SST fronts and the summer sperm whale distribution in the north-west Mediterranean Sea
ABSTRACT The relative distribution of sperm whales (Physeler macrocephalus) and sea surface temperature (SST) fronts have been studied in summer in the north-western Mediterranean Sea. We used passive acoustic data (778 samples) obtained offshore during dedicated surveys between 1999 and 2004 and Pathfinder/Modis remote sensing data to compute front maps and to calculate mean distances from sperm whale detections (N=132) to SST-fronts. Mean distances from sperm whale acoustic detections to SST fronts were significantly lower (10.4 km) than from other acoustic samples to those fronts (17.0 km). The same result was obtained when calculating distances from sperm whales to the North Balearic Front surface signature. If sperm whales are commonly observed along the continental slope, we showed that offshore individuals were located close to SST fronts. This bimodal distribution in the north-western Mediterranean is linked to sperm whale feeding,, demonstrating ecological opportunistic behaviour in this high level predator.
- SourceAvailable from: Mehdi Aissi
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- "Focusing on topographic features in this part of the Mediterranean Sea, habitat selection was associated mainly with the presence of submarine canyons (David, 2000; Aïssi et al., 2012; David and Di-Méglio, 2012). This preference for canyon areas and 'complex' bathymetries has been highlighted by other studies (Croll et al., 1998; Gannier and Praca, 2007; Moulins et al., 2008). "
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.Aquatic Conservation Marine and Freshwater Ecosystems 07/2014; 24(S1). DOI:10.1002/aqc.2411 · 1.76 Impact Factor
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- "In the Mediterranean Sea, different authors have investigated relationships between sperm whale (Physeter macrocephalus) distributions, bottom topographies and environmental parameters (David, 2000; Drouot et al., 2004; Gannier and Praca, 2007; Azzellino et al., 2008; Moulins et al., 2008; Praca and Gannier, 2008; Aissi et al., 2012; David and Di-Méglio, 2012). It has been shown that these animals seem to prefer deep continental slope waters (Azzellino et al., 2008) thought to be areas where mesopelagic cephalopods – the species' preferred prey (Clarke, 1996; Whitehead, 2003) – are most abundant (Azzellino et al., 2008; Praca and Gannier, 2008). "
ABSTRACT: 1. Boat surveys aimed at studying sperm whales in the Tyrrhenian Sea were conducted between 2002 and 2011. During 768 daily surveys, a total effort of 32 602 km was achieved within an area of 8800 km 2 resulting in 92 encounters with 229 sperm whale individuals. 2. Average encounter rates of sperm whales was 0.5 groups per 100 km 2 , with a higher concentration in the vicinity of the submarine canyon of Cuma, confirming the importance for the species of this small hotspot in the Mediterranean Sea. 3. Encounter rates increased with increasing distance from the coast. It is possible that the intense boat traffic and anthropogenic disturbance in the area may be moving animals away from the coast leading to habitat loss. 4. The species–habitat relationship documented in this study has implications for conservation.Aquatic Conservation Marine and Freshwater Ecosystems 07/2014; 24(S1):59-70. DOI:10.1002/aqc.2460 · 1.76 Impact Factor
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- "Within the Pelagos area, previous studies reported partial information on depth and offshore distance preferred by cetaceans (Gannier, 2002; Panigada et al., 2005; Moulins et al., 2007). Some remote-sensing data correlations have been proposed for a few species (Littaye et al., 2004; Gannier & Praca, 2007). However, some heterogeneity is still observed over the predicted suitable habitats due to unknown factors. "
ABSTRACT: This study used Monte Carlo methods to generate simulations that considered the effort distribution to determine the locations of significant aggregations of cetacean sightings inside the northern Pelagos Sanctuary (north-western Mediterranean Sea). For three years, monitoring has been conducted from five motor vessels covering about 30,050 km. The most frequently encountered species were the striped dolphin Stenella coeruleoalba representing 64.7% of all sightings, the fin whale Balaenoptera physalus (17.0%), Cuvier's beaked whale Ziphius cavirostris (9.9%), Risso's dolphin Grampus griseus (4.3%) and the sperm whale Physeter catodon (2.2%). Sightings' positions and effort coverage were distributed over a grid of 5′ longitude and 5′ latitude. Spatial concentrations of sightings were analysed according to the distribution of effort to identify ‘hotspots’ (locations where the species occurred at a significantly greater frequency than expected), and ‘coldspots’ (locations with a significantly lower frequency than expected). Most fin whale hotspots (14) were located on the bathyal plain between 2000 and 2500 m, four hotspots were around the 1000 m isobaths, and one is located close to the seamount off Genoa. Fin whale coldspots were mainly along the coast. Striped dolphin hotspots were widely distributed over two main areas, in waters with depths between 2000 and 2500 m and at the continental slope; coldspots for this species were also mainly along the coast in the northern part of the study area. Many hotspots were found in the Genoa Canyon, and hotspots of striped dolphins, Cuvier's beaked whales, sperm whales and Risso's dolphins overlapped in this region. Some of the hotspots of Cuvier's beaked whales were identified at the seamount in the study area, where no other species was sighted frequently. Risso's dolphin hotspots were mainly near the 1000 m isobath. For sperm whales, several hotspots were identified: three associated with steep slope features (such as canyons or the continental slope), and one was in the centre of the flat area of Pelagos where the depth is 2500 m. This study highlights the ecological importance of particular locations inside the Pelagos Sanctuary—locations that should be protected from anthropogenic degradations for marine mammal conservation.Journal of the Marine Biological Association of the UK 08/2008; 88(06):1273 - 1281. DOI:10.1017/S0025315408000763 · 1.13 Impact Factor