The most visited marine areas by adult and juvenile Audonin’s gulls are near the coast and are partially protected by the Spanish Network of Marine Protected Areas Network (RAMPE). Although this network is revealed as an efficient management tool to protect and conserve the frequented areas by the seabirds, we need management measures to reduce the human pressure on the populations of Audonin’s gull in the littoral of the peninsula.
These conclusions result from the project "La gaviota de Audonin como instrumento para la mejora de la gestión de la RAMPE en el Levante español" (GAUDIN), led by Professor Jacob González Solís-Bou, from the Faculty of Biology and the Biodiversity Research Institute (IRBio) of the University of Barcelona. GAUDIN, carried out with the support from the Biodiversity Foundation from the Ministry for Ecological Transition and the Demographic Challenge, has analysed the overlapping level of the distribution of the Audonin’s gull with RAMPE, as well as the interactions between these birds and the fishing float in and out of these protected spaces in the peninsular eastern and southern waters.
Audonin’s gull: an emblematic species of the Mediterranean
Audonin’s gull (Ichthyatus audouinii) is a vulnerable species in Spain which is specially threatened by accidental bycatches, the dependency on fishery discards, the pollution of the marine environment and the use of breeding areas in highly transformed environments by human activity.
As part of the project, the UB-IRBio team studied the movements of seabirds in the eastern side of the peninsula using global positioning system devices (GPS/GSM) in fifteen individuals in the Regional Park Salinas y Arenales de San Pedro del Pinatar (Murcia), one of the breeding areas of this species. To solve the doubts on the interactions between seabirds and fishing boats, the team combined the telemetric monitoring of the Audonin’s gull with the positioning data of the fishing fleet via satellite using the vessel monitoring system and their own GPS devices.
Juvenile and adult gulls: a differenced pattern
For the first time, the project analysed the differential response of gulls to the interactions and bycatches depending on the age of the individuals. They compared "the use of the marine space and the interactions between the fisheries and the juvenile and adult gulls", notes Raquel Castillo Contreras, scientific coordinator of the project and researcher at the Department of Evolutionary Biology, Ecology and Environmental Sciences and IRBio.
Using the records from the GPS/GSM devices, in the Audonin’s gulls, researchers found that 51% of the adult individuals and only 9% of the young ones are in the marine environment. When the gulls go to the sea, about a third of the recorded locations take place in some of the RAMPE spaces, both in adults and in juvenile individuals.
Regarding the interaction with the fishing fleet, the 92% of the cases take place with trawler and encircling fleets. In particular, about half of it with each fleet in adults, but twice as many with trawlers compared to encircling fleets in the case of juvenile gulls. In general, the interactions take place outside the RAMPE areas. Specifically, only 21% of the interactions regarding adults and 32% in young gulls occur within the RAMPE areas.
Therefore, the most visited marine areas by the monitored Audonin’s gulls and their interactions with fisheries are only partially overlapped with RAMPE, "a result that shows that the gulls that breed in Salinas de San Pedro del Pinatar eat mostly in unprotected areas", concludes Jacob González-Solís, head of the Seabird Ecology Group of the UB-IRBio and membre of the Department of Evolutionary Biology, Ecology and Environmental Sciences and IRBio.
90% of the world nesting population is in Spanish territory
Limiting some human activities during the breeding season and the beginning of the migratory season of the Audonin’s gull in the most frequented RAMPE areas by the birds is one of the management measures presented by the UB-IRBio team to improve the conservation of seabirds. Parallelly, it is necessary to implement measures to reduce the risk of bird bycatches in longline fishing in the Levantine area both inside and outside the RAMPE.
"Although the populations of Audonin’s gull have grown over the last decades, their geographical distribution is still limited and 90% of the world nesting population is in Spanish territory. Therefore, we need to make an effort in monitoring their populations, assessing threats, and designing suitable conservation measures", highlights Àngel Sallent, expert from the Association of Naturalists of the Southeast (ANSE).
As noted by Salvador García, expert from the Spanish Institute of Oceanography (IEO-CSIC), "when it comes to the conservation of seabirds, the involvement of the fishing sector is crucial. In this sense, during the development of the project, we counted on the unconditional collaboration of the fleet in any of their modalities. Fishermen were an active part of the project, and therefore, of the solution to the threats this species is dealing with".
The GAUDIN project counts on the collaboration of the Association of Naturalists of the Southeast (ANSE) and the Spanish Institute of Oceanography (IEO-CSIC), specially, the Research Group Great Pelagics of the Mediterranean. Among the participants are the researchers Marta Riutort, from the Department of Genetics, Microbiology and Statistics and IRBio, and Sarah Saldanha and Leia Navarro, from the Department of Evolutionary Biology, Ecology and Environmental Sciences and IRBio.
Vídeo (Raquel Castillo, UB-IRBio)