Line of action:

Status:

Execution date:

The Risso’s dolphin (Grampus griseus) is the smallest species of the subfamily Globicephalineae (Delphinidae), with a cosmopolitan distribution and whose diet is based mainly on cephalopods (squid, octopus and cuttlefish), but beyond these data, knowledge about this cetacean is very limited, both nationally and globally.

There is little information on the trend of the Mediterranean subpopulation, although several previous studies have noted a decline of up to 50 % of the population in the Ligurian basin. SUBMON considers that its main threat is bycatch by the surface longline fishery (with pelagic gear and gillnets). Likewise, chronic noise from marine construction, seismic surveys, military sonar, etc., can drastically alter the behavior of these specimens and, together with accidental captures, increase the risk of strandings. However, there is very little information on its distribution and abundance in the Levantine-Balearic demarcation, so, according to the entity, it is necessary to obtain more data on the species in order to strengthen its conservation.

This SCARS project has had the objective of broadening the knowledge of the distribution, abundance and movements of the gray pilot whale population inhabiting the demarcation levantino-balearicThe study area is part of marine protected areas (including the Mediterranean Cetacean Migration Corridor and several Natura 2000 Network sites). In this way, the results of the project will contribute to evaluate and improve the conservation status of this species at national and international level, and will help in the future management of state protected areas, according to the entity.

The general objective of the project has been to obtain data to contribute to the improvement of the conservation status of the Risso’s dolphin(Grampus griseus) at national and international level.

The specific objectives were as follows:

• To obtain data on the distribution, abundance and movements of the Risso’s dol phin (Grampus griseus) population in the waters of the Levantine-Balearic demarcation belonging to the Natura 2000 Network and the Mediterranean cetacean migration corridor, as well as other cetacean species present in the area.
• To provide information to help the conservation of the species and increase its level of protection at the national and international level.

• Review and compilation of 132 documents concerning the Risso’s dolphin population in the study area over the last 20 years.
• Development of a sampling map and two data collection campaigns using visual and acoustic line transects at different stations. Visual sampling was carried out on a catamaran with a 15-meter platform. In the 122 sightings made, 8 different species of cetaceans and a total of 168 individuals have been identified, with the striped dolphin being the most sighted species, followed by the fin whale, Cuvier’s beaked whale and long-finned pilot whale, in that order. Acoustic sampling was performed with a three-channel hydrophone, an acoustic signal converter and software for sound visualization and interpretation. A total of 155 acoustic detections were recorded, and 6 different species of cetaceans have been identified by this method: striped dolphin, sperm whale, pilot whale, common dolphin, bottlenose dolphin and Risso’s dolphin (in order of the number of acoustic detections).
• Treatment and analysis of the data obtained in the sampling, making a distribution map of each species sighted. With respect to the Risso’s dolphin, only 3 sightings were obtained, showing a decrease in its presence in continental slope areas and an increase in pelagic areas. This preference had already been detected in previous studies, but in recent years it seems that the species tends to increase its distance from the coast compared to previous years.
• Expansion of the photo-identification catalog and comparison with catalogs from other areas of the Western Mediterranean with our own catalog obtained through marine surveys. In this way, the organization has been able to photo-identify a total of 57 individuals, 26 of which are Risso’s pilot whales. It was detected that some of the individuals were already registered in catalogs of other entities, being identified in the Garraf canyon between 2015 and 2020, which has shown that the specimens maintain their areas of residence, at least over 8 years.
• Elaboration of the scientific article “Insights into the occurrence and distribution of Rissos’s dolphin(Grampus griseus) in the northern sector of the Catalan Sea (Northwestern Mediterranean)”. The results of the study show that the habitat formed in the interior of these canyons is suitable for a great diversity of species, among them the Risso’s dolphin, and other deep-diving cetacean species. It has also been highlighted that the distance to the coast by the species has been increasing throughout the years of sampling, so that the species shows a displacement towards more pelagic areas.
• Proposal and development of several management measures for the conservation of the Risso’s dolphin. These measures could also be applied for protection and conservation purposes for the rest of the cetacean species, which is why the entity has also contributed other management measures aimed at protecting large cetaceans such as the sperm whale, fin whale and Cuvier’s beaked whale, and whose objective is to avoid the risk of collision with maritime traffic.
• Report the results obtained to the corresponding competences to evaluate the conservation status of the Risso’s dolphin, being sent, specifically, to the Subdirectorate General of Terrestrial and Marine Biodiversity, of the General Directorate of Biodiversity, Forests and Desertification of the Ministry for Ecological Transition and the Demographic Challenge, and to the Subdirectorate General of Biodiversity and Natural Environment of the Generalitat de Catalunya (Autonomous Government of Catalonia). In addition, the entity has stated its intention to increase its efforts to obtain more data that will allow it to increase the degree of protectionThe study was carried out not only on the species studied, but also on the habitats in which they are found, given the observations of the presence of calves and feeding behavior in the Catalan submarine canyons, a non-protected area of great ecological value for many of the cetacean species.
• Disclosure and communication of the project, through publications on social networks and notes on the organization’s website, a television report, an article for the Port de Sitges website and the publication of two boat tarpaulins to publicize the project during cetacean sightings. in situ.

The SCARS project has contributed to increase the knowledge of 8 species of cetaceans and, in particular, the Risso’s dol phin (Grampus griseus). In this regard, several extremely interesting results have been obtained for the conservation of the species.

On the one hand, the modification of the behavior of the species over the years has been observed. In previous surveys, the presence of pilot whales in areas close to the coast was relatively common, but the entity has shown that, at present, there is a tendency to move away from the coast and towards pelagic areas, perhaps associated with human activities.

The results of the project have also highlighted the underwater canyons of Catalonia, whose habitats provide food and serve as breeding grounds for numerous species of cetaceans. Therefore, the organization stresses that future efforts should be directed not only to the conservation of cetaceans, but also to the protection of these key areas for their survival.

Another important activity has been the updating of the photo-identification catalog of the Risso’s dolphin in collaboration with other entities dedicated to the study of cetaceans in the Mediterranean, and whose conservation objectives are aligned with those of SUBMON. Thanks to this action, it has been possible to verify that the pilot whales remain within their areas of residence, at least during the 8 years for which there are records of photo-identification data.

The entity has transmitted the results of the project to the relevant public administrations of the Ministry for Ecological Transition and the Demographic Challenge (MITECO) and the Generalitat de Catalunya. In this regard, it has also developed a set of management measures to reduce the impact of threats affecting the Risso’s dolphin. Among them, we can highlight the detailed identification of current or potential threats, at the population level, occurring in the area, in order to determine whether there is an anthropogenic impact on the population of the species; or the effective implementation of the Royal Decree 1727/2007 to promote the training of whale watching tourism companies through awareness campaigns or validated marine stewardship protocols. These measures could also be applied for protection and conservation purposes for the rest of the cetacean species.The organization has also contributed other management measures aimed at protecting large cetaceans such as the sperm whale, fin whale and Cuvier’s beaked whale, and whose objective is to avoid the risk of collision with maritime traffic.

Finally, the dissemination and communication activity of the project has obtained a great reach among social networks, reaching a total of 52,093 users and generating 3,133 interactions during the execution of the project. Also noteworthy is the collection of graphic documentation (photographic and audiovisual) obtained during the two sampling campaigns, not only for its quantity but, especially, for its high quality and professionalism.