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

University of Liège, Luik, Walloon, Belgium
Journal of the Marine Biological Association of the UK (Impact Factor: 1.06). 02/2007; 87(1):187-193. DOI: 10.1017/S0025315407054689


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.

12 Reads
    • "Analysis of movements also shows that individual sperm whales frequently make movements on a scale consistent with the western Mediterranean basin being occupied by a single, albeit imperfectly mixed, population. Such movements are consistent with data from populations in other regions (Whitehead, 2001; Gero et al., 2007; Whitehead et al., 2008) and with previous studies of movements in this region based on a subset of the data presented here (Drouot-Dulau and Gannier, 2007). It is important to understand the limitations of these data and the estimates derived from them. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Sperm whales in the Mediterranean are classified as ‘Endangered’ by the IUCN. They are apparently isolated from adjacent Atlantic populations, and subject to anthropogenic pressures including interactions with illegal driftnet fisheries, ship strikes, ingestion of debris and underwater noise.Photo-identification data opportunistically collected from the western Mediterranean basin show that individual sperm whales regularly move in excess of 500 km across the western basin, suggesting that this area is occupied by a single population.The best abundance estimate for this region is approximately 400 animals, with confidence intervals between 200 and 1000.Given the mortality levels reported in the literature, this figure suggests that the conservation status of sperm whales in this region is very serious. Immediate priority should be placed both on conducting systematic surveys for abundance estimation and on measures to reduce the mortality associated with driftnet fishing. Copyright © 2014 John Wiley & Sons, Ltd.
    No preview · Article · Jul 2014 · Aquatic Conservation Marine and Freshwater Ecosystems
  • Source
    • "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). "
    [Show abstract] [Hide abstract]
    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.
    Full-text · Article · Jul 2014 · Aquatic Conservation Marine and Freshwater Ecosystems
  • Source
    • "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). "
    [Show abstract] [Hide abstract]
    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.
    Full-text · Article · Jul 2014 · Aquatic Conservation Marine and Freshwater Ecosystems
Show more