Ocean (Cañadas and Sagarminaga 2000; Cañadas et al. 2005; de Stephanis et al.
2008a, b). Information on the distribution and relative abundance of cetacean species
in the Alboran Sea are obtained from sightings (e.g. the whale watching industry,
visual surveys, onboard research vessels, etc.) and stranding data (e.g. see RojoNieto et al. 2011; Bellido et al. 2012; Masski and de Stephanis 2015).
The Spanish Institute of Oceanography (IEO) has recorded opportunistic
sightings of eight species of cetaceans. Data recorded between 1991 and 2015
show that 13 cetacean species were stranded on the Alboran coast in this period
(Rojo-Nieto et al. 2011; Masski and de Stephanis 2015).
According to Rojo-Nieto et al. (2011), there were differences between the
numbers of cetaceans stranded on the northern and southern coasts of the Alboran
Sea. Long-finned pilot whales (Globicephala melas) were stranded more frequently
on the north coast, whereas other delphinid species (mainly Stenella coeruleoalba
and Delphinus delphis) were stranded more frequently on the south coast.
In the Strait of Gibraltar, the most abundant species are the common dolphin
(Delphinus delphis) and the striped dolphin (Stenella coeruleoalba). There have also
been many sightings of long-finned pilot whales, sperm whales (Physeter
macrocephalus) (de Stephanis et al. 2008b), and killer whales (Orcinus orca)
(Esteban et al. 2013).
The Alboran Sea has the highest dolphin densities in the western Mediterranean
Sea. Although the common dolphin has decreased in recent decades in the Western
Mediterranean Sea, it remains abundant in the Alboran Sea (Notarbartolo di Sciara
2002; Cañadas and Vázquez 2017), where there have been no changes in population
trends (Cañadas and Hammond 2008). Nevertheless, increased SSTs could reduce
the amount of habitat suitable for the species (Cañadas and Vázquez 2017;
Gambaiani et al. 2008). According to genetic studies and bycatch, common dolphins
have higher genetic similarity with populations inhabiting adjacent the Atlantic
waters than with dolphin populations in the rest of the Mediterranean (reviewed in
Tudela et al. 2003). The most recent abundance estimate for this species in the
Alboran Sea is around 19,000 individuals. Abundance increases from east to west
(Cañadas and Vázquez 2017), which is the same pattern observed through strandings
(Bellido et al. 2012). Giménez et al. (2017) detected spatial segregation between
common and striped dolphin in the Alboran Sea.
Long-finned pilot whales have a large breeding and feeding ground in the
northeast Alboran Sea (Cañadas and Sagarminaga 2000). There is also a resident
long-finned pilot whale community in the Strait of Gibraltar (de Stephanis et al.
2008a). Between 1994 and 2014, the highest number of strandings occurred in 2007
(Torreblanca et al. 2016). In this year and previous years, there was a morbilivirus
outbreak that severely affected the population in the Alboran Sea (Wierucka et al.
2014). According to Raga et al. (1991), the abundance of the pilot whale along the
Spanish Mediterranean coasts decreases towards the north. The Alboran Sea contains the highest abundance.
21 Marine Megafauna and Charismatic Vertebrate Species
725
2008a, b). Information on the distribution and relative abundance of cetacean species
in the Alboran Sea are obtained from sightings (e.g. the whale watching industry,
visual surveys, onboard research vessels, etc.) and stranding data (e.g. see RojoNieto et al. 2011; Bellido et al. 2012; Masski and de Stephanis 2015).
The Spanish Institute of Oceanography (IEO) has recorded opportunistic
sightings of eight species of cetaceans. Data recorded between 1991 and 2015
show that 13 cetacean species were stranded on the Alboran coast in this period
(Rojo-Nieto et al. 2011; Masski and de Stephanis 2015).
According to Rojo-Nieto et al. (2011), there were differences between the
numbers of cetaceans stranded on the northern and southern coasts of the Alboran
Sea. Long-finned pilot whales (Globicephala melas) were stranded more frequently
on the north coast, whereas other delphinid species (mainly Stenella coeruleoalba
and Delphinus delphis) were stranded more frequently on the south coast.
In the Strait of Gibraltar, the most abundant species are the common dolphin
(Delphinus delphis) and the striped dolphin (Stenella coeruleoalba). There have also
been many sightings of long-finned pilot whales, sperm whales (Physeter
macrocephalus) (de Stephanis et al. 2008b), and killer whales (Orcinus orca)
(Esteban et al. 2013).
The Alboran Sea has the highest dolphin densities in the western Mediterranean
Sea. Although the common dolphin has decreased in recent decades in the Western
Mediterranean Sea, it remains abundant in the Alboran Sea (Notarbartolo di Sciara
2002; Cañadas and Vázquez 2017), where there have been no changes in population
trends (Cañadas and Hammond 2008). Nevertheless, increased SSTs could reduce
the amount of habitat suitable for the species (Cañadas and Vázquez 2017;
Gambaiani et al. 2008). According to genetic studies and bycatch, common dolphins
have higher genetic similarity with populations inhabiting adjacent the Atlantic
waters than with dolphin populations in the rest of the Mediterranean (reviewed in
Tudela et al. 2003). The most recent abundance estimate for this species in the
Alboran Sea is around 19,000 individuals. Abundance increases from east to west
(Cañadas and Vázquez 2017), which is the same pattern observed through strandings
(Bellido et al. 2012). Giménez et al. (2017) detected spatial segregation between
common and striped dolphin in the Alboran Sea.
Long-finned pilot whales have a large breeding and feeding ground in the
northeast Alboran Sea (Cañadas and Sagarminaga 2000). There is also a resident
long-finned pilot whale community in the Strait of Gibraltar (de Stephanis et al.
2008a). Between 1994 and 2014, the highest number of strandings occurred in 2007
(Torreblanca et al. 2016). In this year and previous years, there was a morbilivirus
outbreak that severely affected the population in the Alboran Sea (Wierucka et al.
2014). According to Raga et al. (1991), the abundance of the pilot whale along the
Spanish Mediterranean coasts decreases towards the north. The Alboran Sea contains the highest abundance.
21 Marine Megafauna and Charismatic Vertebrate Species
725