Audouin's gull in marine protected areas during breeding and migration

The Seabird Ecology Lab (Faculty of Biology from Universitat de Barcelona and the Institute for Research on Biodiversity-IRBio) is developing the project “GAUDIN: La gaviota de Audouin como instrumento para la mejora de la gestión de la RAMPE en el Levante español” (Audouin’s gull as a tool to improve the management of RAMPE in the Spanish east coast). This project has the support of Fundación Biodiversidad from the Ministry for the Ecological Transition and the Demographic challenge, with the collaboration of the Asociación de Naturalistas del Sureste (ANSE) and the Spanish Institute of Oceanography (IEO).

The main objectives of GAUDIN project are 1) to address the role of the Spanish network of marine protected areas (Spanish acronym: RAMPE) in the conservation of an endangered and endemic species to the Mediterranean Sea, the Audouin’s gull (Ichtyaetus audouinii), and 2) to investigate the interactions between Audouin’s gulls and fishing vessels, in order to improve the management of RAMPE and fisheries. These objectives align with LIFE INTEMARES actions, which aim for an efficient management of marine areas from Natura 2000 with the collaboration of the sectors involved and research as main tools for decision making.

To achieve these objectives, we equipped 18 Audouin’s gulls with GPS/GSM tracking devices (Global Positioning System/Global System for Mobile communications). We placed the devices on both adult individuals (during incubation) and chicks (during chick rearing), between May and July from 2020, in the Regional Park of Salinas y Arenales de San Pedro del Pinatar (Murcia).  These devices can register a location every minute and send this information via the mobile communications network, which will allow us to investigate the movements of Audouin’s gulls with a very high temporal and spatial resolution.

Since Audouin’s gull is a migratory species, we have been able to obtain movement data during the breeding period, when they were at their breeding colony in the Spanish east coast, and also during their migration, when in general they left towards African coasts. Currently, there are 10 GPS/GSM tracking devices that continue functioning, six of them placed on adult gulls and four on juveniles. The positions gathered by all of them add up to 1,200,000.

Preliminary results show that, during the breeding period (we considered May and June), most locations registered by the GPS/GSM tracking devices took place ashore (overall: 69.3%; per age class: 69.1% adults, 100% juveniles), while just a third of them (30.7%; per age class: 30.9% adults, 0% juveniles) were at sea. Regarding the overlap between Audouin’s gull movements and the RAMPE, only a third (31.6%) of the total locations at sea -all belonging to adult gulls- took place within RAMPE spaces. Since juveniles were equipped with tracking devices by the end of June and they stayed in the breeding colony until migrating, all their positions were ashore and they did not use the RAMPE. All the locations registered during the breeding period and their overlap with the RAMPE are depicted in the following map.

With regards to their migration, most adult gulls equipped with GPS/GSM tracking devices left the breeding grounds between late June and late July, while juvenile gulls migrated -in general- after their parents, from mid-July to early August. Some gulls (both adults and juveniles) travelled long distances in a relatively short amount of time, while others made a few stops while migrating. Moreover, some of them are still on the move. Audouin’s gulls have travelled between 400 and 3,400 km in 1 to 40 days, except for one adult gull that did not leave the Iberian Peninsula.

During their migration (here we considered July and August), the percentage of locations ashore registered by the tracking devices varied between age classes (overall: 57.3%; per age class: 46.6% adults, 67.1% juveniles), being slightly lower (in adults) or higher (in juveniles) than the percentage of positions at sea (overall: 42.7%; per age class: 53.4% adults, 32.9% juveniles). As for the overlap with the RAMPE, the use of these spaces by Audouin’s gulls was scarce: only 9.7% of at sea locations occurred within these spaces (per age class: 8,7% adults, 11.2% juveniles).

With regards to the wintering areas, four out of six adult gulls migrated towards the Atlantic coast of Morocco, Western Sahara and Mauritania, while the other two stayed in the Alborán Sea. Overall, the most frequent wintering and migration areas were Dahkla (Río de Oro Peninsula, Western Sahara) and Nouadhibou (Cabo Blanco Peninsula, on the border between Western Sahara and Mauritania). As for the two adult gulls that stayed in the Alboran Sea, they are currently in Moroccan coasts (provinces of Driouch and Nador) and Spanish coasts (Almería), and the latter did not migrate. Regarding the juvenile gulls (five of them migrated, four still have functioning tracking devices), in general they migrated further away from the breeding colony than adult gulls, given that they have already reached Western Sahara, Mauritania and Senegal. The wintering and migration areas more used by juveniles were Nouadhibou (Western Sahara/Mauritania), Nuakchot (Mauritania) and Dakar (Peninsula of Cape Verde, Senegal).

Click on the following map to explore all the migratory routes and wintering areas of Audouin's gulls.

Despite we need to perform detailed spatial and temporal analyses, as well as take interactions with fisheries into account, these preliminary results show that RAMPE spaces are more used by adult Audouin’s gulls, especially during the breeding period. The lower use of RAMPE by both age classes during migration is related to the migratory behaviour of the species, given that they travel long distances outside national territory.

Furthermore, the wintering areas and migratory routes used up until this moment by Audouin’s gulls in general agree with areas previously described as important for their migration (https://tinyurl.com/yy5j5ul7). The Canary Current, characterised by cold and rich waters, has a high productivity in the Atlantic coast of northern Africa, which allows Audouin’s gulls to obtain food (mainly epipelagic fishes) both from natural and anthropogenic sources (fishery discards from fishing vessels and in ports). Agreeing with this, there are industrial and artisanal fishing fleets in Dakhla, Nouadhibou and Dakar, which are probably exploited by Audouin’s gulls. Moreover, the single Audouin’s gull that stayed in Spain frequently visits Adra’s port (Almería), other ports in the area and croplands, which suggest that this non-migratory individual also utilises resources derived from human activities.

These preliminary results contribute with relevant data to the knowledge on movements and use of RAMPE by Audouin’s gulls in the Spanish east coast, as well as on their wintering areas and migratory routes in the Atlantic and Mediterranean coasts of northern Africa. These results, together with the analysis of their interactions with fisheries, will help in achieving the objectives of the GAUDIN project for a better management of RAMPE and fishing activities.