The northern sector of the Mediterranean Cetacean Corridor is confirmed as an important area for deep-diving cetaceans
We finished the AHAB Project, with more than 100 acoustic detections and 70 visual sightings and the first estimate of the abundance of sperm whales in the underwater canyons of northern Catalonia, which has had the support of the Biodiversity Foundation, the Ministry for Ecological Transition and the Demographic Challenge.
The AHAB Project aims to identify the northern area of the Mediterranean Cetacean Corridor, and especially the underwater canyons of Cap de Creus and Palamós, as potential habitats for deep-diving cetaceans, in addition to confirming the area as a feeding area for the sperm whale (Physeter macrocephalus) and establish the connectivity of this species with other areas of importance for sperm whales, such as the Balearic Islands, Liguria or the south of the peninsula and, therefore, the use of the Cetacean Migration Corridor. In addition, it is hoped that this information can help to carry out proper management of this protected area.
Results of the study campaign
Altogether, more than 2000 km were navigated, of which around 680 km were carried out in the study area (Figure 1) and in which six different species of cetaceans were detected, 4 of them being deep-diving species.
In the study area, the most sighted cetacean species was the striped dolphin (Stenella coeruleoalba) followed by the Cuvier’s beaked whale (Ziphius cavirostris), the sperm whale, the long-finned pilot whale (Globicephala melas) and the Risso’s dolphin (Grampus griseus). On the other hand, the most acoustically detected have been the striped dolphin and the sperm whale with the same number of detections, followed by the Cuvier’s beaked whale, pilot whale and pilot whale.
In total, 109 acoustic detections were made, 99 in active effort, and 71 sightings, 46 of them in active effort.
Thanks to the acoustically obtained data, the first estimate of sperm whale abundance has been made in the area of the Cap de Creus and Palamós canyons, obtaining an estimated total abundance of around 21 animals and a density of 0.007162 animals / km2 using spatial modeling. The use of acoustic techniques to detect sperm whales has been very useful when it comes to detecting the animals and establishing angles and distances.
In addition, both groups of females with juveniles and young have been observed, as well as a solitary male.
Sperm whale re-sightings
A total of 12 individuals of sperm whales have been photo-identified, which have been compared with individuals identified in other areas of the Mediterranean, such as the Balearic Islands, the Strait of Gibraltar, and the Gulf of Lion. As a result of the photo-identification, it has been detected that some of the sperm whales observed by SUBMON both during this project and in a previous project, move through the area of the Gulf of León.
On the one hand, one of the individuals observed during the AHAB project was observed a few days later in the north of the Gulf of León in an outing carried out by the Découverte du Vivant entity and, on the other hand, an individual observed by SUBMON in the same area in 2010, within the framework of the LIFE + INDEMARES project (coordinated by the Biodiversity Foundation), was observed 8 years later by the same French entity in the northern area of the Gulf canyons. Both individuals are possibly male and the re-sighting 8 years later supports the importance of the area for the movements of males in this part of the Mediterranean.
The Tursiops Association has identified another possible re-sighting between another of the sperm whales sighted during the AHAB campaign and a male individual observed and identified in the waters of the Balearic Islands in several previous years.
Thus, the underwater canyons of Cap de Creus and Palamós prove to be an area of special importance due to the presence of deep-diving cetaceans, and especially the sperm whale, given their high density. The presence of both males and groups of females would indicate this area as a feeding and breeding area, giving a special value to these canyons. The continuation of this study is considered very important in order to increase the robustness of the results and thus be able to apply management measures in the area for the protection of these animals.