystems, has been recenty debated. Among these, cetaceans are in many situations the most well known component: the habitat preferences of the most frequent species are well documented in the literature and information about their presence and occurrence are generally more easily available than for other pelagic species. In this study an index is proposed to evaluate the biodiversity observed in the cetacean community with respect to the biodiversity expected based on the habitat characteristics of the area. The expected biodiversity is obtained through the application of predictive models using physiographic predictors (e.g. mean depth, sea bed slope etc.) and compared with the observed biodiversity. Cetacean observed biodiversity is assessed based on the data available from the aerial surveys conducted in Ligurian, Tyrrhenian and Ionian seas in the period 2009-2011. The study area is subdvided in subareas. Observed and expected biodiversity were determined for each subarea based on physical habitat characteristics. Deviations from the expected values are interpreted in the context of the existing pressures (ship traffic, pollution, fishing pressure etc.). A Biodiversity lower than expected was found correlated with a higher anthropogenic impact, suggesting that the proposed index may complete the GES definition. Strandings data were also used to evaluate the relative impact of the different pressures in the subareas (e.g. bycatches and collisions etc.). Moreover marker of genetic erosion were evaluated on the dominant species and compared in the different subareas.
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    ABSTRACT: 1. Climate change and human activities impacts are considered to be the main causes of sperm whale habitat alteration. 2. Despite the creation of several marine protected areas in the Mediterranean Sea, the sperm whale status remains ‘endangered’. Its spatial distribution has been reported in different areas of the Mediterranean, among them the Pelagos Sanctuary. 3. Various biophysical parameters have been recognized to influence sperm whale distribution depending on the modelling scale. Hence, this study investigates and predicts sperm whale relative occurrence, taking into account the parameters that affect their habitats in the central Mediterranean Sea, inside and beyond the boundaries of the Pelagos Sanctuary. 4. An artificial neural network (ANN) model was used to predict the probability of sperm whale occurrence in the central Mediterranean Sea, for each cell of a 3 ×3 minute grid using a Visual Basic script to interface with GIS software. The algorithm was trained using species presence/absence data and a set of physiographic variables such as depth, slope, distance to shore and magnetic field. 5. Some geographic areas exhibit a consistently high probability of occurrence and may be identified as highly used areas for special management concern. Thus, this work represents a preliminary evaluation of management and conservation effort outside the Pelagos Sanctuary. The map of sperm whale predicted relative presence can be used to mitigate potentially harmful human activities and to support the design and management of marine protected areas, including the delineation of ecologically meaningful boundaries. Copyright # 2013 John Wiley & Sons, Ltd.
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