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ESR 12:203-214 (2010)  -  DOI:

Habitat use and abundance of striped dolphins in the western Mediterranean Sea prior to the morbillivirus epizootic resurgence

Cédric Cotté1, 2,*, Christophe Guinet2, Isabelle Taupier-Letage1, Estelle Petiau2

1Université de la Méditerranée, OSU/Centre d’Océanologie de Marseille, CNRS, Laboratoire d’Océanographie Physique et de Biogéochimie, Antenne de Toulon, BP330, 83507 La Seyne, France
2Centre d’Études Biologiques de Chizé, CNRS, 79360 Villiers en Bois, France

ABSTRACT: Although the striped dolphin Stenella coeruleoalba has a world status of Least Concern, a recent IUCN Red List assessment has proposed that the Mediterranean population be listed as Vulnerable and stresses the need for an estimate of abundance and distribution. While substantial efforts have been made to study cetaceans in regions of the western Mediterranean Sea (WM), we have little knowledge of their large-scale distribution and interaction with oceanographic features at various scales. We conducted 18 basin-wide surveys from ferry platforms within the WM from early September 2006 to late July 2007 and used spatial modelling to investigate the distribution, abundance and habitat use of striped dolphins. Most striped dolphins were sighted north of the Balearic Islands, where they are closely associated with the counter-clockwise circulation defined by negative absolute dynamic topography. In the Algerian basin, dolphins were mostly found in recent Atlantic water mass. Densities of striped dolphins were also related to high gradients of sea surface temperature and high chlorophyll concentrations. Moreover, we found similar results (1) when the northern and southern data sets were pooled and (2) in the northern area only, where the majority of sightings occurred. These relationships suggest that dolphins were found in dynamic and productive areas generated by mesoscale processes which could create favourable foraging conditions. Despite our relatively small data set, dolphins were found year-round. We estimated the number of striped dolphins in the area between 3° and 6°E to have been 38600 (95% CI: 25900 to 53900) before the resurgence of the morbillivirus epizootic in summer 2007. This is considerably more than the estimate from the 1991 WM survey, which reported a 43% lower abundance, probably affected by the 1990 epizootic. Platforms of opportunity are therefore relevant not only to assess animal ecology but also to monitor population in a given area. Such interanual monitoring is especially important to detect and quantify the response of animal populations, in terms of distribution and density, to environmental stresses.

KEY WORDS: Habitat use · Abundance and distribution modeling · Mesoscale oceanographic processes · Striped dolphin · Morbillivirus epizootics

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Cite this article as: Cotté C, Guinet C, Taupier-Letage I, Petiau E (2010) Habitat use and abundance of striped dolphins in the western Mediterranean Sea prior to the morbillivirus epizootic resurgence. Endang Species Res 12:203-214.

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