Over 800 rays and sharks tagged during the MEDITS survey in the Balearic Islands

The IEO-CSIC leads an ambitious conservation project involving 21 European institutions with the collaboration of the Balearic fishing sector.

Palma, Thursday, September 4, 2025. A team of 19 scientists, led by the Balearic Oceanographic Centre of the Spanish Institute of Oceanography (IEO-CSIC), tagged a total of 848 rays and sharks in the waters of Mallorca, Menorca, Ibiza, and Formentera during the MEDITS 2025 survey.

This activity is part of the EU-cofunded LIFE-PROMETHEUS project, which aims to promote the conservation of cartilaginous fish. The project involves 21 institutions from Italy, Greece, Cyprus, France, and Spain, with case studies focused on the Balearic Islands and coordinated by the IEO-CSIC.

The survey took place aboard the fisheries and oceanographic research vessel Miguel Oliver, operated by the General Secretariat of Fisheries of the Ministry of Agriculture, Fisheries and Food, between June 22 and August 29. The first stage was carried out in the waters around Mallorca and Menorca, while the second focused on the Pityusic Islands. In addition to the staff from the Balearic Oceanographic Centre, researchers from the Málaga Oceanographic Centre, the Institute of Marine Sciences of Andalusia, the General Secretariat of Fisheries, the Society for the Development of Coastal Communities (SOLDECOCOS), and WWF Spain also participated.

Specimens were tagged at different sampling stations around the islands, with the collaboration of the professional fishing sector, whose role is crucial for the recovery of recaptured individuals. In total, 820 individuals from 11 species of rays and 28 individuals from five species of sharks were tagged, including species listed as endangered by the IUCN such as Rostroraja alba and Raja radula, with 40 and 21 specimens tagged respectively. These high numbers of specimens were never captured before.

Thanks to the support of WWF and the collaboration of SOLDECOCOS, two Rostroraja alba specimens were also fitted with multi-parameter satellite tags, enabling the tracking of their movements, depth, temperature, and light levels in their habitats for around 200 days. One was released on the Menorca Channel and the other northwest of Ibiza.

The data obtained through recaptures and satellite tracking will make it possible to estimate essential parameters for the sustainable management of these species, such as mobility, migrations, population connectivity, growth, survival after capture, and population size in the Balearic Islands.

Xisco Ordinas, from the Balearic Oceanographic Centre and principal investigator of the LIFE-PROMETHEUS project in Spain, highlighted the importance of the fishing sector in this experiment: “Without information on the recaptures of tagged individuals, the experiment will not succeed. Among this information, the size of individuals is particularly relevant as it will allow us to estimate the growth rate of these species.”

The main goal of LIFE-PROMETHEUS is to halt the decline of ray and shark populations threatened by fishing pressure by involving the fishing sector in the development of more sustainable practices.

The MEDITS surveys are carried out under the coordination of the IEO-CSIC and the Ministry of Agriculture, Fisheries and Food, which facilitates the use of vessels and equipment for research staff. They are co-financed by the European Union through the European Maritime, Fisheries and Aquaculture Fund (EMFAF) within the National Fisheries Data Collection Program, with results reported to the European Commission in accordance with Regulation (EU) 2017/1004 of the European Parliament and the Council.

The Spanish Institute of Oceanography (IEO, CSIC) is a National Centre of the Spanish National Research Council (CSIC), under the Ministry of Science, Innovation and Universities, dedicated to marine science research, particularly scientific knowledge of the oceans, the sustainability of fishery resources, and the marine environment. The IEO represents Spain in most international scientific and technological forums related to the sea and its resources. It has nine coastal oceanographic centres, five marine aquaculture experimental facilities, 12 tide gauge stations, a satellite image receiving station, and a fleet of five oceanographic vessels, including the Odón de Buen, Ramón Margalef, and Ángeles Alvariño.