[Show abstract][Hide abstract] ABSTRACT: The Marine Strategy Framework Directive (MSFD) requires the assessment of the environmental status in relation to human pressures. In this study the biodiversity of the cetacean community is proposed as MSFD descriptor of the environmental status and its link with anthropogenic pressures is investigated. Functional groups are generally favoured over indicator species since they are thought to better reflect to anthropogenic stressors. Cetaceans are in many situations the most well known component of pelagic ecosystems. Their habitat requirements are known and can be used to evaluate the theoretical biodiversity that should be expected in a certain area. The deviations between the theoretical biodiversity and the actual biodiversity may be used to detect the impacts of human activities. Based on this analysis fishery resulted to be by far the most significant of the existing pressures. Among all the species, bottlenose dolphin was found the most correlated with the fishery sector dynamics.
Marine Environmental Research 09/2014; · 2.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We used generalized additive models (GAMs) as exploratory habitat models for describing the distribution of 2 deep-diving species, Cuvier’s beaked whale Ziphius cavirostris Cuvier, 1823 and sperm whale Physeter catodon Linnaeus, 1758, in the Pelagos Sanctuary (northwestern Mediterranean). We analyzed data collected from research surveys and whale-watching activities during summer months from 2004 to 2007. The dataset encompassed 147 Cuvier’s beaked whale sightings and 52 sperm whale sightings. We defined and applied a post hoc workflow to the data, to minimize false absence bias arising from the unique ecology of the species and the lack of a dedicated sampling design. We calculated a novel topographic predictor, distance from the canyon axis, as a covariate for use in the habitat model. Given the complex topography of the area, the analysis was performed on a high-resolution spatial grid (1 km). Our methods allowed effective use of the non-dedicated sampling dataset for building habitat models of elusive and cryptic species (Cuvier’s beaked whale final model sensitivity = 0.88 and specificity = 0.84; sperm whale final model sensitivity = 0.65 and specificity = 0.77). The GAM results confirmed the preference for submarine canyons for both species and also highlighted the importance of the deeper portion of the Ligurian basin, especially for Cuvier’s beaked whale. Habitat overlap nevertheless is resolved by a well-defined spatial partitioning of the area, with sperm whale occupying the western part and Cuvier’s beaked whale the central and eastern parts.
Marine Ecology Progress Series 08/2014; 508:247-260. · 2.64 Impact Factor
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